‘Should I stay or should I go?’: myosin V function in organelle trafficking

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Abstract
Actin‐ and microtubule‐based motors can propel different cargos along filaments. Within cells, they control the distribution of membrane‐bound compartments by performing complementary tasks. Organelles make long journeys along microtubules, with class V myosins ensuring their capture and their dispersal in actin‐rich regions. Myosin Va is recruited on to diverse organelles, such as melanosomes and secretory vesicles, by a mechanism involving Rab GTPases. The role of myosin Va in the recruitment of secretory vesicles at the plasma membrane reveals that the cortical actin network cannot merely be seen as a physical barrier hindering vesicle access to release sites. In neurons, myosin Va controls the targeting of IP3 (inositol 1,4,5‐trisphosphate)‐sensitive Ca2+ stores to dendritic spines and the transport of mRNAs. These defects probably account for the severe neurological symptoms observed in Griscelli syndrome due to mutations in the MYO5A gene.