Revealing a hidden conducting state in KV10.1 mutants

The KCNH family of potassium channels serves relevant physiological functions in both excitable and non-excitable cells, reflected in the massive consequences of mutations or pharmacological manipulation of their function. This group of channels shares structural homology with other voltage-gated K+ channels, but the mechanisms of gating in this family show significant differences with respect to the canonical electromechanical coupling in these molecules. In particular, the large intracellular domains of KCNH channels play a crucial role in gating that is still only partly understood. Using KCNH1(KV10.1) as a model, we have characterized the behavior of a series of modified channels that could not be explained by the current models. With electrophysiological and biochemical methods combined with mathematical modeling, we show that the uncovering of an open state can explain the behavior of the mutants. This open state, which is not detectable in wild-type channels, appears to lack the rapid flicker block of the conventional open state. Because it is accessed from deep closed states, it elucidates intermediate gating events well ahead of channel opening in the wild type. This allowed us to study gating steps prior to opening, which, for example, explain the mechanism of gating inhibition by Ca2+-Calmodulin and generate a model that describes the characteristic features of KCNH channels gating.

KCNH家族的钾离子通道在可兴奋细胞与不可兴奋细胞中均发挥着至关重要的生理功能，其功能突变或药理干预的广泛后果亦得以体现。该类通道与其他电压门控K+通道在结构上具有同源性，但其门控机制与这些分子中经典的电机械耦合机制相比，表现出显著的差异。特别是，KCNH通道的大型细胞内结构域在门控过程中发挥着至关重要的作用，其机制至今仅部分明了。以KCNH1（KV10.1）为模型，我们已对一系列现有模型无法解释的修改后通道的行为进行了表征。通过电生理学、生化方法与数学模型的结合，我们揭示了开放状态的发现可以解释突变体的行为。这种开放状态，在野生型通道中无法检测到，似乎缺少传统开放状态的快速闪烁阻断。由于其从深层关闭状态中访问，它很好地阐明了野生型通道开放之前的中介门控事件。这使我们能够研究开放步骤之前的门控步骤，例如，解释了Ca2+-钙调蛋白对门控的抑制作用，并构建了一个描述KCNH通道门控特征的模型。