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HGNC Approved Gene Symbol: SNAP23
Cytogenetic location: 15q15.1-q15.2 Genomic coordinates (GRCh38): 15:42,491,129-42,533,058 (from NCBI)
Synaptosomal-associated proteins (SNAPs), such as SNAP23, are involved in the process of membrane fusion in intracellular vesicle traffic (Ravichandran et al., 1996).
Ravichandran et al. (1996) used syntaxin-4 (186591) as bait in expression cloning to isolate novel proteins involved in membrane fusion in other cell types. From a human B-cell lymphocyte library, they identified SNAP23, which shows homology to SNAP25 (600322). SNAP25 is part of a complex, termed 'SNARE,' that is responsible for membrane fusion in neurons. The SNAP23 cDNA encodes a 211-amino acid polypeptide with a predicted mass of 23 kD. Its amino acid sequence is 59% identical to that of SNAP25. Northern blot analysis revealed that SNAP23 is ubiquitously expressed.
Mollinedo and Lazo (1997) used RT-PCR to identify an alternatively spliced variant of SNAP23 in human neutrophils. This isoform, termed SNAP23B, encodes a protein sequence of 158 amino acids with a deduced mass of 17.8 kD. Lazo et al. (2001) determined that SNAP23B lacks a region that is required for nonspecific binding to plasma membranes.
Shukla et al. (2001) identified 3 additional splice variants that they designated SNAP23C, SNAP23D, and SNAP23E, all of which showed deletions in comparison with SNAP23A. With use of variant-specific primers in RT-PCR, they found mRNA for all 5 SNAP23 variants in human eosinophils, peripheral blood mononuclear cells, neutrophils, brain tissue, and basophilic and eosinophilic cell lines. Transfection of a basophilic cell line with reporter constructs for each of these variants revealed a plasma membrane localization for SNAPA and SNAPB, and both membrane and intracellular localization for SNAP23C, SNAPD, and SNAP23E.
Ravichandran et al. (1996) determined that SNAP23 is able to bind to multiple syntaxins as well as to multiple vesicle-associated membrane proteins (see 185880).
Guo et al. (1998) reported that SNAP23 relocates in response to stimulation from plasma membrane lamellipodia-like projections to granule membranes in permeabilized mast cells. While relocation is a prerequisite for secretion, it can occur without membrane fusion and will expedite a subsequent secretory response. After relocation, SNAP23 is required for exocytosis, implying a crucial role in promoting membrane fusion. Thus, relocation of SNAP23 regulates compound exocytosis and links granule-plasma membrane and granule-granule fusions.
Using immunofluorescence and immunoelectron microscopy, Galli et al. (1998) demonstrated that human TIVAMP (VAMP7; 300053), syntaxin-3 (STX3A; 600876), and SNAP23, were insensitive to proteolysis by numerous clostridial neurotoxins (NTs). TIVAMP-containing vesicles were concentrated in the apical domain of epithelial cells. STX3A and SNAP23 were codistributed at the apical plasma membrane, where they formed N-ethyl maleimide-dependent SNARE complexes with TIVAMP and cellubrevin (VAMP3; 603657). Galli et al. (1998) proposed that TIVAMP, STX3A, and SNAP23 participate in exocytotic processes at the apical plasma membrane of epithelial cells and in clostridial NT-resistant pathways.
Using RT-PCR, immunoblot analysis, and immunofluorescence microscopy, Sander et al. (2008) demonstrated that human intestinal mast cells (MCs) expressed SNAP23, STX1B (601485), STX2 (132350), STX3, STX4 (STX4A; 186591), and STX6 (603944), but not SNAP25. MCs also expressed VAMP3, VAMP7, and VAMP8 (603177), but, in contrast with rodent MCs, they expressed only low levels of VAMP2 (185881). VAMP7 and VAMP8 translocated to the plasma membrane and interacted with SNAP23 and STX4 upon activation. Inhibition of STX4, SNAP23, VAMP7, or VAMP8, but not VAMP2 or VAMP3, resulted in markedly reduced high-affinity IgE receptor-mediated histamine release. Sander et al. (2008) concluded that human MCs express a specific pattern of SNAREs and that VAMP7 and VAMP8, but not VAMP2, are required for rapid degranulation.
Lazo et al. (2001) found that the SNAP23 gene has 8 exons, with the initiation codon located in exon 2. They determined that SNAP23B is the result of alternative splicing where exon 5 is joined to exon 7, skipping exon 6.
By fluorescence in situ hybridization, Lazo et al. (2001) mapped the SNAP23 gene to chromosome 15q21-q22. Lazo et al. (2001) suggested that alterations in the SNAP23 gene may be involved in neurologic and other diseases with defects in vesicle-membrane fusion processes that map to 15q15-q21.
Galli, T., Zahraoui, A., Vaidyanathan, V. V., Raposo, G., Tian, J. M., Karin, M., Niemann, H., Louvard, D. A novel tetanus neurotoxin-insensitive vesicle-associated membrane protein in SNARE complexes of the apical plasma membrane of epithelial cells. Molec. Biol. Cell 9: 1437-1448, 1998. [PubMed: 9614185] [Full Text: https://doi.org/10.1091/mbc.9.6.1437]
Guo, Z., Turner, C., Castle, D. Relocation of the t-SNARE SNAP-23 from lamellipodia-like cell surface projections regulates compound exocytosis in mast cells. Cell 94: 537-548, 1998. [PubMed: 9727496] [Full Text: https://doi.org/10.1016/s0092-8674(00)81594-9]
Lazo, P. A., Nadal, M., Ferrer, M., Area, E., Hernandez-Torres, J., Nabokina, S. M., Mollinedo, F., Estivill, X. Genomic organization, chromosomal localization, alternative splicing, and isoforms of the human synaptosome-associated protein-23 gene implicated in vesicle-membrane fusion processes. Hum. Genet. 108: 211-215, 2001. [PubMed: 11354632] [Full Text: https://doi.org/10.1007/s004390100480]
Mollinedo, F., Lazo, P. A. Identification of two isoforms of the vesicle-membrane fusion protein SNAP-23 in human neutrophils and HL-60 cells. Biochem. Biophys. Res. Commun. 231: 808-812, 1997. [PubMed: 9070898] [Full Text: https://doi.org/10.1006/bbrc.1997.6196]
Ravichandran, V., Chawla, A., Roche, P. A. Identification of a novel syntaxin- and synaptobrevin/VAMP-binding protein, SNAP-23, expressed in non-neuronal tissues. J. Biol. Chem. 271: 13300-13303, 1996. [PubMed: 8663154] [Full Text: https://doi.org/10.1074/jbc.271.23.13300]
Sander, L. E., Frank, S. P. C., Bolat, S., Blank, U., Galli, T., Bigalke, H., Bischoff, S. C., Lorentz, A. Vesicle associated membrane protein (VAMP)-7 and VAMP-8, but not VAMP-2 or VAMP-3, are required for activation-induced degranulation of mature human mast cells. Europ. J. Immun. 38: 855-863, 2008. [PubMed: 18253931] [Full Text: https://doi.org/10.1002/eji.200737634]
Shukla, A., Corydon, T. J., Nielsen, S., Hoffmann, H. J., Dahl, R. Identification of three new splice variants of the SNARE protein SNAP-23. Biochem. Biophys. Res. Commun. 285: 320-327, 2001. [PubMed: 11444845] [Full Text: https://doi.org/10.1006/bbrc.2001.5144]