A cytoskeletal demolition worker: myosin II acts as an actin depolymerization agent.
Myosin II motors play several important roles in a variety of cellular processes, some of which involve active assembly/disassembly of cytoskeletal substructures. Myosin II motors have been shown to function in actin bundle turnover in neuronal growth cones and in the recycling of actin filaments during cytokinesis. Close examination had shown an intimate relationship between myosin II motor adenosine triphosphatase activity and actin turnover rate. However, the direct implication of myosin II in actin turnover is still not understood. Herein, we show, using high-resolution cryo-transmission electron microscopy, that myosin II motors control the turnover of actin bundles in a concentration-dependent manner in vitro. We demonstrate that disassembly of actin bundles occurs through two main stages: the first stage involves unbundling into individual filaments, and the second involves their subsequent depolymerization. These evidence suggest that, in addition to their "classical" contractile abilities, myosin II motors may be directly implicated in active actin depolymerization. We believe that myosin II motors may function similarly in vivo (e.g., in the disassembly of the contractile ring by fine tuning the local concentration/activity of myosin II motors).
Haviv
Lior
L
Department of Chemical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel.
Gillo
David
D
Backouche
Frederic
F
Bernheim-Groswasser
Anne
A
D008841:Actin Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D051339:Actin Depolymerizing Factors / Q000502:physiology*; D000199:Actins / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D003599:Cytoskeleton / Q000502:physiology*; D005033:Ethylmaleimide / Q000494:pharmacology; D005456:Fluorescent Dyes; D005982:Glutathione Transferase / Q000378:metabolism; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000502:physiology / Q000648:ultrastructure; D024462:Myosin Type II / Q000502:physiology* / Q000648:ultrastructure; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D051339:Actin Depolymerizing Factors; D000199:Actins; D002352:Carrier Proteins; D005456:Fluorescent Dyes; D006576:Heterocyclic Compounds, 4 or More Rings; D008840:Microfilament Proteins; D020409:Molecular Motor Proteins; D011993:Recombinant Fusion Proteins; C020324:fascin; C472645:blebbistatin; D005982:Glutathione Transferase; D000251:Adenosine Triphosphatases; D024462:Myosin Type II; D005033:Ethylmaleimide