Protein kinase A (PKA) still activates CFTR chloride channel after mutagenesis of all 10 PKA consensus phosphorylation sites

作者：Xiaowei Chang, J.A. Tabcharani, Yanming Hou, Thomas Jensen, Norbert Kartner, Noa Alon, John W. Hanrahan, J.R. Riordan · 发表于：Journal of Biological Chemistry · 年份：1993 · DOI：10.1016/s0021-9258(18)82125-1 · 被引用次数：295 · 研究领域：Ion channel regulation and function、Pluripotent Stem Cells Research、Cardiomyopathy and Myosin Studies

The cystic fibrosis transmembrane conductance regulator (CFTR) plays a central role in transepithelial ion transport by acting as a tightly regulated apical chloride channel. Regulation is achieved by the concerted action of ATP at conserved nucleotide binding folds and serine phosphorylation at multiple sites by protein kinases A (PKA) and C (PKC). A previous investigation concluded that activation by PKA is critically dependent on phosphorylation at four of the nine predicted PKA sites in the R domain (S660A, S737A, S795A, S813A), because a "Quad" mutant lacking these sites could not be activated. We show in the present work that not only can this mutant be phosphorylated and activated, but a mutant in which all 10 predicted PKA sites have been altered still retains significant PKA-activated function. Potentiation of the PKA response by PKC is also preserved in this mutant. Thus CFTR may be regulated by cryptic PKA sites which also mediate interactions between different kinases. Such hierarchical phosphorylation of CFTR by obvious and cryptic PKA sites could provide a metered response to secretagogues.