Structural dynamics determine voltage and pH gating in human voltage-gated proton channel

  1. Shuo Han
  2. Sophia Peng
  3. Joshua Vance
  4. Kimberly Tran
  5. Nhu Do
  6. Nauy Bui
  7. Zhenhua Gui
  8. Shizhen Wang  Is a corresponding author
  1. University of Missouri-Kansas City, United States

Abstract

Voltage-gated ion channels are key players of electrical signaling in cells. As a unique subfamily, voltage-gated proton (Hv) channels are standalone voltage sensors without separate ion conductive pores. Hv channels are gated by both voltage and transmembrane proton gradient (i.e ∆pH), serving as acid extruders in most cells. Amongst their many functions, Hv channels are known for regulating the intracellular pH of human spermatozoa and compensating for the charge and pH imbalances caused by NADPH oxidases in phagocytes. Like the canonical voltage sensors, Hv channels are a bundle of 4 helices (named S1 through S4), with the S4 segment carrying 3 positively charged Arg residues. Extensive structural and electrophysiological studies on voltage-gated ion channels, in general, agree on an outwards movement of the S4 segment upon activating voltage, but the real-time conformational transitions are still unattainable. With purified human voltage-gated proton (hHv1) channels reconstituted in liposomes, we have examined its conformational dynamics, including the S4 segment at different voltage and pHs using single-molecule fluorescence resonance energy transfer (smFRET). Here, we provide the first glimpse of real-time conformational trajectories of the hHv1 voltage sensor and show that both voltage and pH gradient shift the conformational dynamics of the S4 segment to control channel gating. Our results indicate that the S4 segment transits among 3 major conformational states and kinetic analysis suggest that only the transitions between the inward and outward conformations are highly dependent on voltage and pH changes. Our smFRET studies uncover the stochastic conformational dynamics of S4 and demonstrate how voltage and pH shift its conformational distributions to regulate channel gating. Altogether, we propose a kinetic model that explains the mechanisms underlying voltage and pH gating in Hv channels, which may also serve as a general framework for understanding the voltage sensing and gating in other voltage-gated ion channels.

Data availability

The source data of all smFRET traces, contour maps, histograms, as well as liposome flux assay data is deposited in Dryad (Dryad Digital Repository, doi:10.5061/dryad.dv41ns1zs), including Fig 1b, c, d, e, g, h; Fig 2; Fig 3a and b; Fig 4a, b; Fig 5a, Fig 1-figure supplement1a and c, Fig1-figure supplement 2a, b, c; Fig1-figure supplement 3a, b; Fig1-figure supplement 4a and b.

The following data sets were generated

Article and author information

Author details

  1. Shuo Han

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Sophia Peng

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-7434-5445
  3. Joshua Vance

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Kimberly Tran

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Nhu Do

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Nauy Bui

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Zhenhua Gui

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    Competing interests
    The authors declare that no competing interests exist.
  8. Shizhen Wang

    Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
    For correspondence
    wangshizhen@umkc.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1065-4756

Funding

NIH (1R15GM137215-01)

  • Shizhen Wang

University of Missouri-Kansas City (Startup fund)

  • Shizhen Wang

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

Reviewing Editor

  1. Baron Chanda, Washington University in St. Louis, United States

Publication history

  1. Received: August 16, 2021
  2. Preprint posted: August 26, 2021 (view preprint)
  3. Accepted: February 24, 2022
  4. Accepted Manuscript published: March 4, 2022 (version 1)
  5. Version of Record published: March 16, 2022 (version 2)
  6. Version of Record updated: March 16, 2022 (version 3)

Copyright

© 2022, Han 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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  1. Shuo Han
  2. Sophia Peng
  3. Joshua Vance
  4. Kimberly Tran
  5. Nhu Do
  6. Nauy Bui
  7. Zhenhua Gui
  8. Shizhen Wang
(2022)
Structural dynamics determine voltage and pH gating in human voltage-gated proton channel
eLife 11:e73093.
https://doi.org/10.7554/eLife.73093
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