scholarly journals The synaptic vesicle proteins SV2, synaptotagmin and synaptophysin are sorted to separate cellular compartments in CHO fibroblasts.

1993 ◽  
Vol 123 (3) ◽  
pp. 575-584 ◽  
Author(s):  
M B Feany ◽  
A G Yee ◽  
M L Delvy ◽  
K M Buckley
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Cell Lines ◽  
Synaptic Vesicles ◽  
Vesicle Biogenesis ◽  
Intracellular Vesicles ◽  
Cellular Compartments ◽  
Vesicle Proteins

We expressed the synaptic vesicle proteins SV2, synaptotagmin, and synaptophysin in CHO fibroblasts to investigate the targeting information contained by each protein. All three proteins entered different cellular compartments. Synaptotagmin was found on the plasma membrane. Both SV2 and synaptophysin were sorted to small intracellular vesicles, but synaptophysin colocalized with early endosomal markers, while SV2 did not. SV2-containing vesicles did not have the same sedimentation characteristics as authentic synaptic vesicles, even though transfected SV2 was sorted from endosomal markers. We also created cell lines expressing both SV2 and synaptotagmin, both synaptotagmin and synaptophysin, and lines expressing all three synaptic vesicle proteins. In all cases, the proteins maintained their distinct compartmentalizations, were not found in the same organelle, and did not created synaptic vesicle-like structures. These results have important implications for models of synaptic vesicle biogenesis.

VAMP (synaptobrevin) is present in the plasma membrane of nerve terminals

1999 ◽  
Vol 112 (20) ◽  
pp. 3559-3567
Author(s):  
P. Taubenblatt ◽  
J.C. Dedieu ◽  
T. Gulik-Krzywicki ◽  
N. Morel
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Specific Interaction ◽  
Snare Complex ◽  
Nerve Endings ◽  
Morphological Data ◽  
Synaptosomal Plasma Membrane ◽  
Presynaptic Plasma Membrane ◽  
Vesicle Proteins

Synaptic vesicle docking and exocytosis require the specific interaction of synaptic vesicle proteins (such as VAMP/synaptobrevin) with presynaptic plasma membrane proteins (such as syntaxin and SNAP 25). These proteins form a stable, SDS-resistant, multimolecular complex, the SNARE complex. The subcellular distribution of VAMP and syntaxin within Torpedo electric organ nerve endings was studied by immunogoldlabeling of SDS-digested freeze-fracture replicas (Fujimoto, 1995). This technique allowed us to visualize large surface areas of the presynaptic plasma membrane and numerous synaptic vesicles from rapidly frozen nerve endings and synaptosomes. VAMP was found associated with synaptic vesicles, as also shown by conventional electron microscopy immunolabeling, and to the presynaptic plasma membrane (P leaflet). Syntaxin was also detected in the nerve ending plasma membrane, without gold labeling of synaptic vesicles. Comparison of gold particle densities suggests that the presynaptic plasma membrane contains 3 VAMP molecules per molecule of syntaxin. After biotinylation of intact synaptosomes, the synaptosomal plasma membrane was isolated on Streptavidin coated magnetic beads. Its antigenic content was compared to that of purified synaptic vesicles. VAMP was present in both membranes whereas syntaxin and SNAP 25 were highly enriched in the synaptosomal plasma membrane. This membrane has a low content of classical synaptic vesicle proteins (synaptophysin, SV2 and the vesicular acetylcholine transporter). The VAMP to syntaxin stoichiometry in the isolated synaptosomal membrane was estimated by comparison with purified antigens and close to 2, in accordance with morphological data. SDS-resistant SNARE complexes were detected in the isolated presynaptic membrane but absent in purified synaptic vesicles. Taken together, these results show that the presence of VAMP in the plasma membrane of nerve endings cannot result from exocytosis of synaptic vesicles, a process which could, as far as SNAREs are concerned, very much resemble homotypic fusion.

scholarly journals How do you recognize and reconstitute a synaptic vesicle after fusion?

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1734 ◽  
Author(s):  
Natali L. Chanaday ◽  
Ege T. Kavalali
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Membrane Composition ◽  
Synaptic Vesicle Recycling ◽  
Vesicle Recycling ◽  
Molecular Identity ◽  
Daunting Task ◽  
Vesicle Biogenesis ◽  
Vesicle Cycle

Synaptic vesicle recycling is essential for sustained and reliable neurotransmission. A key component of synaptic vesicle recycling is the synaptic vesicle biogenesis process that is observed in synapses and that maintains the molecular identity of synaptic vesicles. However, the mechanisms by which synaptic vesicles are retrieved and reconstituted after fusion remain unclear. The complex molecular composition of synaptic vesicles renders their rapid biogenesis a daunting task. Therefore, in this context, kiss-and-run type transient fusion of synaptic vesicles with the plasma membrane without loss of their membrane composition and molecular identity remains a viable hypothesis that can account for the fidelity of the synaptic vesicle cycle. In this article, we discuss the biological implications of this problem as well as its possible molecular solutions.

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.

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.

Dynamin Mediates Membrane Vesiculation

1998 ◽  
Vol 4 (S2) ◽  
pp. 1022-1023
Author(s):  
Sharon M. Sweitzer ◽  
Jenny E. Hinshaw
Keyword(s):  
Drosophila Melanogaster ◽  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Mechanism Of Action ◽  
Synaptic Vesicles ◽  
Dominant Negative ◽  
Coated Pits ◽  
Vesicle Recycling ◽  
Membrane Vesiculation ◽  
Helical Tubes

Dynamin, a 100 kDa GTPase, is essential for receptor mediated endocytosis and synaptic vesicle recycling; however its mechanism of action is unknown. The requirement for dynamin was first elucidated by the discovery that the shibire gene product in Drosophila melanogaster was homologous to mammalian dynamin-1 (1,2). The shibire flies exhibit a depletion of synaptic vesicles and an accumulation of collared clathrin-coated pits at the plasma membrane of their nerve termini (3). It was later demonstrated that endocytosis was inhibited by the overexpression of dominant negative mutants of dynamin (4,5), and that purified dynamin can self-associate to form spirals which resemble the collars of shibire and structures seen in synaptosomes treated with GTPγS (6,7). These observations led to the speculation that dynamin pinches the clathrin-coated bud from the plasma membrane. In support of this hypothesis, we show that purified recombinant dynamin can bind to a lipid bilayer in a regular and repeating pattern to form helical tubes which vesiculate upon the addition of GTP.

scholarly journals Colocalization of synaptophysin with transferrin receptors: implications for synaptic vesicle biogenesis.

1991 ◽  
Vol 115 (1) ◽  
pp. 151-164 ◽  
Author(s):  
P L Cameron ◽  
T C Südhof ◽  
R Jahn ◽  
P De Camilli
Keyword(s):  
Synaptic Vesicle ◽  
Cell Lines ◽  
Endocrine Cell ◽  
Cho Cells ◽  
Hippocampal Neurons ◽  
Synapse Formation ◽  
Primary Cultures ◽  
Endocytic Pathway ◽  
Transferrin Receptors ◽  
Vesicle Biogenesis

We have reported previously that the synaptic vesicle (SV) protein synaptophysin, when expressed in fibroblastic CHO cells, accumulates in a population of recycling microvesicles. Based on preliminary immunofluorescence observations, we had suggested that synaptophysin is targeted to the preexisting population of microvesicles that recycle transferrin (Johnston, P. A., P. L. Cameron, H. Stukenbrok, R. Jahn, P. De Camilli, and T. C. Südhof. 1989. EMBO (Eur. Mol. Biol. Organ.) J. 8:2863-2872). In contrast to our results, another group reported that expression of synaptophysin in cells which normally do not express SV proteins results in the generation of a novel population of microvesicles (Leube, R. E., B. Wiedenmann, and W. W. Franke. 1989. Cell. 59:433-446). We report here a series of morphological and biochemical studies conclusively demonstrating that synaptophysin and transferrin receptors are indeed colocalized on the same vesicles in transfected CHO cells. These observations prompted us to investigate whether an overlap between the distribution of the two proteins also occurs in endocrine cell lines that endogenously express synaptophysin and other SV proteins. We have found that endocrine cell lines contain two pools of membranes positive for synaptophysin and other SV proteins. One of the two pools also contains transferrin receptors and migrates faster during velocity centrifugation. The other pool is devoid of transferrin receptors and corresponds to vesicles with the same sedimentation characteristics as SVs. These findings suggest that in transfected CHO cells and in endocrine cell lines, synaptophysin follows the same endocytic pathway as transferrin receptors but that in endocrine cells, at some point along this pathway, synaptophysin is sorted away from the recycling receptors into a specialized vesicle population. Finally, using immunofluorescent analyses, we found an overlap between the distribution of synaptophysin and transferrin receptors in the dendrites of hippocampal neurons in primary cultures before synapse formation. Axons were enriched in synaptophysin immunoreactivity but did not contain detectable levels of transferrin receptor immunoreactivity. These results suggest that SVs may have evolved from, as well as coexist with, a constitutively recycling vesicular organelle found in all cells.

scholarly journals The AP-3 Complex Required for Endosomal Synaptic Vesicle Biogenesis is Associated with a Casein Kinase Ια-Like Isoform

2000 ◽  
Vol 11 (8) ◽  
pp. 2591-2604 ◽  
Author(s):  
Victor V. Faundez ◽  
Regis B. Kelly
Keyword(s):  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Enzymatic Reaction ◽  
Casein Kinase ◽  
Small Gtpase ◽  
Casein Kinase I ◽  
Vesicle Membranes ◽  
Vesicle Biogenesis ◽  
Hinge Domain

The formation of small vesicles is mediated by cytoplasmic coats the assembly of which is regulated by the activity of GTPases, kinases, and phosphatases. A heterotetrameric AP-3 adaptor complex has been implicated in the formation of synaptic vesicles from PC12 endosomes ( Faundez et al., 1998 ). When the small GTPase ARF1 is prevented from hydrolyzing GTP, we can reconstitute AP-3 recruitment to synaptic vesicle membranes in an assembly reaction that requires temperatures above 15°C and the presence of ATP suggesting that an enzymatic step is involved in the coat assembly. We have now found an enzymatic reaction, the phosphorylation of the AP-3 adaptor complex, that is linked with synaptic vesicle coating. Phosphorylation occurs in the β3 subunit of the complex by a kinase similar to casein kinase 1α. The kinase copurifies with neuronal-specific AP-3. In vitro, purified casein kinase I selectively phosphorylates the β3A and β3B subunit at its hinge domain. Inhibiting the kinase hinders the recruitment of AP-3 to synaptic vesicles. The same inhibitors that prevent coat assembly in vitro also inhibit the formation of synaptic vesicles in PC12 cells. The data suggest, therefore, that the mechanism of AP-3-mediated vesiculation from neuroendocrine endosomes requires the phosphorylation of the adaptor complex at a step during or after AP-3 recruitment to membranes.

scholarly journals A new life for an old pump: V-ATPase and neurotransmitter release

2014 ◽  
Vol 205 (1) ◽  
pp. 7-9 ◽  
Author(s):  
Stefano Vavassori ◽  
Andreas Mayer
Keyword(s):  
Plasma Membrane ◽  
Complex Formation ◽  
Membrane Fusion ◽  
Synaptic Vesicle ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Snare Complex ◽  
Spontaneous Release ◽  
Synaptic Vesicle Fusion ◽  
Snare Complex Formation

Neurons fire by releasing neurotransmitters via fusion of synaptic vesicles with the plasma membrane. Fusion can be evoked by an incoming signal from a preceding neuron or can occur spontaneously. Synaptic vesicle fusion requires the formation of trans complexes between SNAREs as well as Ca2+ ions. Wang et al. (2014. J. Cell Biol. http://dx.doi.org/jcb.201312109) now find that the Ca2+-binding protein Calmodulin promotes spontaneous release and SNARE complex formation via its interaction with the V0 sector of the V-ATPase.

scholarly journals The synaptic vesicle cycle: a single vesicle budding step involving clathrin and dynamin.

1996 ◽  
Vol 133 (6) ◽  
pp. 1237-1250 ◽  
Author(s):  
K Takei ◽  
O Mundigl ◽  
L Daniell ◽  
P De Camilli
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Hippocampal Neurons ◽  
Coated Vesicles ◽  
Coated Vesicle ◽  
Nerve Terminals ◽  
Vesicle Budding ◽  
Vesicle Cycle ◽  
Single Vesicle

Strong evidence implicates clathrin-coated vesicles and endosome-like vacuoles in the reformation of synaptic vesicles after exocytosis, and it is generally assumed that these vacuoles represent a traffic station downstream from clathrin-coated vesicles. To gain insight into the mechanisms of synaptic vesicle budding from endosome-like intermediates, lysed nerve terminals and nerve terminal membrane subfractions were examined by EM after incubations with GTP gamma S. Numerous clathrin-coated budding intermediates that were positive for AP2 and AP180 immunoreactivity and often collared by a dynamin ring were seen. These were present not only on the plasma membrane (Takei, K., P.S. McPherson, S.L.Schmid, and P. De Camilli. 1995. Nature (Lond.). 374:186-190), but also on internal vacuoles. The lumen of these vacuoles retained extracellular tracers and was therefore functionally segregated from the extracellular medium, although narrow connections between their membranes and the plasmalemma were sometimes visible by serial sectioning. Similar observations were made in intact cultured hippocampal neurons exposed to high K+ stimulation. Coated vesicle buds were generally in the same size range of synaptic vesicles and positive for the synaptic vesicle protein synaptotagmin. Based on these results, we suggest that endosome-like intermediates of nerve terminals originate by bulk uptake of the plasma membrane and that clathrin- and dynamin-mediated budding takes place in parallel from the plasmalemma and from these internal membranes. We propose a synaptic vesicle recycling model that involves a single vesicle budding step mediated by clathrin and dynamin.

scholarly journals Normal Biogenesis and Cycling of Empty Synaptic Vesicles in Dopamine Neurons of Vesicular Monoamine Transporter 2 Knockout Mice

2005 ◽  
Vol 16 (1) ◽  
pp. 306-315 ◽  
Author(s):  
Benjamin G. Croft ◽  
Gabriel D. Fortin ◽  
Amadou T. Corera ◽  
Robert H. Edwards ◽  
Alain Beaudet ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Knockout Mice ◽  
Synaptic Vesicles ◽  
Dopamine Neurons ◽  
Vesicular Monoamine Transporter ◽  
Wild Type ◽  
Monoamine Transporter ◽  
Vesicle Biogenesis ◽  
And Function ◽  
Activity Dependent

The neuronal isoform of vesicular monoamine transporter, VMAT2, is responsible for packaging dopamine and other monoamines into synaptic vesicles and thereby plays an essential role in dopamine neurotransmission. Dopamine neurons in mice lacking VMAT2 are unable to store or release dopamine from their synaptic vesicles. To determine how VMAT2-mediated filling influences synaptic vesicle morphology and function, we examined dopamine terminals from VMAT2 knockout mice. In contrast to the abnormalities reported in glutamatergic terminals of mice lacking VGLUT1, the corresponding vesicular transporter for glutamate, we found that the ultrastructure of dopamine terminals and synaptic vesicles in VMAT2 knockout mice were indistinguishable from wild type. Using the activity-dependent dyes FM1-43 and FM2-10, we also found that synaptic vesicles in dopamine neurons lacking VMAT2 undergo endocytosis and exocytosis with kinetics identical to those seen in wild-type neurons. Together, these results demonstrate that dopamine synaptic vesicle biogenesis and cycling are independent of vesicle filling with transmitter. By demonstrating that such empty synaptic vesicles can cycle at the nerve terminal, our study suggests that physiological changes in VMAT2 levels or trafficking at the synapse may regulate dopamine release by altering the ratio of fillable-to-empty synaptic vesicles, as both continue to cycle in response to neural activity.

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