scholarly journals Quantitative analysis of the native presynaptic cytomatrix by cryoelectron tomography

2010 ◽  
Vol 188 (1) ◽  
pp. 145-156 ◽  
Author(s):  
Rubén Fernández-Busnadiego ◽  
Benoît Zuber ◽  
Ulrike Elisabeth Maurer ◽  
Marek Cyrklaff ◽  
Wolfgang Baumeister ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Attachment Protein ◽  
Readily Releasable Pool ◽  
Protein Receptor ◽  
Membrane Contact ◽  
Synaptic Vesicle Release ◽  
Protein Attachment

The presynaptic terminal contains a complex network of filaments whose precise organization and functions are not yet understood. The cryoelectron tomography experiments reported in this study indicate that these structures play a prominent role in synaptic vesicle release. Docked synaptic vesicles did not make membrane to membrane contact with the active zone but were instead linked to it by tethers of different length. Our observations are consistent with an exocytosis model in which vesicles are first anchored by long (>5 nm) tethers that give way to multiple short tethers once vesicles enter the readily releasable pool. The formation of short tethers was inhibited by tetanus toxin, indicating that it depends on soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor complex assembly. Vesicles were extensively interlinked via a set of connectors that underwent profound rearrangements upon synaptic stimulation and okadaic acid treatment, suggesting a role of these connectors in synaptic vesicle mobilization and neurotransmitter release.

scholarly journals Role of α-SNAP in Promoting Efficient Neurotransmission at the Crayfish Neuromuscular Junction

1999 ◽  
Vol 82 (6) ◽  
pp. 3406-3416 ◽  
Author(s):  
Ping He ◽  
R. Chase Southard ◽  
Dong Chen ◽  
S. W. Whiteheart ◽  
R. L. Cooper
Keyword(s):  
Neuromuscular Junction ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Synaptic Current ◽  
Attachment Protein ◽  
Quantal Analysis ◽  
Sensitive Factor ◽  
Electrophysiological Studies ◽  
Crayfish Neuromuscular Junction

In this manuscript, we address the role of the soluble N-ethylmaleimide sensitive factor attachment protein (α-SNAP) in synaptic transmission at the neuromuscular junction of the crayfish opener muscle. Immunochemcial methods confirm the presence of α-SNAP in these preparations and show that it is concentrated in the synaptic areas. Microinjection and electrophysiological studies show that α-SNAP causes an increase in neurotransmitter release yet does not significantly affect the kinetics. More specific quantal analysis, using focal, macropatch, synaptic current recordings, shows that α-SNAP increases transmitter release by increasing the probability of exocytosis but not the number of potential release sites. These data demonstrate that the role of α-SNAP is to increase the efficiency of neurotransmission by increasing the probability that a stimulus will result in neurotransmitter release. What this suggests is that α-SNAP is critical for the formation and maintenance of a “ready release” pool of synaptic vesicles.

scholarly journals Synaptophysin I selectively specifies the exocytic pathway of synaptobrevin 2/VAMP2

2007 ◽  
Vol 404 (3) ◽  
pp. 525-534 ◽  
Author(s):  
Dario Bonanomi ◽  
Laura Rusconi ◽  
Chiara Agnese Colombo ◽  
Fabio Benfenati ◽  
Flavia Valtorta
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Critical Component ◽  
Attachment Protein ◽  
Protein Protein Interaction ◽  
Protein Mutants ◽  
Vesicle Biogenesis ◽  
Exocytic Pathway ◽  
Protein Attachment

Biogenesis and recycling of synaptic vesicles are accompanied by sorting processes that preserve the molecular composition of the compartments involved. In the present study, we have addressed the targeting of synaptobrevin 2/VAMP2 (vesicle-associated membrane protein 2), a critical component of the synaptic vesicle­-fusion machinery, in a heterotypic context where its sorting is not confounded by the presence of other neuron-specific molecules. Ectopically expressed synaptophysin I interacts with VAMP2 and alters its default surface targeting to a prominent vesicular distribution, with no effect on the targeting of other membrane proteins. Protein–protein interaction is not sufficient for the control of VAMP2 sorting, which is mediated by the C-terminal domain of synaptophysin I. Synaptophysin I directs the sorting of VAMP2 to vesicles before surface delivery, without influencing VAMP2 endocytosis. Consistent with this, dynamin and α-SNAP (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein) mutants which block trafficking at the plasma membrane do not abrogate the effect of synaptophysin I on VAMP2 sorting. These results indicate that the sorting determinants of synaptic vesicle proteins can operate independently of a neuronal context and implicate the association of VAMP2 with synaptophysin I in the specification of the pathway of synaptic vesicle biogenesis.

scholarly journals C2B Polylysine Motif of Synaptotagmin Facilitates a Ca2+-independent Stage of Synaptic Vesicle Priming In Vivo

2006 ◽  
Vol 17 (12) ◽  
pp. 5211-5226 ◽  
Author(s):  
Carin A. Loewen ◽  
Soo-Min Lee ◽  
Yeon-Kyun Shin ◽  
Noreen E. Reist
Keyword(s):  
Synaptic Vesicle ◽  
Membrane Trafficking ◽  
Synaptic Vesicles ◽  
Attachment Protein ◽  
Release Probability ◽  
Synaptotagmin I ◽  
Protein Receptor ◽  
Sensitive Factor ◽  
Vesicle Cycle

Synaptotagmin I, a synaptic vesicle protein required for efficient synaptic transmission, contains a highly conserved polylysine motif necessary for function. Using Drosophila, we examined in which step of the synaptic vesicle cycle this motif functions. Polylysine motif mutants exhibited an apparent decreased Ca2+ affinity of release, and, at low Ca2+, an increased failure rate, increased facilitation, and increased augmentation, indicative of a decreased release probability. Disruption of Ca2+ binding, however, cannot account for all of the deficits in the mutants; rather, the decreased release probability is probably due to a disruption in the coupling of synaptotagmin to the release machinery. Mutants exhibited a major slowing of recovery from synaptic depression, which suggests that membrane trafficking before fusion is disrupted. The disrupted process is not endocytosis because the rate of FM 1-43 uptake was unchanged in the mutants, and the polylysine motif mutant synaptotagmin was able to rescue the synaptic vesicle depletion normally found in sytnull mutants. Thus, the polylysine motif functions after endocytosis and before fusion. Finally, mutation of the polylysine motif inhibits the Ca2+-independent ability of synaptotagmin to accelerate SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-mediated fusion. Together, our results demonstrate that the polylysine motif is required for efficient Ca2+-independent docking and/or priming of synaptic vesicles in vivo.

Recent Breakthroughs in Neurotransmitter Release: Paradigm for Regulated Exocytosis?

Physiology ◽  
1995 ◽  
Vol 10 (1) ◽  
pp. 42-46
Author(s):  
G Thiel
Keyword(s):  
Synaptic Vesicle ◽  
Brain Function ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Vesicle Trafficking ◽  
Regulated Exocytosis ◽  
Intracellular Vesicle ◽  
Vesicle Cycle ◽  
Synaptic Vesicle Cycle

Synaptic vesicles play a fundamental role in brain function by mediating the release of neurotransmitters. Neurons do not use an entirely unique secretion apparatus but rather a modification of the general secretion machinery. Moreover, the synaptic vesicle cycle has many similarities with intracellular vesicle trafficking pathways.

Neurotransmitter Release

2017 ◽  
Author(s):  
Peggy Mason
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Synaptic Cleft ◽  
Fusion Pore ◽  
Synaptic Membrane ◽  
Specialized Region ◽  
Synaptic Vesicle Fusion

The biochemical and physiological processes of neurotransmitter release from an active zone, a specialized region of synaptic membrane, are examined. Synaptic vesicles containing neurotransmitters are docked at the active zone and then primed for release by SNARE complexes that bring them into extreme proximity to the plasma membrane. Entry of calcium ions through voltage-gated calcium channels triggers synaptic vesicle fusion with the synaptic terminal membrane and the consequent diffusion of neurotransmitter into the synaptic cleft. Release results when the fusion pore bridging the synaptic vesicle and plasma membrane widens and neurotransmitter from the inside of the synaptic vesicle diffuses into the synaptic cleft. Membrane from the active zone membrane is endocytosed, and synaptic vesicle proteins are then reassembled into recycled synaptic vesicles, allowing for more rounds of neurotransmitter release.

Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis

2012 ◽  
Vol 92 (4) ◽  
pp. 1915-1964 ◽  
Author(s):  
Haruo Kasai ◽  
Noriko Takahashi ◽  
Hiroshi Tokumaru
Keyword(s):  
Membrane Trafficking ◽  
Synaptic Vesicles ◽  
Cell Types ◽  
Snare Proteins ◽  
Attachment Protein ◽  
Protein Receptor ◽  
Large Dense Core Vesicles ◽  
Sensitive Factor ◽  
The Common ◽  
Kinetics Of

The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.

scholarly journals Botulinum Neurotoxin a Blocks Synaptic Vesicle Exocytosis but Not Endocytosis at the Nerve Terminal

1999 ◽  
Vol 147 (6) ◽  
pp. 1249-1260 ◽  
Author(s):  
Elaine A. Neale ◽  
Linda M. Bowers ◽  
Min Jia ◽  
Karen E. Bateman ◽  
Lura C. Williamson
Keyword(s):  
Synaptic Vesicle ◽  
Nerve Terminal ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Botulinum Neurotoxin ◽  
Vesicle Membrane ◽  
Botulinum Neurotoxin A ◽  
Synaptic Vesicle Exocytosis ◽  
Vesicle Exocytosis ◽  
Botulinum Neurotoxins

The supply of synaptic vesicles in the nerve terminal is maintained by a temporally linked balance of exo- and endocytosis. Tetanus and botulinum neurotoxins block neurotransmitter release by the enzymatic cleavage of proteins identified as critical for synaptic vesicle exocytosis. We show here that botulinum neurotoxin A is unique in that the toxin-induced block in exocytosis does not arrest vesicle membrane endocytosis. In the murine spinal cord, cell cultures exposed to botulinum neurotoxin A, neither K+-evoked neurotransmitter release nor synaptic currents can be detected, twice the ordinary number of synaptic vesicles are docked at the synaptic active zone, and its protein substrate is cleaved, which is similar to observations with tetanus and other botulinal neurotoxins. In marked contrast, K+ depolarization, in the presence of Ca2+, triggers the endocytosis of the vesicle membrane in botulinum neurotoxin A–blocked cultures as evidenced by FM1-43 staining of synaptic terminals and uptake of HRP into synaptic vesicles. These experiments are the first demonstration that botulinum neurotoxin A uncouples vesicle exo- from endocytosis, and provide evidence that Ca2+ is required for synaptic vesicle membrane retrieval.

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