µ-Theraphotoxin-Pn3a inhibition of CaV3.3 channels reveals a novel isoform-selective drug binding site

  1. Jeffrey R McArthur  Is a corresponding author
  2. Jierong Wen
  3. Andrew Hung
  4. Rocio K Finol-Urdaneta
  5. David J Adams
  1. University of Wollongong, Australia
  2. RMIT University, Australia

Abstract

Low voltage-activated calcium currents are mediated by T-type calcium channels CaV3.1, CaV3.2, and CaV3.3, which modulate a variety of physiological processes including sleep, cardiac pace-making, pain, and epilepsy. CaV3 isoforms' biophysical properties, overlapping expression, and lack of subtype-selective pharmacology hinder the determination of their specific physiological roles in health and disease. We have identified μ-theraphotoxin Pn3a as the first subtype-selective spider venom peptide inhibitor of CaV3.3, with >100-fold lower potency against the other T-type isoforms. Pn3a modifies CaV3.3 gating through a depolarizing shift in the voltage dependence of activation thus decreasing CaV3.3-mediated currents in the normal range of activation potentials. Paddle chimeras of KV1.7 channels bearing voltage sensor sequences from all four CaV3.3 domains revealed preferential binding of Pn3a to the S3-S4 region of domain II (CaV3.3DII). This novel T-type channel pharmacological site was explored through computational docking simulations of Pn3a, site-directed mutagenesis, and full domain II swaps between Cav3 channels highlighting it as a subtype-specific pharmacophore. This research expands our understanding of T-type calcium channel pharmacology and supports the suitability of Pn3a as a molecular tool in the study of the physiological roles of CaV3.3 channels.

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All data generated or analysed during this study are included in the manuscript and supporting file

Article and author information

Author details

  1. Jeffrey R McArthur

    Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
    For correspondence
    jeffreym@uow.edu.au
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-2546-7913
  2. Jierong Wen

    School of Science, RMIT University, Melbourne, Australia
    Competing interests
    The authors declare that no competing interests exist.
  3. Andrew Hung

    School of Science, RMIT University, Melbourne, Australia
    Competing interests
    The authors declare that no competing interests exist.
  4. Rocio K Finol-Urdaneta

    Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2157-4532
  5. David J Adams

    Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-7030-2288

Funding

Rebecca L. Cooper Medical Research Foundation (PG2019396)

  • Jeffrey R McArthur

National Health and Medical Research Council (APP1072113)

  • David J Adams

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

© 2022, McArthur et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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