Role of phosphorylation and physiological state in the regulation of the muscular chloride channel CIC-1: A voltage-clamp study on isolated M-interosseus fibers

Chen MF, Jockusch H. Role of phosphorylation and physiological state in the regulation of the muscular chloride channel CIC-1: A voltage-clamp study on isolated M-interosseus fibers. Biochemical and biophysical research communications. 1999;261(2):528-533.Chloride currents (I-Cl) were investigated with the two-electrode voltage-clamp technique in enzymatically isolated fibers from interosseus muscles of wildtype (WT), denervated WT, and myotonic (ADR, ClC-1-deficient) mice. Characteristics of I-Cl were consistent with previous observations on rat muscle fibers and cultured nonmuscle cells transfected with hClC-1 cDNA. In the presence of 0.1 mM anthracene-9-carboxylic acid and in ADR fibers, I-Cl was reduced by > 90%. WT interosseus fibers denervated 6-7 days prior to isolation showed similar to 50% I-Cl compared to control fibers. Addition of 3.3 mu M staurosporine, a nonspecific inhibitor of protein kinases, increased I-Cl. in WT interosseus fibers by a factor of approximately two and altered its kinetic characteristics, We conclude that in dissociated fibers cultured for 1-2 days, in contrast to freshly isolated muscles, chloride conductance is downregulated by a mechanism involving protein phosphorylation. In situ this short-term regulation may complement transcriptional long-term regulation Of ClC-1. (C) 1999 Academic Press