title: Terminal differentiation of chick embryo chondrocytes requires shedding of a cell surface protein that binds 1,25-dihydroxyvitamin D3.
abstract: Endochondral ossification comprises a cascade of cell differentiation culminating in chondrocyte hypertrophy and is negatively controlled by soluble environmental mediators at several checkpoints. Proteinases modulate this control by processing protein signals and/or their receptors. Here, we show that insulin-like growth factor I can trigger hypertrophic development by stimulating production and/or activation of proteinases in some populations of chick embryo chondrocytes. Cell surface targets of the enzymes include 1,25-dihydroxyvitamin D3 membrane-associated rapid response steroid receptor (1,25 D3 MARRS receptor), also known as ERp57/GRp58/ERp60. This protein is anchored to the outer surface of plasma membranes and inhibits late chondrocyte differentiation after binding of 1,25-dihydroxyvitamin D3. Upon treatment with insulin-like growth factor I, 1,25 D3 MARRS receptor is cleaved into two fragments of approximately 30 and 22 kDa. This process is abrogated along with hypertrophic development by E-64 or cystatin C, inhibitors of cysteine proteinases. Cell differentiation is enhanced by treatment with antibodies to 1,25 D3 MARRS receptor that either block binding of the inhibitory ligand 1,25-dihydroxyvitamin D3 or inactivate 1,25 D3 MARRS receptor left intact after treatment with proteinase inhibitors. Therefore, proteolytic shedding of 1,25 D3 MARRS receptor constitutes a molecular mechanism eliminating the 1,25-dihydroxyvitamin D3-induced barrier against late cartilage differentiation and is a potentially important step during endochondral ossification or cartilage degeneration in osteoarthritis.
authors.affiliation: Institute for Physiological Chemistry and Pathobiochemistry, University Hospital of Münster, 48149 Münster, Germany.
authors.forename: Rita
authors.initials: R
authors.lastname: Dreier
authors.forename: Birgit Kathrin
authors.initials: BK
authors.lastname: Günther
authors.forename: Tom
authors.initials: T
authors.lastname: Mainz
authors.forename: Ilka
authors.initials: I
authors.lastname: Nemere
authors.forename: Peter
authors.initials: P
authors.lastname: Bruckner
mesh_terms: D000818:Animals; D001846:Bone Development; D002117:Calcitriol / Q000378:metabolism*; D002454:Cell Differentiation; D002642:Chick Embryo; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism*; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015853:Cysteine Proteinase Inhibitors; D008565:Membrane Proteins; D018167:Receptors, Calcitriol; D007334:Insulin-Like Growth Factor I; D002117:Calcitriol