MMP proteolysis of the human extracellular matrix protein aggrecan is mainly a process of normal turnover.
Although it has been shown that aggrecanases are involved in aggrecan degradation, the role of MMP (matrix metalloproteinase) aggrecanolysis is less well studied. To investigate MMP proteolysis of human aggrecan, in the present study we used neoepitope antibodies against MMP cleavage sites and Western blot analysis to identify MMP-generated fragments in normal and OA (osteoarthritis/osteoarthritic) cartilage, and in normal, knee injury and OA and SF (synovial fluid) samples. MMP-3 in vitro digestion showed that aggrecan contains six MMP cleavage sites, in the IGD (interglobular domain), the KS (keratan sulfate) region, the border between the KS region and CS (chondroitin sulfate) region 1, the CS1 region, and the border between the CS2 and the G3 domain, and kinetic studies showed a specific order of digestion where the cleavage between CS2 and the G3 domain was the most preferred. In vivo studies showed that OA cartilage contained (per dry weight) 3.4-fold more MMP-generated FFGV fragments compared with normal cartilage, and although aggrecanase-generated SF-ARGS concentrations were increased 14-fold in OA and knee-injured patients compared with levels in knee-healthy reference subjects, the SF-FFGV concentrations did not notably change. The results of the present study suggest that MMPs are mainly involved in normal aggrecan turnover and might have a less-active role in aggrecan degradation during knee injury and OA.
Department of Orthopaedics, Clinical Sciences Lund, Lund University, Lund, Sweden. andre.struglics@med.lu.se
André
A
Struglics
Maria
M
Hansson
D051722:ADAM Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000071121:ADAMTS4 Protein; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D053674:Aggrecans / Q000737:chemistry / Q000378:metabolism*; D002358:Cartilage, Articular / Q000201:enzymology / Q000378:metabolism*; D002809:Chondroitin Sulfates / Q000378:metabolism; D005109:Extracellular Matrix / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D007632:Keratan Sulfate / Q000378:metabolism; D007718:Knee Injuries / Q000201:enzymology / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D008875:Middle Aged; D010003:Osteoarthritis / Q000201:enzymology / Q000378:metabolism*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D011348:Procollagen N-Endopeptidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D059748:Proteolysis; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013582:Synovial Fluid / Q000201:enzymology / Q000378:metabolism*; D055815:Young Adult
C508319:ACAN protein, human; D053674:Aggrecans; D061965:Matrix Metalloproteinase Inhibitors; D010446:Peptide Fragments; D011994:Recombinant Proteins; D002809:Chondroitin Sulfates; D007632:Keratan Sulfate; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein