In silico re-engineering of a neurotransmitter to activate KCNQ potassium channels in an isoform-specific manner

Rían W Manville,Geoffrey W Abbott

doi:10.1038/s42003-019-0648-3

Rían W Manville, Geoffrey W Abbott

Open Access

https://doi.org/10.1038/s42003-019-0648-3

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Journal: Communications Biology	Publication Date: Nov 1, 2019
Citations: 10	License type: open-access

Affiliation: University of California, Irvine

Abstract

Voltage-gated potassium (Kv) channel dysfunction causes a variety of inherited disorders, but developing small molecules that activate Kv channels has proven challenging. We recently discovered that the inhibitory neurotransmitter γ-aminobutyric acid (GABA) directly activates Kv channels KCNQ3 and KCNQ5. Here, finding that inhibitory neurotransmitter glycine does not activate KCNQs, we re-engineered it in silico to introduce predicted KCNQ-opening properties, screened by in silico docking, then validated the hits in vitro. Attaching a fluorophenyl ring to glycine optimized its electrostatic potential, converting it to a low-nM affinity KCNQ channel activator. Repositioning the phenyl ring fluorine and/or adding a methylsulfonyl group increased the efficacy of the re-engineered glycines and switched their target KCNQs. Combining KCNQ2- and KCNQ3-specific glycine derivatives synergistically potentiated KCNQ2/3 activation by exploiting heteromeric channel composition. Thus, in silico optimization and docking, combined with functional screening of only three compounds, facilitated re-engineering of glycine to develop several potent KCNQ activators.

Highlights

Voltage-gated potassium (Kv) channel dysfunction causes a variety of inherited disorders, but developing small molecules that activate Kv channels has proven challenging
Consistent with functional selectivity, using measurements of ion permeability series we found that 2FPG induces an increase in relative Na+ permeability in KCNQ2 but not KCNQ3*, whereas 3FMSG induces a similar increase in relative Na+ permeability of KCNQ3* but not KCNQ2
Glycine and glutamate are structurally related to GABA, yet unlike GABA they do not exhibit negative electrostatic surface potential centered on the carbonyl group, an established property of several KCNQ channel openers that activate via KCNQ3W26511

Summary

Introduction

Voltage-gated potassium (Kv) channel dysfunction causes a variety of inherited disorders, but developing small molecules that activate Kv channels has proven challenging. One of the reasons for this is that a great many Kv channel-linked disorders, or channelopathies, arise from loss of function. Retigabine was the first Kv channel opener to reach the clinic, but was withdrawn in 2017 because of off-target side effects—it turns the sclera and skin blue[6]. It is effective at opening KCNQ2/3 channels and was clinically useful, mostly as an add-on therapy, in epilepsy. We recently made the surprising discovery that the predominant inhibitory neurotransmitter γ-aminobutyric acid (GABA) binds in a similar binding pocket to that of retigabine, and activates KCNQ3, KCNQ5, and KCNQ2/3 channels[8]. KCNQ channels, and possibly other Kv channels, thereby possess a binding pocket that accommodates numerous types of small-molecule activators

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