A NOVEL SYNAPTOBREVIN VAMP HOMOLOGOUS PROTEIN (VAMP5) IS INCREASED DURING IN-VITRO MYOGENESIS AND PRESENT IN THE PLASMA-MEMBRANE/

cDNA clones encoding a novel protein (VAMP5) homologous to synaptobrev ins/VAMPs are detected during database searches. The predicted 102-ami no acid VAMP5 harbors a 23-residue hydrophobic region near the carboxy l terminus and exhibits an overall amino acid identity of 33% with syn aptobrevin/VAMP1 and 2 and cellubrevin. Northern blot analysis reveals that the mRNA for VAMP5 is preferentially expressed in the skeletal m uscle and heart, whereas significantly lower levels are detected in se veral other tissues but not in the brain. During in vitro differentiat ion (myogenesis) of C2C12 myoblasts into myotubes, the mRNA level for VAMP5 is increased similar to 8- to 10-fold. Immunoblot analysis using antibodies specific for VAMP5 shows that the protein levels are also elevated similar to 6-fold during in vitro myogenesis of C2C12 cells. Indirect immunofluorescence microscopy and immunoelectron microscopy r eveal that VAMP5 is associated with the plasma membrane as well as int racellular perinuclear and peripheral vesicular structures of myotubes . Epitope-tagged versions of VAMP5 are similarly targeted to the plasm a membrane.