Melanophilin and myosin Va track the microtubule plus end on EB1.
In mouse melanocytes, myosin Va is recruited onto the surface of melanosomes by a receptor complex containing Rab27a that is present in the melanosome membrane and melanophilin (Mlp), which links myosin Va to Rab27a. In this study, we show that Mlp is also a microtubule plus end-tracking protein or +TIP. Moreover, myosin Va tracks the plus end in a Mlp-dependent manner. Data showing that overexpression and short inhibitory RNA knockdown of the +TIP EB1 have opposite effects on Mlp-microtubule interaction, that Mlp interacts directly with EB1, and that deletion from Mlp of a region similar to one in the adenomatous polyposis coli protein involved in EB1 binding blocks Mlp's ability to plus end track argue that Mlp tracks the plus end indirectly [corrected] by hitchhiking on EB1. These results identify a novel +TIP and indicate that vertebrate cells possess a +TIP complex that is similar to the Myo2p-Kar9p-Bim1p complex in yeast. We suggest that the +TIP complex identified in this study may serve to focus the transfer of melanosomes from microtubules to actin at the microtubule plus end.
Wu
Xufeng S
XS
Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Tsan
Grace L
GL
Hammer
John A
JA
D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002522:Chlorocebus aethiops; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances / Q000378:metabolism; D008544:Melanocytes / Q000378:metabolism; D020460:Melanosomes / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D024701:Myosin Type V / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D000075745:rab27 GTP-Binding Proteins
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C405804:EB1 microtubule binding proteins; C492410:MLPH protein, human; D046911:Macromolecular Substances; D008869:Microtubule-Associated Proteins; C435724:Mlph protein, mouse; C492409:Mlph protein, rat; D034741:RNA, Small Interfering; D000075745:rab27 GTP-Binding Proteins; D049452:Green Fluorescent Proteins; D024701:Myosin Type V; C066694:RAB27A protein, human; C512962:Rab27a protein, mouse; C512961:Rab27a protein, rat; D020691:rab GTP-Binding Proteins