small molecules

2026-07-25 | Rosemary metabolite carnosic acid opens Kv1.1 via its voltage sensor and corrects Kv1.1-linked episodic ataxia in mice.

Episodic ataxia type 1 (EA1) is an autosomal dominant neurological disorder caused primarily by loss-of-function mutations in the voltage-gated potassium channel Kv1.1 (KCNA1). Small molecules that restore Kv1.1 activity hold promise as targeted therapies for EA1, yet current pharmacological strategies remain limited. Two electrode voltage-clamp electrophysiology and the Xenopus laevis oocyte expression system were used to study effects of carnosic acid, a phenolic diterpene from Salvia rosmarinus (rosemary) leaf extract on Kv1.1-linked EA1 mutant channels. We assessed ataxia therapeutic efficacy by comparing performance of Kcna1+/+ and Kcna1E283K/+ mice, a model of human EA1, on a balance beam under isoproterenol challenge in the absence or presence of 0.3-mg·kg-1 carnosic acid. Rosemary leaf extract and rosemary metabolite carnosic acid are efficacious Kv1.1 openers. Carnosic acid fully or partially corrects heterozygous, heteromeric Kv1.1 EA1 mutant channel activity in vitro and restores normal function in Kv1.1E283K/+ mice at 0.3 mg·kg-1. Experimental validation of unbiased in silico docking reveals carnosic acid occupies a binding pocket between the S1 and S4 helices of the voltage-sensing domain (VSD) of Kv1.1. Finally, we determined the chemical properties that endow carnosic acid with the ability to open Kv1.1 channels. Our findings uncover a Kv1.1 opener with the potential to reverse EA1 and other Kv1.1-linked disorders.

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2026-06-16 | Data from: Rosemary metabolite carnosic acid opens Kv1.1 via its voltage sensor and corrects Kv1.1-linked episodic ataxia in mice

Background and Purpose: Episodic ataxia type 1 (EA1) is an autosomal dominant neurological disorder caused primarily by loss-of-function mutations in the voltage-gated potassium channel Kv1.1 (KCNA1). Small molecules that restore Kv1.1 activity hold promise as targeted therapies for EA1, yet current pharmacological strategies remain limited. Experimental Approach: Two electrode voltage-clamp electrophysiology and the Xenopus laevis oocyte expression system were used to study effects of carnosic acid, a phenolic diterpene from Salvia rosmarinus (rosemary) leaf extract on Kv1.1-linked EA1 mutant channels. We assessed ataxia therapeutic efficacy by comparing performance of Kcna1+/+ and Kcna1E283K/+ mice, a model of human EA1, on a balance beam under isoproterenol challenge in the absence or presence of 0.3 mg/kg carnosic acid. Key Results: Rosemary leaf extract and rosemary metabolite carnosic acid are efficacious Kv1.1 openers. Carnosic acid fully or partially corrects heterozygous, heteromeric Kv1.1 EA1 mutant channel activity in vitro and restores normal function in Kv1.1E283K/+ mice at 0.3 mg/kg. Experimental validation of unbiased in silico docking reveals carnosic acid occupies a binding pocket between the S1 and S4 helices of the voltage-sensing domain (VSD) of Kv1.1. Finally, we determined the chemical properties that endow carnosic acid with the ability to open Kv1.1 channels. Conclusions and Implications: Our findings uncover a Kv1.1 opener with the potential to reverse EA1 and other Kv1.1-linked disorders.

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2025-01-10 | A conifer metabolite corrects episodic ataxia type 1 by voltage sensor-mediated ligand activation of Kv1.1.

Loss-of-function sequence variants in KCNA1, which encodes the voltage-gated potassium channel Kv1.1, cause Episodic Ataxia Type 1 (EA1) and epilepsy. Due to a paucity of drugs that directly rescue mutant Kv1.1 channel function, current therapeutic strategies for KCNA1-linked disorders involve indirect modulation of neuronal excitability. Native Americans have traditionally used conifer extracts to treat paralysis, weakness, and pain, all of which may involve altered electrical activity and/or Kv1.1 dysfunction specifically. Here, screening conifer extracts, we found that Chamaecyparis pisifera increases wild-type (WT) Kv1.1 activity, as does its prominent metabolite, the abietane diterpenoid pisiferic acid. Uniquely, pisiferic acid also restored function in 12/12 EA1-linked mutant Kv1.1 channels tested in vitro. Crucially, pisiferic acid (1 mg/kg) restored WT function in Kv1.1E283K/+ mice, a model of human EA1. Experimentally validated all-atom molecular dynamics simulations in a neuron-like membrane revealed that the Kv1.1 voltage-sensing domain (VSD) also acts as a ligand-binding domain akin to those of classic ligand-gated channels; binding of pisiferic acid induces a conformational shift in the VSD that ligand-dependently opens the pore. Conifer metabolite pisiferic acid is a promising and versatile therapeutic lead for EA1 and other Kv1.1-linked disorders.

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2024-03-18 | CACNA1Ahaploinsufficiency leads to reduced synaptic function and increased intrinsic excitability

Abstract Haploinsufficiency of the CACNA1A gene, encoding the pore-forming α1 subunit of P/Q-type voltage-gated calcium channels, is associated with a clinically variable phenotype ranging from cerebellar ataxia, to neurodevelopmental syndromes with epilepsy and intellectual disability. To understand the pathological mechanisms of CACNA1A loss-of-function variants, we characterized a human neuronal model for CACNA1A haploinsufficiency, by differentiating isogenic induced pluripotent stem cell lines into glutamatergic neurons, and investigated the effect of CACNA1A haploinsufficiency on mature neuronal networks through a combination of electrophysiology, gene expression analysis, and in silico modeling. We observed an altered network synchronization in CACNA1A +/− networks alongside synaptic deficits, notably marked by an augmented contribution of GluA2-lacking AMPA receptors. Intriguingly, these synaptic perturbations coexisted with increased non-synaptically driven activity, as characterized by inhibition of NMDA and AMPA receptors on micro-electrode arrays. Single-cell electrophysiology and gene expression analysis corroborated this increased intrinsic excitability through reduced potassium channel function and expression. Moreover, we observed partial mitigation of the CACNA1A +/− network phenotype by 4-aminopyridine, a therapeutic intervention for episodic ataxia type 2. In summary, our study pioneers the characterization of a human induced pluripotent stem cell-derived neuronal model for CACNA1A haploinsufficiency, and has unveiled novel mechanistic insights. Beyond showcasing synaptic deficits, this neuronal model exhibited increased intrinsic excitability mediated by diminished potassium channel function, underscoring its potential as a therapeutic discovery platform with predictive validity.

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2024-03-08 | P380: Use of dextrose containing fluids and intralipids in a patient with KCNA1 related neuromyotonia

KCNA1 encodes a potassium voltage-gated channel (Kv1.1). This channel plays a key role in modulating the release of neurotransmitters like GABA and controlling the excitability of neurons in the cerebellum, hippocampus, cortical and peripheral nervous system. Variants in KCNA1 are classically known to cause episodic ataxia/myokymia syndrome type 1 (EA1). EA1 is classically characterized by episodes of ataxia often with vertigo, diaphoresis, and clumsiness along with persistent myokymia. The age of onset is typically younger than 20 years and can be triggered by stressors, exercise, temperature changes, and sudden movements. Since the description of EA1, the phenotype has been expanded substantially. The expanded phenotype includes epilepsy, encephalopathies, hypomagnesemia, and paroxysmal kinesigenic dyskinesia. In addition, several papers have described a neuromyotonia phenotype comprised of episodes of severe muscle stiffness and findings of inguinal or hiatal hernias. Treatment to prevent attacks is limited by lack of clinical trials but commonly used or proposed treatments include Acetazolamide, Phenytoin, Sulthiame, Carbamazepine, and Lamotrigine. We present a family including a 7-year-old female with episodes of neuromyotonia and a familial variant of uncertain significance (VUS) in KCNA1. Birth history was remarkable for maternal pre-eclampsia, kidney stones, and anhydramnios at the end of pregnancy, but no postnatal complications. She presented with symptoms around 6 months of age with episodes of hand stiffening along with emesis. These symptoms are also present in our patient's father, paternal half-sister, and paternal grandmother. Comprehensive testing including electroencephalograms, biochemical and genetic (exome) testing in this family has been unrevealing, aside from familial VUS in KCNA1 which segregates with affected family members. Symptoms progressed to episodes of bilateral extremity and core muscle stiffening multiple times per month lasting hours to days and requiring hospitalization several times per year. Our patient has also required 2 separate surgeries for hiatal hernia, a possible complication associated with the episodic myotonia. Parents also report a baseline waxing and waning of mild generalized hypertonicity. Episodes are triggered by temperature extremes, illness, stress, and fasting. She has required antiepileptic medication since presentation of symptoms with most presently being treated with carbamazepine and Ativan. In the acute setting of an attack requiring medical intervention, our patient has historically been treated with D12.5 IVF and intralipids. This treatment appears effective for our patient but is not a proposed treatment in the literature. Additionally, our patient's father, who shares the KCNA1 variant, and phenotype also received this treatment with good response. Our patient presents with a familial VUS in KCNA1, which segregates with affected family members with episodic myotonia which is a described phenotype associated with pathogenic variants in KCNA1. Current management includes avoidance of triggers, antiepileptic medication, and acetazolamide which is effective in some patients, but acute management during attacks of myotonia is lacking. In addition to recommended treatment of KCNA1 related disorders which our patient has responded well to for prevention of attacks, our patient and her father have had success in acute treatment of attacks with dextrose containing fluids and intralipids. Although this is reported effective treatment in a small family with presumed EA1, since the treatment is relatively benign, medical providers could consider trial of this treatment in patients with EA1 who remain uncontrolled on standard of care medications.

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proteins

2023-12-16 | Selective block of human Kv1.1 channels and an epilepsy-associated gain-of-function mutation by AETX-K peptide.

Abstract Dysfunction of the human voltage‐gated K + channel Kv1.1 has been associated with epilepsy, multiple sclerosis, episodic ataxia, myokymia, and cardiorespiratory dysregulation. We report here that AETX‐K, a sea anemone type I (SAK1) peptide toxin we isolated from a phage display library, blocks Kv1.1 with high affinity ( K i ~ 1.6 pM) and notable specificity, inhibiting other Kv channels we tested a million‐fold less well. Nuclear magnetic resonance (NMR) was employed both to determine the three‐dimensional structure of AETX‐K, showing it to employ a classic SAK1 scaffold while exhibiting a unique electrostatic potential surface, and to visualize AETX‐K bound to the Kv1.1 pore domain embedded in lipoprotein nanodiscs. Study of Kv1.1 in Xenopus oocytes with AETX‐K and point variants using electrophysiology demonstrated the blocking mechanism to employ a toxin‐channel configuration we have described before whereby AETX‐K Lys 23 , two positions away on the toxin interaction surface from the classical blocking residue, enters the pore deeply enough to interact with K + ions traversing the pathway from the opposite side of the membrane. The mutant channel Kv1.1‐L 296 F is associated with pharmaco‐resistant multifocal epilepsy in infants because it significantly increases K + currents by facilitating opening and slowing closure of the channels. Consistent with the therapeutic potential of AETX‐K for Kv1.1 gain‐of‐function‐associated diseases, AETX‐K at 4 pM decreased Kv1.1‐L 296 F currents to wild‐type levels; further, populations of heteromeric channels formed by co‐expression Kv1.1 and Kv1.2, as found in many neurons, showed a K i of ~10 nM even though homomeric Kv1.2 channels were insensitive to the toxin ( K i > 2000 nM).

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