Fernández-Mariño Ana I, Valverde Miguel A, Fernández-Fernández José M
Laboratori de Fisiologia Molecular i Canalopaties, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, C/ Dr. Aiguader 88, Barcelona, 08003, Spain.
Pflugers Arch. 2014 Jul;466(7):1365-75. doi: 10.1007/s00424-013-1379-9. Epub 2013 Oct 26.
Tungstate, a compound with antidiabetic, antiobesity, and antihypertensive properties, activates the large-conductance voltage- and Ca(2+)-dependent K(+) (BK) channel containing either β1 or β4 subunits. The BK activation by tungstate is Mg(2+)-dependent and promotes arterial vasodilation, but only in precontracted mouse arteries expressing β1. In this study, we further explored how the β1 subunit participates in tungstate activation of BK channels. Activation of heterologously expressed human BKαβ1 channels in inside-out patches is fully dependent on the Mg(2+) sensitivity of the BK α channel subunit even at high (10 μM) cytosolic Ca(2+) concentration. Alanine mutagenesis of β1 extracellular residues Y74 or S104, which destabilize the active voltage sensor, greatly decreased the tungstate-induced left-shift of the BKαβ1 G-V curves in either the absence or presence of physiologically relevant cytosolic Ca(2+) levels (10 μM). The weakened tungstate activation of the BKαβ1Y74A and BKαβ1S104A mutant channels was not related to decreased Mg(2+) sensitivity. These results, together with previously published reports, support the idea that the putative binding site for tungstate-mediated BK channel activation is located in the pore-forming α channel subunit, around the Mg(2+) binding site. The role of β1 in tungstate-induced channel activation seems to rely on its interaction with the BK α subunit to modulate channel activity. Loop residues that are essential for the regulation of voltage sensor activation and gating of the BK channel are also relevant for BK activation by tungstate.
钨酸盐是一种具有抗糖尿病、抗肥胖和抗高血压特性的化合物，它可激活包含β1或β4亚基的大电导电压和Ca(2+)依赖性K(+)（BK）通道。钨酸盐对BK通道的激活作用依赖于Mg(2+)，并促进动脉血管舒张，但仅在表达β1的预收缩小鼠动脉中起作用。在本研究中，我们进一步探讨了β1亚基如何参与钨酸盐对BK通道的激活。即使在高（10 μM）胞质Ca(2+)浓度下，在内外翻膜片中异源表达的人BKαβ1通道的激活也完全依赖于BK α通道亚基的Mg(2+)敏感性。β1胞外残基Y74或S104的丙氨酸诱变会使活性电压传感器不稳定，在不存在或存在生理相关胞质Ca(2+)水平（10 μM）的情况下，都会大大降低钨酸盐诱导的BKαβ1 G-V曲线左移。BKαβ1Y74A和BKαβ1S104A突变通道的钨酸盐激活减弱与Mg(2+)敏感性降低无关。这些结果与先前发表的报告一起，支持了这样一种观点，即钨酸盐介导的BK通道激活的假定结合位点位于形成孔的α通道亚基中，围绕Mg(2+)结合位点。β1在钨酸盐诱导的通道激活中的作用似乎依赖于它与BK α亚基的相互作用来调节通道活性。对BK通道电压传感器激活和门控调节至关重要的环残基也与钨酸盐对BK通道的激活有关。
