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

Abstract

L. Role for stress fiber contraction in surface tension development and stretch-activated channel regulation in C2C12 myoblasts. Am J Physiol Cell Physiol 295: C160 -C172, 2008. First published April 23, 2008 doi:10.1152/ajpcell.00014.2008.-Membrane-cytoskeleton interaction regulates transmembrane currents through stretchactivated 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, Cm) 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, Cm, 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 Cm 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 STRETCH-ACTIVATED CHANNELS (SACs) are voltage-independent nonselective ion channels localized on the plasma membrane, where they play an important role as mechanoreceptors (33). These channels, in fact, are gated by tension developed within the lipid bilayer (25) and transduce the mechanical stimulus into increased cation current and Ca 2ϩ influx, thus converting electrical signals into biochemical events involved in the coordination of numerous cellular processes, ranging from cell volume regulation, membrane potential control, and muscle cell contraction to regulation of gene expression and cell differentiation (8, 9, 28). The analysis of mechanotransduction has been focused on the identification of critical molecules and cellular components, such as integrins, focal adhesions, cadherins, gap junctions, and cytoskeleton, which, modulating cell-cell and cell-matrix interactions, contribute to the mechanosensitivity and promote SAC opening (18). However, there is increasing evidence suggesting that actin cytoskeleton reorganization may also...

Functional interaction between TRPC1 channel and connexin-43 protein: a novel pathway underlying S1P action on skeletal myogenesis

“…depends upon the activation of peculiar channels which belong to the TRPC family, and function as storedependent and mechanosensitive channels [4,13,34,46]. Of interest, these channels have been recently implicated in the regulation of numerous physiological and pathological processes, such as skeletal muscle differentiation and Duchenne muscular dystrophy [4,30,46,47].…”

“…mobilization [6,8,9], actin cytoskeletal remodeling, and mechanosensitive stretch-activated cation channel (SAC) opening [10,11]. The formation of stress fibers by S1P has been associated with plasma membrane stretching and, in turn, with SAC activation in C2C12 myoblasts [12,13]. Several members of the transient receptor potential canonical (TRPC) ion channel family are recognized as promising candidates for SACs in different cell types [14], including sensory neurons [15], vascular smooth muscle [16], endothelial cells [17], and skeletal myoblasts [4].…”

Melatonin affects voltage-dependent calcium and potassium currents in MCF-7 cell line cultured either in growth or differentiation medium

“…Linear leak and capacitive currents were canceled on-line using the P/4 procedure. This procedure also minimized the not-voltage dependent currents such as those flowing through intermediate-conductance Ca 2 þ -activated K þ channels, IKCa (Haren et al, 2010), and stretch activated channels (Formigli et al, 2007;Sbrana et al, 2008).…”

“…However, to elucidate this issue, it must be considered that besides the voltage dependent ion channel activation, many other mechanisms may contribute to the establishment of resting membrane potential, such as stretch activated channels (Aydar et al, 2009;Formigli et al, 2007;Sbrana et al, 2008), ionic pumps (2Na/3 K ATPase and Ca 2 þ pump), 3Na/Ca exchanger (Becchetti 2011) and voltage-independent channels as IKCa and K ATP (Abdul et al, 2003;Blackiston et al, 2009;Haren et al, 2010;Klimatcheva and Wonderlin, 1999), and that the complexity of the scenario requires further investigations.…”

Excitation-contraction coupling and mechano-sensitivity in denervated skeletal muscles

“…Notably, in long-term denervation despite the loss of the sarcomeric machinery denervated muscles maintain some fibers able to activate the altered ECC process and to generate force, albeit in lesser amounts. The reduced values of resting membrane resistance and the depolarized resting membrane potential in denervated fibers suggest a leaky sarcolemma [55] and an increase of intracellular Ca 2+ concentration; this is confirmed by the shift in reversal potential of the L-CaC current Excitation-contraction coupling in denervated muscle …”