Exchange of water for sterol underlies sterol egress from a StARkin domain

  1. George Khelashvili
  2. Neha Chauhan
  3. Kalpana Pandey
  4. David Eliezer
  5. Anant K Menon  Is a corresponding author
  1. Weill Cornell Medical College, United States

Abstract

Previously we identified Lam/GramD1 proteins, a family of endoplasmic reticulum membrane proteins with sterol-binding StARkin domains (Gatta et al. eLife 2015), which are implicated in intracellular sterol homeostasis. Here we show how these proteins exchange sterol molecules with membranes. An aperture at one end of the StARkin domain enables sterol to enter/exit the binding pocket. Strikingly, the wall of the pocket is longitudinally fractured, exposing bound sterol to solvent. Large-scale atomistic molecular dynamics simulations reveal that sterol egress involves widening of the fracture, penetration of water into the cavity and consequent destabilization of the bound sterol. The simulations identify polar residues along the fracture that are important for sterol release. Their replacement with alanine affects the ability of the StARkin domain to bind sterol, catalyze inter-vesicular sterol exchange and alleviate the nystatin-sensitivity of lam2D yeast cells. These data suggest an unprecedented, water-controlled mechanism of sterol discharge from a StARkin domain.

Data availability

All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1, 2 and 4.

Article and author information

Author details

  1. George Khelashvili

    Department of Physiology and Biophysics, 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:" 0000-0001-7235-8579
  2. Neha Chauhan

    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:" 0000-0003-1497-3359
  3. Kalpana Pandey

    Department of Biochemistry, Weill Cornell Medical College, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. David Eliezer

    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:" 0000-0002-1311-7537
  5. Anant K Menon

    Department of Biochemistry, Weill Cornell Medical College, New York, United States
    For correspondence
    akm2003@med.cornell.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6924-2698

Funding

National Institutes of Health (R37AG019391)

  • David Eliezer

1923 Fund

  • George Khelashvili

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

Reviewing Editor

  1. Arun Radhakrishnan, University of Texas Southwestern Medical Center, United States

Publication history

  1. Received: November 11, 2019
  2. Accepted: November 29, 2019
  3. Accepted Manuscript published: December 4, 2019 (version 1)
  4. Version of Record published: January 2, 2020 (version 2)

Copyright

© 2019, Khelashvili 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. George Khelashvili
  2. Neha Chauhan
  3. Kalpana Pandey
  4. David Eliezer
  5. Anant K Menon
(2019)
Exchange of water for sterol underlies sterol egress from a StARkin domain
eLife 8:e53444.
https://doi.org/10.7554/eLife.53444

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