Identification of an organelle receptor for myosin-Va.
Little is known about how molecular motors bind to their vesicular cargo. Here we show that myosin-Va, an actin-based vesicle motor, binds to one of its cargoes, the melanosome, by interacting with a receptor-protein complex containing Rab27a and melanophilin, a postulated Rab27a effector. Rab27a binds to the melanosome first and then recruits melanophilin, which in turn recruits myosin-Va. Melanophilin creates this link by binding to Rab27a in a GTP-dependent fashion through its amino terminus, and to myosin-Va through its carboxy terminus. Moreover, this latter interaction, similar to the ability of myosin-Va to colocalize with melanosomes and influence their distribution in vivo, is absolutely dependent on the presence of exon-F, an alternatively spliced exon in the myosin-Va tail. These results provide the first molecular description of an organelle receptor for an actin-based motor, illustrate how alternate exon usage can be used to specify cargo, and further expand the functional repertoire of Rab GTPases and their effectors.
Wu
Xufeng S
XS
Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Rao
Kang
K
Zhang
Hong
H
Wang
Fei
F
Sellers
James R
JR
Matesic
Lydia E
LE
Copeland
Neal G
NG
Jenkins
Nancy A
NA
Hammer
John A
JA
D048868:Adaptor Proteins, Signal Transducing; D017398:Alternative Splicing; D000818:Animals; D000831:Animals, Newborn; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002478:Cells, Cultured; D005091:Exons; D049452:Green Fluorescent Proteins; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D008544:Melanocytes / Q000378:metabolism; D020460:Melanosomes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D024701:Myosin Type V / Q000737:chemistry* / Q000378:metabolism*; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D014162:Transfection; D020798:Two-Hybrid System Techniques; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins; D020826:rab3A GTP-Binding Protein / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D008164:Luminescent Proteins; C435724:Mlph protein, mouse; D020033:Protein Isoforms; D000075745:rab27 GTP-Binding Proteins; D049452:Green Fluorescent Proteins; D024701:Myosin Type V; C512962:Rab27a protein, mouse; D020691:rab GTP-Binding Proteins; D020826:rab3A GTP-Binding Protein