Probing the structural basis for differential KCNQ1 modulation by KCNE1 and KCNE2

Abstract

KCNE1 associates with KCNQ1 to increase its current amplitude and slow the activation gating process, creating the slow delayed rectifier channel that functions as a “repolarization reserve” in human heart. The transmembrane domain (TMD) of KCNE1 plays a key role in modulating KCNQ1 pore conductance and gating kinetics, and the extracellular juxtamembrane (EJM) region plays a modulatory role by interacting with the extracellular surface of KCNQ1. KCNE2 is also expressed in human heart and can associate with KCNQ1 to suppress its current amplitude and slow the deactivation gating process. KCNE1 and KCNE2 share the transmembrane topology and a high degree of sequence homology in TMD and surrounding regions. The structural basis for their distinctly different effects on KCNQ1 is not clear. To address this question, we apply cysteine (Cys) scanning mutagenesis to TMDs and EJMs of KCNE1 and KCNE2. We analyze the patterns of functional perturbation to identify high impact positions, and probe disulfide formation between engineered Cys side chains on KCNE subunits and native Cys on KCNQ1. We also use methanethiosulfonate reagents to probe the relationship between EJMs of KCNE subunits and KCNQ1. Our data suggest that the TMDs of both KCNE subunits are at about the same location but interact differently with KCNQ1. In particular, the much closer contact of KCNE2 TMD with KCNQ1, relative to that of KCNE1, is expected to impact the allosteric modulation of KCNQ1 pore conductance and may explain their differential effects on the KCNQ1 current amplitude. KCNE1 and KCNE2 also differ in the relationship between their EJMs and KCNQ1. Although the EJM of KCNE1 makes intimate contacts with KCNQ1, there appears to be a crevice between KCNQ1 and KCNE2. This putative crevice may perturb the electrical field around the voltage-sensing domain of KCNQ1, contributing to the differential effects of KCNE2 versus KCNE1 on KCNQ1 gating kinetics.

The rs9982601 polymorphism of the region between the SLC5A3/MRPS6 and KCNE2 genes associated with a prevalence of myocardial infarction and subsequent long-term mortality

“…It is also associated with KCNQ1 (potassium voltage-gated channel, KQT-like subfamily, member 1) and suppresses its current amplitude, which results in slowing down the deactivation gating process. 21 Loss of function of any of those 3 proteins (KCNE2, KCNH2, and KCNQ1) may lead to cohort. Afterwards, owing to a very high-effect size, it could potentially be translated into clinical practice, if only appropriate methods are developed.…”

Photo-Cross-Linking of I Ks Demonstrates State-Dependent Interactions between KCNE1 and KCNQ1

“…G-V relationships show that there is no significant shift in the Previously, residue F57 had been shown to interact with KCNQ1 in the resting state of the channel (25,26). As KCNE1 is proposed to shift and rotate within the clefts of the KCNQ1 tetramer during activation (16,17), the unnatural amino acid cross-linking technique was used to investigate the state-dependent interactions that might occur between these subunits. Upon excitation with UV light (350-380 nm), Bpa forms a covalent cross-link with a C-H bond within a 3.1 Å radius (31).…”

“…Various studies have suggested regulatory interactions occur between KCNE1 and the KCNQ1 tetramer at both the VSD and the pore domain. Using a chimeric approach and scanning mutagenesis, interactions have been identified between KCNE1 and the pore domain of KCNQ1 (14)(15)(16). Whereas the extracellular end of the b-subunit transmembrane domain was shown to interact with the extracellular end of the S1 domain of KCNQ1 (17), cysteine scanning mutagenesis experiments and computational models have shown that KCNE1 comes into close contact with the voltage sensor, S4, in KCNQ1 (18)(19)(20).…”

“…In addition to the regions of interaction between the subunits, the dynamics of KCNE1 within the channel's cleft have been key to understanding its regulation of KCNQ1. It has been proposed that the transmembrane helix of KCNE1 rotates during channel gating from a closed to an open state, and that the midsection of the helix leans toward KCNQ1 in a state-dependent manner (16). Supporting a rotational movement of KCNE1 within the cleft of KCNQ1, Xu et al (17) showed by investigating disulfide bond formation that the interactions between S1 of KCNQ1 and KCNE1 varied depending on the state that the channel was in.…”

Control of Slc7a5 sensitivity by the voltage-sensing domain of Kv1 channels

“…BK channels can be modulated simultaneously by both the BKβ and BKγ subunits, which are thought to associate with the pore-forming subunits via transmembrane domains (Gonzalez-Perez et al, 2015;Gonzalez-Perez and Lingle, 2019;Aldrich, 2012, 2010) . Similarly, the widely studied KCNE subunits are transmembrane proteins that have been proposed to integrate into clefts between neighboring voltage-sensing domains to modulate channel function (Murray et al, 2016;Wang et al, 2012;Xu et al, 2013) . Another Kv channel with prominent regulation of channel gating by multiple classes of regulatory proteins is the Kv4 family, which is sensitive to both KChIP (a soluble cytoplasmic protein) and DPP-like proteins (transmembrane), leading to modulation of channel expression and gating (Jerng et al, 2005;Kitazawa et al, 2015;Zagha et al, 2005) .…”