SNAP25
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Synaptosomal-Associated Protein, 25kDa (SNAP-25) is a Target Soluble NSF (N-ethylmaleimide-sensitive factor) Attachment Protein Receptor (
Structure and function
SNAP-25, a
SNAP-25 has been identified to contribute two
To form the SNARE complex, synaptobrevin, syntaxin-1, and SNAP-25 associate and begin to wrap around each other to form a coiled coil quaternary structure. The α-helices of both synaptobrevin and syntaxin-1 bind to those of SNAP-25. Synaptobrevin binds the α-helix near the C-terminus of SNAP-25, while syntaxin-1 binds the α-helix near the N-terminus.[9] Dissociation of the SNARE complex is driven by ATPase N-ethylmaleimide-sensitive fusion (NSF) protein.[13]
SNAP-25 inhibits
Two
| SNAP25a | SNAP25b | |
|---|---|---|
| Structure | N-terminal α-helix
Random coil linker region with four cysteines clustered towards the center C-terminal α-helix |
N-terminal α-helix
Random coil linker region with four cysteines clustered towards the C-terminus C-terminal α-helix |
| Expression | Major SNAP-25 isoform in embryos and developing neural tissue
Minimal expression in adult tissue except in pituitary and adrenal gland tissues |
Minimal expression during development, major isoform in adult neural tissue[18] |
| Localization | Diffuse | Localized to terminals and varicosities[18] |
SNAP-25 not only plays a role in synaptogenesis and the exocytotic release of neurotransmitters, but it also affects spine morphogenesis and density, post synaptic receptor trafficking and neuronal plasticity. Other non-neuronal processes such as metabolism can also be affected by SNAP-25 protein expression.[19][20]
Clinical significance
Developmental and epileptic encephalopathies (DEEs)
Individuals harboring pathogenic heterozygous de novo missense or loss-of-function variants in SNAP-25 often present with an early-onset developmental and epileptic encephalopathy. The core symptoms comprise intellectual disability ranging between mild to profound and early-onset seizures mostly occurring before the age of two years. Further recurrent symptoms include movement disorders, cerebral visual impairment, and brain atrophy.[21] Electrophysiological studies identified aberrant spontaneous neurotransmission as causative and suggest that structurally clustered pathogenic variants lead to similar synaptic phenotypes.[22]
Attention Deficit Hyperactivity Disorder (ADHD)
Consistent with the regulation of synaptic Ca2+ responsiveness, heterozygous deletion of the SNAP-25 gene in mice results in a hyperactive phenotype similar to
Schizophrenia
Studies in the post mortem brains of patients with Schizophrenia have shown that altered protein levels of SNAP-25 are specific to regions of the brain. Reduced SNAP-25 protein expression has been observed in the hippocampus as well as an area of the frontal lobe known as Broadman's area 10 whereas SNAP-25 expression has increased in both the cingulate cortex and prefrontal lobe of Broadman's area 9. The varying levels of SNAP-25 protein found in different areas of the brain have been thought to contribute to the conflicting psychological behaviors (depressive vs. hyperactive) expressed in some Schizophrenic patients.[27][28][29][30]
The blind-drunk (Bdr) mouse model which has a point mutations in the SNAP-25b protein has provided a complex phenotype involving behaviors such as an abnormal circadian rhythm,[31] uncoordinated gait, and disinterest in new objects/toys.[32] Another mouse model generated from Cre-LoxP recombination, showed that conditional knockout (cKO) of the SNAP-25 gene in the forebrain, showed inactive SNAP-25 gene expression in glutamatergic neurons. However, significant glutamate levels were found in the cortex of these cKO mice.[33] These mice also exhibited deficient social skills, impaired learning and memory, enhanced kinesthetic activity, a reduced startle response, impaired self-care, nursing ability and nest-building skills. Antipsychotic drugs such as Clozapine and Riluzole have been shown to significantly reduce the schizophrenic phenotype expressed in SNAP-25 cKO mice.[33]
Alzheimer's disease
Individuals with Alzhiemer's disease have been shown to have decreased presynaptic protein levels and impaired synaptic function in neurons. SNAP-25 can be used as a biomarker in the cerebral spinal fluid (CSF) of patients exhibiting different variations of Alzheimer's disease (prodromal Alzheimer's and overt Alzheimer's). Increased levels of SNAP-25 protein were observed in patients with Alzheimer's compared to control individuals. Additionally, the presence of truncated SNAP-25 protein can be seen in the CSF of some patients with this disease. [34] In five distinct regions of the brain, low levels of SNAP-25 can be seen in patients with Alzheimer's.[35]
Bipolar disorder
A single nucleotide polymorphism in the SNAP-25 gene promoter has been shown to influence the expression levels of the SNAP-25b isoform in the prefrontal cortex. Increased levels of SNAP-25b have been shown to impair synaptic transmission and maturation which could lead to early-onset bipolar disorder (EOBD).The most abundant isoform of SNAP-25 is SNAP-25a during the early weeks of development in mice however in adulthood there is a change and the SNAP-25b isoform increases in the brain. This is shown to correlate with adolescent humans being increasingly diagnosed with EOBD during puberty.[36] It has been suggested that early-onset bipolar disorder is more closely linked to Schizophrenia than to Bipolar Disorder itself. The single nucleotide polymorphism of SNAP-25 (rs6039769) associated with EOBD has been shown to increase the risk of patients developing Schizophrenia.[19]
Botulism
A genome wide association study pointed to the
Epilepsy
Deletion of the SNAP-25b isoform has been shown to cause developmental abnormalities and seizures in mice. High levels of SNAP-25a and the protein syntaxin appear to be linked to seizures found in infantile-epilepsy. SNAP-25
Learning disabilities
In the coloboma hyperactive mutant mouse model where SNAP-25 protein levels are reduced to 50% of the normal level, depolarized neurotransmitter release of dopamine and serotonin were reduced as well as glutamate release. The reduction in glutamate levels can lead to deficient memory and increased learning disabilities.[40] Certain polymorphisms of SNAP-25 (rs363043, rs353016, rs363039, rs363050) have been shown to affect the cognitive behavior, specifically the Intelligence Quotient (IQ)), of patients without pre-existing neurological diseases.[41]
Neonatal development
SNAP-25 protein expression can be altered by sex hormone levels in neonatal rats. Male rats that received an antiestrogen drug showed a 30% decrease in SNAP-25 levels and females treated with estrogen or testosterone showed a 30% increase in SNAP-25 levels.[42] This suggests that synaptosomal proteins, such as SNAP-25, may have a dependence on neonatal hormone levels during brain development in rats. An additional study, showed that SNAP-25 levels in the hippocampus of the brain in neonatal mice were altered if the mother had been exposed to human influenza virus during pregnancy.[43]
Impact in other non-humans
Loss is lethal to Drosophila, but can be fully substituted by overexpression of the related SNAP-24.[10]
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles.[§ 1]
- ^ The interactive pathway map can be edited at WikiPathways: "NicotineDopaminergic_WP1602".
Interactions
SNAP-25 has been shown to
- CPLX1,[44][45]
- ITSN1,[46]
- KIF5B,[47]
- SNAPAP[48] and
- STX11,[49][50]
- STX1A,[44][48][49][51][52][53][54][55][56][57][58]
- STX2,[51][52]
- STX4,[51][52][53][59]
- SYT1,[60][61]
- Syntaxin 3,[51][52][53]
- TRIM9,[57] and
- VAMP2.[44][57][62]
- Synaptotagmin binds SNAP-25 and syntaxins in the presence of Ca2+ (and thus the entire SNARE complex)[10]
References
- ^ a b c GRCh38: Ensembl release 89: ENSG00000132639 – Ensembl, May 2017
- ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000027273 – Ensembl, May 2017
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- ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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Further reading
- Hanson PI, Otto H, Barton N, Jahn R (July 1995). "The N-ethylmaleimide-sensitive fusion protein and alpha-SNAP induce a conformational change in syntaxin". The Journal of Biological Chemistry. 270 (28): 16955–61. PMID 7622514.
- Hata Y, Südhof TC (June 1995). "A novel ubiquitous form of Munc-18 interacts with multiple syntaxins. Use of the yeast two-hybrid system to study interactions between proteins involved in membrane traffic". The Journal of Biological Chemistry. 270 (22): 13022–8. PMID 7768895.
- Chapman ER, An S, Barton N, Jahn R (November 1994). "SNAP-25, a t-SNARE which binds to both syntaxin and synaptobrevin via domains that may form coiled coils". The Journal of Biological Chemistry. 269 (44): 27427–32. PMID 7961655.
- Zhao N, Hashida H, Takahashi N, Sakaki Y (August 1994). "Cloning and sequence analysis of the human SNAP25 cDNA". Gene. 145 (2): 313–4. PMID 8056350.
- Bark IC, Wilson MC (February 1994). "Human cDNA clones encoding two different isoforms of the nerve terminal protein SNAP-25". Gene. 139 (2): 291–2. PMID 8112622.
- Maruyama K, Sugano S (January 1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. PMID 8125298.
- Maglott DR, Feldblyum TV, Durkin AS, Nierman WC (May 1996). "Radiation hybrid mapping of SNAP, PCSK2, and THBD (human chromosome 20p)". Mammalian Genome. 7 (5): 400–1. S2CID 34951074.
- Ravichandran V, Chawla A, Roche PA (June 1996). "Identification of a novel syntaxin- and synaptobrevin/VAMP-binding protein, SNAP-23, expressed in non-neuronal tissues". The Journal of Biological Chemistry. 271 (23): 13300–3. PMID 8663154.
- Rettig J, Sheng ZH, Kim DK, Hodson CD, Snutch TP, Catterall WA (July 1996). "Isoform-specific interaction of the alpha1A subunits of brain Ca2+ channels with the presynaptic proteins syntaxin and SNAP-25". Proceedings of the National Academy of Sciences of the United States of America. 93 (14): 7363–8. PMID 8692999.
- Jagadish MN, Fernandez CS, Hewish DR, Macaulay SL, Gough KH, Grusovin J, et al. (August 1996). "Insulin-responsive tissues contain the core complex protein SNAP-25 (synaptosomal-associated protein 25) A and B isoforms in addition to syntaxin 4 and synaptobrevins 1 and 2". The Biochemical Journal. 317 ( Pt 3) (3): 945–54. PMID 8760387.
- Betz A, Okamoto M, Benseler F, Brose N (January 1997). "Direct interaction of the rat unc-13 homologue Munc13-1 with the N terminus of syntaxin". The Journal of Biological Chemistry. 272 (4): 2520–6. PMID 8999968.
- Araki S, Tamori Y, Kawanishi M, Shinoda H, Masugi J, Mori H, et al. (May 1997). "Inhibition of the binding of SNAP-23 to syntaxin 4 by Munc18c". Biochemical and Biophysical Research Communications. 234 (1): 257–62. PMID 9168999.
- Lane SR, Liu Y (November 1997). "Characterization of the palmitoylation domain of SNAP-25". Journal of Neurochemistry. 69 (5): 1864–9. S2CID 6343703.
- Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S (October 1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. PMID 9373149.
- Okamoto M, Südhof TC (December 1997). "Mints, Munc18-interacting proteins in synaptic vesicle exocytosis". The Journal of Biological Chemistry. 272 (50): 31459–64. PMID 9395480.
- Low SH, Roche PA, Anderson HA, van Ijzendoorn SC, Zhang M, PMID 9452464.
- Poirier MA, Hao JC, Malkus PN, Chan C, Moore MF, King DS, Bennett MK (May 1998). "Protease resistance of syntaxin.SNAP-25.VAMP complexes. Implications for assembly and structure". The Journal of Biological Chemistry. 273 (18): 11370–7. PMID 9556632.
- Prekeris R, Klumperman J, Chen YA, Scheller RH (November 1998). "Syntaxin 13 mediates cycling of plasma membrane proteins via tubulovesicular recycling endosomes". The Journal of Cell Biology. 143 (4): 957–71. PMID 9817754.
- Gonelle-Gispert C, Halban PA, Niemann H, Palmer M, Catsicas S, Sadoul K (April 1999). "SNAP-25a and -25b isoforms are both expressed in insulin-secreting cells and can function in insulin secretion". The Biochemical Journal. 339 ( Pt 1) (1): 159–65. PMID 10085240.
- Ilardi JM, Mochida S, Sheng ZH (February 1999). "Snapin: a SNARE-associated protein implicated in synaptic transmission". Nature Neuroscience. 2 (2): 119–24. S2CID 25524692.
External links
- SNAP25+Protein at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
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