NCBI Summary:
Specificity of vesicular transport is regulated, in part, by the interaction of a vesicle-associated membrane protein termed synaptobrevin/VAMP with a target compartment membrane protein termed syntaxin. These proteins, together with SNAP25 (synaptosome-associated protein of 25 kDa), form a complex which serves as a binding site for the general membrane fusion machinery. Synaptobrevin/VAMP and syntaxin are believed to be involved in vesicular transport in most, if not all cells, while SNAP25 is present almost exclusively in the brain, suggesting that a ubiquitously expressed homolog of SNAP25 exists to facilitate transport vesicle/target membrane fusion in other tissues. The protein encoded by this gene is structurally and functionally similar to SNAP25 and binds tightly to multiple syntaxins and synaptobrevins/VAMPs. It is an essential component of the high affinity receptor for the general membrane fusion machinery and is an important regulator of transport vesicle docking and fusion. Two alternative transcript variants encoding different protein isoforms have been described for this gene. [provided by RefSeq, Jul 2008]
General function
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Cellular localization
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Ovarian function
Oocyte maturation, Early embryo development
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SNAP23 is required for constitutive and regulated exocytosis in mouse oocytes. Mehlmann LM et al. (2019) Mammalian oocytes are stored in the ovary for prolonged periods, arrested in meiotic prophase. During this period, their plasma membranes are constantly being recycled by endocytosis and exocytosis. However, the function of this membrane turnover is unknown. Here, we investigated the requirement for exocytosis in the maintenance of meiotic arrest. Using//// Trim-away, a newly developed method for rapidly and specifically depleting proteins in oocytes, we have identified the SNARE protein, SNAP23, to be required for meiotic arrest. Degradation of SNAP23 causes premature meiotic resumption in follicle-enclosed oocytes. The reduction in SNAP23 is associated with loss of gap junction communication between the oocyte and surrounding follicle cells. Reduction of SNAP23 protein also inhibits regulated exocytosis in response to a Ca2+ stimulus (cortical granule exocytosis), as measured by lectin staining and cleavage of ZP2. Our results show an essential role for SNAP23 in two key processes that occur in mouse oocytes and eggs.//////////////////
Expression regulated by
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Ovarian localization
Oocyte
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Preparation of the Cortical Reaction: Maturation-Dependent Migration of SNARE Proteins, Clathrin, and Complexin to the Porcine Oocyte's Surface Blocks Membrane Traffic until Fertilization. Tsai PS et al. The cortical reaction is a calcium-dependent exocytotic process, in which the content of secretory granules is released into the peri-vitellin space immediately after fertilization, and this serves to prevent polyspermic-fertilization. In this study we investigated the involvement and the organization of Soluble N-ethylmaleimide-sensitive factor [NSF] Attachment Protein Receptor (SNARE) proteins in the docking and fusion of the cortical granule membrane with the oolemma in porcine oocytes. During meiotic maturation secretory vesicles (labeled with a granule specific binding lectin, PNA) migrated toward the oocyte's surface. This surface orientated redistribution behavior was also observed for the oocyte-specific SNARE proteins SNAP 23 and VAMP 1 that co-localized with the PNA-labeled structures in the cortex area just under the oolemma and to the exclusive localization area of complexin (a trans-SNARE complex stabilizing protein). The coming together of these proteins serves to prevent the spontaneous secretion of the docked cortical granules, and to prepare the oocyte's surface for the cortical reaction, which should immediately be compensated probably by a clathrin-mediated endocytosis. In vitro fertilization resulted in the secretion of the cortical granule content and the concomitant release of complexin and clathrin into the oocyte's cytosol and this is considered to stimulate the observed endocytosis of SNARE containing membrane vesicles.