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Encyclopedia > Synaptic vesicle

In a neuron, synaptic vesicles, also called neurotransmitter vesicles, store the various neurotransmitters that are released during calcium-regulated exocytosis at the presynaptic terminal into the synaptic cleft of a synapse. The vesicles are essential for the propagation of nerve impulses between neurons and are constantly recreated by the cell. Drawing by Santiago Ramón y Cajal of cells in the pigeon cerebellum. ... Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... Exocytosis is the process by which a cell is able to get rid of large molecules or materials including wastes through its membrane. ... In a synapse between two neurons, the cell that releases the neurotransmitter is referred to as the presynaptic cell. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ... Illustration of the major elements in a prototypical synapse. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ... It has been suggested that extracellular be merged into this article or section. ...

Contents


Formation

Synaptic vesicles are made of a lipid bilayer in which transport proteins specific to each type of neurotransmitter are inserted. Neurotransmitters are moved from the cell's cytoplasm into the vesicles by vesicular transporters that rely on active transport mechanisms involving an exchange of protons (H+ ions). The necessary proton gradient is created by hydrogen ATPase, which breaks down ATP for energy. Vesicular glutamate transporters, for example, sequester glutamate into vesicles by this process. A diagonal molecular slab from the DPPC lipid bilayer simulation1; color scheme: PO4 - green, N(CH3)3 - violet, water - blue, terminal CH3 - yellow, O - red, glycol C - brown, chain C - grey. ... A transport protein is a protein involved in facilitated diffusion. ... Cytoplasm is like jelly-like material that fills cells. ... Active transport is the mediated transport of biochemicals, and other atomic/molecular substances, across membranes. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide primarily known in biochemistry as the molecular currency of intracellular energy transfer. ... Glutamate transporters exist in the membranes of neurons and glial cells to remove excess amounts of the amino acid neurotransmitters glutamate and aspartate from the synapse. ...


The stoichiometry for the movement of different neurotransmitters into a vesicle is given in the following table. In chemistry, stoichiometry (sometimes called reaction stoichiometry distinguishing itself from composition stoichiometry) is the study and calculation of quantitative (measurable) relationships of the reactants and products in chemical reactions (chemical equations). ...

Neurotransmitter type(s) Inward movement Outward movement
norepinephrine, dopamine, histamine, serotonin and acetylcholine neurotransmitter+ 2 H+
GABA and glycine neurotransmitter 1 H+
glutamate neurotransmitter- + Cl- 1 H+

Norepinephrine or noradrenaline is a catecholamine and a phenethylamine with chemical formula C8H11NO3. ... Dopamine is a chemical naturally produced in the body. ... Histamine is a biogenic amine chemical involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. ... Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesised in serotonergic neurons in the central nervous system and enterochromaffin cells in the gastrointestinal tract. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Chemical structure of GABA Gamma-aminobutyric acid (GABA) is a neurotransmitter in widely divergent species. ... Glycine (Gly, G) is a nonpolar amino acid. ... Glutamate is the anion of glutamic acid. ...

Neurotransmitter release

Neurotransmitters are released when vesicles fuse with the cell's plasma membrane at "active zones" of a synapse. Vesicles are scattered throughout the synapse, with some docked at the active zones, and the majority away from the active zone. When the action potential arrives at the synapse, the resulting increase in positive charge [depolarization] opens voltage-gated calcium channels and allows Ca++ to flow into the cell. The influx of Ca++ triggers a series of protein interactions, including SNAREs and Synaptotagmins, and causes the vesicle membrane to be fused with the presynaptic plasma membrane at the active zone, and the release of neurotransmitters from the vesicles. Drawing of a cell membrane A cell membrane (or plasma membrane or plasmalemma) is the part of any biological cell that covers the cell. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...


The vesicles' membranes fuse with the presynaptic membrane, and the contents of the vesicles are released into the synaptic space. Membrane material from the vesicles is recycled by the cell through endocytosis: bulk endocytosis occurs or clathrin-coated pits form, and the newly formed vesicles merge with endosomes. New vesicles bud off from endosomes after the material is processed (Kandel et al, 2000). In a synapse between two neurons, the cell that releases the neurotransmitter is referred to as the presynaptic cell. ... Endocytosis is a process whereby cells absorb material (molecules such as proteins) from outside by engulfing it with their cell membrane. ... Clathrin is a protein that is the major constituent of the coat of the coated pits and coated vesicles formed during endocytosis of materials at the surface of cells. ... In biology an endosome is a membrane-bound compartment inside cells. ...


The material in vesicles may also be released through the kiss and run pathway, in which the vesicles only fuse slightly with the membrane, not integrating themselves fully into it. Instead they form a fusion pore, a small opening which is possibly made of two hemichannels, through which neurotransmitters may flow (Kandel et al, 2000). That way, the fusion pore can close and the cell need not go through the processes of exocytosis and endocytosis, making the kiss and run process the fastest means of vesicle recycling. However, less neurotransmitters are released this way, so it is mainly used when the synapse needs to release small or normal amounts of the materials (Kandel et al, 2000).


Enzymatic mechanism

Vesicles are normally tethered by proteins called synapsins to actin filaments or other cytoskeletal elements within the cell. The influx of Ca++ causes the activation of the [[Calcium/calmodulin-dependent protein kinase|Ca++/calmodulin-dependent protein kinase]], which phosphorylates synapsin, causing it to release the vesicles from where they are tethered. The synapsins are a family of proteins that have long been implicated in the regulation of neurotransmitter release at synapses. ... This article or section should be merged with actin Microfilaments or actin filaments are made up of two twisted monomeric actin subunits. ... Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule. ...


Newly released vesicles must be targeted to active sites, a job possibly carried out by proteins called Rab3A and Rab3C. Next the vesicles must be docked at the site where they are to be released. One theory about how they accomplish this is that a protein on the vesicle, called a vesicle SNARE, or v-SNARE, binds with a similar protein, a target or t-SNARE, which is on the membrane where the vesicle is to dock. In order for the vesicle to be recycled after neurotransmitter release, the association between t- and v-SNARES must be undone. This process is accomplished by the cytoplasmic proteins N-ethylmaleimide-sensitive fusion protein (NSF) and soluble NSF attachment protein (SNAP). SNARE proteins (an acronym derived from soluble NSF attachment receptor) are a large protein superfamily consisting of more than 60 members in yeast and mammalian cells. ... SNARE proteins (an acronym derived from soluble NSF attachment receptor) are a large protein superfamily consisting of more than 60 members in yeast and mammalian cells. ... SNARE proteins (an acronym derived from soluble NSF attachment receptor) are a large protein superfamily consisting of more than 60 members in yeast and mammalian cells. ...


Effects of neurotoxins

Some neurotoxins, such as batrachotoxin, are known to destroy synaptic vesicles. The tetanus toxin damages VAMP, a type of v-SNARE (Kandel et al, 2000). Botulinum toxins damage t-SNARES and v-SNARES and thus inhibit synaptic transmission (Kandel et al, 2000). A spider toxin called α-Latrotoxin binds to neurexins, damaging vesicles and causing massive release of neurotransmitters. It has been suggested that Neurotoxicity be merged into this article or section. ... Batrachotoxins are extremely potent cardiotoxic and neurotoxic steroidal alkaloids found in certain species of frogs (poison dart frog), Melyridae beetles and birds (Pitohui, Ifrita kowaldi). ... Tetanus is a serious and often fatal disease caused by the neurotoxin tetanospasmin which is produced by the Gram-positive, obligate anaerobic bacterium Clostridium tetani. ... The word vamp, Vamp, or VAMP can mean any of the following: A musical term for a repeating figure. ... Botulin toxin or botox is the toxic compound produced by the bacterium Clostridium botulinum. ... Suborders Araneomorphae Mesothelae Mygalomorphae See the taxonomy section for families Spiders are invertebrate animals that produce silk, and have eight legs and no wings. ...


Reference

  • Kandel E.R., Schwartz, J.H., Jessell, T.M. 2000. Principles of Neural Science, 4th ed., pp.269-273. McGraw-Hill, New York.

  Results from FactBites:
 
Evidence for a Primary Endocytic Vesicle Involved in Synaptic Vesicle Biogenesis -- Provoda et al. 275 (10): 7004 -- ... (7337 words)
secretory vesicle analogous to synaptic vesicles or insulin-responsive
The TfR colocalizes with the GLUT1-containing vesicle in glycerol velocity gradients.
The GLUT1-containing vesicles in the glycerol gradient are not fragments of the plasma membrane.
davis lab > projects > vesicle recycling (760 words)
In the acidic lumen of a synaptic vesicle, the GFP is quenched.
Upon fusion of the vesicle with the plasma membrane (exocytosis) the GFP is exposed to the higher pH of the synaptic cleft and fluorescence increases.
Upon vesicle reformation, the GFP remains fluorescent and is subsequently quenched during the reacidification associated with the loading of neurotransmitter into the synaptic vesicle.
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