title: Chondrocalcin is internalized by chondrocytes and triggers cartilage destruction via an interleukin-1β-dependent pathway.
abstract: Chondrocalcin is among the most highly synthesized polypeptides in cartilage. This protein is released from its parent molecule, type II pro-collagen, after secretion by chondrocytes. A participation of extracellular, isolated chondrocalcin in mineralization was proposed more than 25 years ago, but never demonstrated. Here, exogenous chondrocalcin was found to trigger MMP13 secretion and cartilage destruction ex vivo in human cartilage explants and did so by modulating the expression of interleukin-1β in primary chondrocyte cultures in vitro. Chondrocalcin was found internalized by chondrocytes. Uptake was found mediated by a single 18-mer peptide of chondrocalcin, which does not exhibit homology to any known cell-penetrating peptide. The isolated peptide, when artificially linked as a tetramer, inhibited gene expression regulation by chondrocalcin, suggesting a functional link between uptake and gene expression regulation. At the same time, the tetrameric peptide potentiated chondrocalcin uptake by chondrocytes, suggesting a cooperative mechanism of entry. The corresponding peptide from type I pro-collagen supported identical cell-penetration, suggesting that this property may be conserved among C-propeptides of fibrillar pro-collagens. Structural modeling localized this peptide to the tips of procollagen C-propeptide trimers. Our findings shed light on unexpected function and mechanism of action of these highly expressed proteins from vertebrates.
authors.affiliation: Molecular, Cellular, Therapeutic Engineering & Glycosyl Transferases (MolCelTeG), UMR 7365 CNRS-Université de Lorraine, Biopôle du Campus Biologie-Santé, Faculté de Médecine, 9, Avenue de la Forêt de Haye, BP 184, 54505 Vandoeuvre-lès-Nancy, France.
authors.forename: Claudie
authors.initials: C
authors.lastname: Bantsimba-Malanda
authors.forename: Justine
authors.initials: J
authors.lastname: Cottet
authors.forename: Patrick
authors.initials: P
authors.lastname: Netter
authors.forename: Dominique
authors.initials: D
authors.lastname: Dumas
authors.forename: Didier
authors.initials: D
authors.lastname: Mainard
authors.forename: Jacques
authors.initials: J
authors.lastname: Magdalou
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Vincourt
mesh_terms: D000911:Antibodies, Monoclonal; D001152:Arsenicals; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D002358:Cartilage, Articular / Q000187:drug effects*; D019902:Chondrocytes / Q000378:metabolism*; D024043:Collagen Type II / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D015202:Protein Engineering; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D001152:Arsenicals; D002135:Calcium-Binding Proteins; D024043:Collagen Type II; D053583:Interleukin-1beta; C040072:chondrocalcin; C029341:oxophenylarsine
keywords: BSA; COL; Chondrocytes; Collagen; Endocytosis; GAG; HRP; IL-1β; IL1-RI; Interleukin-1beta; MMP13; Matrix metalloprotease-13; Metalloprotease; Osteoarthritis; PAO; PFA; bovine serum albumin; collagen; glycosaminoglycan; horseradish peroxidase; interleukin-1 receptor I; paraformaldehyde; phenylarsine oxide