Role of Binding and Nucleoside Diphosphate Kinase A (NDPK‐A) in the Regulation of CFTR by AMP‐Activated Protein Kinase (AMPK)

Abstract

A better understanding of CFTR Cl− channel regulation could suggest new therapies for cystic fibrosis. AMPK binds to the CFTR C‐terminal tail, phosphorylates, and inhibits PKA‐activated CFTR gating, processes that are not well understood. PKA‐induced CFTR gating was unchanged by AMPK addition in excised inside‐out patch‐clamp recordings, suggesting the importance of other factor(s) in intact cells. NDPK‐A interacts with both AMPK and CFTR in overlay blots of airway epithelia. Binding studies in Xenopus oocytes and transfected HEK‐293 cells revealed that a peptide fragment of CFTR that binds AMPK (CFTR‐1420‐57) disrupted this interaction. Transduction of this peptide into Calu‐3 cells enhanced forskolin‐induced whole‐cell CFTR conductance. Injection of CFTR‐1420‐57 into Xenopus oocytes blocked AMPK‐dependent inhibition of cAMP‐stimulated CFTR conductance, as measured by two‐electrode voltage clamp. AMPK activation inhibited CFTR conductance with co‐expression of wild‐type NDPK‐A in Xenopus oocytes, but co‐expression of a catalytically inactive H118F mutant blocked this inhibition. These results suggest that NDPK‐A exists in a cellular complex with AMPK and CFTR and is required for the AMPK‐dependent regulation of CFTR. We propose that NDPK‐A may make ATP readily available for AMPK‐mediated phosphorylation and regulation of CFTR under conditions of metabolic stress. (Supported by NIH and CFF)