Mechanosensitivity of an epithelial Na+ channel in planar lipid bilayers: Release from Ca2+ block

被引:44
|
作者
Ismailov, II [1 ]
Berdiev, BK [1 ]
Shlyonsky, VG [1 ]
Benos, DJ [1 ]
机构
[1] UNIV ALABAMA,DEPT PHYSIOL & BIOPHYS,BIRMINGHAM,AL 35294
关键词
D O I
10.1016/S0006-3495(97)78766-6
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
A family of novel epithelial Na+ channels (ENaCs) have recently been cloned from several different tissues. Three homologous subunits (alpha, beta, gamma-ENaCs) form the core conductive unit of Na+-selective, amiloride-sensitive channels that are found in epithelia. We here report the results of a study assessing the regulation of alpha, beta, gamma-rENaC by Ca2+ in planar lipid bilayers. Buffering of the bilayer bathing solutions to [Ca2+] < 1 nM increased single-channel open probability by fivefold. Further investigation of this phenomenon revealed that Ca2+ ions produced a voltage-dependent block, affecting open probability but not the unitary conductance of ENaC. Imposing a hydrostatic pressure gradient across bilayers containing alpha,beta,gamma-rENaC markedly reduced the sensitivity of these channels to inhibition by [Ca2+]. Conversely, in the nominal absence of Ca2+, the channels lost their sensitivity to mechanical stimulation. These results suggest that the previously observed mechanical activation of ENaCs reflects a release of the channels from block by Ca2+.
引用
收藏
页码:1182 / 1192
页数:11
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