Lab of Biomechanics, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, PR China.
J Biomech. 2010 Nov 16;43(15):3015-9. doi: 10.1016/j.jbiomech.2010.06.018. Epub 2010 Jul 29.
Large conductance Ca(2+)-activated K(+) (BK) channels are responsible for changes in chemical and physical signals such as Ca(2+), Mg(2+) and membrane potentials. Previously, we reported that a BK channel cloned from chick heart (SAKCaC) is activated by membrane stretch. Molecular cloning and subsequent functional characterization of SAKCaC have shown that both the membrane stretch and intracellular Ca(2+) signal allosterically regulate the channel activity via the linker of the gating ring complex. Here we investigate how these two gating principles interact with each other. We found that stretch force activated SAKCaC in the absence of cytoplasmic Ca(2+). Lack of Ca(2+) bowl (a calcium binding motif) in SAKCaC diminished the Ca(2+)-dependent activation, but the mechanosensitivity of channel was intact. We also found that the abrogation of STREX (a proposed mechanosensing apparatus) in SAKCaC abolished the mechanosensitivity without altering the Ca(2+) sensitivity of channels. These observations indicate that membrane stretch and intracellular Ca(2+) could independently modulate SAKCaC activity.
大电导钙激活钾（BK）通道负责改变化学和物理信号，如 Ca(2+)、Mg(2+)和膜电位。以前，我们报道了从鸡心中克隆的 BK 通道（SAKCaC）可被膜拉伸激活。对 SAKCaC 的分子克隆和随后的功能表征表明，膜拉伸和细胞内 Ca(2+)信号都通过门控环复合物的连接体变构调节通道活性。在这里，我们研究了这两个门控原理如何相互作用。我们发现，在没有细胞质 Ca(2+)的情况下，拉伸力可激活 SAKCaC。SAKCaC 中缺乏 Ca(2+)碗（一个钙结合基序）会降低 Ca(2+)依赖性激活，但通道的机械敏感性仍然完整。我们还发现，SAKCaC 中 STREX（一种拟议的机械感觉装置）的缺失消除了机械敏感性，而不改变通道对 Ca(2+)的敏感性。这些观察结果表明，膜拉伸和细胞内 Ca(2+)可以独立地调节 SAKCaC 的活性。
