Multistate Structural Modeling and Voltage-Clamp Analysis of Epilepsy/Autism Mutation Kv10.2–R327H Demonstrate the Role of This Residue in Stabilizing the Channel Closed State

Abstract

Voltage-gated potassium channel Kv10.2 (KCNH5) is expressed in the nervous system, but its functions and involvement in human disease are poorly understood. We studied a human Kv10.2 channel mutation (R327H) recently identified in a child with epileptic encephalopathy and autistic features. Using multistate structural modeling, we demonstrate that the Arg327 residue in the S4 helix of voltage-sensing domain has strong ionic interactions with negatively charged residues within the S1-S3 helices in the resting (closed) and early-activation state but not in the late-activation and fully-activated (open) state. The R327H mutation weakens ionic interactions between residue 327 and these negatively charged residues, thus favoring channel opening. Voltage-clamp analysis showed a strong hyperpolarizing (ϳ70 mV) shift of voltage dependence of activation and an acceleration of activation. Our results demonstrate the critical role of the Arg327 residue in stabilizing the channel closed state and explicate for the first time the structural and functional change of a Kv10.2 channel mutation associated with neurological disease.

Depolarized Inactivation Overcomes Impaired Activation to Produce DRG Neuron Hyperexcitability in a Nav1.7 Mutation in a Patient with Distal Limb Pain

“…We have previously studied a voltagegated potassium channel mutation (K v 10.2-R327H) associated with epilepsy/ autism (Yang et al, 2013b). R327 is one of the critical positively charged residues (R2) within the S4 helix of the K v 10.2 channel.…”

“…Using multistate modeling, we showed that R327 has strong ionic interaction with negatively charged residues of the S1-S3 helices in the closed but not open state of the channel. The R327H K v 10.2 mutation weakens these interactions, thus making it easier to open the channel (Yang et al, 2013b).…”

“…Multistate structural modeling of Na v 1.7 DIII VSD Multistate modeling provides a high-resolution method for predicting atomic-level changes associated with the gating of a voltage-gated ion channel as it transits from closed to activated and back to closed states (Yang et al, 2013b). Because the IFM inactivation particle is not located within a membrane-spanning segment that can be accurately modeled, channel inactivation is not amenable to analysis by multistate modeling.…”

“…Modeling of the Na v 1.7 channel was performed based on previously described methods (Yang et al, , 2013b. Briefly, the sequence of voltage-sensing domain (VSD) of Na v 1.7 domain III was aligned to K v 1.2/K v 2.1 "paddle chimera" voltage-gated K ϩ channel (Long et al, 2007) using ClustalW2 and manually refined based on previous studies (Yarov-Yarovoy et al, 2012).…”

“…Modeling of the Na v 1.7 channel was performed based on previously described methods (Yang et al, , 2013b. Briefly, the sequence of voltage-sensing domain (VSD) of Na v 1.7 domain III was aligned to K v 1.2/K v 2.1 "paddle chimera" voltage-gated K ϩ channel (Long et al, 2007) using ClustalW2 and manually refined based on previous studies (Yarov-Yarovoy et al, 2012). Modeling of the S1-S4 VSD in six gating states was performed with SWISS-MODEL Bordoli et al, 2009) based on templates generated in an ultra-long molecular dynamics simulation (Jensen et al, 2012) and refined as described previously (Yang et al, , 2013a.…”