1
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Kitchen GB, Hopwood T, Gali Ramamoorthy T, Downton P, Begley N, Hussell T, Dockrell DH, Gibbs JE, Ray DW, Loudon ASI. The histone methyltransferase Ezh2 restrains macrophage inflammatory responses. FASEB J 2021; 35:e21843. [PMID: 34464475 PMCID: PMC8573545 DOI: 10.1096/fj.202100044rrr] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 07/06/2021] [Accepted: 07/23/2021] [Indexed: 01/02/2023]
Abstract
Robust inflammatory responses are critical to survival following respiratory infection, with current attention focused on the clinical consequences of the Coronavirus pandemic. Epigenetic factors are increasingly recognized as important determinants of immune responses, and EZH2 is a prominent target due to the availability of highly specific and efficacious antagonists. However, very little is known about the role of EZH2 in the myeloid lineage. Here, we show EZH2 acts in macrophages to limit inflammatory responses to activation, and in neutrophils for chemotaxis. Selective genetic deletion in macrophages results in a remarkable gain in protection from infection with the prevalent lung pathogen, pneumococcus. In contrast, neutrophils lacking EZH2 showed impaired mobility in response to chemotactic signals, and resulted in increased susceptibility to pneumococcus. In summary, EZH2 shows complex, and divergent roles in different myeloid lineages, likely contributing to the earlier conflicting reports. Compounds targeting EZH2 are likely to impair mucosal immunity; however, they may prove useful for conditions driven by pulmonary neutrophil influx, such as adult respiratory distress syndrome.
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Affiliation(s)
- Gareth B. Kitchen
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
- Manchester University NHS Foundation Trust, Manchester Academic Health Science CentreManchesterUK
| | - Thomas Hopwood
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
| | - Thanuja Gali Ramamoorthy
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
| | - Polly Downton
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
| | - Nicola Begley
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
| | - Tracy Hussell
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
| | - David H. Dockrell
- Department of Infection Medicine and MRC Centre for Inflammation ResearchUniversity of EdinburghEdinburghUK
| | - Julie E. Gibbs
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
| | - David W. Ray
- NIHR Oxford Biomedical Research Centre, John Radcliffe HospitalOxfordUK
- Oxford Centre for Diabetes, Endocrinology and MetabolismUniversity of OxfordOxfordUK
| | - Andrew S. I. Loudon
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Sciences CentreManchesterUK
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Flannery SE, Pastorelli F, Wood WHJ, Hunter CN, Dickman MJ, Jackson PJ, Johnson MP. Comparative proteomics of thylakoids from Arabidopsis grown in laboratory and field conditions. Plant Direct 2021; 5:e355. [PMID: 34712896 PMCID: PMC8528093 DOI: 10.1002/pld3.355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/21/2021] [Accepted: 09/28/2021] [Indexed: 06/13/2023]
Abstract
Compared to controlled laboratory conditions, plant growth in the field is rarely optimal since it is frequently challenged by large fluctuations in light and temperature which lower the efficiency of photosynthesis and lead to photo-oxidative stress. Plants grown under natural conditions therefore place an increased onus on the regulatory mechanisms that protect and repair the delicate photosynthetic machinery. Yet, the exact changes in thylakoid proteome composition which allow plants to acclimate to the natural environment remain largely unexplored. Here, we use quantitative label-free proteomics to demonstrate that field-grown Arabidopsis plants incorporate aspects of both the low and high light acclimation strategies previously observed in laboratory-grown plants. Field plants showed increases in the relative abundance of ATP synthase, cytochrome b 6 f, ferredoxin-NADP+ reductases (FNR1 and FNR2) and their membrane tethers TIC62 and TROL, thylakoid architecture proteins CURT1A, CURT1B, RIQ1, and RIQ2, the minor monomeric antenna complex CP29.3, rapidly-relaxing non-photochemical quenching (qE)-related proteins PSBS and VDE, the photosystem II (PSII) repair machinery and the cyclic electron transfer complexes NDH, PGRL1B, and PGR5, in addition to decreases in the amounts of LHCII trimers composed of LHCB1.1, LHCB1.2, LHCB1.4, and LHCB2 proteins and CP29.2, all features typical of a laboratory high light acclimation response. Conversely, field plants also showed increases in the abundance of light harvesting proteins LHCB1.3 and CP29.1, zeaxanthin epoxidase (ZEP) and the slowly-relaxing non-photochemical quenching (qI)-related protein LCNP, changes previously associated with a laboratory low light acclimation response. Field plants also showed distinct changes to the proteome including the appearance of stress-related proteins ELIP1 and ELIP2 and changes to proteins that are largely invariant under laboratory conditions such as state transition related proteins STN7 and TAP38. We discuss the significance of these alterations in the thylakoid proteome considering the unique set of challenges faced by plants growing under natural conditions.
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Affiliation(s)
- Sarah E. Flannery
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - Federica Pastorelli
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - William H. J. Wood
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - C. Neil Hunter
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - Mark J. Dickman
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffieldUK
| | - Philip J. Jackson
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffieldUK
| | - Matthew P. Johnson
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
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3
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Emmott E, de Rougemont A, Hosmillo M, Lu J, Fitzmaurice T, Haas J, Goodfellow I. Polyprotein processing and intermolecular interactions within the viral replication complex spatially and temporally control norovirus protease activity. J Biol Chem 2019; 294:4259-4271. [PMID: 30647130 PMCID: PMC6422069 DOI: 10.1074/jbc.ra118.006780] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Indexed: 11/26/2022] Open
Abstract
Norovirus infections are a major cause of acute viral gastroenteritis and a significant burden on global human health. A vital process for norovirus replication is the processing of the nonstructural polyprotein by a viral protease into the viral components required to form the viral replication complex. This cleavage occurs at different rates, resulting in the accumulation of stable precursor forms. Here, we characterized how precursor forms of the norovirus protease accumulate during infection. Using stable forms of the protease precursors, we demonstrated that all of them are proteolytically active in vitro, but that when expressed in cells, their activities are determined by both substrate and protease localization. Although all precursors could cleave a replication complex-associated substrate, only a subset of precursors lacking the NS4 protein were capable of efficiently cleaving a cytoplasmic substrate. By mapping the full range of protein-protein interactions among murine and human norovirus proteins with the LUMIER assay, we uncovered conserved interactions between replication complex members that modify the localization of a protease precursor subset. Finally, we demonstrate that fusion to the membrane-bound replication complex components permits efficient cleavage of a fused substrate when active polyprotein-derived protease is provided in trans These findings offer a model for how norovirus can regulate the timing of substrate cleavage throughout the replication cycle. Because the norovirus protease represents a key target in antiviral therapies, an improved understanding of its function and regulation, as well as identification of interactions among the other nonstructural proteins, offers new avenues for antiviral drug design.
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Affiliation(s)
- Edward Emmott
- From the Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom,
| | - Alexis de Rougemont
- the National Reference Centre for Gastroenteritis Viruses, Labology of Biology and Pathology, University Hospital Dijon Bourgogne, Dijon 21700, France
- the AgroSup Dijon, PAM UMR A 02.102 Bourgogne Franche-Comte University, Dijon 21000, France, and
| | - Myra Hosmillo
- From the Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom
| | - Jia Lu
- From the Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom
| | - Timothy Fitzmaurice
- From the Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom
| | - Jürgen Haas
- the Division of Infection and Pathway Medicine, University of Edinburgh Medical School, Edinburgh EH16 4SB, United Kingdom
| | - Ian Goodfellow
- From the Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom,
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Batchelor M, Wolny M, Baker EG, Paci E, Kalverda AP, Peckham M. Dynamic ion pair behavior stabilizes single α-helices in proteins. J Biol Chem 2019; 294:3219-3234. [PMID: 30593502 PMCID: PMC6398138 DOI: 10.1074/jbc.ra118.006752] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 12/17/2018] [Indexed: 11/06/2022] Open
Abstract
Ion pairs are key stabilizing interactions between oppositely charged amino acid side chains in proteins. They are often depicted as single conformer salt bridges (hydrogen-bonded ion pairs) in crystal structures, but it is unclear how dynamic they are in solution. Ion pairs are thought to be particularly important in stabilizing single α-helix (SAH) domains in solution. These highly stable domains are rich in charged residues (such as Arg, Lys, and Glu) with potential ion pairs across adjacent turns of the helix. They provide a good model system to investigate how ion pairs can contribute to protein stability. Using NMR spectroscopy, small-angle X-ray light scattering (SAXS), and molecular dynamics simulations, we provide here experimental evidence that ion pairs exist in a SAH in murine myosin 7a (residues 858-935), but that they are not fixed or long lasting. In silico modeling revealed that the ion pairs within this α-helix exhibit dynamic behavior, rapidly forming and breaking and alternating between different partner residues. The low-energy helical state was compatible with a great variety of ion pair combinations. Flexible ion pair formation utilizing a subset of those available at any one time avoided the entropic penalty of fixing side chain conformations, which likely contributed to helix stability overall. These results indicate the dynamic nature of ion pairs in SAHs. More broadly, thermodynamic stability in other proteins is likely to benefit from the dynamic behavior of multi-option solvent-exposed ion pairs.
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Affiliation(s)
- Matthew Batchelor
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Marcin Wolny
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Emily G Baker
- the School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| | - Emanuele Paci
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Arnout P Kalverda
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
| | - Michelle Peckham
- From the School of Molecular and Cellular Biology and the Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom and
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5
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Spiliotopoulos A, Blokpoel Ferreras L, Densham RM, Caulton SG, Maddison BC, Morris JR, Dixon JE, Gough KC, Dreveny I. Discovery of peptide ligands targeting a specific ubiquitin-like domain-binding site in the deubiquitinase USP11. J Biol Chem 2019; 294:424-436. [PMID: 30373771 PMCID: PMC6333900 DOI: 10.1074/jbc.ra118.004469] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 10/11/2018] [Indexed: 11/25/2022] Open
Abstract
Ubiquitin-specific proteases (USPs) reverse ubiquitination and regulate virtually all cellular processes. Defined noncatalytic domains in USP4 and USP15 are known to interact with E3 ligases and substrate recruitment factors. No such interactions have been reported for these domains in the paralog USP11, a key regulator of DNA double-strand break repair by homologous recombination. We hypothesized that USP11 domains adjacent to its protease domain harbor unique peptide-binding sites. Here, using a next-generation phage display (NGPD) strategy, combining phage display library screening with next-generation sequencing, we discovered unique USP11-interacting peptide motifs. Isothermal titration calorimetry disclosed that the highest affinity peptides (KD of ∼10 μm) exhibit exclusive selectivity for USP11 over USP4 and USP15 in vitro Furthermore, a crystal structure of a USP11-peptide complex revealed a previously unknown binding site in USP11's noncatalytic ubiquitin-like (UBL) region. This site interacted with a helical motif and is absent in USP4 and USP15. Reporter assays using USP11-WT versus a binding pocket-deficient double mutant disclosed that this binding site modulates USP11's function in homologous recombination-mediated DNA repair. The highest affinity USP11 peptide binder fused to a cellular delivery sequence induced significant nuclear localization and cell cycle arrest in S phase, affecting the viability of different mammalian cell lines. The USP11 peptide ligands and the paralog-specific functional site in USP11 identified here provide a framework for the development of new biochemical tools and therapeutic agents. We propose that an NGPD-based strategy for identifying interacting peptides may be applied also to other cellular targets.
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Affiliation(s)
- Anastasios Spiliotopoulos
- From the Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD
- the School of Veterinary Medicine and Science, Sutton Bonington Campus, College Road, Sutton Bonington, Leicestershire LE12 5RD
| | - Lia Blokpoel Ferreras
- From the Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD
| | - Ruth M Densham
- the Birmingham Centre for Genome Biology and Institute of Cancer and Genomic Sciences, Medical and Dental Schools, University of Birmingham, Birmingham B15 2TT, and
| | - Simon G Caulton
- From the Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD
| | - Ben C Maddison
- ADAS, School of Veterinary Medicine and Science, Bonington Campus, College Road, Sutton Bonington, Leicestershire LE12 5RD, United Kingdom
| | - Joanna R Morris
- the Birmingham Centre for Genome Biology and Institute of Cancer and Genomic Sciences, Medical and Dental Schools, University of Birmingham, Birmingham B15 2TT, and
| | - James E Dixon
- From the Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD
| | - Kevin C Gough
- the School of Veterinary Medicine and Science, Sutton Bonington Campus, College Road, Sutton Bonington, Leicestershire LE12 5RD,
| | - Ingrid Dreveny
- From the Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD,
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6
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Ren Z, Qi D, Pugh N, Li K, Wen B, Zhou R, Xu S, Liu S, Jones AR. Improvements to the Rice Genome Annotation Through Large-Scale Analysis of RNA-Seq and Proteomics Data Sets. Mol Cell Proteomics 2019; 18:86-98. [PMID: 30293062 PMCID: PMC6317475 DOI: 10.1074/mcp.ra118.000832] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/31/2018] [Indexed: 01/22/2023] Open
Abstract
Rice (Oryza sativa) is one of the most important worldwide crops. The genome has been available for over 10 years and has undergone several rounds of annotation. We created a comprehensive database of transcripts from 29 public RNA sequencing data sets, officially predicted genes from Ensembl plants, and common contaminants in which to search for protein-level evidence. We re-analyzed nine publicly accessible rice proteomics data sets. In total, we identified 420K peptide spectrum matches from 47K peptides and 8,187 protein groups. 4168 peptides were initially classed as putative novel peptides (not matching official genes). Following a strict filtration scheme to rule out other possible explanations, we discovered 1,584 high confidence novel peptides. The novel peptides were clustered into 692 genomic loci where our results suggest annotation improvements. 80% of the novel peptides had an ortholog match in the curated protein sequence set from at least one other plant species. For the peptides clustering in intergenic regions (and thus potentially new genes), 101 loci were identified, for which 43 had a high-confidence hit for a protein domain. Our results can be displayed as tracks on the Ensembl genome or other browsers supporting Track Hubs, to support re-annotation of the rice genome.
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Affiliation(s)
- Zhe Ren
- From the ‡BGI-Shenzhen, Shenzhen 518083, China
| | - Da Qi
- From the ‡BGI-Shenzhen, Shenzhen 518083, China
| | - Nina Pugh
- §Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK
| | - Kai Li
- From the ‡BGI-Shenzhen, Shenzhen 518083, China
| | - Bo Wen
- ‖Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030;; ¶Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, Texas 77030
| | - Ruo Zhou
- From the ‡BGI-Shenzhen, Shenzhen 518083, China
| | - Shaohang Xu
- From the ‡BGI-Shenzhen, Shenzhen 518083, China
| | - Siqi Liu
- From the ‡BGI-Shenzhen, Shenzhen 518083, China;.
| | - Andrew R Jones
- §Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK;.
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7
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Jennings E, Esposito D, Rittinger K, Thurston TLM. Structure-function analyses of the bacterial zinc metalloprotease effector protein GtgA uncover key residues required for deactivating NF-κB. J Biol Chem 2018; 293:15316-15329. [PMID: 30049795 PMCID: PMC6166728 DOI: 10.1074/jbc.ra118.004255] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 07/23/2018] [Indexed: 12/03/2022] Open
Abstract
The closely related type III secretion system zinc metalloprotease effector proteins GtgA, GogA, and PipA are translocated into host cells during Salmonella infection. They then cleave nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) transcription factor subunits, dampening activation of the NF-κB signaling pathway and thereby suppressing host immune responses. We demonstrate here that GtgA, GogA, and PipA cleave a subset of NF-κB subunits, including p65, RelB, and cRel but not NF-κB1 and NF-κB2, whereas the functionally similar type III secretion system effector NleC of enteropathogenic and enterohemorrhagic Escherichia coli cleaved all five NF-κB subunits. Mutational analysis of NF-κB subunits revealed that a single nonconserved residue in NF-κB1 and NF-κB2 that corresponds to the P1' residue Arg-41 in p65 prevents cleavage of these subunits by GtgA, GogA, and PipA, explaining the observed substrate specificity of these enzymes. Crystal structures of GtgA in its apo-form and in complex with the p65 N-terminal domain explained the importance of the P1' residue. Furthermore, the pattern of interactions suggested that GtgA recognizes NF-κB subunits by mimicking the shape and negative charge of the DNA phosphate backbone. Moreover, structure-based mutational analysis of GtgA uncovered amino acids that are required for the interaction of GtgA with p65, as well as those that are required for full activity of GtgA in suppressing NF-κB activation. This study therefore provides detailed and critical insight into the mechanism of substrate recognition by this family of proteins important for bacterial virulence.
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Affiliation(s)
- Elliott Jennings
- From the Section of Microbiology, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ and
| | - Diego Esposito
- the Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, United Kingdom
| | - Katrin Rittinger
- the Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, United Kingdom
| | - Teresa L M Thurston
- From the Section of Microbiology, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ and
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Papakyriakou A, Reeves E, Beton M, Mikolajek H, Douglas L, Cooper G, Elliott T, Werner JM, James E. The partial dissociation of MHC class I-bound peptides exposes their N terminus to trimming by endoplasmic reticulum aminopeptidase 1. J Biol Chem 2018; 293:7538-7548. [PMID: 29599287 PMCID: PMC5961055 DOI: 10.1074/jbc.ra117.000313] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 03/22/2018] [Indexed: 01/19/2023] Open
Abstract
Endoplasmic reticulum aminopeptidase 1 (ERAP1) and ERAP2 process N-terminally extended antigenic precursors for optimal loading onto major histocompatibility complex class I (MHC I) molecules. We and others have demonstrated that ERAP1 processes peptides bound to MHC I, but the underlying mechanism is unknown. To this end, we utilized single-chain trimers (SCT) of the ovalbumin-derived epitope SIINFEKL (SL8) tethered to the H2-Kb MHC I determinant from mouse and introduced three substitutions, E63A, K66A, and W167A, at the A-pocket of the peptide-binding groove in the MHC I heavy chain, which interact with the N termini of peptides. These variants significantly decreased SL8-presenting SCT at the cell surface in the presence of ERAP1, but did not affect overall SCT expression, indicating that ERAP1 trims the SL8 N terminus. Comparison of the X-ray crystal structures of WT and three variant SCTs revealed only minor perturbations of the peptide-binding domain in the variants. However, molecular dynamics simulations suggested that SL8 can dissociate partially within a sub-microsecond timescale, exposing its N terminus to the solvent. We also found that the C terminus of MHC I-bound SL8 remains deeply buried in the F-pocket of MHC I. Furthermore, free-energy calculations revealed that the three SCT variants exhibit lower free-energy barriers of N terminus dissociation than the WT Kb Taken together, our results are consistent with a previously observed model in which the partial dissociation of bound peptides from MHC I exposes their N terminus to trimming by ERAP1, whereas their C terminus is anchored at the F-pocket.
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Affiliation(s)
- Athanasios Papakyriakou
- From the Centre for Biological Sciences, Faculty of Natural & Environmental Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
| | - Emma Reeves
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
- Centre for Cancer Immunology, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton SO16 6YD, United Kingdom
| | - Mary Beton
- From the Centre for Biological Sciences, Faculty of Natural & Environmental Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
| | - Halina Mikolajek
- From the Centre for Biological Sciences, Faculty of Natural & Environmental Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
| | - Leon Douglas
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
| | - Grace Cooper
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
- Centre for Cancer Immunology, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton SO16 6YD, United Kingdom
| | - Tim Elliott
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
- Centre for Cancer Immunology, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton SO16 6YD, United Kingdom
| | - Jörn M Werner
- From the Centre for Biological Sciences, Faculty of Natural & Environmental Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
| | - Edward James
- Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom, and
- Centre for Cancer Immunology, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton SO16 6YD, United Kingdom
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