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

Ruiming Zhao, Arwa Qasim, Punyanuch Sophanpanichkul, Hui Dai, Maha Nayak, Inbal Sher, Jordan Chill, Steve A.N. Goldstein

Research output: Contribution to journalArticlepeer-review

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 (Ki ~ 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 Lys23, 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-L296F 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-L296F 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 Ki of ~10 nM even though homomeric Kv1.2 channels were insensitive to the toxin (Ki > 2000 nM).

Original languageEnglish
Article numbere23381
JournalFASEB Journal
Volume38
Issue number1
DOIs
StatePublished - Jan 2024

Bibliographical note

Publisher Copyright:
© 2023 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.

Keywords

  • AETX-K
  • Kv1.1
  • NMR
  • epilepsy
  • venom peptide

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