The Cystic Fibrosis Transmembrane Conductance Regulator Impedes Proteolytic Stimulation of the Epithelial Na+ Channel

被引:80
作者
Gentzsch, Martina [1 ,2 ]
Dang, Hong [1 ]
Dang, Yan [1 ]
Garcia-Caballero, Agustin [1 ]
Suchindran, Hamsa [1 ]
Boucher, Richard C. [1 ,3 ]
Stutts, M. Jackson [1 ,3 ]
机构
[1] Univ N Carolina, Cyst Fibrosis Pulm Res & Treatment Ctr, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Dept Cell & Dev Biol, Chapel Hill, NC 27599 USA
[3] Univ N Carolina, Dept Med, Chapel Hill, NC 27599 USA
基金
美国国家卫生研究院;
关键词
SURFACE LIQUID VOLUME; SODIUM-CHANNEL; GAMMA-SUBUNIT; SERINE PROTEASES; XENOPUS-OOCYTES; ACTIVATING PROTEASE; NASAL EPITHELIUM; AIRWAY EPITHELIA; IN-VIVO; ENAC;
D O I
10.1074/jbc.M110.155259
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) that prevent its proper folding and trafficking to the apical membrane of epithelial cells. Absence of cAMP-mediated Cl- secretion in CF airways causes poorly hydrated airway surfaces in CF patients, and this condition is exacerbated by excessive Na+ absorption. The mechanistic link between missing CFTR and increased Na+ absorption in airway epithelia has remained elusive, although substantial evidence implicates hyperactivity of the epithelial Na+ channel (ENaC). ENaC is known to be activated by selective endoproteolysis of the extracellular domains of its alpha- and gamma-subunits, and it was recently reported that ENaC and CFTR physically associate in mammalian cells. We confirmed this interaction in oocytes by co-immunoprecipitation and found that ENaC associated with wild-type CFTR was protected from proteolytic cleavage and stimulation of open probability. In contrast, Delta F508 CFTR, the most common mutant protein in CF patients, failed to protect ENaC from proteolytic cleavage and stimulation. In normal airway epithelial cells, ENaC was contained in the anti-CFTR immunoprecipitate. In CF airway epithelial cultures, the proportion of full-length to total alpha-ENaC protein signal was consistently reduced compared with normal cultures. Our results identify limiting proteolytic cleavage of ENaC as a mechanism by which CFTR down-regulates Na+ absorption.
引用
收藏
页码:32227 / 32232
页数:6
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