Molecular mechanism of voltage-dependent potentiation of KCNH potassium channels.

Gucan Dai,William N Zagotta

doi:10.7554/elife.26355

Abstract

EAG-like (ELK) voltage-gated potassium channels are abundantly expressed in the brain. These channels exhibit a behavior called voltage-dependent potentiation (VDP), which appears to be a specialization to dampen the hyperexitability of neurons. VDP manifests as a potentiation of current amplitude, hyperpolarizing shift in voltage sensitivity, and slowing of deactivation in response to a depolarizing prepulse. Here we show that VDP of D. rerio ELK channels involves the structural interaction between the intracellular N-terminal eag domain and C-terminal CNBHD. Combining transition metal ion FRET, patch-clamp fluorometry, and incorporation of a fluorescent noncanonical amino acid, we show that there is a rearrangement in the eag domain-CNBHD interaction with the kinetics, voltage-dependence, and ATP-dependence of VDP. We propose that the activation of ELK channels involves a slow open-state dependent rearrangement of the direct interaction between the eag domain and CNBHD, which stabilizes the opening of the channel.

Highlights

Ion channels in the KCNH family (EAG, ERG and ELK) are voltage-gated potassium channels important for nervous system function, cardiac physiology, and cancer biology (Warmke and Ganetzky, 1994; Ganetzky et al, 1999; Pardo et al, 1999; Morais-Cabral and Robertson, 2015) (Figure 1— figure supplement 1)
By simultaneously measuring channel current and transition metal ion FRET (tmFRET) using patch-clamp fluorometry (PCF) (Zheng and Zagotta, 2003), we showed that the distance between the eag domain and cyclic nucleotide-binding homology domain (CNBHD) decreases with the time course, voltage-dependence, and ATP-dependence of voltage-dependent potentiation (VDP)
We show zELK channels exhibit VDP that results from the channel undergoing a slow state-dependent transition to a mode with a more favorable opening transition

Summary

Introduction

Ion channels in the KCNH family (EAG, ERG and ELK) are voltage-gated potassium channels important for nervous system function, cardiac physiology, and cancer biology (Warmke and Ganetzky, 1994; Ganetzky et al, 1999; Pardo et al, 1999; Morais-Cabral and Robertson, 2015) (Figure 1— figure supplement 1). The analogous cyclic nucleotide-binding pocket of the CNBHD is occupied by an ‘intrinsic ligand’ from a short sequence at the C-terminal end of the CNBHD (Marques-Carvalho et al, 2012; Brelidze et al, 2012) This intrinsic ligand regulates KCNH channel function (Marques-Carvalho et al, 2012; Brelidze et al, 2012; Zhao et al, 2017)

Methods

Results

Conclusion