title: Proteolytic processing causes extensive heterogeneity of tissue matrilin forms.
abstract: The matrilins are a family of multidomain extracellular matrix proteins with adapter functions. The oligomeric proteins have a bouquet-like structure and bind to a variety of different ligands whereby the avidity of their interactions is dependent on the number of subunits and domains present. Here we show the contribution of post-translational proteolytic processing to the heterogeneity of matrilins seen in tissue extracts and cell culture supernatants. A cleavage site after two glutamate residues in the hinge region close to the C-terminal coiled-coil oligomerization domain is conserved among the matrilins. Cleavage at this site yields molecules that lack almost complete subunits. The processing is least pronounced in matrilin-1 and particularly complex in matrilin-2, which contains additional cleavage sites. Replacement of the hinge region in matrilin-4 by the matrilin-1 hinge region had no marked effect on the processing. A detailed study revealed that matrilin-4 is processed already in the secretory pathway and that the activation of the responsible enzymes is dependent on proprotein convertase activity. Matrilin-3 and -4, but not matrilin-1 subunits present in matrilin-1/-3 hetero-oligomers, were identified as substrates for ADAMTS4 and ADAMTS5, whereas ADAMTS1 did not cleave any matrilin. A neo-epitope antibody raised against the N terminus of the C-terminal cleavage product of matrilin-4 detected processed matrilin-4 in cultures of primary chondrocytes as well as on cartilage sections showing that the conserved cleavage site is used in vivo.
authors.affiliation: Center for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany.
authors.forename: Harald W A
authors.initials: HW
authors.lastname: Ehlen
authors.forename: Gerhard
authors.initials: G
authors.lastname: Sengle
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Klatt
authors.forename: Anja
authors.initials: A
authors.lastname: Talke
authors.forename: Stefan
authors.initials: S
authors.lastname: Müller
authors.forename: Mats
authors.initials: M
authors.lastname: Paulsson
authors.forename: Raimund
authors.initials: R
authors.lastname: Wagener
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000071097:ADAMTS1 Protein; D000071121:ADAMTS4 Protein; D000071116:ADAMTS5 Protein; D000818:Animals; D064236:Cartilage Oligomeric Matrix Protein; D019902:Chondrocytes / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D064235:Matrilin Proteins; D051379:Mice; D011348:Procollagen N-Endopeptidase / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary
chemical_list: D064236:Cartilage Oligomeric Matrix Protein; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; C577539:MATN1 protein, human; C577541:MATN2 protein, human; C577548:MATN4 protein, human; C577540:Matn1 protein, mouse; C577546:Matn3 protein, mouse; D064235:Matrilin Proteins; C577553:TSP5 protein, human; D051722:ADAM Proteins; D000071097:ADAMTS1 Protein; C103859:ADAMTS1 protein, human; D000071116:ADAMTS5 Protein; C121532:ADAMTS5 protein, human; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein; C000603918:ADAMTS4 protein, human; C000603919:Adamts4 protein, mouse