title: Myosin-Va proteolysis by Ca2+/calpain in depolarized nerve endings from rat brain.
abstract: Myosin-Va is a molecular motor that may participate in synaptic vesicle cycling. Calpain cleaves myosin-Va in vitro at methionine 1141 in the tail domain. We show that intracellular proteolysis of myosin-Va occurs in rat cortical synaptosomes depolarized in the presence of calcium, evidenced by the formation of an 80 k polypeptide that co-migrates in SDS-PAGE with the 80 k fragment produced by the in vitro proteolysis of myosin-Va by calpain. Anti-myosin-Va antibody recognized this polypeptide in Western blots and immunoprecipitated it from synaptosome extracts. Calpastatin, a calpain-specific inhibitor, or leupeptin, a general cysteine protease inhibitor, suppressed or blocked formation of the 80 k polypeptide depending on membrane permeability. We conclude that myosin-Va undergoes intracellular proteolysis by endogenous calpain, when synaptosomes are depolarized in the presence of calcium, at the same cleavage site previously identified in vitro, thus, making it a target for calcium signaling during synaptic activation.
authors.affiliation: Department of Cellular and Molecular Biology, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, 14049-900 Ribeirão Preto, SP, Brazil.
authors.forename: Luciana
authors.initials: L
authors.lastname: Casaletti
authors.forename: Sinji B F
authors.initials: SB
authors.lastname: Tauhata
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Moreira
authors.forename: Roy E
authors.initials: RE
authors.lastname: Larson
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D008854:Microscopy, Electron; D018995:Myosin Heavy Chains / Q000378:metabolism*; D024701:Myosin Type V / Q000378:metabolism*; D009411:Nerve Endings / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats
chemical_list: C513081:Myo5a protein, rat; D002154:Calpain; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D002118:Calcium