title: Regulation of myosin II dynamics by phosphorylation and dephosphorylation of its light chain in epithelial cells.
abstract: Nonmuscle myosin II, an actin-based motor protein, plays an essential role in actin cytoskeleton organization and cellular motility. Although phosphorylation of its regulatory light chain (MRLC) is known to be involved in myosin II filament assembly and motor activity in vitro, it remains unclear exactly how MRLC phosphorylation regulates myosin II dynamics in vivo. We established clones of Madin Darby canine kidney II epithelial cells expressing MRLC-enhanced green fluorescent protein or its mutants. Time-lapse imaging revealed that both phosphorylation and dephosphorylation are required for proper dynamics of myosin II. Inhibitors affecting myosin phosphorylation and MRLC mutants indicated that monophosphorylation of MRLC is required and sufficient for maintenance of stress fibers. Diphosphorylated MRLC stabilized myosin II filaments and was distributed locally in regions of stress fibers where contraction occurs, suggesting that diphosphorylation is involved in the spatial regulation of myosin II assembly and contraction. We further found that myosin phosphatase or Zipper-interacting protein kinase localizes to stress fibers depending on the activity of myosin II ATPase.
authors.affiliation: RIKEN, Center for Developmental Biology, Kobe 650-0047, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Watanabe
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoya
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Yonemura
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis / Q000378:metabolism; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002478:Cells, Cultured; D064550:Death-Associated Protein Kinases; D004285:Dogs; D004847:Epithelial Cells / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D009154:Mutation; D018994:Myosin Light Chains / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D024462:Myosin Type II / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D043263:Myosin-Light-Chain Phosphatase / Q000032:analysis / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000378:metabolism; D022502:Stress Fibers / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D051017:Apoptosis Regulatory Proteins; D018994:Myosin Light Chains; D064550:Death-Associated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D043263:Myosin-Light-Chain Phosphatase; D000251:Adenosine Triphosphatases; D024462:Myosin Type II