title: Cleavage of cartilage oligomeric matrix protein (thrombospondin-5) by matrix metalloproteinases and a disintegrin and metalloproteinase with thrombospondin motifs.
abstract: Cartilage oligomeric matrix protein (COMP) is a pentameric glycoprotein present in cartilage, tendon and ligament. Fragments of the molecule are present in the diseased cartilage, synovial fluid and serum of patients with knee injuries, osteoarthritis and rheumatoid arthritis. Although COMP is a substrate for several matrix metalloproteinases (MMPs), the enzymes responsible for COMP degradation in vivo have yet to be identified. In this study we utilised well-established bovine cartilage culture models to examine IL-1alpha-stimulated COMP proteolysis in the presence and absence of MMP inhibitors. COMP was released from bovine nasal cartilage, in response to IL-1alpha, at an intermediate time between proteoglycans and type II collagen, when soluble MMP levels in the culture medium were undetectable. The major fragment of COMP released following IL-1alpha-stimulation migrated with an apparent molecular mass of approximately 110 kDa (Fragment-110) and co-migrated with both the major fragment present in human arthritic synovial fluid samples and the product of COMP cleavage by purified MMP-9. However, the broad-spectrum MMP and ADAM inhibitor BB94 only partially inhibited the formation of Fragment-110 and failed to inhibit COMP release significantly. Therefore the results of these studies indicate a role for proteinases other than MMPs in the degradation of COMP in bovine cartilage. It was further demonstrated that purified COMP was cleaved by ADAMTS-4, but not ADAMTS-1 or -5, to yield a fragment which co-migrated with Fragment-110. Therefore this is the first demonstration of COMP as a substrate for ADAMTS-4, although it remains to be determined whether this enzyme plays a role in COMP degradation in vivo.
authors.affiliation: Academic Rheumatology, University of Bristol, Avon Orthopaedic Centre, Southmead Hospital, BS10 5NB, Bristol, UK.
authors.forename: Sally C
authors.initials: SC
authors.lastname: Dickinson
authors.forename: Mireille N
authors.initials: MN
authors.lastname: Vankemmelbeke
authors.forename: David J
authors.initials: DJ
authors.lastname: Buttle
authors.forename: Krisztina
authors.initials: K
authors.lastname: Rosenberg
authors.forename: Dick
authors.initials: D
authors.lastname: Heinegård
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Hollander
mesh_terms: D051722:ADAM Proteins; D000071121:ADAMTS4 Protein; D020816:Amino Acid Motifs; D000818:Animals; D002356:Cartilage / Q000187:drug effects / Q000378:metabolism*; D064236:Cartilage Oligomeric Matrix Protein; D002417:Cattle; D046508:Culture Techniques; D019483:Disintegrins / Q000737:chemistry / Q000378:metabolism*; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D064235:Matrilin Proteins; D020782:Matrix Metalloproteinases / Q000737:chemistry / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism; D011348:Procollagen N-Endopeptidase; D013582:Synovial Fluid / Q000378:metabolism; D019699:Thrombospondins / Q000737:chemistry / Q000378:metabolism
chemical_list: D064236:Cartilage Oligomeric Matrix Protein; D019483:Disintegrins; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D007375:Interleukin-1; D064235:Matrilin Proteins; C577553:TSP5 protein, human; D019699:Thrombospondins; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases; D008666:Metalloendopeptidases; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein; C000603918:ADAMTS4 protein, human