Gating and regulation of KCNH (ERG, EAG, and ELK) channels by intracellular domains

Abstract

The KCNH family comprises the ERG, EAG, and ELK voltage-activated, potassium-selective channels. Distinct from other K channels, KCNH channels contain unique structural domains, including a PAS (Per-Arnt-Sim) domain in the N-terminal region and a CNBHD (cyclic nucleotide-binding homology domain) in the C-terminal region. The intracellular PAS domains and CNBHDs interact directly and regulate some of the characteristic gating properties of each type of KCNH channel. The PAS-CNBHD interaction regulates slow closing (deactivation) of hERG channels, the kinetics of activation and pre-pulse dependent population of closed states (the Cole-Moore shift) in EAG channels and voltage-dependent potentiation in ELK channels. KCNH channels are all regulated by an intrinsic ligand motif in the C-terminal region which binds to the CNBHD. Here, we focus on some recent advances regarding the PAS-CNBHD interaction and the intrinsic ligand.

Overcoming challenges of HERG potassium channel liability through rational design: Eag1 inhibitors for cancer treatment

“…Although the Drosophila eag channel's amino acid sequence was immediately recognized as compatible with a potassium channel monomer, 6 with an array of six transmembrane segments (S1–S6), several substantial differences with known potassium channels became evident already at the time. On the one hand, the large intracellular domains displaying a PAS domain in the N‐ 24 and a cyclic nucleotide‐binding domain in the C‐terminus (which is occupied by a ligand from the same protein and not by cyclic nucleotides 24 ) represent a characteristic feature of KCNH channels 25 . On the other hand, although the channels are reasonably selective for K + , the “signature sequence” at the selective filter of Shaker ‐type channels (GYGD) 26 is different in this family (GFGN).…”

Molecular Insights Into the Gating Kinetics of the Cardiac hERG Channel, Illuminated by Structure and Molecular Dynamics

“…The regulation of different conformational changes of hERG channels is so complicated that it is difficult to elucidate the exact mechanism of gating kinetics because almost all domains are involved in this regulation ( Codding et al, 2020 ). Some domains at the C-terminus and N-terminus, particularly the PAS domain and cNBD, have been proven to play key roles in the regulatory mechanism.…”

“…Some domains at the C-terminus and N-terminus, particularly the PAS domain and cNBD, have been proven to play key roles in the regulatory mechanism. They may affect the interaction between the PAS domain in one subunit and the cNBD in an adjacent subunit, called the PAS/cNBD complex ( Codding et al, 2020 ; Morais-Cabral and Robertson, 2015 ; Adaixo et al, 2013 ) ( Figure 4 ). This physical interaction between the different domains of different subunits can produce electrical activity through further coupling, which is a classic explanation for the changes in different conformational states of VGK channels.…”

Structural determinants of voltage-dependent gating of Kv10.1

“…This arrangement where domains of different subunits interact with each other compensates for the conventional domain swapping in Kv channels, where the voltage sensor of one subunit interacts with the pore domain of an adjacent subunit. KCNH, HCN, and CNG channels all lack the classical domain swapping and instead swap their intracellular domains (Codding et al, 2020). In addition to the eag -CNBHD interaction, inter-subunit interaction occurs through the C-linker; A', B' α-helices lie on top of C', D' α-helices from a neighboring subunit (elbow-on-shoulder) (James and Zagotta, 2018).…”

“…Cladogram of Voltage-gated K + channels (Kv) HCN and CNG are closer relatives to the KCNH than to the KCNA family. Adapted from(Codding et al, 2020)…”