Laboratory of Neurobiology, Graduate School of Integrated Sciences of Life, Hiroshima University, Kagamiyama 1-7-1, 739-8521, Higashi-Hiroshima, Japan.
Pflugers Arch. 2024 Oct;476(10):1493-1516. doi: 10.1007/s00424-024-02982-5. Epub 2024 Jul 15.
The voltage-dependent potassium channels (Kv channels) show several different types of inactivation. N-type inactivation is a fast inactivating mechanism, which is essentially an open pore blockade by the amino-terminal structure of the channel itself or the auxiliary subunit. There are several functionally discriminatable slow inactivation (C-type, P-type, U-type), the mechanism of which is supposed to include rearrangement of the pore region. In some Kv1 channels, the actual inactivation is brought about by coupling of N-type and C-type inactivation (N-C coupling). In the present study, we focused on the N-C coupling of the Aplysia Kv1 channel (AKv1). AKv1 shows a robust N-type inactivation, but its recovery is almost thoroughly from C-type inactivated state owing to the efficient N-C coupling. In the I8Q mutant of AKv1, we found that the inactivation as well as its recovery showed two kinetic components apparently correspond to N-type and C-type inactivation. Also, the cumulative inactivation which depends on N-type mechanism in AKv1 was hindered in I8Q, suggesting that N-type inactivation of I8Q is less stable. We also found that Zn specifically accelerates C-type inactivation of AKv1 and that H382 in the pore turret is involved in the Zn binding. Because the region around Ile (I8) in AKv1 has been suggested to be involved in the pre-block binding of the amino-terminal structure, our results strengthen a hypothesis that the stability of the pre-block state is important for stable N-type inactivation as well as the N-C coupling in the Kv1 channel inactivation.
电压门控钾通道（Kv 通道）表现出几种不同类型的失活。N 型失活是一种快速失活机制，本质上是通道本身或辅助亚基的氨基末端结构对孔的阻塞。有几种功能上可区分的慢失活（C 型、P 型、U 型），其机制被认为包括孔区的重排。在一些 Kv1 通道中，实际的失活是通过 N 型和 C 型失活的偶联（N-C 偶联）引起的。在本研究中，我们专注于 Aplysia Kv1 通道（AKv1）的 N-C 偶联。AKv1 表现出很强的 N 型失活，但由于有效的 N-C 偶联，其恢复几乎完全来自 C 型失活状态。在 AKv1 的 I8Q 突变体中，我们发现失活及其恢复明显表现出两个动力学成分，分别对应于 N 型和 C 型失活。此外，在 AKv1 中依赖于 N 型机制的累积失活在 I8Q 中受到阻碍，表明 I8Q 的 N 型失活不太稳定。我们还发现 Zn 特异性加速 AKv1 的 C 型失活，并且孔塔中的 H382 参与 Zn 的结合。因为 AKv1 中 Ile （I8）周围的区域被认为参与氨基末端结构的预阻塞结合，所以我们的结果强化了这样一个假设，即预阻塞状态的稳定性对于 Kv1 通道失活中的稳定 N 型失活以及 N-C 偶联都很重要。
