Slac2-c (synaptotagmin-like protein homologue lacking C2 domains-c), a novel linker protein that interacts with Rab27, myosin Va/VIIa, and actin.
Slac2-a (synaptotagmin-like protein (Slp) homologue lacking C2 domains-a)/melanophilin is a melanosome-associated protein that links Rab27A on melanosomes with myosin Va, an actin-based motor protein, and formation of the tripartite protein complex (Rab27A.Slac2-a.myosin Va) has been suggested to regulate melanosome transport (Fukuda, M., Kuroda, T. S., and Mikoshiba, K. (2002) J. Biol. Chem. 277, 12432-12436). Here we report the structure of a novel form of Slac2, named Slac2-c, that is homologous to Slac2-a. Slac2-a and Slac2-c exhibit the same overall structure, consisting of a highly conserved N-terminal Slp homology domain (about 50% identity) and a less conserved C-terminal myosin Va-binding domain (about 20% identity). As with other Slac2 members and the Slp family, the Slp homology domain of Slac2-c was found to interact specifically with the GTP-bound form of Rab27A/B both in vitro and in intact cells, and the C-terminal domain of Slac2-c interacted with myosin Va and myosin VIIa. In addition, we discovered that the most C-terminal conserved region of Slac2-a (amino acids 400-590) and Slac2-c (amino acids 670-856), which is not essential for myosin Va binding, directly binds actin and that expression of these regions in PC12 cells and melanoma cells colocalized with actin filaments at the cell periphery, suggesting a novel role of Slac2-a/c in capture of Rab27-containing organelles in the actin-enriched cell periphery.
Fukuda
Mitsunori
M
Fukuda Initiative Research Unit, RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. mnfukuda@brain.riken.go.jp.
Kuroda
Taruho S
TS
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002135:Calcium-Binding Proteins; D002460:Cell Line; D003001:Cloning, Molecular; D017931:DNA Primers; D004398:Dyneins; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000378:metabolism*; D024701:Myosin Type V / Q000378:metabolism*; D000081412:Myosin VIIa; D009218:Myosins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D016501:Neurites / Q000502:physiology / Q000648:ultrastructure; D016716:PC12 Cells; D010673:Pheochromocytoma; D011817:Rabbits; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D050857:Synaptotagmins; D014162:Transfection; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins
D000199:Actins; D002135:Calcium-Binding Proteins; D017931:DNA Primers; C000631455:MYO7A protein, human; C501262:MYRIP protein, human; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; C513082:Myo5a protein, mouse; C513081:Myo5a protein, rat; C000631456:Myo7a protein, mouse; C000631457:Myo7a protein, rat; D000081412:Myosin VIIa; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D033921:Vesicular Transport Proteins; D000075745:rab27 GTP-Binding Proteins; D050857:Synaptotagmins; D024701:Myosin Type V; C512962:Rab27a protein, mouse; C512961:Rab27a protein, rat; D018995:Myosin Heavy Chains; D009218:Myosins; D004398:Dyneins; D020691:rab GTP-Binding Proteins