Purification of the CIC-0 chloride channel from Torpedo california electroplax identification of a phosphorylation site for cAMP-dependent protein kinase

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

Chloride currents (I(Cl)) were investigated with the two-electrode voltage-clamp technique in enzymatically isolated fibers from interosseus muscles of wild-type (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 approximately 50% I(Cl) compared to control fibers. Addition of 3.3 microM 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.