Regulation of single Cl- channel conductance by insulin and tyrosine phosphatase.
The apical membrane of distal nephron epithelium (A6) had a Ca(2+)-activated outwardly rectifying Cl- channel with single-channel conductances of 3 pS for outward current and 0.8 pS for inward current. The single-channel conductance for inward current was dependent on cytosolic Ca2+ concentration. Insulin increased the single-channel conductance for the inward current by increasing Ca2+ sensitivity about 300-fold. The insulin action was diminished by vanadyl hydroperoxide (vanadate, an inhibitor of protein tyrosine phosphatase (PTP)). Application of protein tyrosine kinase, p60c-src, reversibly diminished the insulin-induced increase in single-channel conductance. Further, the application of PTP to the cytosolic surface of the inside-out patch membrane, like insulin, increased single-channel conductance. PTP-mediated dephosphorylation of the phospho-tyrosine of the channel protein, as a mechanism of intracellular signaling of insulin action, is a novel mechanism for regulating single-channel conductance by modulating Ca2+ sensitivity.
Shintani
Y
Y
Division of Respiratory Research, Hospital for Sick Children Research Institute, University of Toronto, Ontario, Canada.
Marunaka
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000502:physiology; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009399:Nephrons / Q000502:physiology*; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000494:pharmacology*; D014638:Vanadates / Q000494:pharmacology
D018118:Chloride Channels; D004791:Enzyme Inhibitors; D007328:Insulin; C076715:pervanadate; D014638:Vanadates; D016392:Proto-Oncogene Proteins pp60(c-src); D017027:Protein Tyrosine Phosphatases; D002118:Calcium