CFTR directly mediates nucleotide-regulated glutathione flux.
Studies have shown that expression of cystic fibrosis transmembrane conductance regulator (CFTR) is associated with enhanced glutathione (GSH) efflux from airway epithelial cells, implicating a role for CFTR in the control of oxidative stress in the airways. To define the mechanism underlying CFTR-associated GSH flux, we studied wild-type and mutant CFTR proteins expressed in Sf9 membranes, as well as purified and reconstituted CFTR. We show that CFTR-expressing membrane vesicles mediate nucleotide-activated GSH flux, which is disrupted in the R347D pore mutant, and in the Walker A K464A and K1250A mutants. Further, we reveal that purified CFTR protein alone directly mediates nucleotide-dependent GSH flux. Interestingly, although ATP supports GSH flux through CFTR, this activity is enhanced in the presence of the non-hydrolyzable ATP analog AMP-PNP. These findings corroborate previous suggestions that CFTR pore properties can vary with the nature of the nucleotide interaction. In conclusion, our data demonstrate that GSH flux is an intrinsic function of CFTR and prompt future examination of the role of this function in airway biology in health and disease.
Hospital for Sick Children, Department of Physiology, University of Toronto, Toronto, Ontario M5G 1X8.
Ilana
I
Kogan
Mohabir
M
Ramjeesingh
Canhui
C
Li
Jackie F
JF
Kidd
Yanchun
Y
Wang
Elaine M
EM
Leslie
Susan P C
SP
Cole
Christine E
CE
Bear
D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000502:physiology*; D005978:Glutathione / Q000378:metabolism*; D011510:Proteolipids; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D018411:Spodoptera
D011510:Proteolipids; D011994:Recombinant Proteins; C020485:proteoliposomes; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005978:Glutathione