Relative properties and localizations of synaptic vesicle protein isoforms: the case of the synaptophysins

Fykse, Else Marie; Takei, Kohji; Walch‐Solimena, Christiane; Geppert, Martin; Jahn, Reinhard; Camilli, Pietro De; Sudhof, T. C.

doi:10.1523/jneurosci.13-11-04997.1993

Cited by 123 publications

(98 citation statements)

References 30 publications

(38 reference statements)

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“…This pattern is very similar to that observed for other synaptic vesicle proteins, for example synaptophysins, which are expressed in an ubiquitously (synaptophysin 1) and a variably distributed isoform (synaptophysin 2/synaptoporin; Ref. 29). Rab3D is also present in the brain, but its levels were too low to allow localization.…”

Section: Discussionsupporting

confidence: 80%

Localization Versus Function of Rab3 Proteins

Schlüter

Khvotchev

Jahn

et al. 2002

Journal of Biological Chemistry

150

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Rab3A, Rab3B, Rab3C, and Rab3D constitute a family of GTP-binding proteins that are implicated in regulated exocytosis. Various localizations and distinct functions have been proposed for different and occasionally even for the same Rab3 protein. This is exemplified by studies demonstrating that deletion of Rab3A in knock-out mice results in dysregulation of the final stages of exocytosis, whereas overexpression of Rab3A in neuroendocrine cells causes nearly complete inhibition of Ca 2؉-triggered exocytosis. We have now examined the properties of all Rab3 proteins in the same assays, with the long-term goal of identifying a common conceptual framework for their functions. Using quantitative immunoblotting, we found that all four Rab3 proteins were expressed in brain and endocrine tissues, although at widely different levels. Rab3A, Rab3B, and Rab3C co-localized to synaptic and secretory vesicles consistent with potential redundancy, whereas Rab3D was expressed at high levels only in the endocrine pituitary (where it was more abundant than Rab3A, Rab3B, and Rab3C combined), in exocrine glands, and in adipose tissue. In transfected PC12 cells, all four Rab3 proteins strongly inhibited Ca 2؉ -triggered exocytosis. Except for a mutation that fixes Rab3 into a permanently GDP-bound state, all Rab3 mutations tested had no effect on this inhibition, including a mutation in the calmodulin-binding site that was described as inactivating (Coppola, T., Perret-Menoud, V., Lü thi, S., Farnsworth, C. C., Glomset, J. A., and Regazzi, R. (1999) EMBO J. 18, 5885-5891). Unexpectedly, overexpression of wild type Rab3A and permanently GTP-bound mutant Rab3A in PC12 cells caused a loss of secretory vesicles and an increase in constitutive, Ca 2؉ -independent exocytosis that correlated with the inhibition of regulated Ca 2؉ -triggered exocytosis. Our data indicate that overexpression of Rab3 in PC12 cells impairs the normal control of the final step in exocytosis, thereby converting the regulated secretory pathway into a constitutive pathway. These results offer an hypothesis that reconciles Rab3 transfection and knockout studies by suggesting that Rab3 functions as a gatekeeper of a late stage in exocytosis.

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Section: Discussionsupporting

confidence: 80%

Localization Versus Function of Rab3 Proteins

Schlüter

Khvotchev

Jahn

et al. 2002

Journal of Biological Chemistry

150

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“…Monoclonal antibody Cl 71.1, specific for SNAP-25, was raised using recombinant SNAP-25 and will be described in detail elsewhere (D.Bruns and R.Jahn, manuscript in preparation). A rabbit serum directed against synaptoporin (Fykse et al, 1993) and a monoclonal antibody directed against SCAMP (Brand and Castle, 1993) McMahon et al, 1992) using Ficoll density gradient centrifugation as the last purification step. For solubilization, 1 mg of synaptosomal protein was pelleted and dissolved in 1 ml of ice-cold extraction buffer (140 mM KCI, 20 mM HEPES-KOH pH 7.3, 2 mM EDTA, unless indicated otherwise) containing 1% (v/v) Triton X-100.…”

Section: Antibodiesmentioning

confidence: 99%

Synaptobrevin binding to synaptophysin: a potential mechanism for controlling the exocytotic fusion machine.

et al. 1995

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The synaptic vesicle protein synaptobrevin (VAMP) has recently been implicated as one of the key proteins involved in exocytotic membrane fusion. It with similar efficiency, whereas the non-neuronal isoform cellubrevin displayed a lower affinity towards synaptophysin. Treatment with high NaCl concentrations resulted in a dissociation of the synaptobrevin-synaptophysin complex. In addition, the interaction of synaptobrevin with synaptophysin was irreversibly abolished by low amounts of SDS, while the interaction with syntaxin I was enhanced. We conclude that synaptophysin selectively interacts with synaptobrevin in a complex which excludes the t-SNAP receptors syntaxin I and SNAP-25, suggesting a role for synaptophysin in the control of exocytosis.

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“…A comparison of the synaptoporin staining patterns, however, showed that the distribution of synaptoporin was indistinguishable between wild type and SCAMP1 knockout mice (data not shown). The synaptic vesicle protein synaptoporin is an isoform of synaptophysin that is highly concentrated in mossy fiber terminals of the CA3 region (21). It is therefore a marker that is sensitive to changes in the structural organization of the hippocampus.…”

Section: Essential Functions Of Scamp1 32552mentioning

confidence: 99%

Analysis of SCAMP1 Function in Secretory Vesicle Exocytosis by Means of Gene Targeting in Mice

Fernández‐Chacón¹,

Toledo²,

Hammer³

et al. 1999

Journal of Biological Chemistry

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Secretory carrier membrane proteins (SCAMPs) comprise a family of ubiquitous membrane proteins of transport vesicles with no known function. Their universal presence in all cells suggests a fundamental role in membrane traffic. SCAMPs are particularly highly expressed in organelles that undergo regulated exocytosis, such as synaptic vesicles and mast cell granules. Of the three currently known SCAMPs, SCAMP1 is the most abundant. To investigate the possible functions of SCAMP1, we generated mice that lack SCAMP1. SCAMP1-deficient mice are viable and fertile. They exhibit no changes in the overall architecture or the protein composition of the brain or alterations in peripheral organs. Capacitance measurements in mast cells demonstrated that exocytosis could be triggered reliably by GTP␥S in SCAMP1-deficient cells. The initial overall capacitance of mast cells was similar between wild type and mutant mice, but the final cell capacitance after completion of exocytosis, was significantly smaller in SCAMP1-deficient cells than in wild type cells. Furthermore, there was an increased proportion of reversible fusion events, which may have caused the decrease in the overall capacitance change observed after exocytosis. Our data show that SCAMP1 is not essential for exocytosis, as such, and does not determine the stability or size of secretory vesicles, but is required for the full execution of stable exocytosis in mast cells. This phenotype could be the result of a function of SCAMP1 in the formation of stable fusion pores during exocytosis or of a role of SCAMP1 in the regulation of endocytosis after formation of fusion pores. SCAMPs1 represent a family of membrane proteins present in transport vesicles (1-7). The three SCAMPs that have been identified in mammals (2) are proteins of 35-40 kDa that are composed of an N-terminal cytoplasmic sequence followed by four transmembrane regions and a short cytoplasmic tail. SCAMPs are highly conserved evolutionarily and very homologous to each other. Although they were originally discovered as components of secretory granules in exocrine glands (8), SCAMPs were later found to be present in all cells tested on post-Golgi transport vesicles (3-7). SCAMPs are particularly abundant in vesicles that are subject to regulated exocytosis, such as mast cell granules, exocrine granules, and synaptic vesicles. The three SCAMP proteins are differentially expressed in tissues and are not universally co-expressed in all cells (2). Only one of the three SCAMPs, SCAMP1, appears to be present at high levels on synaptic vesicles that lack SCAMPs 2 and 3 (Refs. 1 and 2 and footnote 2).The function of SCAMPs are unknown. Their ubiquitous presence in transport vesicles in all cells indicates a fundamental role in membrane traffic. The enrichment of SCAMPs in secretory vesicles that are subject to regulated exocytosis followed by rapid endocytosis suggests a function in exo-or endocytosis. Interestingly, SCAMP1 and SCAMP3 are tyrosinephosphorylated in vivo by the epidermal growth factor receptor tyr...

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Relative properties and localizations of synaptic vesicle protein isoforms: the case of the synaptophysins

Cited by 123 publications

References 30 publications

Localization Versus Function of Rab3 Proteins

Localization Versus Function of Rab3 Proteins

Synaptobrevin binding to synaptophysin: a potential mechanism for controlling the exocytotic fusion machine.

Analysis of SCAMP1 Function in Secretory Vesicle Exocytosis by Means of Gene Targeting in Mice

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