Disease relevance of Snap25

• The localization of the genetic abnormality in coloboma mice using the Snap gene marker will provide a powerful tool for studying the biologic basis of locomotor hyperactivity [1].
• Mouse model of hyperkinesis implicates SNAP-25 in behavioral regulation [2].
• Cleavage of SNAP-25 and VAMPs by treatment with botulinum toxin A (BoNT A) and tetanus toxin (TeTx), respectively, effectively inhibited amylase secretion stimulated by the physiological agonist CCK-8 [3].
• However, both in dorsal root ganglion neurons and in PC-12 cells we found no differences in the ultrastructure nor in the localization of synaptosomal-associated protein 25 between growth cones with and without toxin treatment [4].
• In E. coli MPT83 was expressed as a 23kDa antigen whereas in the rapid growing mycobacterium Mycobacterium smegmatis the protein was expressed as a 25kDa protein indicating post-translational modification of the protein by M. smegmatis [5].

Psychiatry related information on Snap25

• When a transgene encoding SNAP-25 was bred into the coloboma strain to complement the Snap deletion, the hyperactivity expressed by these mice was rescued, returning these corrected mice to normal levels of locomotor activity [2].

High impact information on Snap25

• Thus, alpha Snap is essential for apical protein localization and cell fate determination in neuroepithelial cells [6].
• To address this question, we examined neuroexocytosis from chromaffin cells of Snap25 null mice rescued by the two splice variants SNAP-25a and SNAP-25b and the ubiquitously expressed homolog SNAP-23 [7].
• The SNARE complex, consisting of synaptobrevin, syntaxin, and SNAP-25, is essential for calcium-triggered exocytosis in neurosecretory cells [7].
• However, this organelle did not contain SV2, another synaptic vesicle protein, nor did it contain presynaptic membrane proteins, such as syntaxin 1A or SNAP-25, or other known anterograde motor proteins, such as kinesin and KIF3 [8].
• The priming step of synaptic vesicle exocytosis is thought to require the formation of the SNARE complex, which comprises the proteins synaptobrevin, SNAP-25 and syntaxin [9].

Chemical compound and disease context of Snap25

• Transgenic rescue of SNAP-25 restores dopamine-modulated synaptic transmission in the coloboma mutant [10].
• The hyperkinesis is ameliorated by low doses of the psychostimulant D-amphetamine and can be rescued genetically by a transgene encoding SNAP-25, located within the Cm deletion [11].
• Cholesterol oxidase [E.C.1.1.3.6 from Brevibacterium sp.] was used to oxidize cholesterol [12].
• Using recombinant DNA methods, a segment of SNAP-25 (aa residues 134-206) spanning the toxin cleavage site was prepared as a fusion protein to the maltose-binding protein in Escherichia coli [13].
• The percentage of chromosomal aberrations reached 23 +/- 0.73, 10.5 +/- 0.64 and 15 +/- 1.4 after treatment with the highest tested dose of profenofos, buprofezin and Super Royal, respectively [14].

Biological context of Snap25

• However, axonal growth and the early topographic arrangement of thalamocortical fiber pathways appear normal in the Snap25 KO, where action potential mediated synaptic vesicle release is disrupted [15].
• Patch-clamp recordings in fetal Snap25-null mutant cortex demonstrated that ablation of SNAP-25 eliminated evoked GABA(A) receptor-mediated postsynaptic responses while leaving a low level of spontaneous AP-independent events intact, supporting the involvement of SNAP-25 in the regulated synaptic transmission of early developing GABAergic neurons [16].
• In hippocampal cell cultures of wild-type mice, punctate staining of SNAP-25 colocalized with both GABAergic and glutamatergic synaptic markers, whereas stimulus-evoked vesicular recycling was abolished at terminals of both transmitter phenotypes in Snap25-/- neurons [16].
• Spontaneous locomotor hyperactivity in a mouse mutant with a deletion including the Snap gene on chromosome 2 [1].
• Analysis of genomic DNA revealed that the Snap gene dosage in Cm/+ mice was 50% lower than control littermates [1].

Anatomical context of Snap25

• The gene encoding the synaptosomal-associated protein--25 kDa (SNAP-25) was mapped by analysis of somatic cell hybrids and an intersubspecies backcross to mouse Chromosome 2 [1].
• These findings suggest that rabphilin is involved in the docking step of regulated exocytosis in PC12 cells, possibly through interaction between the C2B domain and SNAP-25 [17].
• The C2B domain of rabphilin directly interacts with SNAP-25 and regulates the docking step of dense core vesicle exocytosis in PC12 cells [17].
• These results show that Ca2+ modulates dynamic docking of granules to the plasma membrane and that this process is due to a Ca2+-dependent interaction between SNAP-25 and Synaptotagmin 1 [18].
• Our results thus provide evidence that SNAP-25 is critical for evoked GABA release during development and is expressed in the presynaptic terminals of mature GABAergic neurons, consistent with its function as a component of a fundamental core SNARE complex required for stimulus-driven neurotransmission [16].

Associations of Snap25 with chemical compounds

• Members of the SNARE (soluble N -ethylmaleimide-sensitive fusion protein attachment protein receptor) superfamily [syntaxins, VAMPs (vesicle-associated membrane proteins) and SNAP25 (synaptosome-associated protein-25)-related proteins] are required for intracellular membrane-fusion events in eukaryotes [19].
• The predicted amino acid sequence also includes a cluster of four closely spaced cysteine residues, similar to the metal binding domains of some metalloproteins, suggesting that the SNAP-25 polypeptide may have the potential to coordinately bind metal ions [20].
• Removal of cholesterol in the plasma membrane by methyl-beta-cyclodextrin facilitated both redistribution of ECFP-SNAP25 and sequential exocytosis by threefold [21].
• Thus, the relative expression levels of SNAP-25 and SNAP-23 might control the mode (regulated vs. basal) of granule release by forming docking complexes at different Ca(2+) thresholds [22].
• We report that the increased raft association of SNAP-23 occurs due to the substitution of a highly conserved phenylalanine residue present in SNAP-25 with a cysteine residue [23].

Physical interactions of Snap25

• Interestingly, we found that SNARE motif-exposed syntaxin 1A mutants were retained in endoplasmic reticulum (ER) and failed to transport to the cell surface in the absence of SNAP-25, suggesting that the exposure of the SNARE motif causes ER retention and complexation with SNAP-25 helps the ER escape [24].
• Moreover, both alpha1A isoforms form part of the P/Q-channels-SNARE complexes in situ because they are coimmunoprecipitated from solubilized chromaffin cell membranes by a monoclonal SNAP-25 antibody [25].
• Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25 [26].

Co-localisations of Snap25

• However, during the first stages of the cell transdifferentiation process, SNAP-25 migrates alone out to the developing growth cone and what will become the nerve endings and varicosities of the mature neurites; alpha1A follows and colocalizes to SNAP-25 in the now mature processes [25].

Regulatory relationships of Snap25

• Homozygotes do not survive beyond gestation day 6; heterozygotes (Cm/+) have a normal life-span but express reduced levels of SNAP-25 mRNA and protein in the brain [27].
• Endocytosis of SNAP25 is regulated by ADP-ribosylation factor (ARF)6 (through phosphatidylinositol bisphosphate synthesis) and is dependent upon F-actin [28].

Other interactions of Snap25

• Differential control of the releasable vesicle pools by SNAP-25 splice variants and SNAP-23 [7].
• In the docking assay, addition of Ca2+ induces the formation of a SNAP-25-Synaptotagmin 1 complex [18].
• In neurons, assembly of SNARE core complexes comprising the presynaptic membrane-associated SNAREs syntaxin 1 and SNAP25, and the vesicle-associated SNARE VAMP2, is necessary for synaptic vesicle exocytosis [19].
• One such factor, Snapin, has been reported to be a brain-specific protein that interacts with SNAP25, and regulates association of the putative Ca2+-sensor synaptotagmin with the synaptic SNARE complex [Ilardi, Mochida and Sheng (1999) Nat. Neurosci. 2, 119-124] [19].
• Disruption of the gene encoding SNAP-25, a component of the soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor complex required for regulated neuroexocytosis, eliminates evoked but not spontaneous neurotransmitter release (Washbourne et al., 2002) [29].
• From these results, we conclude that progesterone-progesterone receptor-mediated SNAP25 expression in cumulus oocyte complexes and granulosa cells regulates cytokine and chemokine secretion via an exocytosis system [30].

Analytical, diagnostic and therapeutic context of Snap25

• To evaluate the significance of the SNAP25-expressing cells, we used RNA amplification from single cells, followed by RT-PCR [31].
• Consistent with the protein fractionation, light and electron microscopic immunocytochemistry indicated that SNAP-25 is located within the presynaptic terminals of hippocampal mossy fibers and the inner molecular layer of the dentate gyrus [20].
• Immunoblotting analysis with specific antibody to Ser187, a protein kinase C (PKC) phosphorylation site of SNAP-25, revealed that the specific phosphorylation was correspondingly decreased, which was correlated with morphine-induced inhibition of PKC activity [32].
• In the present study, the expression of SNAP-25, a t-SNARE protein essential for vesicle release, was found to be dramatically regulated in hippocampus after chronic morphine treatment, which was visualized with two-dimensional gel electrophoresis [32].
• Next, to determine the function of SNAP-25, we evaluated the change in CG exocytosis with a membrane dye, tetramethylammonium-1,6-diphenyl-1,3,5-hexatriene, after microinjection of a botulinum neurotoxin A (BoNT/A), which selectively cleaves SNAP-25 in MII eggs [33].

References