title: Membrane-bound myo1c powers asymmetric motility of actin filaments.
abstract: Class I myosins are molecular motors that link cellular membranes to the actin cytoskeleton and play roles in membrane tension generation, membrane dynamics, and mechanosignal transduction. The widely expressed myosin-Ic (myo1c) isoform binds tightly to phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] via a pleckstrin homology domain located in the myo1c tail, which is important for its proper cellular localization. In this study, we found that myo1c can power actin motility on fluid membranes composed of physiological concentrations of PtdIns(4,5)P(2) and that this motility is inhibited by high concentrations of anionic phospholipids. Strikingly, this motility occurs along curved paths in a counterclockwise direction (i.e., the actin filaments turn in leftward circles). A biotinylated myo1c construct containing only the motor domain and the lever arm anchored via streptavidin on a membrane containing biotinylated lipid can also generate asymmetric motility, suggesting that the tail domain is not required for the counterclockwise turning. We found that the ability to produce counterclockwise motility is not a universal characteristic of myosin-I motors, as membrane-bound myosin-Ia (myo1a) and myosin-Ib (myo1b) are able to power actin gliding, but the actin gliding has no substantial turning bias. This work reveals a possible mechanism for establishing asymmetry in relationship to the plasma membrane.
authors.affiliation: The Pennsylvania Muscle Institute and Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA.
authors.forename: Serapion
authors.initials: S
authors.lastname: Pyrpassopoulos
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Feeser
authors.forename: Jessica N
authors.initials: JN
authors.lastname: Mazerik
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Tyska
authors.forename: E Michael
authors.initials: EM
authors.lastname: Ostap
mesh_terms: D048248:Acanthamoeba castellanii; D008841:Actin Cytoskeleton / Q000502:physiology*; D001798:Blood Proteins; D002462:Cell Membrane / Q000378:metabolism; D042002:Chromatin Assembly and Disassembly; D008051:Lipid Bilayers / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000378:metabolism; D009068:Movement; D024461:Myosin Type I / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D010750:Phosphoproteins
chemical_list: D001798:Blood Proteins; D008051:Lipid Bilayers; D020409:Molecular Motor Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D010750:Phosphoproteins; C039077:platelet protein P47; D024461:Myosin Type I