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  • Title: Deactivation of CFTR-Cl conductance by endogenous phosphatases in the native sweat duct.
    Author: Reddy MM, Quinton PM.
    Journal: Am J Physiol; 1996 Feb; 270(2 Pt 1):C474-80. PubMed ID: 8779909.
    Abstract:
    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.
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