1. Structural Biology and Molecular Biophysics

Cryo-EM structure of the mechanically activated ion channel OSCA1.2

  1. Sebastian Jojoa Cruz
  2. Kei Saotome
  3. Swetha E Murthy
  4. Che Chun (Alex) Tsui
  5. Mark SP Sansom
  6. Ardem Patapoutian  Is a corresponding author
  7. Andrew B Ward  Is a corresponding author
  1. The Scripps Research Institute, United States
  2. University of Oxford, United Kingdom
https://doi.org/10.7554/eLife.41845
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Cite this article
  1. Sebastian Jojoa Cruz
  2. Kei Saotome
  3. Swetha E Murthy
  4. Che Chun (Alex) Tsui
  5. Mark SP Sansom
  6. Ardem Patapoutian
  7. Andrew B Ward
(2018)
Cryo-EM structure of the mechanically activated ion channel OSCA1.2
eLife 7:e41845.
https://doi.org/10.7554/eLife.41845
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Abstract

Mechanically activated ion channels underlie touch, hearing, shear-stress sensing, and response to turgor pressure. OSCA/TMEM63s are a newly-identified family of eukaryotic mechanically activated ion channels opened by membrane tension. The structural underpinnings of OSCA/TMEM63 function are not explored. Here, we elucidate high resolution cryo-electron microscopy structures of OSCA1.2, revealing a dimeric architecture containing eleven transmembrane helices per subunit and surprising topological similarities to TMEM16 proteins. We locate the ion permeation pathway within each subunit by demonstrating that a conserved acidic residue is a determinant of channel conductance. Molecular dynamics simulations reveal membrane interactions, suggesting the role of lipids in OSCA1.2 gating. These results lay a foundation to decipher how the structural organization of OSCA/TMEM63 is suited for their roles as MA ion channels.

Data availability

Cryo-EM maps of OSCA1.2 in nanodiscs and LMNG have been deposited to the Electron Microscopy Data Bank under accession codes 9112 and 9113. Atomic coordinates of OSCA1.2 in nanodiscs and LMNG have been deposited to the PDB under IDs 6MGV and 6MGW. Due to their large size (300Gb+), the raw data files are available upon request to the corresponding author(s).

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Article and author information

Author details

  1. Sebastian Jojoa Cruz

    Department of Neuroscience, The Scripps Research Institute, La Jolla, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-4392-3898

  2. Kei Saotome

    Department of Neuroscience, The Scripps Research Institute, La Jolla, United States
    Competing interests
    The authors declare that no competing interests exist.

  3. Swetha E Murthy

    Department of Neuroscience, The Scripps Research Institute, La Jolla, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-9580-3380

  4. Che Chun (Alex) Tsui

    Department of Biochemistry, University of Oxford, Oxford, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-4886-9824

  5. Mark SP Sansom

    Department of Biochemistry, University of Oxford, Oxford, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6360-7959

  6. Ardem Patapoutian

    Department of Neuroscience, The Scripps Research Institute, La Jolla, United States
    For correspondence
    ardem@scripps.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-0726-7034

  7. Andrew B Ward

    Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, United States
    For correspondence
    andrew@scripps.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-7153-3769

Funding

Howard Hughes Medical Institute

  • Ardem Patapoutian

Croucher Foundation

  • Che Chun (Alex) Tsui

National Institute of Neurological Disorders and Stroke (1R35NS105067)

  • Ardem Patapoutian

Ray Thomas Edwards Foundation

  • Andrew B Ward

Wellcome (208361/Z/17/Z)

  • Mark SP Sansom

Biotechnology and Biological Sciences Research Council (BB/N000145/1)

  • Mark SP Sansom

Biotechnology and Biological Sciences Research Council (BB/R00126X/1)

  • Mark SP Sansom

Engineering and Physical Sciences Research Council (EP/R004722/1)

  • Mark SP Sansom

Jane Coffin Childs Memorial Fund for Medical Research

  • Kei Saotome

Skaggs-Oxford Scholarship

  • Che Chun (Alex) Tsui

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

Copyright

© 2018, Jojoa Cruz 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. Sebastian Jojoa Cruz
  2. Kei Saotome
  3. Swetha E Murthy
  4. Che Chun (Alex) Tsui
  5. Mark SP Sansom
  6. Ardem Patapoutian
  7. Andrew B Ward
(2018)
Cryo-EM structure of the mechanically activated ion channel OSCA1.2
eLife 7:e41845.
https://doi.org/10.7554/eLife.41845

Share this article

https://doi.org/10.7554/eLife.41845

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Further reading

    1. Structural Biology and Molecular Biophysics

    Structure-guided mutagenesis of OSCAs reveals differential activation to mechanical stimuli

    Sebastian Jojoa-Cruz, Adrienne E Dubin ... Andrew B Ward
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    The dimeric two-pore OSCA/TMEM63 family has recently been identified as mechanically activated ion channels. Previously, based on the unique features of the structure of OSCA1.2, we postulated the potential involvement of several structural elements in sensing membrane tension (Jojoa-Cruz et al., 2018). Interestingly, while OSCA1, 2, and 3 clades are activated by membrane stretch in cell-attached patches (i.e. they are stretch-activated channels), they differ in their ability to transduce membrane deformation induced by a blunt probe (poking). Here, in an effort to understand the domains contributing to mechanical signal transduction, we used cryo-electron microscopy to solve the structure of Arabidopsis thaliana (At) OSCA3.1, which, unlike AtOSCA1.2, only produced stretch- but not poke-activated currents in our initial characterization (Murthy et al., 2018). Mutagenesis and electrophysiological assessment of conserved and divergent putative mechanosensitive features of OSCA1.2 reveal a selective disruption of the macroscopic currents elicited by poking without considerable effects on stretch-activated currents (SAC). Our results support the involvement of the amphipathic helix and lipid-interacting residues in the membrane fenestration in the response to poking. Our findings position these two structural elements as potential sources of functional diversity within the family.

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    OSCA/TMEM63 are an evolutionarily conserved family of mechanically activated ion channels

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    Mechanically activated (MA) ion channels convert physical forces into electrical signals, and are essential for eukaryotic physiology. Despite their importance, few bona-fide MA channels have been described in plants and animals. Here, we show that various members of the OSCA and TMEM63 family of proteins from plants, flies, and mammals confer mechanosensitivity to naïve cells. We conclusively demonstrate that OSCA1.2, one of the Arabidopsis thaliana OSCA proteins, is an inherently mechanosensitive, pore-forming ion channel. Our results suggest that OSCA/TMEM63 proteins are the largest family of MA ion channels identified, and are conserved across eukaryotes. Our findings will enable studies to gain deep insight into molecular mechanisms of MA channel gating, and will facilitate a better understanding of mechanosensory processes in vivo across plants and animals.

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