title: The fingerprint of antimitochondrial antibodies and the etiology of primary biliary cholangitis.
abstract: The identification of environmental factors that lead to loss of tolerance has been coined the holy grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has hypothesized that a modified peptide within PDC-E2, the major mitochondrial autoantigen, will have been immunologically recognized at the time of loss of tolerance. Herein, we successfully applied intein technology to construct a PDC-E2 protein fragment containing amino acid residues 177-314 of PDC-E2 by joining a recombinant peptide spanning residues 177-252 (PDC-228) with a 62-residue synthetic peptide from 253 to 314 (PP), which encompasses PDC-E2 inner lipoyl domain (ILD). We named this intein-constructed fragment PPL. Importantly, PPL, as well as lipoic acid conjugated PPL (LA-PPL) and xenobiotic 2-octynoic acid conjugated PPL (2OA-PPL), are recognized by AMA. Of great importance, AMA has specificity for the 2OA-modified PDC-E2 ILD peptide backbone distinct from antibodies that react with native lipoylated PDC-E2 peptide. Interestingly, this unique AMA subfraction is of the immunoglobulin M isotype and more dominant in early-stage primary biliary cholangitis (PBC), suggesting that exposure to 2OA-PPL-like compounds occurs early in the generation of AMA. To understand the structural basis of this differential recognition, we analyzed PPL, LA-PPL, and 2OA-PPL using electron paramagnetic resonance spectroscopy, with confirmations by enzyme-linked immunosorbent assay, immunoblotting, and affinity antibody analysis. We demonstrate that the conformation of PDC-E2 ILD is altered when conjugated with 2OA, compared to conjugation with lipoic acid.
  
  
  
  A molecular understanding of the conformation of xenobiotic-modified PDC-E2 is critical for understanding xenobiotic modification and loss of tolerance in PBC with widespread implications for a role of environmental chemicals in the induction of autoimmunity. (Hepatology 2017;65:1670-1682).
authors.affiliation: Department of Rheumatology and Immunology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.|Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.
authors.forename: Zongwen
authors.initials: Z
authors.lastname: Shuai
authors.affiliation: Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.|College of Environmental Science and Engineering, Yangzhou University, Yangzhou, China.
authors.forename: Jinjun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Molecular Medicine, University of California Davis School of Medicine, Davis, CA.
authors.forename: Madhu
authors.initials: M
authors.lastname: Badamagunta
authors.affiliation: Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.
authors.forename: Jinjung
authors.initials: J
authors.lastname: Choi
authors.affiliation: Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.
authors.forename: Guoxiang
authors.initials: G
authors.lastname: Yang
authors.affiliation: Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.
authors.forename: Weici
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Kenny
authors.affiliation: Department of Chemistry, University of California Davis School of Medicine, Davis, CA.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Guggenheim
authors.affiliation: Department of Chemistry, University of California Davis School of Medicine, Davis, CA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Kurth
authors.affiliation: Department of Pathology, Emory University School of Medicine, Atlanta, GA.
authors.forename: Aftab A
authors.initials: AA
authors.lastname: Ansari
authors.affiliation: Department of Molecular Medicine, University of California Davis School of Medicine, Davis, CA.
authors.forename: John
authors.initials: J
authors.lastname: Voss
authors.affiliation: Department of Microbiology, Nursing and Health Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Ross L
authors.initials: RL
authors.lastname: Coppel
authors.affiliation: Section of Digestive Diseases, International Center for Digestive Health, Department of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Invernizzi
authors.affiliation: Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.
authors.forename: Patrick S C
authors.initials: PSC
authors.lastname: Leung
authors.affiliation: Division of Rheumatology/Allergy and Clinical Immunology, University of California Davis School of Medicine, Davis, CA.
authors.forename: M Eric
authors.initials: ME
authors.lastname: Gershwin
mesh_terms: D000915:Antibody Affinity; D001323:Autoantibodies / Q000097:blood*; D016022:Case-Control Studies; D002761:Cholangitis / Q000097:blood / Q000139:chemically induced* / Q000276:immunology; D004578:Electron Spin Resonance Spectroscopy; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D047668:Inteins; D008928:Mitochondria / Q000276:immunology*; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000737:chemistry / Q000187:drug effects* / Q000276:immunology; D015262:Xenobiotics / Q000633:toxicity*
chemical_list: D001323:Autoantibodies; D015262:Xenobiotics; D030481:Pyruvate Dehydrogenase (Lipoamide)