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Encyclopedia > Signal transduction

In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in what is thought of as a "second messenger pathway". Such processes are usually rapid, lasting on the order of milliseconds in the case of ion flux, to minutes for the activation of protein and lipid mediated kinase cascades. In many signal transduction processes, the number of proteins and other molecules participating in these events increases as the process eminates from the initial stimulus, resulting in a "signal cascade" and often results in a relatively small stimulus eliciting a large response. Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: βίος, bio, life; and λόγος, logos, knowledge), also referred to as the biological sciences, is the study of living organisms utilizing the scientific method. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... It has been suggested that this article or section be merged with Electrophysiology. ... Biochemistry is the study of the chemical processes in living organisms. ... For other uses, see Chemical reaction (disambiguation). ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... In biology, second messengers are low-weight diffusible molecules that are used in signal transduction to relay signals within a cell. ... A Biochemical Cascade is a series of chemical reactions in which the products of one reaction are consumed in the next reaction. ...


In bacteria and other single-cell organisms, the variety of signal transduction processes of which the cell is capable influences how many ways it can react and respond to its environment. In multicellular organisms, a multitude of different signal transduction processes are required for coordinating the behavior of individual cells to support the function of the organism as a whole. As may be expected, the more complex the organism, the more complex the repertoire of signal transduction processes the organism must possess. Thus, sensing of both the external and internal environment at the cellular level, relies on signal transduction. Many disease processes such as diabetes, heart disease, autoimmunity and cancer arise from defects in signal transduction pathways, further highlighting the critical importance of signal transduction to biology as well as medicine. Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... “Life on Earth” redirects here. ... Multicellular organisms are those organisms containing more than one cell, and having differentiated cells that perform specialized functions. ... Senses are the physiological methods of perception. ... This article is about the disease that features high blood sugar. ... Atherosclerosis is a disease affecting arterial blood vessels. ... Autoimmunity is the failure of an organism to recognize its own constituent parts (down to the sub-molecular levels) as self, which results in an immune response against its own cells and tissues. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...

Overview of signal transduction pathways
Overview of signal transduction pathways


Image File history File links Size of this preview: 800 × 587 pixelsFull resolution (1858 × 1364 pixel, file size: 253 KB, MIME type: image/png) new version of old figure self-made in illustrator. ... Image File history File links Size of this preview: 800 × 587 pixelsFull resolution (1858 × 1364 pixel, file size: 253 KB, MIME type: image/png) new version of old figure self-made in illustrator. ...

Contents

History

Occurrence of the term “signal transduction” The total number of papers published in each year since 1977 containing the specific phrase “signal transduction” in either their title or abstract section, are plotted. These figures were extracted through an analysis of the papers contained within the MEDLINE database.
Occurrence of the term “signal transduction” The total number of papers published in each year since 1977 containing the specific phrase “signal transduction” in either their title or abstract section, are plotted. These figures were extracted through an analysis of the papers contained within the MEDLINE database.

The earliest published scientific paper recorded in the MEDLINE database as containing the specific term "signal transduction" within its text was published in 1972.[1] Prior to 1977 articles can be found that use the term "signal transmission" or "sensory transduction" within their title or abstract.[2][3] However it is not until 1977 that papers start to appear with the specific term "signal transduction" within their abstract, and 1979 before this specific term appears within a paper title.[4][5] One source attributes the widespread use of the term signal transduction to a 1980 review article by Rodbell.[6][7] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... It has been suggested that GoPubMed be merged into this article or section. ... In scientific publishing, a paper is a scientific article that is published in a scientific journal. ... It has been suggested that GoPubMed be merged into this article or section. ... An abstract is a brief summary of a research article, thesis, review, conference proceeding or any in-depth analysis of a particular subject or discipline, and is often used to help the reader quickly ascertain the papers purpose. ...


As can be seen from the graph to the right it wasn't until the late 1980s/early 1990s that research papers directly addressing signal transduction processes began to appear in large numbers in the scientific literature. The occurrence of a specific term within the title or abstract of a scientific paper is usually a good indicator that the paper addresses a specifically related area of research. While there may be considered to be a number of landmark or important discoveries in the field of signal transduction, such as the link made by Rodbell between metabolic regulation and the activity of GTP and GTP-binding proteins,[7] much of our current understanding of signal transduction processes is as a result of numerous contributions made to the field over many years by numerous different research groups all over the world. Scientific literature is the totality of publications that report original empirical and theoretical work in the sciences and social sciences. ... A scientific method or process is considered fundamental to the scientific investigation and acquisition of new knowledge based upon physical evidence. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ...


The total number of scientific papers related to signal transduction published since 1st Jan 1977 up to the 31st December 2007 was 48,377 of which only 11,211 were reviews of other papers This article or section does not cite its references or sources. ...


Signaling Molecules

Signal transduction usually involves the binding of small extracellular signaling molecules to receptors that face outwards from the plasma membrane and trigger events inside the cell. However, steroids represent an example of extracellular signalling molecules that may cross the plasma membrane due to their lipophilic or hydrophobic nature.[8] Many steroids, but not all, have receptors within the cytoplasm and usually act by stimulating the binding of their receptors to the promoter region of steroid responsive genes.[9] Within multicellular organisms there are a diverse number of small molecules and polypeptides that serve to coordinate a cell's individual biological activity within the context of the organism as a whole. These molecules have been functionally classified as: Illustration depicting extracellular matrix (basement membrane and interstitial matrix) in relation to epithelium, endothelium and connective tissue In biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... This article is about the chemical family of steroids. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... This article or section does not cite its references or sources. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... Organelles. ... for disambiguation of the term promoter, see the promoter Wiktionary article In genetics, a promoter is a DNA sequence that enables a gene to be transcribed. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ...

It is important to note that most of these classifications do not take into account the molecular nature of each class member. For example, as a class, neurotransmitters consist of neuropeptides such as endorphins[17] and small molecules such as serotonin[18] and dopamine.[19] Hormones are also a generic class of molecule able to initiate signal transduction, these include insulin (a polypeptide),[20] testosterone (a steroid),[21] and epinephrine (an amino acid derivative, in essence a small organic molecule).[22] Hormone is also the NATO reporting name for the Soviet/Russian Kamov Ka-25 military helicopter. ... Melatonin, 5-methoxy-N-acetyltryptamine, is a hormone found in all living creatures from algae[1] to humans, at levels that vary in a diurnal cycle. ... Growth factor is any of about twenty small proteins that attach to specific receptors on the surface of stem cells in bone marrow and promote differentiation and maturation of these cells into morphotic constituents of blood. ... Epidermal Growth Factor or EGF is a 6045 Da protein with 53 amino acid residues and three intramolecular disulfide bonds. ... Illustration depicting extracellular matrix (basement membrane and interstitial matrix) in relation to epithelium, endothelium and connective tissue In biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ... Fibronectin is a high-molecular-weight glycoprotein containing about 5% carbohydrate that binds to receptor proteins that span the cells membrane, called integrins. ... Cytokines are small protein molecules that are the core of communication between immune system cells, and even between immune system cells and cells belonging to other tissue types. ... Interferon-gamma or IFN-g is a dimerized soluble cytokine which is a Type II Interferon. ... Chemokines are a class of chemotactic cytokines, or small secreted protein signals. ... Regulated upon activation, normal T-cell expressed, and presumably secreted or RANTES is an 8kDa protein classified as a chemotactic cytokine or chemokine. ... Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a presynaptic and a postsynaptic neuron. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Neurotrophins are a family of molecules that encourage survival of nervous tissue. ... Nerve growth factor (NGF), is a small secreted protein which induces the differentiation and survival of particular target neurons (nerve cells). ... A Neuropeptide is any of the variety of peptides found in neural tissue; e. ... Endorphins are endogenous opioid biochemical compounds. ... Serotonin (pronounced ) (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system (CNS) and enterochromaffin cells in the gastrointestinal tract of animals including humans. ... For other uses, see Dopamine (disambiguation). ... Insulin (from Latin insula, island, as it is produced in the Islets of Langerhans in the pancreas) is an anabolic polypeptide hormone that regulates carbohydrate metabolism. ... Testosterone is a steroid hormone from the androgen group. ... This article is about the chemical family of steroids. ... “Adrenaline” redirects here. ... Phenylalanine is one of the standard amino acids. ... Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting primarily of carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, halogens as well...


The classification of one molecule into one class of another is not exact. For example, epinephrine and norepinephrine secreted by the central nervous system act as neurotransmitters. However, epinephrine when secreted by the adrenal medulla acts as a hormone. “Adrenaline” redirects here. ... Norepinephrine (INN)(abbr. ... A diagram showing the CNS: 1. ... “Adrenaline” redirects here. ... In mammals, the adrenal glands are the triangle-shaped endocrine glands that sit atop the kidneys. ... Norepinephrine A hormone (from Greek όρμή - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ...


Environmental stimuli

In addition to many of the regular signal transduction stimuli listed above, in complex organisms, there are also examples of additional environmental stimuli that initiate signal transduction processes. Environmental stimuli may also be molecular in nature (as above) or more physical, such as, light striking cells in the retina of the eye,[23] odorants binding to odorant receptors in the nasal epithelium,[24] and bitter and sweet tastes stimulating taste receptors in the taste buds.[25] Certain microbial molecules e.g. viral nucleotides, bacterial lipopolysaccharides, or protein antigens are able to elicit an immune system response against invading pathogens, mediated via signal transduction processes. An immune response may occur independently from signal transduction stimulation by other molecules, as is the case for signal transduction via the Toll-like receptor or with help from stimulatory molecules located at the cell surface of other cells, as is the case for T-cell receptor signalling. Human eye cross-sectional view. ... An Odorant is an substance that can be smelled. ... Bold text == Headline text == minni hi. ... The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. ... A Mu-opioid G protein-coupled receptor with its agonist Figure 1. ... Taste buds (or lingual papillae) are small structures on the upper surface of the tongue that provide information about the taste of food being eaten. ... A nucleotide is a chemical compound that consists of a heterocyclic base, a sugar, and one or more phosphate groups. ... Lipopolysaccharide (captions are in French) Lipopolysaccharide (LPS) is a large molecule consisting of a lipid and a polysaccharide (carbohydrate) joined by a covalent bond. ... For the server security software, see Microsoft Forefront. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ... The T cell receptor or TCR is responsible for recognizing antigen bound to Major histocompatibility complex (MHC). ...


Unicellular organisms may also respond to environmental stimuli via the activation of signal transduction pathways. For example slime molds secrete cyclic AMP upon starvation which stimulates individual cells in the immediate environment to aggregate.[26] Yeast also use mating factors to determine the mating types of other yeast and participate in sexual reproduction.[27] Families & Genera Dictyosteliidae     Dictyostelium     Polysphondylium     Coenonia Actyosteliidae     Acytostelium The dictyostelids are a group of cellular slime moulds. ... Structure of cAMP Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3-5-cyclic adenosine monophosphate) is a molecule that is important in many biological processes; it is derived from adenosine triphosphate (ATP). ... Typical divisions Ascomycota (sac fungi) Saccharomycotina (true yeasts) Taphrinomycotina Schizosaccharomycetes (fission yeasts) Basidiomycota (club fungi) Urediniomycetes Sporidiales Yeasts are a growth form of eukaryotic microorganisms classified in the kingdom Fungi, with approximately 1,500 species described. ... The yeast Saccharomyces cerevisiae is a simple single celled eukaryote with both a diploid and haploid mode of existence. ...


If a cell lacks the specific receptor protein for detection of a particular stimulus, then the cell can be said to be "blind" to the stimulus.


Cellular responses

Activation of genes,[28] alterations in metabolism,[29] the continued proliferation and death of the cell,[30] and the stimulation or suppression of locomotion,[31] are some of the cellular responses to extracellular stimulation that require signal transduction. Gene activation leads to further cellular effects, since the protein products of many of the responding genes include enzymes and transcription factors themselves. Transcription factors produced as a result of a signal transduction cascade can in turn activate yet more genes. Therefore an initial stimulus can trigger the expression of an entire cohort of genes, and this in turn can lead to the activation of any number of complex physiological events. These events include the increased uptake of glucose from the blood stream stimulated by insulin[29] and the migration of neutrophils to sites of infection stimulated by bacterial products. The set of genes and the order in which they are activated in response to stimuli are often referred to as a "genetic program".[32] A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... For other uses, see Gene (disambiguation). ... A few of the metabolic pathways in a cell. ... This does not adequately cite its references or sources. ... A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (pronounced apo tō sis) is a process of suicide by a cell in a multicellular organism. ... Chemotaxis is a kind of taxis, in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = blend) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... Insulin (from Latin insula, island, as it is produced in the Islets of Langerhans in the pancreas) is an anabolic polypeptide hormone that regulates carbohydrate metabolism. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... In biology, a genetic program of a cell is a physiological change brought about by a temporal pattern of activation of a particular subset of genes. ...


Neurotransmitters are ligands that are capable of binding to ion channel proteins resulting in their opening to allow the rapid flow of a particular ion across the plasma membrane.[15] This results in an altering of the cell's membrane potential and is important for processes such as the neural conduction of electrochemical impulses. Ligands can be freely soluble,[11] or can be found on the surface of other cells or within the extracellular matrix.[12] Such cell surface or extracellular matrix ligands signal between cells when they come in contact with each other, such as when a phagocytic cell presents antigens to lymphocytes, or upon adhesion to the extracellular matrix, as when integrins at the cell surface of fibroblasts engage fibronectin.[33] Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a presynaptic and a postsynaptic neuron. ... Ion channels are pore-forming proteins that help to establish and control the small voltage gradient that exists across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient. ... Membrane potential (or transmembrane potential or transmembrane potential difference or transmembrane potential gradient), is the electrical potential difference (voltage) across a cells plasma membrane. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Epidermal Growth Factor or EGF is a 6045 Da protein with 53 amino acid residues and three intramolecular disulfide bonds. ... Illustration depicting extracellular matrix (basement membrane and interstitial matrix) in relation to epithelium, endothelium and connective tissue In biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... For the server security software, see Microsoft Forefront. ... Antigen presentation stimulates T cells to become either cytotoxic CD8+ cells or helper CD4+ cells. ... An integrin, or integrin receptor, is an integral membrane protein in the plasma membrane of cells. ... A fibroblast is a cell that makes the structural fibers and ground substance of connective tissue. ... Fibronectin is a high-molecular-weight glycoprotein containing about 5% carbohydrate that binds to receptor proteins that span the cells membrane, called integrins. ...


Most mammalian cells require stimulation to control not only cell division, but also survival. In the absence of growth factor stimulation, programmed cell death ensues in most cells. Such requirements for extra-cellular stimulation are necessary for controlling cell behavior in both the context of unicellular and multi-cellular organisms. Signal transduction pathways are so central to biological processes that it is not surprising that a large number of diseases have been attributed to their dysregulation. Growth factor is a protein that acts as a signaling molecule between cells (like cytokines and hormones) that attaches to specific receptors on the surface of a target cell and promotes differentiation and maturation of these cells. ... A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (pronounced apo tō sis) is a process of suicide by a cell in a multicellular organism. ...


Discussed below are how signal transduction via various classes of receptor may lead to the above cellular responses.


Types of receptor

Receptors can be roughly divided into two major classes:

  1. Intracellular receptors and
  2. Cell-surface receptors.

Ligand gated ion channel receptors are a class of receptor that may occur both at the cell-surface or intracellularly. In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ... The cell membrane (also called the plasma membrane or plasmalemma) is a semipermeable lipid bilayer common to all living cells. ... Ligand-gated ion channel is a broad term that refers to any ion channel that is gated (i. ... In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ...


Receptors that are solely intracellular include those for steroid hormones, thyroid hormone, retinoic acid and derivatives of vitamin D3. In contrast to ligands that bind to cell surface receptors, in order to initiate signal transduction these ligands must cross the cell membrane. See the intracellular receptors section below for more details. In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ... Steroid hormones are steroids which act as hormones. ... The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are tyrosine-based hormones produced by the thyroid gland. ... Retinoic acid, or Retin-A or vitamin A acid, is a carotenoid organic compound that is a component of visual pigments. ... Vitamin D is a fat soluble vitamin that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. ... Look up cell membrane in Wiktionary, the free dictionary. ... Overview of signal transduction pathways In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in...


Cell-surface receptors

Cell-surface receptors are integral transmembrane proteins and recognise the vast majority of extracellular signaling molecules. Transmembrane receptors span that the plasma membrane of the cell, with one part of the receptor on the outside of the cell (the extracellular domain) and the other on the inside of the cell (the intracellular domain). Signal transduction occurs as a result of stimulatory molecule or ligand binding to their extracellular domain, the ligand itself does not pass through the plasma membrane prior to receptor binding. A transmembrane protein is a protein that spans the entire biological membrane. ... Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cells plasma membrane, but also in the membranes of some subcellular compartments and organelles. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... It has been suggested that this article or section be merged with ligand. ...


Binding of a ligand to a cell-surface receptor stimulates a series of events inside the cell with different types of receptor stimulating different intracellular responses. Receptors typically only respond to the binding of a specific ligand. Upon binding the ligand initiates the transmission of a signal across the plasma membrane by inducing a change in the shape or conformation of the intracellular part of the receptor. Often, such changes in conformation result in either the activation of an enzymatic activity contained within the receptor or exposes a binding site for other signaling proteins within the cell. Once these proteins bind to the receptor they themselves may become active and propagate the signal into the cytoplasm. It has been suggested that this article or section be merged with ligand. ... In chemistry, a chemical conformation is the spatial arrangement of atoms in a molecule. ...


In eukaryotic cells, most intracellular proteins activated by a ligand/receptor interaction possess an enzymatic activity. These enzymes include heterotrimeric G proteins, small GTPases, various protein kinases and phosphatases, lipid kinases and hydrolases. Some receptor stimulated enzymes create specific second messengers including cyclic nucleotides, such as cyclic AMP (cAMP) and cyclic GMP (cGMP), Phosphatidylinositol derivatives, such as Phosphatidylinositol-triphosphate (PIP3), Diacylglycerol (DAG) and Inositol-triphosphate (IP3). IP3 controlling the release of intracellular calcium stores into the cytoplasm (see second messengers section later in this article). Other activated proteins interact with adaptor proteins. Adaptor proteins facilitate interactions between other signaling proteins, and coordinate the formation of signaling complexes necessary in order to produce an appropriate cellular response to a particular stimulus. Enzymes and adaptor proteins are both responsive to various second messenger molecules. Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... G-proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. ... In biology, small GTPases are small (20-25 KDa) proteins that bind to guanosine triphosphate GTP. This family of proteins are homologous to Ras GTPases and also called the Ras superfamily GTPases. ... A protein kinase is an enzyme that modifies other proteins by chemically adding phosphate groups to them (phosphorylation). ... Protein phosphatases are enzymes that remove phosphate groups that have been attached to amino acid residues of proteins by protein kinases. ... Phosphoinositide 3-kinases (PI 3-kinases or PI3Ks) are a family of related enzymes that are capable of phosphorylating the 3 position hydroxyl group of the inositol ring of phosphatidylinositol (PtdIns)[1]. The various 3-phosphorylated phosphoinositides that are produced by PI 3-kinases (PtdIns3P, PtdIns(3,4)P2, PtdIns... Phospholipase C is a key enzyme in phosphatidylinositol (PIP2) metabolism and lipid signaling pathways. ... In biology, second messengers are low-weight diffusible molecules that are used in signal transduction to relay signals within a cell. ... A cyclic nucleotide is any nucleotide in which the phosphate group is bonded to two of the sugars hydroxyl groups, forming a cyclical or ring structure. ... Structure of cAMP Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3-5-cyclic adenosine monophosphate) is a molecule that is important in many biological processes; it is derived from adenosine triphosphate (ATP). ... Cyclic guanosine monophosphate (cGMP) is a second messenger derived from GTP. Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). ... Chemical structure of sn-1-stearoyl-2-arachidonoyl phosphatidylinositol Phosphatidylinositol (abbreviated PtdIns, or PI) is a minor phospholipid component of eukaryotic cell membranes. ... Phosphatidylinositol (3,4,5)-trisphosphate commonly abbreviated to PIP3 is the product of the class I phosphoinositide 3-kinases (PI 3-kinases) activity on PI(4,5)P2. ... OWNEDOWNEDOWNED ... IP3 can refer to the following: Inositol triphosphate (biochemistry) Third-order_intercept_point (radiocommunication) This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... IP3 can refer to the following: Inositol triphosphate (biochemistry) Third-order_intercept_point (radiocommunication) This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... Overview of signal transduction pathways In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in... An adaptor protein is a protein which is accessory to main proteins in signal transduction. ...


Many of the enzymes activated as part of the signal transduction mechanism and also many adaptor proteins have been found to possess specialized protein domains that bind to specific secondary messenger molecules. For example, calcium ions bind specifically to the EF hand domains of calmodulin, allowing this molecule to bind and activate Calmodulin dependent kinase. PIP3 binds specifically to the Pleckstrin homology domains of proteins such as the kinase protein AKT again with an activatory activity. Within a protein, a structural domain (domain) is an element of overall structure that is self-stabilizing and often folds independently of the rest of the protein chain. ... The EF hand is a helix-turn-helix structural motif in proteins. ... oommen sir is a fool. ... Calmodulin dependent kinase (Camk) is a kinase enzyme. ... Pleckstrin homology domain (PH domain) is a protein region of approximately 120 amino acids that can bind Phosphatidylinositol lipids within biological membranes (such as Phosphatidylinositol (3,4,5)-trisphosphate and phosphatidylinositol (4,5)-bisphosphate), and proteins such as the βγ-subunits of heterotrimeric G proteins and protein kinase C. Through these... Akt, also known as protein kinase B (PKB) is an important molecule in mammalian cellular signaling. ...


There are many different classes of transmembrane receptor that recognise many different extracellular signalling molecules. Specific example receptors discussed in this article are:

  1. G-protein coupled receptors - e.g. Chemokine receptors
  2. Receptor tyrosine kinases - e.g. Growth factor receptors,
  3. Integrins
  4. Toll-like receptors

Further examples are given in the transmembrane receptor article. Wikipedia does not yet have an article with this exact name. ... Chemokines are a family of pro-inflammatory activation-inducible cytokines, or small protein signals secreted by cells. ... The receptor tyrosine kinase (RTK) family of cell surface receptors shows a high affinity to numerous growth signals. ... Growth factor is a protein that acts as a signaling molecule between cells (like cytokines and hormones) that attaches to specific receptors on the surface of a target cell and promotes differentiation and maturation of these cells. ... An integrin, or integrin receptor, is an integral membrane protein in the plasma membrane of cells. ... Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ... Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cells plasma membrane, but also in the membranes of some subcellular compartments and organelles. ...


G-protein coupled receptors

For more details on this topic, see G-protein coupled receptor.
Signal transduction from a G-protein linked receptor following interaction with its hormone ligand
Signal transduction from a G-protein linked receptor following interaction with its hormone ligand

G-protein coupled receptors (GPCRs) are a family of integral membrane proteins that possess seven membrane-spanning domains, and are linked to a guanine nucleotide binding protein (or G protein). Many receptors make up this family, including adrenergic receptors, olfactory receptors, opioid receptors, chemokine receptors and rhodopsin. In cell biology, G-protein-coupled receptors, also known as GPCR, seven transmembrane receptors, heptahelical receptors, or 7TM receptors, are a class of transmembrane receptors. ... Image File history File links Download high-resolution version (837x481, 71 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Adenylate cyclase Cyclic adenosine monophosphate Epinephrine Adrenergic receptor ... Image File history File links Download high-resolution version (837x481, 71 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Adenylate cyclase Cyclic adenosine monophosphate Epinephrine Adrenergic receptor ... An Integral Membrane Protein (IMP) is a protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. ... G-proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. ... Epinephrine Norepinephrine The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines. ... Olfactory receptors are a type of G protein-coupled receptor in olfactory receptor neurons. ... To meet Wikipedias quality standards, this article may require cleanup. ... Typical structure of a chemokine receptor, with seven transmembrane domains and a characteristic DRY motif in the second intracellular domain. ... A rhodopsin molecule (yellow) with bound retinal (orange), embedded in a cell membrane (lipids shown as green, head groups as red/blue). ...


Signal transduction by a GPCR begins with an inactive G protein coupled with the receptor. An inactive G protein exists as a heterotrimer, a molecule composed of three different protein subunits. Once the GPCR recognizes a ligand, the shape (conformation) of the receptor changes to mechanically activate the G protein, and causes one subunit (Gα) to dissociate from the other two G-protein subunits (Gβ and Gγ); the dissociation exposes sites on the G-protein subunits that interact with other molecules.[34] The activated G protein subunits detach from the receptor and initiate signaling from many downstream effector proteins, including phosphodiesterases and adenylyl cyclases, phospholipases, and ion channels that permit the release of second messenger molecules such as cyclic AMP (cAMP), cyclic GMP (cGMP), inositol triphosphate (IP3), diacylglycerol (DAG), and calcium (Ca2+) ions.[35] For example, a rhodopsin molecule in the plasma membrane of a retina cell in the eye that was activated by a photon can activate up to 2000 effector molecules (in this case, transducin) per second. A phosphodiesterase (PDE) is an enzyme that catalyzes the hydrolysis of phosphodiester bonds. ... Adenylate cyclase (EC 4. ... A phospholipase is an enzyme that converts phospholipids into fatty acids and other lipophilic substances. ... Ion channels are present in the membranes that surround all biological cells. ... Structure of cAMP cAMP represented in three ways, the left with sticks-representation, the middle with structure formula, and the right with space filled representation. ... Cyclic guanosine monophosphate (cGMP) is a second messenger derived from GTP. Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). ... Inositol triphosphate or inositol 1,4,5-triphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a second messenger molecule used in signal transduction in biological cells. ... Calcium plays a vital role in the biochemistry of the cell, particularly in signal transduction pathways. ... A rhodopsin molecule (yellow) with bound retinal (orange), embedded in a cell membrane (lipids shown as green, head groups as red/blue). ... Human eye cross-sectional view. ... For other uses, see Eye (disambiguation). ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... Transducin is the name given to the G-protein alpha-subunits that are naturally expressed in vertebrate retina rods and cones. ...


The total strength of signal amplification by a GPCR is determined by:

  • The lifetime of the ligand-receptor-complex. If the ligand-receptor-complex is stable, it takes longer for the ligand to dissociate from its receptor, thus the receptor will remain active for longer and will activate more effector proteins.
  • The amount and lifetime of the receptor-effector protein-complex. The more effector protein is available to be activated by the receptor, and the faster the activated effector protein can dissociate from the receptor, the more effector protein will be activates in the same amount of time.
  • Deactivation of the activated receptor. A receptor that is engaged in a hormone-receptor-complex can be deactivated, either by covalent modification (for example, phosphorylation), or by internalization (see ubiquitin).

The idea that G-protein coupled receptors, specifically chemokine receptors participate in cancer development is suggested by a study where a point mutation was inserted into the gene encoding the chemokine receptor CXCR2. Cells transfected with the CXCR2 mutant underwent a malignant transformation.[36] The result of the point mutation was the expression of CXCR2 in an active conformation, despite the absence of chemokine binding (the CXCR2 mutant is said to be "constitutively active"). Ubiquitin is a very conserved small regulatory protein that is ubiquitous in eukaryotes. ... A point mutation, or substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide. ... For other uses, see Gene (disambiguation). ... Chemokines are a family of pro-inflammatory activation-inducible cytokines, or small protein signals secreted by cells. ... Transfection describes the introduction of foreign material into eukaryotic cells. ... This article is about biological mutants. ... Malignant transformation is the change of cells from benign to malignant behavior. ... A point mutation, or substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the...


Receptor Tyrosine Kinases

Receptor tyrosine kinases (RTKs) are transmembrane proteins with an intracellular kinase domain and an extracellular domain that binds ligand. There are many RTK proteins that are classified into subfamilies depending on their structural properties and ligand specificity. These include many growth factor receptors such as insulin receptor and the insulin-like growth factor receptors, and many others receptors.[37] To conduct their biochemical signals, RTKs need to form dimers in the plasma membrane. The dimer is stabilized by ligand binding by the receptor. Interaction between the two cytoplasmic domains of the dimer is thought to stimulate autophosphorylation of tyrosines within the cytoplasmic tyrosine kinase domains of the RTKs causing their conformational changes. The kinase domain of the receptors is subsequently activated, initiating signaling cascades of phosphorylation of downstream cytoplasmic molecules. These signals are essential to various cellular processes, such as control of cell growth, differentiation, metabolism, and migration.[37] The receptor tyrosine kinase (RTK) family of cell surface receptors shows a high affinity to numerous growth signals. ... In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific target molecules (substrates); the process is termed phosphorylation. ... In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... Growth factor is a protein that acts as a signaling molecule between cells (like cytokines and hormones) that attaches to specific receptors on the surface of a target cell and promotes differentiation and maturation of these cells. ... Insulin (from Latin insula, island, as it is produced in the Islets of Langerhans in the pancreas) is an anabolic polypeptide hormone that regulates carbohydrate metabolism. ... The Insulin-like Growth Factor 1 (IGF-1) Receptor is a transmembrane receptor that is activated by IGF-1 and by the related growth factor IGF-II. It belongs to the large class of tyrosine kinase receptors. ... Sucrose, or common table sugar, is composed of glucose and fructose. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... A phosphorylated serine residue Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule or the introduction of a phosphate group into an organic molecule. ... Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ... A few of the metabolic pathways in a cell. ... Cell migration is a central process in the development and maintenance of multicellular organisms. ...


As is the case with G-Protein coupled receptors, proteins that bind GTP play a major role in transmission of signal from the activated RTK into the cell. In this case the G proteins are members of the Ras, Rho and Ral families, referred to collectively as small G proteins. These proteins act as molecular switches that are usually tethered to membranes by isoprenyl groups linked to their carboxyl ends. Thus, upon activation they are responsible for the recruitment of proteins to specific membrane subdomains where they participate in signaling. Activated RTKs in turn activate small G proteins which in turn activate Guanine Nucleotide Exchange Factors, such as SOS1. Once activated, these exchange factors can activate many more small G-proteins, thus amplifying the receptors initial signal. In molecular biology, Ras is the name of a protein, the gene that encodes it, and the family and superfamily of proteins to which it belongs. ... 1. ... In biology, small GTPases are small (20-25 kDa) proteins that bind to guanosine triphosphate GTP. This family of proteins are homologous to Ras GTPases and also called the Ras superfamily GTPases. ... Guanine Nucleotide Exchange Factors are a class of proteins that bind to small G-Proteins such as members of the Rho and Ras families of GTPases, and force the release of bound guanine nucleotide. ... SOS1 (Son of Sevenless 1) is gene encoding a GTPase activating protein that acts as a nucleotide exchange factor for Ras-GTPase. ...


As with the mutation of G-protein coupled receptors, the mutation of certain RTK genes can result in the expression of receptors that exist in a constitutively activate state. Such mutated RTK genes may act as oncogenes, genes that contribute to the initiation or progression of cancer.[38] It has been suggested that mutant be merged into this article or section. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... An oncogene is a gene that can cause a cell to develop into a tumor cell, possibly resulting in cancer. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...


Integrins

For more details on this topic, see Integrin.
An overview of integrin mediated signal transduction, adapted from Hehlgens et al (2007).
An overview of integrin mediated signal transduction, adapted from Hehlgens et al (2007).[39]

Integrins are produced by a wide variety of cell types and play a role in the attachment of a cell to the extracellular matrix (ECM) and to other cells, and in the signal transduction of signals received from extracellular matrix components such as fibronectin, collagen and laminin. Ligand binding to the extracellular domain of integrins induce a conformational change within the protein and a clustering of the protein at the cell surface, in order to initiate signal transduction. Integrins lack kinase activity and integrin mediated signal transduction is achieved through a variety of intracellular protein kinases and adaptor molecules such as integrin-linked kinase (ILK), focal-adhesion kinase (FAK), talin, paxillin, parvins, p130Cas, Src-family kinases and GTPases of the Rho family. The main protein coordinating signal transduction being ILK.[39] As shown in the overview to the right, cooperative integrin and receptor tyrosine kinase signalling determins cellular survival, apoptosis, proliferation and differentiation. An integrin, or integrin receptor, is an integral membrane protein in the plasma membrane of cells. ... Image File history File links Size of this preview: 751 × 600 pixelsFull resolution (1014 × 810 pixel, file size: 123 KB, MIME type: image/jpeg)This image was adapted from a figure produce in a paper titled Signalling via integrins: Implications for cell survival and anticancer strategies, Hehlgans et al 2007... Image File history File links Size of this preview: 751 × 600 pixelsFull resolution (1014 × 810 pixel, file size: 123 KB, MIME type: image/jpeg)This image was adapted from a figure produce in a paper titled Signalling via integrins: Implications for cell survival and anticancer strategies, Hehlgans et al 2007... A cell type is a distinct morphological or functional form of cell. ... Illustration depicting extracellular matrix (basement membrane and interstitial matrix) in relation to epithelium, endothelium and connective tissue In biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ... Fibronectin is a high-molecular-weight glycoprotein containing about 5% carbohydrate that binds to receptor proteins that span the cells membrane, called integrins. ... Tropocollagen triple helix. ... Laminins are the major non-collagenous component of the basal lamina, such as those on which cells of an epithelium sit. ... Integrin-linked kinase (ILK) is a 59kDa protein originally identified while conducting a yeast-two hybrid screen with integrin ß1 as the bait protein (Hannigan et al. ... We dont have an article called Talin Start this article Search for Talin in. ... Paxillin is a signal transduction adaptor protein. ... Src is a family of proto-oncogenic tyrosine kinases originally discovered by J. Michael Bishop and Harold E. Varmus. ... GTPases are a large family of enzymes that can bind and hydrolyze GTP. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases. ... 1. ... Integrin-linked kinase (ILK) is a 59kDa protein originally identified while conducting a yeast-two hybrid screen with integrin ß1 as the bait protein (Hannigan et al. ... A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (pronounced apo tō sis) is a process of suicide by a cell in a multicellular organism. ... The word proliferation can refer to: Nuclear proliferation Chemical weapon proliferation the spread in use of other weapons systems Cell proliferation According to Gloria Anzaldúa (1990), the difference between appropriation and proliferation is that the first steals and harms; the second helps heal breaches of knowledge. ... Differentiation can mean the following: In biology: cellular differentiation; evolutionary differentiation; In mathematics: see: derivative In cosmogony: planetary differentiation Differentiation (geology); Differentiation (logic); Differentiation (marketing). ...


Important differences exist between integrin signaling in circulating blood cells and non-circulating blood cells such as epithelial cells. Integrins at the cell-surface of circulating cells are inactive under normal physiological conditions. For example cell-surface integrins on circulating leukocytes are maintained in an inactive state in order to avoid epithelial cell attachment. Only in response to appropriate stimuli are leukocyte integrins converted into an active form, such as those received at the site of an inflamatory response. Similarly, it is important that integrins at the cell surface of circulating platelets are kept in an inactive state under normal conditions, in order to avoid thrombosis. Epithelial cells, in contrast have active integrins at their cell surface under normal conditions, which help to maintain their stable adhesion to underlying stromal cells, which provide appropriate signals in order to maintain their survival and differentiation.[40] In zootomy, epithelium is a tissue composed of a layer of cells. ... The cell membrane (also called the plasma membrane or plasmalemma) is a semipermeable lipid bilayer common to all living cells. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... White Blood Cells is also the name of a White Stripes album. ... An abscess on the skin, showing the redness and swelling characteristic of inflammation. ... A 250 ml bag of newly collected platelets. ... Thrombosis is the formation of a clot or thrombus inside a blood vessel, obstructing the flow of blood through the circulatory system. ...


Toll-Like Receptors

For more details on this topic, see toll-like receptor.

When activated, Toll-like receptors (TLRs) recruit adapter molecules within the cytoplasm of cells in order to propagate a signal. Four adapter molecules are known to be involved in signaling. These proteins are known as MyD88, Tirap (also called Mal), Trif, and Tram.[41][42][43] The adapters activate other molecules within the cell, including certain protein kinases (IRAK1, IRAK4, TBK1, and IKKi) that amplify the signal, and ultimately lead to the induction or suppression of genes that orchestrate the inflammatory response. In all, thousands of genes are activated by TLR signaling, and collectively, the TLRs constitutes one of the most powerful and important gateways for gene modulation. Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ...


Ligand-gated ion channel receptors

For more details on this topic, see ligand gated ion channel.

A ligand-activated ion channel will recognize its ligand, and then undergo a structural change that opens a gap (channel) in the plasma membrane through which ions can pass. These ions will then relay the signal. An example for this mechanism is found in the receiving cell, or post-synaptic cell of a neural synapse. Ligand-gated ion channel The Ligand-gated ion channels, also referred to as LGICs, or ionotropic receptors, are a group of intrinsic transmembrane ion channels that are opened or closed in response to binding of a chemical messenger, as opposed to voltage-gated ion channels or stretch-activated ion channels. ... Illustration of the major elements in a prototypical synapse. ...


By contrast, other ion channels open in response to a change in cell potential, that is, the difference of the electrical charge across the membrane. In neurons, this mechanism underlies the action potentials that travel along nerves. The influx of ions that occurs in response to ligand gated ion channels often induce action potentials by depolarizing the membrane of the post-synaptic cells which results in the wave like opening of voltage gated ion channels. In addition, calcium ions are also commonly allowed into the cell during ligand induced ion channel opening. This calcium can act as a classical second messenger, setting in motion signal transduction cascades and altering the cellular physiology of the responding cell. This may result in strengthening of the synapse between the pre- and post synaptic cells by remodeling the dendritic spines involved in the synapse. In biological cells that are electrically at rest, the cytosol possesses a uniform electric potential or voltage compared to the extracellular solution. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... Nerves (yellow) Nerves redirects here. ... Close up of the dendrite of a striatal medium spiny neuron. ...


Intracellular receptors

Further information: Intracellular receptor

Intracellular receptors include nuclear receptors and cytoplasmic receptors, and are soluble proteins localized within the nucleoplasm or the cytoplasm respectively. The typical ligands for nuclear receptors are lipophilic hormones, with steroid hormones (for example, testosterone, progesterone and cortisol) and derivatives of vitamin A and D among them. In order to reach its receptor and initiate signal transduction, the hormone must pass through the plasma membrane, usually by passive diffusion. The nuclear receptors are ligand-activated transcription activators; on binding with the ligand (the hormone), they will pass through the nuclear membrane into the nucleus and enable the transcription of a certain gene and, thus, the production of a protein. Intracellular receptors or nuclear receptors are a class of receptor located inside the cell rather than on its cell membrane. ... Nuclear receptors are a class of intracellular receptors which function as ligand activated transcription factors which up or down regulate the expression of genes. ... Similar to the cytoplasm of a cell, the nucleus contains nucleoplasm or nuclear sap. ... Organelles. ... This article or section does not cite its references or sources. ... This article is about the chemical family of steroids. ... Testosterone is a steroid hormone from the androgen group. ... Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. ... Cortisol is a corticosteroid hormone produced by the adrenal cortex (in the adrenal gland). ... Retinol (Vitamin A) For the record label, see Vitamin Records A vitamin is an organic compound required in tiny amounts for essential metabolic reactions in a living organism. ... In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... The nuclear envelope refers to the double membrane of the nucleus that encloses genetic material in eukaryotic cells. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... For other uses, see Gene (disambiguation). ...


The nuclear receptors that were activated by the hormones attach at the DNA at receptor-specific Hormone Responsive Elements (HREs), DNA sequences that are located in the promoter region of the genes that are activated by the hormone-receptor complex. As this enables the transcription of the according gene, these hormones are also called inductors of gene expression. The activation of gene transcription is much slower than signals that directly affect existing proteins. As a consequence, the effects of hormones that use nucleic receptors are usually long-term. Although the signal transduction via these soluble receptors involves only a few proteins, the details of gene regulation are yet not well understood. The nucleic receptors all have a similar, modular structure: A promoter is a regulatory region of DNA located upstream (towards the 5 region) of a gene, providing a control point for regulated gene transcription. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the...

N-AAAABBBBCCCCDDDDEEEEFFFF-C

where CCCC is the DNA-binding domain that contains zinc fingers, and EEEE the ligand-binding domain. The latter is also responsible for dimerization of most nuclearic receptors prior to DNA binding. As a third function, it contains structural elements that are responsible for transactivation, used for communication with the translational apparatus. The zinc fingers in the DNA-binding domain stabilize DNA binding by holding contact to the phosphate backbone of the DNA. The DNA sequences that match the receptor are usually hexameric repeats, either normal, inverted or everted. The sequences are quite similar, but their orientation and distance are the parameters by which the DNA-binding domains of the receptors can tell them apart. Cartoon representation of the protein Zif268 (blue) containing three zinc fingers in complex with DNA (orange). ... Dimerization is the formation of a polymer from two similar chemical structures. ... Stimulation of transcription mediated by a transcription factor which binds to DNA and elicits the activation of adjacent proteins. ...


Steroid receptors are a subclass of nuclear receptors, located primarily within the cytosol. In the absence of steroid hormone, the receptors cling together in a complex called an aporeceptor complex, which also contains chaperone proteins (also known as heatshock proteins or Hsps). The Hsps are necessary to activate the receptor by assisting the protein to fold in a way such that the signal sequence which enables its passage into the nucleus is accessible.
Steroid receptors can also have a repressive effect on gene expression, when their transactivation domain is hidden so it cannot activate transcription. Furthermore, steroid receptor activity can be enhanced by phosphorylation of serine residues at their N-terminal end, as a result of another signal transduction pathway, for example, a by a growth factor. This behaviour is called crosstalk. Steroid hormone receptors are generally intracellular receptors that perform signal transduction for steroid hormones. ... A chaperone protein catalyzes the correct folding of other proteins within the cell. ... A heat shock protein (HSP) is a group of proteins which increase their expression when the cells which contain them are exposed to elevated temperatures. ... Protein folding is the process by which a protein assumes its characteristic functional shape or tertiary structure, also known as the native state. ... The term signal sequence can refer to any of the following: protein targeting signal peptide This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Growth factor is a protein that acts as a signaling molecule between cells (like cytokines and hormones) that attaches to specific receptors on the surface of a target cell and promotes differentiation and maturation of these cells. ... In biology, the term crosstalk refers to the phenomenon that signal components in signal transduction can be shared between different signal pathways and responses to a signal inducing condition (e. ...


RXR- and orphan-receptors These nuclear receptors can be activated by There are three retinoic acid receptors (RAR), RAR-alpha, RAR-beta, and RAR-gamma. ...

  • a classic endocrine-synthesized hormone that entered the cell by diffusion.
  • a hormone that was built within the cell (for example, retinol) from a precursor or prohormone, which can be brought to the cell through the bloodstream.
  • a hormone that was completely synthesized within the cell, for example, prostaglandin.

These receptors are located in the nucleus and are not accompanied by chaperone proteins. In the absence of hormone, they bind to their specific DNA sequence, repressing the gene. Upon activation by the hormone, they activate the transcription of the gene they were repressing. Retinol, the animal form of vitamin A, is a yellow fat-soluble, antioxidant vitamin important in vision and bone growth. ... A protein precursor is an inactive protein (or peptide) that can be turned into an active form by posttranslational modification. ... A prohormone is a chemical compound that is a precursor to an actual hormone (usually an anabolic like testosterone or some variant), which is taken in order to boost the body’s available hormone supply. ... E1 - Alprostadil I2 - Prostacyclin A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. ...


Certain intracellular receptors of the immune system are examples of cytoplasmic receptors. Recently identified NOD like receptors (NLRs) reside in the cytoplasm of specific eukaryotic cells and interact with particular ligands, such as microbial molecules, using a leucine-rich repeat (LRR) motif that is similar to the ligand binding motif of the extracellular receptors known as TLRs. Some of these molecules (e.g. NOD1 and NOD2) interact with an enzyme called RICK kinase (or RIP2 kinase) that activates NF-κB signaling, while others (e.g. NALP3) interact with inflammatory caspases (e.g. caspase 1) and initiate processing of particular cytokines (e.g. interleukin-1β).[44] Similar receptors exist inside plant cells and are called Plant R Proteins. Another type of cytoplasmic receptor also has a role in immune surveillance. These receptors are known as RNA Helicases and include RIG-I, MDA5 and LGP2.[45] A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Pattern recognition receptors, or PRRs, are a class of cell surface receptors which are employed by the cells of the immune system to identify foreign (disease-associated) biomolecules in the body. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... An example of a leucine-rich repeat protein, a porcine ribonuclease inhibitor (PDB ID 2BNH). ... NF-κB, or Nuclear Factor kappa B, is a nuclear transcription factor found in all cell types and is involved in cellular responses to stimuli such as stress, cytokines, free radicals, ultraviolet irradiation, and bacterial or viral antigens. ... Caspases are a group of cysteine proteases, enzymes with a crucial cysteine residue that can cleave other proteins after an aspartic acid residue, a specificity which is unusual among proteases. ... Caspase 1 is an enzyme that proteolytically cleaves other proteins, such as the precursor forms of the inflammatory cytokines interleukin 1-β and interleukin 18, into active mature peptides. ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... Interleukin-1 (IL-1) is one of the first cytokines ever described. ...


Second Messengers

Intracellular signal transduction is largely carried out by second messenger molecules. In biology, second messengers are low-weight diffusible molecules that are used in signal transduction to relay signals within a cell. ...


Ca2+ concentration is usually maintained at a very low level in the cytosol by sequestration in the smooth endoplasmic reticulum and the mitochondria. Ca2+ release from the endoplasmic reticulum into the cytosol results in the binding of the released Ca2+ to signaling proteins that are then activated. There are two combined receptor/ion channel proteins that perform the task of controlled transport of Ca2+: The cytosol (cf. ...

  • The InsP3-receptor will transport Ca2+ upon interaction with inositol triphosphate (thus the name) on its cytosolic side. It consists of four identical subunits.
  • The ryanodine receptor is named after the plant alkaloid ryanodine. It is similar to the InsP3 receptor and stimulated to transport Ca2+ into the cytosol by recognizing Ca2+ on its cytosolic side, thus establishing a feedback mechanism; a small amount of Ca2+ in the cytosol near the receptor will cause it to release even more Ca2+. It is especially important in neurons and muscle cells. In heart and pancreas cells, another second messenger (cyclic ADP ribose) takes part in the receptor activation. The localized and time-limited activity of Ca2+ in the cytosol is also called a Ca2+ wave. Once released into the cytosol from intracellular stores or extracellular sources, Ca2+ acts as a signal molecule within the cell. This works by tightly limiting the time and space when Ca2+ is free (and thus active). Therefore, the concentration of free Ca2+ within the cell is usually very low; it is stored within organelles, usually the endoplasmic reticulum (sarcoplasmic reticulum in muscle cells), where it is bound to molecules like calreticulin.

Ca2+ is used in a multitude of processes, among them muscle contraction, release of neurotransmitter from nerve endings, vision in retina cells, proliferation, secretion, cytoskeleton management, cell migration, gene expression and metabolism. The three main pathways that lead to Ca2+ activation are : Inositol triphosphate or inositol 1,4,5-triphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a second messenger molecule used in signal transduction in biological cells. ... Ryanodine receptors form a class of calcium channels in various forms of muscle. ... For other uses, see Plant (disambiguation). ... Chemical structure of ephedrine, a phenethylamine alkaloid An alkaloid is, strictly speaking, a naturally occurring amine produced by a plant,[1] but amines produced by animals and fungi are also called alkaloids. ... Structural formula Ryanodine is an poisonous alkaloid found in the South American plant Ryania speciosa. ... In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Structure of a skeletal muscle Muscle is one of the four tissue types. ... The heart and lungs, from an older edition of Grays Anatomy. ... The pancreas is a gland organ in the digestive and endocrine systems of vertebrates[2]. It is both exocrine (secreting pancreatic juice containing digestive enzymes) and endocrine (producing several important hormones, including insulin, glucagon, and somatostatin). ... Cyclic ADP Ribose popularly known as cADPR is a cyclic adenine nucleotide (like cAMP) with two phosphate groups present on 5 OH of the adenosine (like ADP), further connected to another ribose at the 5 position which in turn closes the cycle by glycosidic bonding to the Nitrogen1 of the... Schematic of typical animal cell, showing subcellular components. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... Calreticulin is a protein that binds Ca2+ ions (a second messenger molecule in signal transduction), rendering it inactive. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... In psychology, visual perception is the ability to interpret visible light information reaching the eyes which is then made available for planning and action. ... Human eye cross-sectional view. ... The term cell growth is used in two different ways in biology. ... Secretion is the process of segregating, elaborating, and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. ... The eukaryotic cytoskeleton. ... Cell migration is a central process in the development and maintenance of multicellular organisms. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... A few of the metabolic pathways in a cell. ...

  1. G protein regulated pathways
  2. Pathways regulated by receptor-tyrosine kinases
  3. Ligand- or current-regulated ion channels

There are two different ways in which Ca2+ can regulate proteins: G-proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. ... Tyrosine kinases are a subclass of protein kinase, see there for the principles of protein phosphorylation A tyrosine kinase (EC 2. ... Ion channels are pore-forming proteins that help to establish and control the small voltage gradient that exists across the plasma membrane of all living cells (see cell potential) by allowing the flow of ions down their electrochemical gradient. ...

  1. A direct recognition of Ca2+ by the protein.
  2. Binding of Ca2+ in the active site of an enzyme

One of the best studied interactions of Ca2+ with a protein is the regulation of calmodulin by Ca2+. Calmodulin itself can regulate other proteins, or be part of a larger protein (for example, phosphorylase kinase). The Ca2+/calmodulin complex plays an important role in proliferation, mitosis and neural signal transduction. The active site of an enzyme is the binding site where catalysis occurs. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... oommen sir is a fool. ... Phosphorylase kinase is a serine/threonine-specific protein kinase which converts phosphorylase b to Phosphorylase a. ... Mitosis is the way that in which a cell duplicates its chromosomes to generate two identical nuclei. ...


Lipophilic second messenger molecules These molecules are all derived from lipids that normally reside in cellular membranes. Enzymes stimulated by activated receptors modify these lipids, converting them into second messengers. One example of lipophilic second messenger molecule is diacylglycerol, required for the activation of protein kinase C. Others are ceramide, the eicosanoids and lysophosphatidic acid. This article or section does not cite its references or sources. ... OWNEDOWNEDOWNED ... A protein kinase is an enzyme that can transfer a phosphate group from a donor molecule (usually ATP) to an amino acid residue of a protein. ... Ceramides are a family of lipid molecules. ... In biochemistry, eicosanoids are a class of oxygenated hydrophobic molecules that largely function as autocrine and paracrine mediators. ... Lysophosphatidic acid (LPA) is a phospholipid derivative that acts as a potent signaling molecule. ...


Nitric oxide (NO) as second messenger The gas nitric oxide is a free radical which diffuses through the plasma membrane and affects nearby cells. NO is made from arginine and oxygen by the enzyme NO synthase, with citrulline as a by-product. NO works mainly through activation of its target receptor, the enzyme soluble guanylate cyclase, which when activated, produces the second messenger cyclic guanosine monophosphate (cGMP). NO can also act through covalent modification of proteins or their metal cofactors. Some of these modifications are reversible and work through a redox mechanism. In high concentrations, NO is toxic, and is thought to be responsible for some damage after a stroke. NO serves multiple functions. These include: R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... Arginine (symbol Arg or R) is an α-amino acid. ... The nitric oxide synthases (NOS) are a group of enzymes (EC 1. ... The chemical compound citrulline is an α-amino acid (AA). ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... For other uses, see Stroke (disambiguation). ...

  1. Relaxation of blood vessels.
  2. Regulation of exocytosis of neurotransmitters.
  3. Cellular immune response.
  4. Modulation of the Hair Cycle.
  5. Production and maintenance of penile erections.
  6. Activation of apoptosis by initiating signals which lead to H2AX phosphorylation

f you all The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... Neuron A (transmitting) to neuron B (receiving) 1. ... Chemical structure of D-aspartic acid, a common amino acid neurotransmitter. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Bald redirects here; for other uses see Bald (disambiguation). ... The erection of the penis, clitoris or a nipple is its enlarged and firm state. ...

See also

Recently, a novel theory called Functional Selectivity (also referred to in the literature as “agonist trafficking”, “biased agonism”, “differential engagement” and “protean agonism”) has been proposed to broaden conventional definitions of pharmacology. ... A Mu-opioid G protein-coupled receptor with its agonist Figure 1. ... GTPases are a large family of enzymes that can bind and hydrolyze GTP. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases. ... Protein phosphatases are enzymes that remove phosphate groups that have been attached to amino acid residues of proteins by protein kinases. ... Diagram showing key components of the MAPK/ERK pathway. ... Redox signaling is the concept that free radicals, reactive oxygen species (ROS), and other electronically-activated species act as messengers in biological systems. ...

References

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Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st Century. ... is the 65th day of the year (66th in leap years) in the Gregorian calendar. ...

Further reading

Non-technical
  • Cosma Shalizi's "Signal transduction" Notebook from 2003-01-20 used under the GFDL with permission
  • Werner R. Loewenstein, The Touchstone of Life: Molecular Information, Cell Communication, and the Foundations of Life, Oxford University Press, 1999, ISBN 0-19-514057-5
Technical
  • Gomperts, Kramer, Tatham, "Signal Transduction", AP/Elsevier [2002], ISBN 0122896319. Reference book, for more information: http://www.cellbiol.net .
  • Gerhard Krauss, Biochemistry of Signal Transduction and Regulation, Wiley-VCH, 1999, ISBN 3-527-30378-2
  • John T. Hancock, Cell Signalling, Addison-Wesley, 1998 ISBN 0-582-31267-1

This article is about the year. ... This article is about the year. ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ...

External links


  Results from FactBites:
 
The Individualist: Signal transduction (3021 words)
Signal transduction usually involves the binding of extracellular signaling molecules to receptors that face outwards from the membrane and trigger events inside.
The important value for the strength of the signal relayed by the receptor is the concentration of the hormone-receptor complex, which is defined by the affinity of the hormone for the receptor, the concentration of the hormone and, of course, the concentration of the receptor.
A principle of signal transduction is the signal amplification.
  More results at FactBites »

 
 

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