Journal article

Endoplasmic reticulum chaperones stabilize ligand-receptive MR1 molecules for efficient presentation of metabolite antigens

Hamish EG McWilliam, Jeffrey YW Mak, Wael Awad, Matthew Zorkau, Sebastian Cruz-Gomez, Hui Jing Lim, Yuting Yan, Sam Wormald, Laura F Dagley, Sidonia BG Eckle, Alexandra J Corbett, Haiyin Liu, Shihan Li, Scott JJ Reddiex, Justine D Mintern, Ligong Liu, James McCluskey, Jamie Rossjohn, David P Fairlie, Jose A Villadangos

Proceedings of the National Academy of Sciences of USA | NATL ACAD SCIENCES | Published : 2020

Abstract

The antigen-presenting molecule MR1 (MHC class I-related protein 1) presents metabolite antigens derived from microbial vitamin B2 synthesis to activate mucosal-associated invariant T (MAIT) cells. Key aspects of this evolutionarily conserved pathway remain uncharacterized, including where MR1 acquires ligands and what accessory proteins assist ligand binding. We answer these questions by using a fluorophore-labeled stable MR1 antigen analog, a conformation-specific MR1 mAb, proteomic analysis, and a genome-wide CRISPR/Cas9 library screen. We show that the endoplasmic reticulum (ER) contains a pool of two unliganded MR1 conformers stabilized via interactions with chaperones tapasin and tapas..

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Grants

Awarded by Australian Research Council (ARC)


Awarded by ARC


Awarded by National Health and Medical Research Council


Awarded by ARC Centre of Excellence in Advanced Molecular Imaging Grant


Funding Acknowledgements

We thank Dr. Louise Boyle (University of Cambridge) for the kind gift of the plasmids for TAPBPR expression and PeTe4 mAb; Prof. Peter Cresswell for the kind gift of the 148.3 and PaSta1 mAbs; and the Antibody Services Facility and Genomics Hub (Walter and Eliza Hall Institute) and the Melbourne Cytometry Platform from the Doherty Institute node and the Biological Optical Microscopy Platform (University of Melbourne) for expert assistance. H.E.G.M. is supported by an Australian Research Council (ARC) Discovery Early Career Researcher Award (DE170100575), a University of Melbourne Early Career Researcher Grant, and the AMP Tomorrow Fund; A.J.C. is supported by an ARC Future Fellowship (FT160100083); S.B.G.E. is supported by an ARC Discovery Early Career Researcher Award (DE170100407); J.R. is supported by an ARC Australian Laureate Fellowship; D.P.F. and J.A.V. are supported by National Health and Medical Research Council Research Fellowships (1117017, 1058193). This research was supported by a National Health and Medical Research Council Program Grant (1113293), an ARC Discovery Grant (170102471), and an ARC Centre of Excellence in Advanced Molecular Imaging Grant (CE140100011).