Department of Physiology and Biophysics, University of Washington, Seattle, WA.
Department of Physiology and Biophysics, University of Washington, Seattle, WA
J Gen Physiol. 2018 Apr 2;150(4):625-635. doi: 10.1085/jgp.201711989. Epub 2018 Mar 22.
KCNH voltage-gated potassium channels (EAG, ERG, and ELK) play significant roles in neuronal and cardiac excitability. They contain cyclic nucleotide-binding homology domains (CNBHDs) but are not directly regulated by cyclic nucleotides. Instead, the CNBHD ligand-binding cavity is occupied by an intrinsic ligand, which resides at the intersubunit interface between the N-terminal eag domain and the C-terminal CNBHD. We show that, in ELK channels, this intrinsic ligand is critical for voltage-dependent potentiation (VDP), a process in which channel opening is stabilized by prior depolarization. We demonstrate that an exogenous peptide corresponding to the intrinsic ligand can bind to and regulate zebrafish ELK channels. This exogenous intrinsic ligand inhibits the channels before VDP and potentiates the channels after VDP. Furthermore, using transition metal ion fluorescence resonance energy transfer and a fluorescent noncanonical amino acid L-Anap, we show that there is a rearrangement of the intrinsic ligand relative to the CNBHD during VDP. We propose that the intrinsic ligand switches from antagonist to agonist as a result of a rearrangement of the eag domain-CNBHD interaction during VDP.
KCNH 电压门控钾通道（EAG、ERG 和 ELK）在神经元和心肌兴奋性中起重要作用。它们包含环核苷酸结合同源结构域（CNBHD），但不受环核苷酸的直接调节。相反，CNBHD 的配体结合腔被一种内在配体占据，该配体位于 N 端 eag 结构域和 C 端 CNBHD 之间的亚基界面上。我们表明，在 ELK 通道中，这种内在配体对于电压依赖性增强（VDP）至关重要，VDP 是指通道开放通过先前去极化而稳定的过程。我们证明，与内在配体相对应的外源性肽可以结合并调节斑马鱼 ELK 通道。这种外源性内在配体在 VDP 之前抑制通道，并在 VDP 之后增强通道。此外，我们使用过渡金属离子荧光共振能量转移和荧光非典型氨基酸 L-Anap 表明，在 VDP 过程中，内在配体相对于 CNBHD 发生了重排。我们提出，由于 VDP 期间 eag 结构域-CNBHD 相互作用的重排，内在配体从拮抗剂转变为激动剂。
