Disease relevance of Vamp2

• Similarly, tetanus toxin cleaved VAMP2 in synaptic vesicles [1].
• Cleavage of those proteins by clostridium toxins shows that SNAP-25 (synaptic vesicle associated protein) and syntaxin are involved but not synaptobrevin 2 [2].
• A recombinant adenovirus containing VAMP-2 (synaptobrevin-2) was fused to the green fluorescent protein (GFP) and microinjected into the region of the lumbar motor neurons [3].
• Tremor and zitter, causative mutant genes for epilepsy with spongiform encephalopathy in spontaneously epileptic rat (SER), are tightly linked to synaptobrevin-2 and prion protein genes, respectively [4].

High impact information on Vamp2

• Recently tetanus toxin was shown to proteolytically degrade synaptobrevin II (also named VAMP-2), a synaptic vesicle-specific protein, in vitro and in nerve terminals [5].
• Here we show that one element of this recognition process is the v-SNARE, VAMP-2, because tetanus toxin, which cleaves VAMP-2, inhibited the formation of synaptic vesicles and their coating with AP3 in vitro [6].
• AP3-containing complexes isolated from coated vesicles could be immunoprecipitated by a VAMP-2 antibody [6].
• Using both live cell imaging of endogenous synaptotagmin Ia (sytIa) as well as pHluorin-tagged sytIa and VAMP-2, we show here that synaptic vesicle proteins interchange with a large pool on the cell axonal surface whose concentration is approximately 10-fold lower than that in SVs [7].
• A mutation in the cytoplasmic domain of VAMP2 that inhibits endocytosis abolished its axonal polarization [8].

Chemical compound and disease context of Vamp2

• Here, we show that botulinum toxin type G cleaves rat synaptobrevin 2 between Ala81 and Ala82, a peptide bond that differs from those attacked by tetanus toxin and the botulinal toxins types B, D, and F. Synaptobrevin isoforms carrying a Gly in the P1 position are poor substrates [9].

Biological context of Vamp2

• The 69 amino acids which comprise the hydrophilic core are highly homologous to Torpedo VAMP-1, with only 2 amino acid substitutions in rat VAMP-1 and 6 in rat VAMP-2 [10].
• CONCLUSIONS: VAMP-2 and cellubrevin may play integral roles in exocytosis of the pancreatic and parotid acinar cells, whereas VAMP-1 is restricted to nerves that innervate the acini and may function to modulate exocrine activity [11].
• v- and t-SNARE protein expression in models of insulin resistance: normalization of glycemia by rosiglitazone treatment corrects overexpression of cellubrevin, vesicle-associated membrane protein-2, and syntaxin 4 in skeletal muscle of Zucker diabetic fatty rats [12].
• The predicted amino acid sequence of VAMP-2B differs from VAMP-2 at its carboxy-terminal end [13].
• Thus alternative RNA splicing does not affect VAMP-2 sorting in PC12 cells [13].

Anatomical context of Vamp2

• Furthermore, using chemical cross-linking of rat brain membranes, we identified nSec1 complexes containing syntaxin1A, but not SNAP-25 or VAMP2 [14].
• Synaptophysin I controls the targeting of VAMP2/synaptobrevin II to synaptic vesicles [15].
• In addition, VAMP2 was found to travel in vesicles that constitutively fuse with the plasma membrane [15].
• Whereas VAMP-2 is more highly expressed in the whole brain, VAMP-1 is expressed at a higher level in the spinal cord [10].
• Palmitoylation of synaptobrevin 2 was also confirmed using endogenous synaptobrevin 2 present in PC-12 cells and synaptobrevin 2 expressed with a vacciniavirus system in Cos cells [16].

Associations of Vamp2 with chemical compounds

• [3H]Palmitoylation of synaptobrevin 2 was resistant to chloroform/methanol extraction, but sensitive to reducing agents indicating a covalent fatty acid bond to cysteine residues [16].
• In conclusion, VAMP2, a component of the neuronal SNARE complex, is expressed in vesicles carrying AQP2, suggesting a role in vasopressin-regulated vesicle trafficking of AQP2 water channels [1].
• Restoration of normoglycemia and normoinsulinemia in ZDF rats with rosiglitazone (30 micromol/kg) normalized cellubrevin, VAMP-2, and syntaxin 4 protein to levels approaching those observed in lean control animals [12].
• Chronic blockade of glutamate receptors enhances presynaptic release and downregulates the interaction between synaptophysin-synaptobrevin-vesicle-associated membrane protein 2 [17].
• After subcellular fractionation on continuous sucrose gradients, VAMP-2 and cellubrevin were found to be associated with both types of secretory vesicle [18].

Physical interactions of Vamp2

• Vesicle-associated membrane protein-2 (synaptobrevin-2) forms a complex with synaptophysin [19].
• These components make a soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor complex with VAMP2 and mediate the synaptic vesicle docking/fusion machinery [20].
• In the neuron, the plasma membrane SNAREs syntaxin 1a and SNAP25 bind to VAMP2 found on neurotransmitter-containing vesicles [21].
• Studies to evaluate how the Ca2+sensor protein calmodulin might regulate this process led to the identification of a consensus calmodulin binding motif in the v-SNARE VAMP2 [22].

Co-localisations of Vamp2

• These data demonstrate the functional significance of SNAP-25 as a SNARE protein in the parietal cell and show the dynamic stimulation-associated redistribution of VAMP-2 from H,K-ATPase-rich tubulovesicles to co-localize with SNAP-25 on the apical plasma membrane [23].
• In L6 skeletal myoblasts, which display insulin-dependent traffic of GLUT4, we show that VAP-33 colocalized significantly with VAMP-2 using indirect confocal immunofluorescence and biochemical cosegregation [24].

Other interactions of Vamp2

• Labeling of synaptic vesicles prepared from adult brain with [3H]palmitate revealed synaptobrevin 2 besides synaptotagmin 1 as major palmitoylated proteins [16].
• Furthermore, skeletal muscle and the muscle cell line also expressed cellubrevin, a VAMP-2 homologue of 17 kDa; which is much less abundant in brain cells [25].
• Coexpression of VAMP2 with synaptophysin I (SypI), a major resident of SVs, restored the correct sorting of VAMP2 to SVs [15].
• Large varicosities containing VAMP-2- and Hrs-2 immunocreactivity were seen in salt-loaded animals [26].
• When recombinant taxilin was incubated with the extract from the rat brain crude membrane fraction, recombinant taxilin bound to syntaxin-1s free of at least VAMP2, SNAP-25, and Munc18 [27].

Analytical, diagnostic and therapeutic context of Vamp2

• Immunoblotting revealed specific labeling of VAMP2 (18-kD band) but not VAMP1 in membrane fractions prepared from kidney inner medulla [1].
• VAMP2 immunolabeling colocalized with AQP2 labeling in intracellular vesicles, as determined by immunoelectron microscopy after double immunolabeling of isolated vesicles [1].
• We studied VAMP-2 and -3 expression and localization in isolated perfused TALs by confocal microscopy and found that both of them were located in the subapical space of the TAL [28].
• Immunohistochemical analysis did not reveal any detectable changes in VAMP-1- or VAMP-2-like immunoreactivity in the motoneurone cell soma after axotomy [29].
• Salt-loading (2% NaCl as drinking water), an animal model which increases the expression and secretion of hormones from hypothalamic magnocellular neurons, resulted in significantly increased mRNA levels for VAMP-2 (36%, 28%), munc-18 (74%, 68%) and SNAP-25a (59%, 77%) in the PVN and SON, respectively [26].

References