title: ERAP2 functional knockout in humans does not alter surface heavy chains or HLA-B27, inflammatory cytokines or endoplasmic reticulum stress markers.
abstract: BACKGROUND
  Single nucleotide polymorphisms in ERAP2 are strongly associated with ankylosing spondylitis (AS). One AS-associated single nucleotide polymorphism, rs2248374, causes a truncated ERAP2 protein that is degraded by nonsense-mediated decay. Approximately 25% of the populations of European ancestry are therefore natural ERAP2 knockouts. We investigated the effect of this associated variant on HLA class I allele presentation, surface heavy chains, endoplasmic reticulum (ER) stress markers and cytokine gene transcription in AS.
  
  
  METHODS
  Patients with AS and healthy controls with either AA or GG homozygous status for rs2248374 were studied. Antibodies to CD14, CD19-ECD, HLA-A-B-C, Valpha7.2, CD161, anti-HC10 and anti-HLA-B27 were used to analyse peripheral blood mononuclear cells. Expression levels of ER stress markers (GRP78 and CHOP) and proinflammatory genes (tumour necrosis factor (TNF), IL6, IL17 and IL22) were assessed by qPCR.
  
  
  RESULTS
  There was no significant difference in HLA-class I allele presentation or major histocompatibility class I heavy chains or ER stress markers GRP78 and CHOP or proinflammatory gene expression between genotypes for rs2248374 either between cases, between cases and controls, and between controls.
  
  
  CONCLUSIONS
  Large differences were not seen in HLA-B27 expression or cytokine levels between subjects with and without ERAP2 in AS cases and controls. This suggests that ERAP2 is more likely to influence AS risk through other mechanisms.
authors.affiliation: Centre for Neurogenetics and Statistical Genomics, Queensland Brain Institute, University of Queensland, St Lucia, Queensland, Australia University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Philip C
authors.initials: PC
authors.lastname: Robinson
authors.affiliation: University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Eugene
authors.initials: E
authors.lastname: Lau
authors.affiliation: University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Patricia
authors.initials: P
authors.lastname: Keith
authors.affiliation: University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Max C
authors.initials: MC
authors.lastname: Lau
authors.affiliation: University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Gethin P
authors.initials: GP
authors.lastname: Thomas
authors.affiliation: University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Linda A
authors.initials: LA
authors.lastname: Bradbury
authors.affiliation: University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Brown
authors.affiliation: University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia.
authors.forename: Tony J
authors.initials: TJ
authors.lastname: Kenna
mesh_terms: D000626:Aminopeptidases / Q000235:genetics* / Q000276:immunology; D016022:Case-Control Studies; D016207:Cytokines / Q000235:genetics* / Q000276:immunology; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000235:genetics* / Q000276:immunology; D015870:Gene Expression; D015796:HLA-B27 Antigen / Q000235:genetics* / Q000276:immunology; D006360:Heat-Shock Proteins / Q000235:genetics / Q000276:immunology; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000276:immunology; D020381:Interleukin-17 / Q000235:genetics / Q000276:immunology; D015850:Interleukin-6 / Q000235:genetics / Q000276:immunology; D007378:Interleukins / Q000235:genetics / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000276:immunology; D013167:Spondylitis, Ankylosing / Q000235:genetics* / Q000276:immunology; D051742:Transcription Factor CHOP / Q000235:genetics / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000276:immunology; D000097043:Interleukin-22
chemical_list: D000626:Aminopeptidases; D016207:Cytokines; D000091342:Endoplasmic Reticulum Chaperone BiP; D015796:HLA-B27 Antigen; D006360:Heat-Shock Proteins; D007143:Immunoglobulin Heavy Chains; D020381:Interleukin-17; D015850:Interleukin-6; D007378:Interleukins; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell; D051742:Transcription Factor CHOP; D014409:Tumor Necrosis Factor-alpha; D000097043:Interleukin-22; C497249:DDIT3 protein, human; C000717247:HSPA5 protein, human; C508600:IL6 protein, human; C503944:ERAP2 protein, human
keywords: Ankylosing Spondylitis; Cytokines; Gene Polymorphism