Protein kinase C activates chloride conductance in C127 cells stably expressing the cystic fibrosis gene

Abstract

The regulatory domain (R domain) of the cystic fibrosis transmembrane conductance regulator (CFTR) is phosphorylated by protein kinase A and protein kinase C (PKC) in vivo (Picciotto, M. R., Cohn, J. A., Bertuzzi, G., Greengard, P., and Nairn, A. C. (1992) J. Biol. Chem. 267, 12742-12752), but so far the functional effect of the PKC-dependent phosphorylation has not been clarified. We investigated the effect of PKC on the CFTR-mediated Cl- transport by treating with phorbol 12-myristate 13-acetate (PMA), the cell line C127i stably expressing CFTR wild type (C127 CFTRw/t), or CFTR bearing the most common mutation deltaF508 (C127 CFTRdF508). We show that PMA activates Cl- efflux in C127 CFTRw/t, but not in C127 CFTRdF508 and C127i. The PMA-dependent activation of CFTR is not mediated by increase of intracellular [cAMP] and is not the result of a primary activation of a K+ conductive pathway. These results strongly suggest that PKC activates directly CFTR-mediated Cl- transport.