Procollagen synthesis and extracellular matrix deposition in MG-63 osteosarcoma cells.
We compared the procollagen synthetic properties of MG-63 osteosarcoma cells with those of cultured human skin fibroblasts. In both cells, the expressions of type I and III procollagens are largely dependent on the constant presence of ascorbate and coordinately decreased by the neutral polymer dextran T-40. The amino-terminal propeptides of pro-alpha 1 and pro-alpha 2 chains of type I procollagen are phosphorylated and those of the pro-alpha 1 and pN-alpha 1 chains of type III procollagen both phosphorylated and sulfated, there being no difference in net charge in the propeptides between these cell types. The major differences between MG-63 and normal fibroblasts are the exceptionally high relative synthesis of type III procollagen by MG-63 cells, up to about 40% of the total of types I and III (6% in cultured skin fibroblasts), and the inability of ascorbate-supplemented MG-63 cells to deposit collagens into an insoluble pericellular matrix. A longer dextran treatment shifts up to one-fourth of the proline-labeled extracellular macromolecules into the matrix fraction within 4 days (in control 4%). Despite processing of the procollagens to the respective collagens in the matrix, neither control matrices nor those induced by dextran induced increased production of alkaline phosphatase. In cultures up to 4 days postconfluence the proportion of type III collagen produced tended to increase over that in early confluent cultures. With respect to collagen production, the MG-63 cell line is not a representative of the osteoblast lineage but rather resembles a proliferative wound fibroblast.
Jukkola
A
A
Department of Medical Biochemistry, University of Oulu, Finland.
Risteli
L
L
Melkko
J
J
Risteli
J
J
D001205:Ascorbic Acid / Q000378:metabolism; D002460:Cell Line; D005109:Extracellular Matrix / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D012516:Osteosarcoma / Q000378:metabolism*; D011347:Procollagen / Q000096:biosynthesis* / Q000378:metabolism; D012867:Skin / Q000378:metabolism; D014407:Tumor Cells, Cultured
D011347:Procollagen; D001205:Ascorbic Acid