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Thomas MA, Naik P, Wang H, Giles JT, Girgis AA, Kim SY, Johnson TP, Curran AM, Crawford JD, Jahanbani S, Bingham CO, Robinson WH, Na CH, Darrah E. The monocyte cell surface is a unique site of autoantigen generation in rheumatoid arthritis. Proc Natl Acad Sci U S A 2024; 121:e2304199121. [PMID: 38630712 PMCID: PMC11047081 DOI: 10.1073/pnas.2304199121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 03/22/2024] [Indexed: 04/19/2024] Open
Abstract
Although anti-citrullinated protein autoantibodies (ACPAs) are a hallmark serological feature of rheumatoid arthritis (RA), the mechanisms and cellular sources behind the generation of the RA citrullinome remain incompletely defined. Peptidylarginine deiminase IV (PAD4), one of the key enzymatic drivers of citrullination in the RA joint, is expressed by granulocytes and monocytes; however, the subcellular localization and contribution of monocyte-derived PAD4 to the generation of citrullinated autoantigens remain underexplored. In this study, we demonstrate that PAD4 displays a widespread cellular distribution in monocytes, including expression on the cell surface. Surface PAD4 was enzymatically active and capable of citrullinating extracellular fibrinogen and endogenous surface proteins in a calcium dose-dependent manner. Fibrinogen citrullinated by monocyte-surface PAD4 could be specifically recognized over native fibrinogen by a panel of eight human monoclonal ACPAs. Several unique PAD4 substrates were identified on the monocyte surface via mass spectrometry, with citrullination of the CD11b and CD18 components of the Mac-1 integrin complex being the most abundant. Citrullinated Mac-1 was found to be a target of ACPAs in 25% of RA patients, and Mac-1 ACPAs were significantly associated with HLA-DRB1 shared epitope alleles, higher C-reactive protein and IL-6 levels, and more erosive joint damage. Our findings implicate the monocyte cell surface as a unique and consequential site of extracellular and cell surface autoantigen generation in RA.
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Affiliation(s)
- Mekha A. Thomas
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
| | - Pooja Naik
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
| | - Hong Wang
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
| | - Jon T. Giles
- Division of Rheumatology, Columbia University, College of Physicians and Surgeons, New York, NY10032
| | - Alexander A. Girgis
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD21224
| | - Seok-Young Kim
- Department of Neurology, Institute for Cell Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD21205
| | - Tory P. Johnson
- Section of Infections of the Nervous System, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD20892
| | - Ashley M. Curran
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
| | - Jonathan D. Crawford
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
| | - Shaghayegh Jahanbani
- Division of Immunology and Rheumatology, Stanford University, Stanford, CA94304
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA94550
| | - Clifton O. Bingham
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
| | - William H. Robinson
- Division of Immunology and Rheumatology, Stanford University, Stanford, CA94304
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA94550
| | - Chan Hyun Na
- Department of Neurology, Institute for Cell Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD21205
| | - Erika Darrah
- Division of Rheumatology, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD21224
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Christophorou MA, Sharma P, Zhang X. Citrullination: new tricks for an old mod. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220235. [PMID: 37778381 PMCID: PMC10542443 DOI: 10.1098/rstb.2022.0235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 09/04/2023] [Indexed: 10/03/2023] Open
Affiliation(s)
| | - Priyanka Sharma
- Institute of Pharmacology and Structural Biology (IPBS-UMR5089), 205 Rte de Narbonne, Toulouse 31400, France
| | - Xuesen Zhang
- College of Basic Medical Science, China Medical University, Shenyang 110122, China
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