Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI, 48109, USA.
Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, MI, 48109, USA.
Sci Rep. 2022 Apr 8;12(1):5950. doi: 10.1038/s41598-022-10003-7.
Cardiac hERG channels comprise at least two subunits, hERG 1a and hERG 1b, and drive cardiac action potential repolarization. hERG 1a subunits contain a cytoplasmic PAS domain that is absent in hERG 1b. The hERG 1a PAS domain regulates voltage sensor domain (VSD) movement, but hERG VSD behavior and its regulation by the hERG 1a PAS domain have not been studied at physiological temperatures. We recorded gating charge from homomeric hERG 1a and heteromeric hERG 1a/1b channels at near physiological temperatures (36 ± 1 °C) using pulse durations comparable in length to the human ventricular action potential. The voltage dependence of deactivation was hyperpolarized relative to activation, reflecting VSD relaxation at positive potentials. These data suggest that relaxation (hysteresis) works to delay pore closure during repolarization. Interestingly, hERG 1a VSD deactivation displayed a double Boltzmann distribution, but hERG 1a/1b deactivation displayed a single Boltzmann. Disabling the hERG 1a PAS domain using a PAS-targeting antibody similarly transformed hERG 1a deactivation from a double to a single Boltzmann, highlighting the contribution of the PAS in regulating VSD movement. These data represent, to our knowledge, the first recordings of hERG gating charge at physiological temperature and demonstrate that VSD relaxation (hysteresis) is present in hERG channels at physiological temperature.
心脏 hERG 通道至少由两个亚基组成，即 hERG 1a 和 hERG 1b，并驱动心脏动作电位复极化。hERG 1a 亚基包含一个细胞质 PAS 结构域，而 hERG 1b 则没有。hERG 1a 的 PAS 结构域调节电压传感器结构域（VSD）的运动，但 hERG 的 VSD 行为及其被 hERG 1a PAS 结构域的调节在生理温度下尚未得到研究。我们在接近生理温度（36±1°C）下，使用与人类心室动作电位长度相当的脉冲持续时间，记录了同型 hERG 1a 和异型 hERG 1a/1b 通道的门控电荷。失活的电压依赖性相对于激活向超极化方向移动，反映出 VSD 在正电位下的松弛。这些数据表明，松弛（滞后）在复极化过程中有助于延迟孔的关闭。有趣的是，hERG 1a VSD 的失活呈现出双 Boltzmann 分布，但 hERG 1a/1b 的失活则呈现出单 Boltzmann 分布。使用针对 PAS 的抗体使 hERG 1a 的 PAS 结构域失活，同样将 hERG 1a 的失活从双 Boltzmann 转变为单 Boltzmann，这突出了 PAS 在调节 VSD 运动中的作用。据我们所知，这些数据代表了在生理温度下首次记录 hERG 门控电荷，并证明了在生理温度下，VSD 松弛（滞后）存在于 hERG 通道中。
