title: Random walk of processive, quantum dot-labeled myosin Va molecules within the actin cortex of COS-7 cells.
abstract: Myosin Va (myoVa) is an actin-based intracellular cargo transporter. In vitro experiments have established that a single myoVa moves processively along actin tracks, but less is known about how this motor operates within cells. Here we track the movement of a quantum dot (Qdot)-labeled myoVa HMM in COS-7 cells using total internal reflectance fluorescence microscopy. This labeling approach is unique in that it allows myoVa, instead of its cargo, to be tracked. Single-particle analysis showed short periods (</=0.5 s) of ATP-sensitive linear motion. The mean velocity of these trajectories was 604 nm/s and independent of the number of myoVa molecules attached to the Qdot. With high time (16.6 ms) and spatial (15 nm) resolution imaging, Qdot-labeled myoVa moved with sequential 75 nm steps per head, at a rate of 16 s(-1), similarly to myoVa in vitro. Monte Carlo modeling suggests that the random nature of the trajectories represents processive myoVa motors undergoing a random walk through the dense and randomly oriented cortical actin network.
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington, Vermont, USA.
authors.forename: Shane R
authors.initials: SR
authors.lastname: Nelson
authors.forename: M Yusuf
authors.initials: MY
authors.lastname: Ali
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Trybus
authors.forename: David M
authors.initials: DM
authors.lastname: Warshaw
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002417:Cattle; D002522:Chlorocebus aethiops; D003599:Cytoskeleton / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009010:Monte Carlo Method; D009068:Movement; D018995:Myosin Heavy Chains / Q000032:analysis / Q000378:metabolism*; D024701:Myosin Type V / Q000032:analysis / Q000378:metabolism*; D045663:Quantum Dots; D013194:Staining and Labeling
chemical_list: D000199:Actins; C513082:Myo5a protein, mouse; D024701:Myosin Type V; D018995:Myosin Heavy Chains