Paradoxical stimulation of a DEG ENaC channel by amiloride
Paradoxical stimulation of a DEG ENaC channel by amiloride
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DOI：
10.1074/jbc.274.22.15500
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发表时间：
1999-05-28
影响因子：
4.8
通讯作者：
Welsh, MJ
中科院分区：
文献类型：
--
作者：
Adams, CM;Snyder, PM;Welsh, MJ
细胞外阿米洛利抑制所有已知的DEG/ENaC离子通道，包括质子激活的人神经元阳离子通道BNC1。早期的研究表明，质子引起构象变化，激活BNC1，使残基430暴露在细胞外溶液中，在这里，我们证明，除了阻断BNC1，阿米洛利还暴露残基430，这一结果表明，像质子一样，阿米洛利可能能够激活通道。为了验证这一假设，我们在BNC1孔中引入了一个突变，减少了阿米洛利的阻断，并发现阿米洛利刺激了这些通道。阿米洛利的抑制是电压依赖的，提示阻塞在孔内，而刺激不是，提示结合到细胞外的位置。这些数据表明，阿米洛利可以对BNC1产生两种不同的影响，他们提出了两种不同的相互作用部位。结果提示，胞外阿米洛利结合可能具有类似于BNC1中的质子或其他DEG/ENaC通道中的胞外配体的刺激作用。
Extracellular amiloride inhibits all known DEG/ENaC ion channels, including BNC1, a proton-activated human neuronal cation channel. Earlier studies showed that protons cause a conformational change that activates BNC1 and exposes residue 430 to the extracellular solution, Here we demonstrate that, in addition to blocking BNC1, amiloride also exposes residue 430, This result suggested that, like protons, amiloride might be capable of activating the channel. To test this hypothesis, we introduced a mutation in the BNC1 pore that reduces amiloride block, and found that amiloride stimulated these channels. Amiloride inhibition was voltage-dependent, suggesting block within the pore, whereas stimulation was not, suggesting binding to an extracellular site. These data show that amiloride can have two distinct effects on BNC1, and they suggest two different interaction sites. The results suggest that extracellular amiloride binding may have a stimulatory effect similar to that of protons in BNC1 or extracellular ligands in other DEG/ENaC channels.