title: Slac2-a/melanophilin, the missing link between Rab27 and myosin Va: implications of a tripartite protein complex for melanosome transport.
abstract: Myosin Va is a member of the unconventional class V myosin family, and a mutation in the myosin Va gene causes pigment granule transport defects in human Griscelli syndrome and dilute mice. How myosin Va recognizes its cargo (i.e. melanosomes), however, has remained undetermined over the past decade. In this study, we discovered Slac2-a/melanophilin to be the "missing link" between myosin Va and GTP-Rab27A present in the melanosome. Deletion analysis and site-directed mutagenesis showed that the N-terminal Slp (synaptotagmin-like protein) homology domain of Slac2-a specifically binds Rab27A/B isoforms and that the C-terminal half directly binds the globular tail of myosin Va. The tripartite protein complex (Rab27A.Slac2-a.myosin Va) in melanoma cells was further confirmed by immunoprecipitation. The discovery that myosin Va indirectly recognizes its cargo through Slac2-a, a novel Rab27A/B effector, should shed light on molecular recognition of its specific cargo by class V myosin.
authors.affiliation: Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. mnfukuda@brain.riken.go.jp
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
authors.forename: Taruho S
authors.initials: TS
authors.lastname: Kuroda
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D017353:Gene Deletion; D006801:Humans; D020460:Melanosomes / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000378:metabolism*; D024701:Myosin Type V / Q000737:chemistry / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D014162:Transfection; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018076:DNA, Complementary; C492410:MLPH protein, human; C435724:Mlph protein, mouse; C513082:Myo5a protein, mouse; D020033:Protein Isoforms; D000075745:rab27 GTP-Binding Proteins; C077511:MYO5A protein, human; D024701:Myosin Type V; C066694:RAB27A protein, human; C512962:Rab27a protein, mouse; D018995:Myosin Heavy Chains; D020691:rab GTP-Binding Proteins