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The adaptor protein melanophilin regulates dynamic myosin- Va: cargo interaction and dendrite development in melanocytes

Robinson, Christopher L.; Evans, Richard D.; Sivarasa, Kajana; Ramalho, Jose S.; Briggs, Deborah A.; Hume, Alistair N.

The adaptor protein melanophilin regulates dynamic myosin- Va: cargo interaction and dendrite development in melanocytes Thumbnail


Christopher L. Robinson

Richard D. Evans

Kajana Sivarasa

Jose S. Ramalho

Deborah A. Briggs


Regulation of organelle transport by the cytoskeleton is fundamental for eukaryotic survival. Cytoskeleton motors are typically modular proteins with conserved motor and diverse cargo binding domains. Motor:cargo interactions are often indirect and mediated by adaptor proteins e.g. Rab GTPases. Rab27a, via effector melanophilin (Mlph), recruits myosin-Va to melanosomes and thereby disperses them into melanocytes dendrites. To better understand how adaptors regulate motor:cargo interaction we used single melanosome fluorescence recovery after photo-bleaching (smFRAP) to characterise the association kinetics between myosin-Va, its adaptors and melanosomes. We found that myosin-Va and Mlph rapidly recovered after photo-bleaching, while Rab27a did not, indicating that myosin-Va and Mlph dynamically associate with melanosomes and Rab27a does not. This suggests that dynamic Rab27a:effector interaction rather than Rab27a melanosome:cytosol cycling regulates myosin-Va:melanosome association. Accordingly a Mlph-Rab27a fusion protein reduced myosin-Va smFRAP, indicating that it stabilised melanosomal myosin-Va. Finally, we tested the functional importance of dynamic myosin-Va:melanosome interaction. We found that while a myosin-Va-Rab27a fusion protein dispersed melanosomes in myosin-Va deficient cells, dendrites were significantly less elongated than in wild-type cells. Given that dendrites are the prime sites of melanosome transfer from melanocytes to keratinocytes we suggest that dynamic myosin-Va:melanosome interaction is important for pigmentation in vivo.

Journal Article Type Article
Acceptance Date Jan 25, 2019
Online Publication Date Feb 14, 2019
Publication Date Mar 15, 2019
Deposit Date Mar 4, 2019
Publicly Available Date Apr 15, 2019
Journal Molecular Biology of the Cell
Electronic ISSN 1939-4586
Publisher American Society for Cell Biology
Peer Reviewed Peer Reviewed
Volume 30
Issue 6
Pages 731-809
Keywords Organelle transport; Myosin-Va; Melanosome; Rab27a; Melanophilin; Fluorescence recovery after photo-bleaching
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