Structural basis of Ca2+-dependent activation and lipid transport by a TMEM16 scramblase

Abstract

The lipid distribution of plasma membranes of eukaryotic cells is asymmetric and phospholipid scramblases disrupt this asymmetry by mediating the rapid, nonselective transport of lipids down their concentration gradients. As a result, phosphatidylserine is exposed to the outer leaflet of membrane, an important step in extracellular signaling networks controlling processes such as apoptosis, blood coagulation, membrane fusion and repair. Several TMEM16 family members have been identified as Ca2+-activated scramblases but the mechanisms underlying their Ca2+-dependent gating and their effects on the surrounding lipid bilayer remain poorly understood. Here we describe three high-resolution cryo-electron microscopy structures of a fungal scramblase from Aspergillus fumigatus, afTMEM16, reconstituted in lipid nanodiscs. These structures reveal that Ca2+-dependent activation of the scramblase entails global rearrangement of the transmembrane and cytosolic domains. These structures, together with functional experiments, suggest that activation of the protein thins the membrane near the transport pathway to facilitate rapid transbilayer lipid movement.

Data availability

CryoEM data have been deposited in the EMPDB database under accession codes: 6E0H, 6DZ7, 6E1O, EMD-8931, EMD-8948, EMD-8959. Raw EM micrographs and un-masked maps are in the process of being deposited.Key parameters of the fluorescence time courses are detailed in the tables and figures and representative traces used in the figures have been provided as source data files. The raw fluorescence time courses are available upon request to the corresponding author.

The following data sets were generated

Article and author information

Author details

  1. Maria E Falzone

    Department of Biochemistry, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6738-7017
  2. Jan Rheinberger

    Department of Anesthesiology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-9901-2065
  3. Byoung-Cheol Lee

    Department of Anesthesiology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Thasin Peyear

    Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Linda Sasset

    Department of Pathology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Ashleigh M Raczkowski

    Simons Electron Microscopy Center, New York Structural Biology Center, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Edward T Eng

    Simons Electron Microscopy Center, New York Structural Biology Center, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8014-7269
  8. Annarita Di Lorenzo

    Department of Pathology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  9. Olaf S Andersen

    Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  10. Crina M Nimigean

    Department of Anesthesiology, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6254-4447
  11. Alessio Accardi

    Department of Biochemistry, Weill Cornell Medical College, New York, United States
    For correspondence
    ala2022@med.cornell.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6584-0102

Funding

National Institute of General Medical Sciences (R01GM106717)

  • Alessio Accardi

National Institute of Neurological Disorders and Stroke (R21NS10451)

  • Annarita Di Lorenzo

Irma T. Hirschl Trust

  • Alessio Accardi

Margaret and Herman Sokol Fellowship

  • Maria E Falzone

National Research Foundation of Korea (2013R1A6A3A03064407)

  • Byoung-Cheol Lee

Agouron Institute (F00316)

  • Edward T Eng

Simons Foundation (349247)

  • Edward T Eng

National Institute of General Medical Sciences (GM103310)

  • Edward T Eng

National Institute of General Medical Sciences (1R01GM124451-02)

  • Crina M Nimigean

Korean Ministry of Science (18-BR-01-02)

  • Byoung-Cheol Lee

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

Reviewing Editor

  1. László Csanády, Semmelweis University, Hungary

Version history

  1. Received: October 30, 2018
  2. Accepted: January 2, 2019
  3. Accepted Manuscript published: January 16, 2019 (version 1)
  4. Version of Record published: January 31, 2019 (version 2)
  5. Version of Record updated: February 1, 2019 (version 3)

Copyright

© 2019, Falzone 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. Maria E Falzone
  2. Jan Rheinberger
  3. Byoung-Cheol Lee
  4. Thasin Peyear
  5. Linda Sasset
  6. Ashleigh M Raczkowski
  7. Edward T Eng
  8. Annarita Di Lorenzo
  9. Olaf S Andersen
  10. Crina M Nimigean
  11. Alessio Accardi
(2019)
Structural basis of Ca2+-dependent activation and lipid transport by a TMEM16 scramblase
eLife 8:e43229.
https://doi.org/10.7554/eLife.43229

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https://doi.org/10.7554/eLife.43229