Myosin light chain phosphorylation-dependent modulation of volume-regulated anion channels in macrovascular endothelium

The Rho/Rho-associated kinsase (ROK) pathway has been shown to modulate vol ume-regulated anion channels (VRAC) in cultured calf pulmonary artery endot helial (CPAE) cells, Since Rho/ROK can increase myosin light chain phosphor ylation, we have now studied the effects of inhibitors of myosin light chai n kinase (MLCK) or myosin light chain phosphatase (MLCP) on VRAC in CPAE, A pplication of ML-9, an MLCK inhibitor, inhibited VRAC, both when applied ex tracellularly or when dialyzed into the cell. a similar inhibitory effect w as obtained by dialyzing the cells with AV25, a specific MLCK inhibitory pe ptide. Conversely, NIPP1(191-210), an MLCP inhibitory peptide, potentiated the activation of VRAC by a 25% hypotonic stimulus. These data indicate tha t activation of VRAC is modulated by MLC phosphorylation, (C) 2000 Federati on of European Biochemical Societies.