Therapeutic small molecule modulation of Kv channels

University Of California-Irvine, Irvine CA

Investigators

Linked publications, trials & patents

Abstract

Project Summary Neuronal Kv7 (KCNQ) and Kv1 (KCNA1) subfamily voltage-gated potassium (Kv) channel loss-of-function causes developmental epileptic encephalopathy, ataxia, hereditary spastic paraplegia (HSP) and addiction. In this project we focus on the mechanistic basis and potential therapeutic utility of plant-derived diterpenes and hydroxybenzoic acids that are extremely well tolerated in rodent and human safety studies, cross the blood- brain-barrier, and which we recently discovered to be potent, efficacious openers of neuronal Kv7 and Kv1 channels. Addiction and epilepsy represent major health burdens in the US and globally, and new approaches to their treatment are desperately warranted. Episodic ataxia and HSP are relatively rare and therefore can especially benefit from therapeutic development in academia; in turn, treatments developed for episodic ataxia can inform development of therapies for epilepsy and potentially other forms of ataxia. In this project we take a multidisciplinary approach incorporating molecular dynamics (MD) simulations, site-directed mutagenesis, electrophysiology, and in vivo testing in existing and novel mouse models. In Aim 1, we will pursue the molecular basis of action and isoform selectivity of the diterpene carnosic acid (CA), which we recently discovered to be a highly efficacious and isoform-selective Kv7.3/5 channel opener, and to Kv7.3/5-dependently inhibit cocaine- seeking behavior in mice. We now intend to delineate how CA opens Kv7.3 but not Kv7.2 using all-atom MD simulations, mutagenesis and electrophysiology. We propose similar studies for gentisic acid (GTA), a hydroxybenzoic acid we recently found to be the most potent known opener of Kv7.3 and Kv7.2/3. The studies are translationally highly significant because of the potential for CA to treat psychotropic drug addiction, and for GTA as a lead anticonvulsant compound. In Aim 2, we will determine the molecular basis of action of pisiferic acid (PA) and gallic acid (GA), another diterpene and hydroxybenzoic acid, respectively, that we found to be novel Kv1.1/Kv1.2 channel openers that can reverse the effects of Kv1.1 and Kv1.2 mutations that cause ataxia, epilepsy and HSP. We will use experimentally validated MD simulations of entire Kv1.1 and Kv1.2 channels in model neuronal lipid membranes, to determine how PA and GA achieve efficacy, potency and selectivity. Extensive preliminary data support an exciting paradigm in which PA co-opts the Kv1.1 voltage sensor to act as a ligand-binding/gating domain. We will also test the ability of PA and GA to rescue in vitro a broader panel of ataxia, epilepsy, and HSP-linked Kv1.1 and/or Kv1.2 mutants. We have already discovered that PA reverses EA1 in vivo in our new mouse model of Kv1.1-linked Episodic Ataxia Type 1 (EA1). In Aim 3, we will conduct in vivo testing of the therapeutic efficacy of PA and GA in mouse models of EA1 and Kv1.2-linked ataxia/epilepsy/HSP, and PK studies. The project will uncover transformative mechanistic paradigms for small molecule opening of voltage gated ion channels in general, whilst also providing a complete picture of the mode of action of four safe, efficacious, selective and/or potent Kv channel openers with true therapeutic potential.