Mechanosensitivity of an epithelial Na+ channel in planar lipid bilayers: Release from Ca2+ block
Mechanosensitivity of an epithelial Na+ channel in planar lipid bilayers: Release from Ca2+ block
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DOI：
10.1016/s0006-3495(97)78766-6
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发表时间：
1997-03-01
影响因子：
3.4
通讯作者：
Benos, DJ
中科院分区：
文献类型：
--
作者：
Ismailov, II;Berdiev, BK;Benos, DJ
最近从几种不同的组织中克隆了一系列新型上皮 Na+ 通道 (ENaC)。三个同源亚基（α、β、γ-ENaC）形成上皮细胞中 Na+ 选择性、阿米洛利敏感通道的核心传导单元。我们在这里报告了一项研究的结果，该研究评估了平面脂质双层中 Ca2+ 对 α、β、γ-rENaC 的调节。将双层沐浴溶液缓冲至 [Ca2+] < 1 nM 使单通道开放概率增加五倍。对这一现象的进一步研究表明，Ca2+离子产生电压依赖性阻断，影响开路概率，但不影响 ENaC 的单一电导。在含有 α、β、γ-rENaC 的双层上施加静水压力梯度显着降低了这些通道对 [Ca2+] 抑制的敏感性。相反，在名义上缺乏 Ca2+ 的情况下，通道失去了对机械刺激的敏感性。这些结果表明，先前观察到的 ENaCs 机械激活反映了通道被 Ca2+ 阻断的释放。
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+.