title: Interactions and regulation of molecular motors in Xenopus melanophores.
abstract: Many cellular components are transported using a combination of the actin- and microtubule-based transport systems. However, how these two systems work together to allow well-regulated transport is not clearly understood. We investigate this question in the Xenopus melanophore model system, where three motors, kinesin II, cytoplasmic dynein, and myosin V, drive aggregation or dispersion of pigment organelles called melanosomes. During dispersion, myosin V functions as a "molecular ratchet" to increase outward transport by selectively terminating dynein-driven minus end runs. We show that there is a continual tug-of-war between the actin and microtubule transport systems, but the microtubule motors kinesin II and dynein are likely coordinated. Finally, we find that the transition from dispersion to aggregation increases dynein-mediated motion, decreases myosin V--mediated motion, and does not change kinesin II--dependent motion. Down-regulation of myosin V contributes to aggregation by impairing its ability to effectively compete with movement along microtubules.
authors.affiliation: Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Gross
authors.forename: M Carolina
authors.initials: MC
authors.lastname: Tuma
authors.forename: Sean W
authors.initials: SW
authors.lastname: Deacon
authors.forename: Anna S
authors.initials: AS
authors.lastname: Serpinskaya
authors.forename: Amy R
authors.initials: AR
authors.lastname: Reilein
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Gelfand
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002461:Cell Line, Transformed; D004398:Dyneins / Q000378:metabolism; D016547:Kinesins; D008547:Melanophores / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D020409:Molecular Motor Proteins / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D024701:Myosin Type V / Q000378:metabolism; D010670:Phenylthiourea / Q000494:pharmacology; D010860:Pigments, Biological / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology*; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; D020409:Molecular Motor Proteins; D009124:Muscle Proteins; D010860:Pigments, Biological; C499376:XKLP3 protein, Xenopus; D029867:Xenopus Proteins; C074152:kinesin-II; D010670:Phenylthiourea; D014442:Monophenol Monooxygenase; D024701:Myosin Type V; D004398:Dyneins; D016547:Kinesins