NH2-terminal inactivation peptide binding to C-type-inactivated Kv channels
NH2-terminal inactivation peptide binding to C-type-inactivated Kv channels
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DOI：
10.1085/jgp.200308956
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发表时间：
2004-05-01
影响因子：
3.8
通讯作者：
Fedida, D
中科院分区：
文献类型：
--
作者：
Kurata, HT;Wang, ZR;Fedida, D
在许多电压门控 K+ 通道中，N 型失活显着加速 C 型失活的发生，但对失活恢复的影响很小或不存在。我们利用C型失活K+通道的Na+渗透性来表征Kv1.A的失活肽与Kv1.4和Kvl.5的C型失活状态之间的强相互作用。 Kv1.4 失活肽的存在导致通常通过 C 型失活通道观察到的 Na+ 尾电流衰减较慢，有效阻断峰值 Na+ 尾电流，并延迟峰值尾电流。通过向移液管填充溶液中添加季铵离子来模拟这些效应。这些观察结果支持了失活肽和细胞内季铵离子的共同作用机制，并且还证明了 Kv 通道内前庭在 C 型失活开始之前和之后在细胞质中暴露。我们还研究了在去除C型失活的条件下N型失活的过程，以比较失活肽与开放通道和C型失活通道的相互作用。在 C 型缺陷形式的 Kv1.4 或 Kv1.5 通道中，Kv1.4 失活球的行为类似于开放通道阻断剂，并且由此产生的失活尾电流减慢比在 C 型失活通道中观察到的要弱得多。我们提出了一个动力学模型，该模型复制了失活肽对 C 型失活通道的慢 Na+ 尾部的影响。失活肽和 C 型失活状态之间的稳定结合导致电流衰减更慢，并且 Na+ 尾电流幅度降低，这是由于从失活恢复过程中穿过的 Na+ 渗透状态的通道转换更慢。
In many voltage-gated K+ channels, N-type inactivation significantly accelerates the onset of C-type inactivation, but effects on recovery from inactivation are small or absent. We have exploited the Na+ permeability of C-type-inactivated K+ channels to characterize a strong interaction between the inactivation peptide of Kv1.A and the C-type-inactivated state of Kv1.4 and Kvl.5. The presence of the Kv1.4 inactivation peptide results in a slower decay of the Na+ tail currents normally observed through C-type-inactivated channels, an effective blockade of the peak Na+ tail current, and also a delay of the peak tail current. These effects are mimicked by addition of quaternary ammonium ions to the pipette-filling solution. These observations support a common mechanism of action of the inactivation peptide and intracellular quaternary ammonium ions, and also demonstrate that the Kv channel inner vestibule is cytosolically exposed before and after the onset of C-type inactivation. We have also examined the process of N-type inactivation under conditions where C-type inactivation is removed, to compare the interaction of the inactivation peptide with open and C-type-inactivated channels. In C-type-deficient forms of Kv1.4 or Kv1.5 channels, the Kv1.4 inactivation ball behaves like an open channel blocker, and the resultant slowing of deactivation tail currents is considerably weaker than observed in C-type-inactivated channels. We present a kinetic model that duplicates the effects of the inactivation peptide on the slow Na+ tail of C-type-inactivated channels. Stable binding between the inactivation peptide and the C-type-inactivated state results in slower current decay, and a reduction of the Na+ tail current magnitude, due to slower transition of channels through the Na+-permeable states traversed during recovery from inactivation.