Altered channel gating mechanism for CFTR inhibition by a high-affinity thiazolidinone blocker.
The thiazolidinone CFTR(inh)-172 was identified recently as a potent and selective blocker of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel. Here, we characterized the CFTR(inh)-172 inhibition mechanism by patch-clamp and short-circuit analysis using cells stably expressing wild-type and mutant CFTRs. CFTR(inh)-172 did not alter CFTR unitary conductance (8 pS), but reduced open probability by >90% with K(i) approximately 0.6 microM. This effect was due to increased mean channel closed time without changing mean channel open time. Short-circuit current experiments indicated similar CFTR(inh)-172 inhibitory potency (K(i) approximately 0.5 microM) for inhibition of Cl(-) current in wild-type, G551D, and G1349D CFTR; however, K(i) was significantly reduced to 0.2 microM for DeltaF508 CFTR. Our studies provide evidence for CFTR inhibition by CFTR(inh)-172 by a mechanism involving altered CFTR gating.
Taddei
Alessandro
A
Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, 16148 Genoa, Italy.
Folli
Chiara
C
Zegarra-Moran
Olga
O
Fanen
Pascale
P
Verkman
A S
AS
Galietta
Luis J V
LJ
D000818:Animals; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000187:drug effects / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects*; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D018408:Patch-Clamp Techniques; D051381:Rats; D011916:Rats, Inbred F344; D013844:Thiazoles / Q000494:pharmacology*
D018118:Chloride Channels; D013844:Thiazoles; D019005:Cystic Fibrosis Transmembrane Conductance Regulator