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.

Abstract

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.

Citation

Robinson, C. L., Evans, R. D., Sivarasa, K., Ramalho, J. S., Briggs, D. A., & Hume, A. N. (2019). The adaptor protein melanophilin regulates dynamic myosin- Va: cargo interaction and dendrite development in melanocytes. Molecular Biology of the Cell, 30(6), 731-809. https://doi.org/10.1091/mbc.E18-04-0237

• 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
• DOI: https://doi.org/10.1091/mbc.E18-04-0237
• Keywords: Organelle transport; Myosin-Va; Melanosome; Rab27a; Melanophilin; Fluorescence recovery after photo-bleaching
• Public URL: https://nottingham-repository.worktribe.com/output/1604198
• Publisher URL: https://www.molbiolcell.org/doi/10.1091/mbc.E18-04-0237
• Contract Date: Mar 5, 2019