title: Downregulation of rheumatoid arthritis-related antigen RA-A47 (HSP47/colligin-2) in chondrocytic cell lines induces apoptosis and cell-surface expression of RA-A47 in association with CD9.
abstract: Previously, we showed that gene expression of the rheumatoid arthritis-related antigen RA-A47, which is identical to human heat shock protein (HSP)47, was downregulated in chondrocytes by inflammatory cytokines such as TNFalpha. Associated with this phenomenon, RA-A47 appeared on the cell surface concomitant with upregulation of metabolic factors related to cartilage destruction. The upregulation of the metabolic factors could be achieved by downregulation of RA-A47 expression with ra-a47-specific anti-sense oligonucleotide. Here, we show that the enhanced surface expression of RA-A47 on a chondrocytic cell line, HCS-2/8 was also a direct result of RA-A47 downregulation by ra-a47 anti-sense oligonucleotide, independent of the cytokine effects. Moreover, cell-surface expression of CD9, a beta1 integrin-associated transmembrane protein that is involved in cell adhesion and cell motility events, was enhanced in the ra-a47 anti-sense oligonucleotide-treated cells. The CD9 was colocalized with RA-A47 on the cell surface, where it may have affected integrin signaling. Furthermore, Annexin-V binding to the cell surface and the level of a number of apoptosis-related genes including caspase-9 were increased after ra-a47 anti-sense oligonucleotide treatment, suggesting that enhanced surface expression of RA-A47 and CD9 may be initiating apoptosis. Differential screening using a cDNA gene array showed induction of metallothionein-III and chemokine receptor CXCR4 and of factors of the Notch signaling pathway by the anti-sense treatment, but not by TNFalpha. Thus, here we show for the first time an alternative mechanism of inducing apoptosis by downregulating molecular chaperones, independent of the action of TNFalpha. The surface-exposed RA-A47 may induce autoantibodies and inflammatory reactions in autoimmune disease situations such as rheumatoid arthritis.
authors.affiliation: Department of Biochemistry and Molecular Dentistry, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Hattori
authors.forename: Klaus
authors.initials: K
authors.lastname: von der Mark
authors.forename: Harumi
authors.initials: H
authors.lastname: Kawaki
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Yutani
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kubota
authors.forename: Tohru
authors.initials: T
authors.lastname: Nakanishi
authors.forename: Heidi
authors.initials: H
authors.lastname: Eberspaecher
authors.forename: Benoit
authors.initials: B
authors.lastname: de Crombrugghe
authors.forename: Masaharu
authors.initials: M
authors.lastname: Takigawa
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism*; D000954:Antigens, Surface / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001323:Autoantibodies / Q000378:metabolism; D002356:Cartilage / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D019902:Chondrocytes / Q000276:immunology / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation / Q000235:genetics; D050958:HSP47 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008668:Metallothionein / Q000235:genetics; D018832:Molecular Chaperones / Q000235:genetics; D020320:Oligoribonucleotides, Antisense / Q000494:pharmacology; D011485:Protein Binding / Q000502:physiology; D051883:Receptor, Notch2; D019718:Receptors, CXCR4 / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics; D015843:Serpins / Q000235:genetics / Q000378:metabolism*; D060245:Tetraspanin 29; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D017304:Annexin A5; D015703:Antigens, CD; D000954:Antigens, Surface; D001323:Autoantibodies; C554869:CD9 protein, human; D050958:HSP47 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D016023:Integrins; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; C497764:NOTCH2 protein, human; D020320:Oligoribonucleotides, Antisense; D051883:Receptor, Notch2; D019718:Receptors, CXCR4; D011956:Receptors, Cell Surface; C494660:SERPINH1 protein, human; D015843:Serpins; D060245:Tetraspanin 29; D014409:Tumor Necrosis Factor-alpha; D008668:Metallothionein; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases