Reddy M M, Quinton P M
Division of Biomedical Sciences, University of California, Riverside 92521, USA.
Am J Physiol. 1996 Feb;270(2 Pt 1):C474-80. doi: 10.1152/ajpcell.1996.270.2.C474.
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.
囊性纤维化跨膜传导调节因子（CFTR）是一种磷酸化激活的氯离子通道。然而，关于体内CFTR氯离子传导（CFTR-GCl）失活的内源性机制，人们了解甚少。我们研究了内源性磷酸酶对微灌注的基底外侧通透的天然汗腺导管顶端膜中腺苷3',5'-环磷酸（cAMP）和ATP诱导的CFTR-GCl的调节作用。通过测量顶端氯离子扩散电位和GCl来监测CFTR-GCl的激活，去除cAMP后其会自发失活。磷酸酶抑制剂（氟化物、钒酸盐和冈田酸）混合物可防止CFTR-GCl活性的这种自发丧失。我们研究了这些磷酸酶拮抗剂各自对cAMP洗脱后CFTR-GCl失活速率的影响。与钒酸盐或氟化物不同，冈田酸实际上可防止cAMP洗脱后CFTR-GCl的失活。我们得出结论，蛋白磷酸酶1和2A中的一种或两种负责体内CFTR-GCl的去磷酸化失活。
