title: Recruitment of a myosin heavy chain kinase to actin-rich protrusions in Dictyostelium.
abstract: Nonmuscle myosin II plays fundamental roles in cell body translocation during migration and is typically depleted or absent from actin-based cell protrusions such as lamellipodia, but the mechanisms preventing myosin II assembly in such structures have not been identified [1-3]. In Dictyostelium discoideum, myosin II filament assembly is controlled primarily through myosin heavy chain (MHC) phosphorylation. The phosphorylation of sites in the myosin tail domain by myosin heavy chain kinase A (MHCK A) drives the disassembly of myosin II filaments in vitro and in vivo [4]. To better understand the cellular regulation of MHCK A activity, and thus the regulation of myosin II filament assembly, we studied the in vivo localization of native and green fluorescent protein (GFP)-tagged MHCK A. MHCK A redistributes from the cytosol to the cell cortex in response to stimulation of Dictyostelium cells with chemoattractant in an F-actin-dependent manner. During chemotaxis, random migration, and phagocytic/endocytic events, MHCK A is recruited preferentially to actin-rich leading-edge extensions. Given the ability of MHCK A to disassemble myosin II filaments, this localization may represent a fundamental mechanism for disassembling myosin II filaments and preventing localized filament assembly at sites of actin-based protrusion.
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Steimle
authors.forename: S
authors.initials: S
authors.lastname: Yumura
authors.forename: G P
authors.initials: GP
authors.lastname: Côté
authors.forename: Q G
authors.initials: QG
authors.lastname: Medley
authors.forename: M V
authors.initials: MV
authors.lastname: Polyakov
authors.forename: B
authors.initials: B
authors.lastname: Leppert
authors.forename: T T
authors.initials: TT
authors.lastname: Egelhoff
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology; D004023:Dictyostelium / Q000201:enzymology / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport
chemical_list: D000199:Actins; D000242:Cyclic AMP; D009219:Myosin-Light-Chain Kinase