Role of CFTR’s intrinsic adenylate kinase activity in gating of the Cl− channel

The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl−channel in the ATP-binding cassette (ABC) transporter protein family. CFTR features the modular design characteristic of ABC transporters, which includes two membrane-spanning domains forming the channel pore, and two ABC nucleotide-binding domains that interact with ATP and contain the enzymatic activity coupled to normal gating. Like other ABC transporters CFTR is an ATPase (ATP + H2O → ADP + Pi). Recent work has shown that CFTR also possesses intrinsic adenylate kinase activity (ATP + AMP ⇆ ADP + ADP). This finding raises important questions: How does AMP influence CFTR gating? Why does ADP inhibit CFTR current? Which enzymatic activity gates CFTR in vivo? Are there implications for other ABC transporters? This minireview attempts to shed light on these questions by summarizing recent advances in our understanding of the role of the CFTR adenylate kinase activity for channel gating.