title: The mechanical role of VASP in an Arp2/3-complex-based motility assay.
abstract: The comet motility assay, inspired by Listeria locomotion, has been used extensively as an in vitro model to study the structural and motile properties of the actin cytoskeleton. However, there are no quantitative measurements of the mechanical properties of these actin comets. In this work, we use nanoindentation based on atomic force microscopy to measure the elastic modulus of actin comets grown on  1-μm-diameter beads in an Arp2/3 (actin-related proteins 2 and 3)-complex-dependent fashion in the absence and in the presence of VASP (vasodilator-stimulated phosphoprotein). Recruitment of VASP to the bead surface had no effect on the initial velocity or morphology of the comets. Instead, we observed an improved contact of the comets with the beads and an increased elastic modulus of the comets. The VASP-mediated increase in elastic modulus was dependent on both concentration and ionic strength. In conclusion, we propose that VASP plays a mechanical role in Arp2/3-complex-dependent motility by amplifying the elastic modulus of the thus assembled actin network and, consequently, by strengthening its cohesion for persistent protrusion.
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada B3H 3J5.
authors.forename: Sandy
authors.initials: S
authors.lastname: Suei
authors.forename: Rajveer
authors.initials: R
authors.lastname: Seyan
authors.forename: Philippe
authors.initials: P
authors.lastname: Noguera
authors.forename: John
authors.initials: J
authors.lastname: Manzi
authors.forename: Julie
authors.initials: J
authors.lastname: Plastino
authors.forename: Laurent
authors.initials: L
authors.lastname: Kreplak
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051377:Actin-Related Protein 2 / Q000378:metabolism*; D051378:Actin-Related Protein 3 / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology*; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D018482:Muscle, Skeletal / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011817:Rabbits; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein