Sl. Rogers et al., Regulation of melanosome movement in the cell cycle by reversible association with myosin V, J CELL BIOL, 146(6), 1999, pp. 1265-1275
Previously, we have shown that melanosomes of Xenopus laevis melanophores a
re transported along both microtubules and actin filaments in a coordinated
manner, and that myosin V is bound to purified melanosomes (Rogers, S., an
d V.I. Gelfand, 1998. Curr. Biol, 8:161-164), In the present study, we have
demonstrated that myosin V is the actin-based motor responsible for melano
some transport. To examine whether myosin V was regulated in a cell cycle-d
ependent manner, purified melanosomes were treated with interphase- or meta
phase-arrested Xenopus egg extracts and assayed for in vitro motility along
Nitella actin filaments. Motility of organelles treated with mitotic extra
ct was found to decrease dramatically, as compared with untreated interphas
e extract-treated melanosomes, This mitotic inhibition of motility correlat
ed with the dissociation of myosin V from melanosomes, but the activity of
soluble motor remained unaffected, Furthermore, we find that myosin V heavy
chain is highly phosphorylated in metaphase extracts versus interphase ext
racts. We conclude that organelle transport by myosin V is controlled by a
cell cycle-regulated association of this motor to organelles, and that this
binding is likely regulated by phosphorylation of myosin V during mitosis.