title: Out-of-equilibrium dynamics in the cytoskeleton of the living cell.
abstract: We report here measurements of rheological properties of the human airway smooth muscle cell using forced nanoscale motions of Arg-Gly-Asp RGD-coated microbeads tightly bound to the cytoskeleton. With changes of forcing amplitude, the storage modulus showed small but systematic nonlinearities, especially after treatment with a contractile agonist. In a dose-dependent manner, a large oscillatory shear applied from a few seconds up to 400 s caused the cytoskeleton matrix to soften, a behavior comparable to physical rejuvenation observed in certain inert soft materials; the stiffness remained constant for as long as the large oscillatory shear was maintained, but suddenly fell with shear cessation. Stiffness then followed a slow scale-free recovery, a phenomenon comparable to physical aging. However, acetylated low-density lipoprotein acLDL-coated microbeads, which connect mainly to scavenger receptors, did not show similar out-of-equilibrium behaviors. Taken together, these data demonstrate in the cytoskeleton of the living cell behaviors with all the same signatures as that of soft inert condensed systems. This unexpected intersection of condensed matter physics and cytoskeletal biology suggests that trapping, intermittency, and approach to kinetic arrest represent central mesoscale features linking underlying molecular events to integrative cellular functions.
authors.affiliation: Molecular and Integrative Physiological Sciences, Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, Massachusetts 02115, USA.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Lenormand
authors.forename: Predrag
authors.initials: P
authors.lastname: Bursac
authors.forename: James P
authors.initials: JP
authors.lastname: Butler
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Fredberg
mesh_terms: D000465:Algorithms; D001120:Arginine / Q000737:chemistry; D001224:Aspartic Acid / Q000737:chemistry; D001703:Biophysics / Q000379:methods; D003585:Cell Biology; D003599:Cytoskeleton / Q000378:metabolism*; D005998:Glycine / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008280:Magnetics; D009130:Muscle, Smooth / Q000166:cytology*; D009218:Myosins / Q000378:metabolism; D009842:Oligopeptides / Q000737:chemistry; D011312:Pressure; D013314:Stress, Mechanical; D013997:Time Factors; D014132:Trachea / Q000166:cytology*
chemical_list: D009842:Oligopeptides; D001224:Aspartic Acid; C047981:arginyl-glycyl-aspartic acid; D001120:Arginine; D009218:Myosins; D005998:Glycine