Activation of the osmo-sensitive chloride conductance involves P21rho and is accompanied by a transient reorganization of the F-actin cytoskeleton.

Abstract

Hypo-osmotic stimulation of human Intestine 407 cells rapidly activated compensatory CL- and K+ conductances that limited excessive cell swelling and, finally, restored the original cell volume. Osmotic cell swelling was accompanied by a rapid and transient reorganization of the F-actin cytoskeleton, affecting both stress fibers as well as apical ruffles. In addition, an increase in total cellular F-actin was observed. Pretreatment of the cells with recombinant Clostridium botulinum C3 exoenzyme, but not with mutant enzyme (C3-E173Q) devoid of ADP-ribosyltransferase activity, greatly reduced the activation of the osmo-sensitive anion efflux, suggesting a role for the ras-related GTPase p21rho. In contrast, introducing dominant negative N17-p21rac into the cells did not affect the volume-sensitive efflux. Cell swelling-induced reorganization of F-actin coincided with a transient, C3 exoenzyme-sensitive tyrosine phosphorylation of p125 focal adhesion kinase (p125FAK) as well as with an increase in phosphatidylinositol-3-kinase (PtdIns-3-kinase) activity. Pretreatment of the cells with wortmannin, a specific inhibitor of PtdIns-3-kinase, largely inhibited the volume-sensitive ion efflux. Taken together, our results indicate the involvement of a p21rho signaling cascade and actin filaments in the activation of volume-sensitive chloride channels.

Role of Rho and Rho kinase in the activation of volume‐regulated anion channels in bovine endothelial cells

“…However, the expression of RhoA in CPAE cells suggests that the observed effects can at least partially be ascribed to this isoform. Tilly et al (1996) proposed p125…”

Role of volume-regulated and calcium-activated anion channels in cell volume homeostasis, cancer and drug resistance

“…23,24 In agreement with this, VRAC is in several cell types demonstrated to be Rho and Rho-kinase regulated. [23][24][25] Activation of VRAC following a modest hypoosmotic challenge is potentiated following cholesterol depletion (Fig. 9D) 26 apparently due to an increased open probability of the channel.…”

Signalling drought in guard cells

“…For example, osmotic swelling would rapidly activate K + and Cl -efflux through voltage-dependent channels in intestine cells that experience frequent changes in their environmental osmolarity. Loss of osmolytes reduces the osmogradient across the cell membrane and prevents further swelling (and bursting) and eventually restores cellular volume (Tilly et al 1996).…”