Fluorescein derivatives potentiate CFTR by altering the ATP affinity and efficacy of channel gating
作者单位：Istituto di BiofisicaCNRVia DeMarini 616149 GenoaItaly Department of Physiology and PharmacologyUniversity of BristolBristolBS8 1TDUK
会议名称：《2008北京国际生理科学学术大会》
会议日期：2008年
学科分类：1001[医学-基础医学(可授医学、理学学位)] 10[医学]
基 金：supported by the CF Trust BBSRC and Italian Cystic Fibrosis Research Foundation
关 键 词：CFTR channel gating ATP affinity gating efficacy
摘 要：The fluorescein derivative phloxine B is a potent modulator of the cystic fibrosis transmembrane conductance regulator(CFTR)Cl *** micromolar concentrations of phloxine B potentiate ATP-dependent channel gating,whereas higher concentrations occlude the channel *** determine whether fluorescein derivatives (FDs)affect the ATP affinity of CFTR and the efficacy of channel gating,we investigated the effects of FDs on the gating behaviour of CFTR using excised inside-out membrane patches from C127 cells expressing wild-type human *** employed a simple linear three-state scheme(C(?)C(?)O)to describe CFTR channel *** this scheme,C represents the long duration closed state separating channel openings,C the brief closures that interrupt channel openings,and O the open *** between the three states are described by the forward rate constantsβ,β and the backward rate constantsα andα.Given that CFTR is an agonist-activated channel gated by intracellular ATP and this scheme is reminiscent of the del Castillo-Katz mechanism,we can calculate the ATP affinity(α/β)and gating efficacy of CFTR(β/α).The FDs phloxine B(1μmol/L)and eosin Y(1μmol/L) augment channel gating by prolonging mean burst duration(MBD)without changing the interburst interval(IBI), whereas dichlorofluorescein(DCF;20μmol/L)decreases the IBI without changing MBD(n=4-15).Interestingly, phloxine B(1μmol/L)and DCF(20μmol/L)decreasedα/β(enhanced affinity),whereas only phloxine B(1μmol/L) elevatedβ/α(augmented gating efficacy).To understand better how FDs affect the relationship between the ATP affinity and gating efficacy,we examined the ATP-dependence of channel gating(n5).Increasing ATP concentrations enhanced markedly both the ATP affinity and gating efficacy of ***,phloxine B(1μmol/L) augmented both the ATP affinity and gating efficacy of CFTR,particularly at low ATP *** interpret our results to suggest that the ATP affinity and gating efficacy of CFTR are t