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This Article Full Text Full Text (PDF) All Versions of this Article: 295/1/C160    most recent 00014.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Sbrana, F. Articles by Formigli, L. PubMed PubMed Citation Articles by Sbrana, F. Articles by Formigli, L.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Role for stress fiber contraction in surface tension development and stretch-activated channel regulation in C2C12 myoblasts

¹Department of Physics, Centro Studi Dinamiche Complesse, University of Florence, Florence; ²Department of Anatomy, Histology, Forensic Medicine, University of Florence, Florence; ³Department of Biochemical Sciences, University of Florence, Florence; ⁴Department of Physiological Sciences, University of Florence, Florence; and ⁵ISC-CNR, Institute for Complex Systems, Sesto Fiorentino, Florence, Italy

Submitted 11 January 2008 ; accepted in final form 11 May 2008

Membrane-cytoskeleton interaction regulates transmembrane currents through stretch-activated channels (SACs); however, the mechanisms involved have not been tested in living cells. We combined atomic force microscopy, confocal immunofluorescence, and patch-clamp analysis to show that stress fibers (SFs) in C2C12 myoblasts behave as cables that, tensed by myosin II motor, activate SACs by modifying the topography and the viscoelastic (Young's modulus and hysteresis) and electrical passive (membrane capacitance, C_m) properties of the cell surface. Stimulation with sphingosine 1-phosphate to elicit SF formation, the inhibition of Rho-dependent SF formation by Y-27632 and of myosin II-driven SF contraction by blebbistatin, showed that not SF polymerization alone but the generation of tensional forces by SF contraction were involved in the stiffness response of the cell surface. Notably, this event was associated with a significant reduction in the amplitude of the cytoskeleton-mediated corrugations in the cell surface topography, suggesting a contribution of SF contraction to plasma membrane stretching. Moreover, C_m, used as an index of cell surface area, showed a linear inverse relationship with cell stiffness, indicating participation of the actin cytoskeleton in plasma membrane remodeling and the ability of SF formation to cause internalization of plasma membrane patches to reduce C_m and increase membrane tension. SF contraction also increased hysteresis. Together, these data provide the first experimental evidence for a crucial role of SF contraction in SAC activation. The related changes in cell viscosity may prevent SAC from abnormal activation.

actin remodeling; atomic force microscopy, Young's modulus; membrane capacitance; hysteresis