title: Regulation of melanosome movement in the cell cycle by reversible association with myosin V.
abstract: Previously, we have shown that melanosomes of Xenopus laevis melanophores are transported along both microtubules and actin filaments in a coordinated manner, and that myosin V is bound to purified melanosomes (Rogers, S., and 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 melanosome transport. To examine whether myosin V was regulated in a cell cycle-dependent manner, purified melanosomes were treated with interphase- or metaphase-arrested Xenopus egg extracts and assayed for in vitro motility along Nitella actin filaments. Motility of organelles treated with mitotic extract was found to decrease dramatically, as compared with untreated or interphase extract-treated melanosomes. This mitotic inhibition of motility correlated 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 extracts. 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.
authors.affiliation: Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Rogers
authors.forename: R L
authors.initials: RL
authors.lastname: Karcher
authors.forename: J T
authors.initials: JT
authors.lastname: Roland
authors.forename: A A
authors.initials: AA
authors.lastname: Minin
authors.forename: W
authors.initials: W
authors.lastname: Steffen
authors.forename: V I
authors.initials: VI
authors.lastname: Gelfand
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000199:Actins / Q000037:antagonists & inhibitors / Q000378:metabolism; D020418:Algal Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D000460:Chlorophyta; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism; D008543:Melanins / Q000378:metabolism; D020460:Melanosomes / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D024701:Myosin Type V; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017384:Sequence Deletion; D014162:Transfection; D014982:Xenopus laevis
chemical_list: D000199:Actins; D020418:Algal Proteins; D002148:Calmodulin-Binding Proteins; D008543:Melanins; D020409:Molecular Motor Proteins; D009419:Nerve Tissue Proteins; C078829:chicken brain myosin-V p190; D024701:Myosin Type V