title: Matrix metalloproteinase-13 influences ERK signalling in articular rabbit chondrocytes.
abstract: OBJECTIVE
  Matrix metalloproteinase-13 (MMP-13) is an extracellular MMP that cleaves type II collagen, the major protein component of cartilage, with high specificity and has been implicated in the pathology of osteoarthritis. The present study aimed to characterize the binding and internalization kinetics of MMP-13 in normal rabbit chondrocytes and whether MMP-13 affected cell signalling.
  
  
  METHODS
  Rabbit chondrocytes were used in [125I]-MMP-13 binding assays to investigate the MMP-13 binding kinetics and Western analysis allowed for the assessment of intracellular signalling cascades.
  
  
  RESULTS
  Rabbit chondrocytes were found to express the cartilage-specific genes aggrecan and type II collagen throughout their in vitro culture period. Appreciable specific cell-association of [125I]-MMP-13 was detected after 10 min of exposure to the ligand and equilibrium was obtained after 2 h. Binding of [125I]-MMP-13 to chondrocytes was specific and approached saturation at 75 nM. Internalization of MMP-13 was evident after 20 min, reached a maximum at 30 min and had returned to baseline by 90 min. Addition of receptor-associated protein (RAP) inhibited the internalization of MMP-13 indicating a likely role for low-density lipoprotein receptor-related protein-1 (LRP1) in this process. Interestingly the presence of MMP-13 induced phosphorylation of the extracellular signal-regulated kinase 1/2 (ERK1/2) protein showing that there is initiation of a signalling process in response to MMP-13 being bound and internalized by rabbit chondrocytes. However, this activation does not involve the MMP-13 internalization receptor LRP1.
  
  
  CONCLUSIONS
  These studies demonstrate and characterize the MMP-13 binding and internalization system in rabbit chondrocytes and indicate that MMP-13 may regulate the phenotype of the chondrocytes through this receptor system.
authors.affiliation: Department of Physiology and Biophysics, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
authors.forename: L J
authors.initials: LJ
authors.lastname: Raggatt
authors.forename: S C
authors.initials: SC
authors.lastname: Jefcoat
authors.forename: I
authors.initials: I
authors.lastname: Choudhury
authors.forename: S
authors.initials: S
authors.lastname: Williams
authors.forename: M
authors.initials: M
authors.lastname: Tiku
authors.forename: N C
authors.initials: NC
authors.lastname: Partridge
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D002358:Cartilage, Articular / Q000201:enzymology*; D019902:Chondrocytes / Q000201:enzymology*; D024043:Collagen Type II / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism*; D011817:Rabbits
chemical_list: D053674:Aggrecans; D024043:Collagen Type II; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D048049:Extracellular Signal-Regulated MAP Kinases; D053509:Matrix Metalloproteinase 13