title: Characterization of opticin digestion by proteases involved in osteoarthritis development.
abstract: OBJECTIVE
  Opticin is a class III member of the small leucine-rich repeat proteoglycan (SLRP) family, produced in articular joint tissues. In normal and osteoarthritic (OA) cartilage, opticin is degraded. This study aimed to assess whether human cartilage opticin is degraded by the main proteases involved in OA pathophysiology, and to determine the protease cleavage sites of this SLRP.
  
  
  METHODS
  We analyzed the proteolytic activity of matrix metalloproteinases (MMPs)-1, -2, -3, -7, -8 and -9, and ADAMTS-4 and -5 on proteoglycan extracts from normal and moderately fibrillated OA human cartilage, and on recombinant human opticin. Opticin degradation was analyzed by Western blotting and cleavage sites were determined by sequence analysis.
  
  
  RESULTS
  All eight proteases digested opticin from proteoglycan extracts from both normal and OA samples, as well as recombinant human opticin, MMP-2 and MMP-7 are the proteases that degrade recombinant human opticin most efficiently. The opticin cleavage site determined for these MMPs was between the glycosylation and leucine-rich repeat domains. MMP-7 had two additional digestion sites near the N-terminal end of opticin.
  
  
  CONCLUSIONS
  Opticin is a substrate for several MMPs and aggrecanases involved during OA cartilage degradation, and seems to be a preferential substrate for MMP-7. The role of opticin in cartilage degeneration could be related to decreased levels of intact opticin, followed by its proteolytic degradation, which in turn may stimulate some of the modifications observed in the OA cartilage, such as neovascularisation and changes in the extracellular matrix.
authors.affiliation: Cellular Inflammation and Cartilage Research Group, IMIM (Hospital del Mar Research Institute), C/Dr. Aigüader 88, 08003 Barcelona, Spain. Electronic address: ltio@imim.es.
authors.forename: Laura
authors.initials: L
authors.lastname: Tío
authors.affiliation: Osteoarthritis Research Unit, University of Montreal Hospital Research Centre (CRCHUM), Montreal, Quebec, Canada.
authors.forename: Johanne
authors.initials: J
authors.lastname: Martel-Pelletier
authors.affiliation: Osteoarthritis Research Unit, University of Montreal Hospital Research Centre (CRCHUM), Montreal, Quebec, Canada.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Pelletier
authors.affiliation: Institute of Human Development, University of Manchester and Manchester Royal Eye Hospital and Centre for Advanced Discovery and Experimental Therapeutics, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Bishop
authors.affiliation: Department of Surgery, McGill University, Genetics Unit, Shriners Hospital for Children, Montreal, Quebec, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Roughley
authors.affiliation: Cellular Inflammation and Cartilage Research Group, IMIM (Hospital del Mar Research Institute), C/Dr. Aigüader 88, 08003 Barcelona, Spain.
authors.forename: Aina
authors.initials: A
authors.lastname: Farran
authors.affiliation: Cellular Inflammation and Cartilage Research Group, IMIM (Hospital del Mar Research Institute), C/Dr. Aigüader 88, 08003 Barcelona, Spain; Department of Rheumatology, Universitat Autònoma de Barcelona, Hospital del Mar, Barcelona, Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Benito
authors.affiliation: Cellular Inflammation and Cartilage Research Group, IMIM (Hospital del Mar Research Institute), C/Dr. Aigüader 88, 08003 Barcelona, Spain; Department of Rheumatology, Universitat Autònoma de Barcelona, Hospital del Mar, Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Monfort
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000201:enzymology*; D005109:Extracellular Matrix / Q000201:enzymology; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D006801:Humans; D020782:Matrix Metalloproteinases / Q000378:metabolism; D020370:Osteoarthritis, Knee / Q000201:enzymology* / Q000503:physiopathology; D010447:Peptide Hydrolases / Q000378:metabolism*; D011509:Proteoglycans / Q000378:metabolism*
chemical_list: D016326:Extracellular Matrix Proteins; C404108:OPTC protein, human; D011509:Proteoglycans; D010447:Peptide Hydrolases; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases
keywords: Aggrecanases; Metalloproteases; Opticin; Osteoarthritis; Small leucine-rich repeat proteoglycans