These authors contributed equally to this work.
Rab7 and Rab27a control two motor protein activities involved in melanosomal transport
Article first published online: 24 JUL 2006
Pigment Cell Research
Volume 19, Issue 5, pages 412–423, October 2006
How to Cite
Jordens, I., Westbroek, W., Marsman, M., Rocha, N., Mommaas, M., Huizing, M., Lambert, J., Naeyaert, J. M. and Neefjes, J. (2006), Rab7 and Rab27a control two motor protein activities involved in melanosomal transport. Pigment Cell Research, 19: 412–423. doi: 10.1111/j.1600-0749.2006.00329.x
Present address: Ingrid Jordens, Department of Biochemistry, Cellular Biology and Molecular Biology, Northwestern University, Evanston, IL, USA
- Issue published online: 24 JUL 2006
- Article first published online: 24 JUL 2006
- Received 17 February 2006, revised and accepted for publication 1 June 2006
- motor proteins;
- myosin Va;
- Rab7-interacting lysosomal protein;
Melanosomes are lysosome-related organelles that synthesize, store and transport melanin. In epidermal melanocytes, melanosomes mature and are transferred to surrounding keratinocytes, which is essential for skin and coat colour. Mouse coat colour mutants reveal a critical role for the small GTPase Rab27a, which recruits myosin Va through its effector protein melanophilin/Slac2a. Here we have studied how two different Rab GTPases control two motor proteins during subsequent phases in transport of melanosomes. We show that the small GTPase Rab7 mainly associates with early and intermediate stage melanosomes and Rab27a to intermediate and mature melanosomes. Rab27a is found in an active state on mature melanosomes in the tips of the dendrites. The Rab7–Rab7-interacting lysosomal protein–dynein pathway only controls early and intermediate stage melanosomes because the mature melanosomes lack Rab7 and associate with the actin network through Rab27a recruited MyoVa. Thus two Rab proteins regulate two different motor proteins, thereby controlling complementary phases in melanosome biogenesis: Rab7 controls microtubule-mediated transport of early and Rab27a the subsequent actin-dependent transport of mature melanosomes.