Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) plays a central role in transepithelial fluid and electrolyte transport as a Cl− channel and also as a regulator of other transporters. CFTR channel function is widely deviated among several different CFTR epithelia whereas any CFTR subtype has never been identified. Recent evidence suggests that ion channels can target to membrane lipid raft and associate with other regulatory proteins. In this study, we have investigated the role of cholesterol, an important component of lipid raft, in the regulation of CFTR channel function using patch-clamp technique. In cell-attached patches, cholesterol-depletion by cyclodextrin treatment inhibited CFTR channel activity Po from 0.35±0.03 to 0.15±0.02 with decreasing burst duration (Tb) from 2.3±0.3 to 0.31±0.03 msec and interburst duration (Tib) from 3.4±0.6 to 1.8±0.03 msec (n = 5). On the contrary, cholesterol-enrichment by treatment with cyclodextrin-solubilized cholesterol slowed the CFTR channel gating with prolonging Tb to 5.6±1.1 msec and Tib to 10.8±3.5 msec (n = 5). These results indicate that cholesterol plays a critical role in regulation of CFTR channel kinetics. We also found that CFTR channels expressed in Hi-5 insect cell line which is known not to synthesize cholesterol exhibited a similar gating kinetics to those in cholesterol-depleted NIH3T3 cells. We speculate that CFTR channels localize to lipid raft and are tissue-specifically modulated. [J Physiol Sci. 2006;56 Suppl:S81]
