title: Rab27A-binding protein Slp2-a is required for peripheral melanosome distribution and elongated cell shape in melanocytes.
abstract: The synaptotagmin-like protein (Slp) family is implicated in regulating Rab27A-mediated membrane transport, but how it might do this is unknown. Here we report that Slp2-a, a previously uncharacterized Rab27A-binding protein in melanocytes, controls melanosome distribution in the cell periphery and regulates the morphology of melanocytes. Slp2-a is the most abundantly expressed of the Slp- and Slac2-family proteins in melanocytes and colocalizes with Rab27A on melanosomes. Knockdown of endogenous Slp2-a protein by small-interfering RNAs (siRNAs) markedly reduced the number of melanosomes in the cell periphery of mouse melanocytes ('peripheral dilution'). Expression of siRNA-resistant Slp2-a (Slp2-a(SR)) rescued the peripheral dilution of melanosomes induced by Slp2-a siRNAs, but Slp2-a(SR) mutants, which failed to interact with either phospholipids or Rab27A, did not. Loss of Slp2-a protein also induced a change in melanocyte morphology, from their normal elongated shape to a more rounded shape, which depended on the phospholipid-binding activity of Slp2-a, but not on its Rab27A-binding activity. By contrast, knockdown of Slac2-a (also called melanophilin), another Rab27A-binding protein in melanocytes, caused perinuclear aggregation of melanosomes alone without altering cell shape. These results reveal the differential and sequential roles of Rab27A-binding proteins in melanosome transport in melanocytes.
authors.affiliation: Fukuda Initiative Research Unit, RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Taruho S
authors.initials: TS
authors.lastname: Kuroda
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002451:Cell Compartmentation / Q000235:genetics; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000378:metabolism; D048430:Cell Shape / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics; D008544:Melanocytes / Q000166:cytology / Q000378:metabolism*; D020460:Melanosomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D008565:Membrane Proteins; C435724:Mlph protein, mouse; D010743:Phospholipids; D011993:Recombinant Fusion Proteins; C424134:Sytl2 protein, mouse; D000075745:rab27 GTP-Binding Proteins; C512962:Rab27a protein, mouse; D020691:rab GTP-Binding Proteins