期刊
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
卷 441, 期 2-3, 页码 341-350出版社
SPRINGER-VERLAG
DOI: 10.1007/s004240000430
关键词
amiloride; cytosolic pH; epithelial sodium channel (ENaC); Na+ transport; proton-coupled oligopeptide transporter (PepT-1); Xenopus laevis oocyte
类别
Gain-of-function mutations of the epithelial Na+ channel (ENaC) cause a rare form of hereditary hypertension, Liddle's syndrome. How these mutations lead to increased channel activity is not yet fully understood. Since wild-type ENaC (wt-ENaC) is highly pH-sensitive, we wondered whether an altered pH-sensitivity of ENaC might contribute to the hyperactivity of ENaC with Liddle's syndrome mutation (Liddle-ENaC). Using Xenopus laevis oocytes as an expression system, we compared the pH-sensitivity of wt-ENaC (alpha beta gamma rENaC) and Liddle-ENaC (alpha beta (R564stop)gamma rENaC). Oocytes were assayed fur an amiloride-sensitive (2 muM) inward current (DeltaI(ami)) at -60 mV holding potential and cytosolic pH was altered by changing the extracellular pH in the presence of 60 mM sodium acetate. Alternatively, cytosolic acidification was achieved by proton loading the cells using a proton-coupled oligopeptide transporter (PepT-1) co-expressed ill the oocytes together with ENaC, Cytosolic but not extracellular acidification substantially reduced DeltaI(ami) while cytosolic alkalinisation had a stimulatory effect. This pH-sensitivity was largely preserved in oocytes expressing Liddle-ENaC. The inhibition of wt-ENaC and Liddle-ENaC by cytosolic acidification was independent of so-called sodium-feedback inhibition, since it was not associated with a concomitant increase in intracellular Na+ concentration estimated from the reversal potential of DeltaI(ami). In addition C-terminal deletions in the alpha or gamma subunits or in all three subunits of ENaC did not abolish the inhibitory effect of cytosolic acidification. We conclude that ENaC's pH-sensitivity is not mediated by its cytoplasmic C-termini and that an altered pi-I-sensitivity of ENaC does not contribute to the pathophysiology of Liddle's syndrome.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据