Molecular mechanism of anion permeation through CFTR channel pore

Abstract

Cystic fibrosis is an inherited disease caused by mutations in a single gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), a member of ATP-binding cassette (ABC) proteins superfamily. Several approaches have been applied to determine the pore-lining domains or residues including mutagenesis study of residues in transmembrane (TM) segments by identifying their contribution to CFTR channel functional features. However, we do not know which and how many TMs contribute to the channel pore of CFTR. For the purpose of revealing the architecture of CFTR channel pore, we used site-directed mutagenesis to construct single and double mutated CFTR channel and then investigated their functional variation by using patch clamp recording. Our results suggestted that TM1 and TM6 played very important roles in CFTR channel pore forming and the amino acid residue T338 in TM6 could interact with the residues K95 and Q98 in TM1. Therefore, we proposed that these residues form a selectivity filter of the CFTR channels. Subsequently, we found that the residue T338 in TM6 could also interact with the residues T1142A and W1145A in TM12. Since the mutations of T1142A and W1145A did not impact the channel current of CFTR, we suggestted that the residues T1142 and W1145 in TM12 might support the wall structure of CFTR channel pore and affect the channel function indirectly by interacting with T338 in TM6.