title: Expression and regulation of aggrecanase in arthritis: the role of TGF-beta.
abstract: Aggrecanases are key matrix-degrading enzymes that act by cleaving aggrecan at the Glu(373)-Ala(374) site. While these fragments have been detected in osteoarthritis (OA) and rheumatoid arthritis (RA) cartilage and synovial fluid, no information is available on the regulation or expression of the two key aggrecanases (aggrecanase-1 and aggrecanase-2) in synovial tissue (ST) or fibroblast-like synoviocytes (FLS). The aggrecanase-1 gene was constitutively expressed by both RA and OA FLS. Real-time PCR demonstrated that TGF-beta significantly increased aggrecanase-1 gene expression in FLS. Aggrecanase-1 induction peaked after 24 h of TGF-beta stimulation. The expression of aggrecanase-1 mRNA was significantly greater in RA ST than in OA or nonarthritis ST. Aggrecanase-2 mRNA and protein were constitutively produced by nonarthritis, OA, and RA FLS but were not increased by IL-1, TNF-alpha, or TGF-beta. Furthermore, OA, RA, and nonarthritis ST contained similar amounts of immunoreactive aggrecanase-2. The major form of the aggrecanase-2 enzyme was 70 kDa in nonarthritis ST, whereas a processed 53-kDa form was abundant in RA ST. Therefore, aggrecanase-1 and -2 are differentially regulated in FLS. Both are constitutively expressed, but aggrecanase-1 is induced by cytokines, especially TGF-beta. In contrast, aggrecanase-2 protein may be regulated by a post-translational mechanism in OA and RA ST. Synovial and FLS production of aggrecanase can contribute to cartilage degradation in RA and OA.
authors.affiliation: Division of Rheumatology, Allergy, and Immunology, University of California at San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamanishi
authors.forename: David L
authors.initials: DL
authors.lastname: Boyle
authors.forename: Melody
authors.initials: M
authors.lastname: Clark
authors.forename: Rich A
authors.initials: RA
authors.lastname: Maki
authors.forename: Micky D
authors.initials: MD
authors.lastname: Tortorella
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Arner
authors.forename: Gary S
authors.initials: GS
authors.lastname: Firestein
mesh_terms: D051722:ADAM Proteins; D000071121:ADAMTS4 Protein; D000071116:ADAMTS5 Protein; D000595:Amino Acid Sequence; D000818:Animals; D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D001666:Binding Sites, Antibody; D002417:Cattle; D002478:Cells, Cultured; D016207:Cytokines / Q000502:physiology; D004306:Dose-Response Relationship, Immunologic; D004789:Enzyme Activation / Q000276:immunology; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D007106:Immune Sera / Q000737:chemistry / Q000378:metabolism; D008666:Metalloendopeptidases / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D010003:Osteoarthritis / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D011348:Procollagen N-Endopeptidase; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D013583:Synovial Membrane / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D016207:Cytokines; D007106:Immune Sera; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; C121532:ADAMTS5 protein, human; D008666:Metalloendopeptidases; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein