Inhibition of cystic fibrosis transmembrane conductance regulator by novelinteraction with the metabolic sensor AMP-activated protein kinase

The cystic fibrosis transmembrane conductance regulator (CFTR) is an ATP-ga ted Cl- channel that regulates other epithelial transport proteins by uncha racterized mechanisms. We employed a yeast two-hybrid screen using the COOH -terminal 70 residues of CFTR to identify proteins that might be involved i n such interactions. The alpha 1 (catalytic) subunit of AMP-activated prote in kinase (AMPK) was identified as a dominant and novel interacting protein . The interaction is mediated by residues 1420-1457 in CFTR and by the COOH -terminal regulatory domain of alpha 1-AMPK. Mutations of two protein traff icking motifs within the 38-amino acid region in CFTR each disrupted the in teraction. GST-fusion protein pull-down assays in vitro and in transfected cells confirmed the CFTR-alpha 1-AMPK interaction and also identified alpha 2-AMPK as an interactor with CFTR AMPK is coexpressed in CFTR-expressing c ell lines and shares an apical distribution with CFTR in rat nasal epitheli um. AMPK phosphorylated full-length CFTR in vitro, and AMPK coexpression wi th CFTR in Xenopus oocytes inhibited cAMP-activated CFTR whole-cell Cl- con ductance by approximately 35-50%. Because AMPK is a metabolic sensor in cel ls and responds to changes in cellular ATP, regulation of CFTR by AMPK may be important in inhibiting CFTR under conditions of metabolic stress, there by linking transepithelial transport to cell metabolic state.