title: Proteolysis by Granzyme B Enhances Presentation of Autoantigenic Peptidylarginine Deiminase 4 Epitopes in Rheumatoid Arthritis.
abstract: Proteolysis of autoantigens can alter normal MHC class II antigen processing and has been implicated in the induction of autoimmune diseases. Many autoantigens are substrates for the protease granzyme B (GrB), but the mechanistic significance of this association is unknown. Peptidylarginine deiminase 4 (PAD4) is a frequent target of autoantibodies in patients with rheumatoid arthritis (RA) and a substrate for GrB. RA is strongly associated with specific MHC class II alleles, and elevated levels of GrB and PAD4 are found in the joints of RA patients, suggesting that GrB may alter the presentation of PAD4 by RA-associated class II alleles. In this study, complementary proteomic and immunologic approaches were utilized to define the effects of GrB cleavage on the structure, processing, and immunogenicity of PAD4. Hydrogen-deuterium exchange and a cell-free MHC class II antigen processing system revealed that proteolysis of PAD4 by GrB induced discrete structural changes in PAD4 that promoted enhanced presentation of several immunogenic peptides capable of stimulating PAD4-specific CD4+ T cells from patients with RA. This work demonstrates the existence of PAD4-specific T cells in patients with RA and supports a mechanistic role for GrB in enhancing the presentation of autoantigenic CD4+ T cell epitopes.
authors.affiliation: Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, Maryland 21224, United States.
authors.forename: Erika
authors.initials: E
authors.lastname: Darrah
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine , Baltimore Maryland 21205, United States.
authors.forename: AeRyon
authors.initials: A
authors.lastname: Kim
authors.affiliation: Department of Molecular Therapeutics, The Scripps Research Institute , Jupiter, Florida 33458, United States.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Biological Chemistry, Mass Spectrometry and Proteomics Facility, Johns Hopkins University School of Medicine , Baltimore Maryland 21205, United States.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Boronina
authors.affiliation: Department of Biological Chemistry, Mass Spectrometry and Proteomics Facility, Johns Hopkins University School of Medicine , Baltimore Maryland 21205, United States.
authors.forename: Robert N
authors.initials: RN
authors.lastname: Cole
authors.affiliation: Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, Maryland 21224, United States.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fava
authors.affiliation: Division of Rheumatology, Columbia University, College of Physicians and Surgeons , New York, New York 10027, United States.
authors.forename: Jon T
authors.initials: JT
authors.lastname: Giles
authors.affiliation: Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, Maryland 21224, United States.
authors.forename: Clifton O
authors.initials: CO
authors.lastname: Bingham III
authors.affiliation: Department of Molecular Therapeutics, The Scripps Research Institute , Jupiter, Florida 33458, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Chalmers
authors.affiliation: Department of Molecular Therapeutics, The Scripps Research Institute , Jupiter, Florida 33458, United States.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Griffin
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine , Baltimore Maryland 21205, United States.
authors.forename: Scheherazade
authors.initials: S
authors.lastname: Sadegh-Nasseri
authors.affiliation: Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, Maryland 21224, United States.
authors.forename: Antony
authors.initials: A
authors.lastname: Rosen
mesh_terms: D000368:Aged; D000595:Amino Acid Sequence; D017951:Antigen Presentation; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D001323:Autoantibodies / Q000096:biosynthesis; D001324:Autoantigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D001665:Binding Sites; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000473:pathology; D016022:Case-Control Studies; D041961:Deuterium Exchange Measurement; D018984:Epitopes, T-Lymphocyte / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D053804:Granzymes / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D006801:Humans; D006867:Hydrolases / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D008958:Models, Molecular; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D054730:Protein Interaction Domains and Motifs; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases; D059748:Proteolysis; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D013379:Substrate Specificity
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D018984:Epitopes, T-Lymphocyte; D011994:Recombinant Proteins; D006867:Hydrolases; C509213:GZMB protein, human; D053804:Granzymes; C000629235:PADI4 protein, human; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases
keywords: antigen presentation; antigen processing; autoantigen; autoimmunity; epitope; hydrogen−deuterium exchange; mass spectrometry; peptidylarginine deiminase; rheumatoid arthritis; shared epitope