Conformational changes in the Niemann-Pick type C1 protein NCR1 drive sterol translocation

Kelly M. Frain, Emil Dedic, Lynette Nel, Anastasiia Bohush, Esben Olesen, Katja Thaysen, Daniel Wüstner, David L. Stokes, Bjørn Panyella Pedersen

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

2 Citations (Scopus)

Abstract

The membrane protein Niemann-Pick type C1 (NPC1, named NCR1 in yeast) is central to sterol homeostasis in eukaryotes. Saccharomyces cerevisiae NCR1 is localized to the vacuolar membrane, where it is suggested to carry sterols across the protective glycocalyx and deposit them into the vacuolar membrane. However, documentation of a vacuolar glycocalyx in fungi is lacking, and the mechanism for sterol translocation has remained unclear. Here, we provide evidence supporting the presence of a glycocalyx in isolated S. cerevisiae vacuoles and report four cryo-EM structures of NCR1 in two distinct conformations, named tense and relaxed. These two conformations illustrate the movement of sterols through a tunnel formed by the luminal domains, thus bypassing the barrier presented by the glycocalyx. Based on these structures and on comparison with other members of the Resistance-Nodulation-Division (RND) superfamily, we propose a transport model that links changes in the luminal domains with a cycle of protonation and deprotonation within the transmembrane region of the protein. Our model suggests that NPC proteins work by a generalized RND mechanism where the proton motive force drives conformational changes in the transmembrane domains that are allosterically coupled to luminal/extracellular domains to promote sterol transport.

Original languageEnglish
Article numbere2315575121
JournalProceedings of the National Academy of Sciences of the United States of America
Volume121
Issue15
Pages (from-to)e2315575121
ISSN0027-8424
DOIs
Publication statusPublished - Apr 2024

Keywords

  • cryo-EM
  • glycocalyx
  • Niemann–Pick type C protein
  • sterol uptake
  • vacuole
  • Sterols/metabolism
  • Niemann-Pick C1 Protein/metabolism
  • Membrane Glycoproteins/metabolism
  • Saccharomyces cerevisiae/genetics
  • Carrier Proteins/metabolism
  • Natural Cytotoxicity Triggering Receptor 1/metabolism

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