Deactivation of CFTR-Cl conductance by endogenous phosphatases in the native sweat duct.
Cystic fibrosis transmembrane conductance regulator (CFTR) is a phosphorylation-activated Cl channel. However, very little is known about the endogenous mechanism(s) of deactivation of CFTR-Cl conductance (CFTR-GCl) in vivo. We studied the action of endogenous phosphatases in regulation of the adenosine 3',5'-cyclic monophosphate (cAMP)- and ATP-induced CFTR-GCl in the apical membrane of microperfused preparations of basolaterally permeabilized native sweat duct. Activation of CFTR-GCl was monitored by measuring the apical Cl diffusion potentials and GCl, which spontaneously deactivated on removal of cAMP. This spontaneous loss of CFTR-GCl activity could be prevented by a cocktail of phosphatase inhibitors (fluoride, vanadate, and okadaic acid). We studied the effects of each of these phosphatase antagonists on the rate of deactivation of CFTR-GCl after cAMP washout. In contrast to vanadate or fluoride, okadaic acid virtually prevented deactivation of CFTR-GCl after cAMP washout. We conclude that either or both protein phosphatases 1 and 2A are responsible for the dephosphorylation deactivation of CFTR-GCl in vivo.
Reddy
M M
MM
Division of Biomedical Sciences, University of California, Riverside 92521, USA.
Quinton
P M
PM
D000328:Adult; D002712:Chlorides / Q000502:physiology*; D000242:Cyclic AMP / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D005459:Fluorides / Q000494:pharmacology; D006801:Humans; D008297:Male; D019319:Okadaic Acid / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D013545:Sweat Glands / Q000187:drug effects / Q000502:physiology*; D014638:Vanadates / Q000494:pharmacology
C505032:CFTR protein, human; D002712:Chlorides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D019319:Okadaic Acid; D014638:Vanadates; D000242:Cyclic AMP; D010744:Phosphoric Monoester Hydrolases; D005459:Fluorides