title: The Human Leukocyte Antigen (HLA)-B27 Peptidomein Vivo, in Spondyloarthritis-susceptible HLA-B27 Transgenic Rats and the Effect of Erap1 Deletion.
abstract: HLA-B27 is a class I major histocompatibility (MHC-I) allele that confers susceptibility to the rheumatic disease ankylosing spondylitis (AS) by an unknown mechanism. ERAP1 is an aminopeptidase that trims peptides in the endoplasmic reticulum for binding to MHC-I molecules. ERAP1 shows genetic epistasis with HLA-B27 in conferring susceptibility to AS. Male HLA-B27 transgenic rats develop arthritis and serve as an animal model of AS, whereas female B27 transgenic rats remain healthy. We used large scale quantitative mass spectrometry to identify over 15,000 unique HLA-B27 peptide ligands, isolated after immunoaffinity purification of the B27 molecules from the spleens of HLA-B27 transgenic rats. Heterozygous deletion of Erap1, which reduced the Erap1 level to less than half, had no qualitative or quantitative effects on the B27 peptidome. Homozygous deletion of Erap1 affected approximately one-third of the B27 peptidome but left most of the B27 peptidome unchanged, suggesting the possibility that some of the HLA-B27 immunopeptidome is not processed in the presence of Erap1. Deletion of Erap1 was permissive for the AS-like phenotype, increased mean peptide length and increased the frequency of C-terminal hydrophobic residues and of N-terminal Ala, Ser, or Lys. The presence of Erap1 increased the frequency of C-terminal Lys and Arg, of Glu and Asp at intermediate residues, and of N-terminal Gly. Several peptides of potential interest in AS pathogenesis, previously identified in human cell lines, were isolated. However, rats susceptible to arthritis had B27 peptidomes similar to those of non-susceptible rats, and no peptides were found to be uniquely associated with arthritis. Whether specific B27-bound peptides are required for AS pathogenesis remains to be determined. Data are available via ProteomeXchange with identifier PXD005502.
authors.affiliation: From the ‡Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Eilon
authors.initials: E
authors.lastname: Barnea
authors.affiliation: From the ‡Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Dganit
authors.initials: D
authors.lastname: Melamed Kadosh
authors.affiliation: From the ‡Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Haimovich
authors.affiliation: §Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8884.
authors.forename: Nimman
authors.initials: N
authors.lastname: Satumtira
authors.affiliation: §Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8884.
authors.forename: Martha L
authors.initials: ML
authors.lastname: Dorris
authors.affiliation: ¶Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8816.
authors.forename: Mylinh T
authors.initials: MT
authors.lastname: Nguyen
authors.affiliation: ¶Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8816.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hammer
authors.affiliation: ‖NIAMS, National Institutes of Health, Bethesda, Maryland 20892-1560.
authors.forename: Tri M
authors.initials: TM
authors.lastname: Tran
authors.affiliation: ‖NIAMS, National Institutes of Health, Bethesda, Maryland 20892-1560.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Colbert
authors.affiliation: §Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8884; admon@technion.ac.il joel.taurog@utsouthwestern.edu.
authors.forename: Joel D
authors.initials: JD
authors.lastname: Taurog
authors.affiliation: From the ‡Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel; admon@technion.ac.il joel.taurog@utsouthwestern.edu.
authors.forename: Arie
authors.identifier: 0000-0003-0504-3950
authors.initials: A
authors.lastname: Admon
mesh_terms: D000626:Aminopeptidases / Q000235:genetics*; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D017353:Gene Deletion; D020022:Genetic Predisposition to Disease; D015796:HLA-B27 Antigen / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D010455:Peptides / Q000032:analysis*; D060066:Protein Interaction Maps; D040901:Proteomics / Q000379:methods*; D051381:Rats; D055647:Rats, Transgenic; D013167:Spondylitis, Ankylosing / Q000235:genetics* / Q000378:metabolism
chemical_list: D015796:HLA-B27 Antigen; D010455:Peptides; D000626:Aminopeptidases; C000620840:Erap1 protein, rat