title: Altered PKR Signalling and C / EBPβ Expression is Associated with HLA-B27 Expression in Monocytic Cells.
abstract: Infection caused by certain gram-negative bacteria, e.g. Salmonella, can trigger inflammatory joint disease reactive arthritis (ReA). It is suggested that the disease-triggering bacteria or bacterial components persist in patients for an abnormally long time. Development of ReA is strongly associated with tissue antigen HLA-B27. Previously, we reported an enhanced replication of Salmonella enteritidis and altered p38 MAP kinase signalling in HLA-B27-expressing monocytic cells. Here we aimed to investigate the role of HLA-B27 in regulation of double-stranded RNA-activated kinase (PKR)-related signalling in Salmonella-infected or Salmonella lipopolysaccharide (LPS)-stimulated human U937 monocytic cells, as PKR has been reported to modify p38 signalling in Salmonella-infected cells. In cells expressing HLA-B27, PKR is overexpressed and hypophosphorylated, and the expression of transcription factor CCAAT enhancer binding protein beta (C/EBPβ) is increased upon Salmonella infection and LPS stimulation. The expression of C/EBPβ is PKR-dependent in LPS-stimulated mock cells, whereas in LPS-stimulated B27 cells the majority of C/EBPβ is expressed in a PKR-independent manner. Our results show that the expression of HLA-B27 disturbs the PKR-mediated signalling pathway. Moreover, altered signalling is related to misfolding-linked Glu45 in the B pocket of the HLA-B27 heavy chain. We suggest that the expression of HLA-B27 HCs modulates the intracellular environment of monocyte/macrophages and the mechanisms that are important in eliminating intracellular S. enteritidis by altering the intracellular signalling. This phenomenon is at least partly dependent on the misfolding feature of the B27 molecule. These observations offer a novel mechanism by which HLA-B27 may modulate inflammatory response induced by ReA-triggering bacteria.
authors: National Institute for Health and Welfare, Turku, FinlandNIAMS, National Institutes of Health, Bethesda, MD, USADepartment of Medical Microbiology, University of Turku, Turku, Finland.
authors: A S
authors: AS
authors: Sahlberg
authors: National Institute for Health and Welfare, Turku, FinlandNIAMS, National Institutes of Health, Bethesda, MD, USADepartment of Medical Microbiology, University of Turku, Turku, Finland.
authors: M
authors: M
authors: Ruuska
authors: National Institute for Health and Welfare, Turku, FinlandNIAMS, National Institutes of Health, Bethesda, MD, USADepartment of Medical Microbiology, University of Turku, Turku, Finland.
authors: R A
authors: RA
authors: Colbert
authors: National Institute for Health and Welfare, Turku, FinlandNIAMS, National Institutes of Health, Bethesda, MD, USADepartment of Medical Microbiology, University of Turku, Turku, Finland.
authors: K
authors: K
authors: Granfors
authors: National Institute for Health and Welfare, Turku, FinlandNIAMS, National Institutes of Health, Bethesda, MD, USADepartment of Medical Microbiology, University of Turku, Turku, Finland.
authors: M A
authors: MA
authors: Penttinen
mesh_terms: D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics* / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D005786:Gene Expression Regulation; D015796:HLA-B27 Antigen / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology; D010766:Phosphorylation; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D000091402:Prohibitins; D017510:Protein Folding; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D012480:Salmonella Infections / Q000382:microbiology; D012477:Salmonella enteritidis / Q000276:immunology* / Q000302:isolation & purification; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; C545012:CEBPB protein, human; D015796:HLA-B27 Antigen; D008070:Lipopolysaccharides; C000717331:PHB2 protein, human; C104647:PRKRA protein, human; D000091402:Prohibitins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D013755:Tetradecanoylphorbol Acetate