Electrodiffusional ATP movement through the cystic fibrosis transmembrane conductance regulator.

Abstract

Expression of the cystic fibrosis transmembrane conductance regulator (CFTR), and of at least one other member of the ATP-binding cassette family of transport proteins, P-glycoprotein, is associated with the electrodiffusional movement of the nucleotide ATP. Evidence directly implicating CFTR expression with ATP channel activity, however, is still missing. Here it is reported that reconstitution into a lipid bilayer of highly purified CFTR of human epithelial origin enables the permeation of both Cl- and ATP. Similar to previously reported data for in vivo ATP current of CFTR-expressing cells, the reconstituted channels displayed competition between Cl- and ATP and had multiple conductance states in the presence of Cl- and ATP. Purified CFTR-mediated ATP currents were activated by protein kinase A and ATP (1 mM) from the "intracellular" side of the molecule and were inhibited by diphenylamine-2-carboxylate, glibenclamide, and anti-CFTR antibodies. The absence of CFTR-mediated electrodiffusional ATP movement may thus be a relevant component of the pleiotropic cystic fibrosis phenotype.