title: The dissipative contribution of myosin II in the cytoskeleton dynamics of myoblasts.
abstract: We have determined the microrheological response of the actin meshwork for individual cells. We applied oscillating forces with an optical tweezer to a micrometric bead specifically bound to the actin meshwork of C2 myoblasts, and measured the amplitude and phase shift of the induced cell deformation. For a non-perturbed single cell, we have shown that the elastic and loss moduli G' and G'' behave as power laws f (alpha) and f (beta) of the frequency f (0.01<f <50 Hz), alpha and beta being in the range 0.15-0.35. This demonstrates that the dissipation mechanisms in a single cell involve a broad and continuous distribution of relaxation times. After adding blebbistatin, an inhibitor of myosin II activity, the exponent of G' decreases to about 0.10, and G'' becomes roughly constant for 0.01<f<10 Hz. The actin meshwork appears less rigid and less dissipative than in the control experiment. This is consistent with an inhibition of ATPase and reduction of the gliding mobility of myosin II on actin filaments. In this frequency range, the actomyosin activity appears as an essential mechanism allowing the cell to adapt to an external mechanical stress.
authors.affiliation: Laboratoire de Biorhéologie et Hydrodynamique Physico-chimique, UMR 7057 associée au CNRS et à l'Université Paris 7, Case courrier 7056-2, place Jussieu, 75251 Paris Cedex 05, France.
authors.forename: Martial
authors.initials: M
authors.lastname: Balland
authors.forename: Alain
authors.initials: A
authors.lastname: Richert
authors.forename: François
authors.initials: F
authors.lastname: Gallet
mesh_terms: D000818:Animals; D002460:Cell Line; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D004548:Elasticity; D004735:Energy Transfer / Q000187:drug effects / Q000502:physiology; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D051379:Mice; D044085:Microfluidics / Q000379:methods*; D008846:Micromanipulation / Q000379:methods*; D032446:Myoblasts / Q000187:drug effects / Q000502:physiology*; D024462:Myosin Type II / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; C472645:blebbistatin; D024462:Myosin Type II