Alteration of the kinetics of type I procollagen synthesis in human osteosarcoma cells by 1,25-dihydroxyvitamin D3.
The kinetics of type I procollagen synthesis in a human osteosarcoma cell line, MG 63, were investigated after treatment with 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D3), a hormonal inducer of phenotypic differentiation. Pulse label and chase experiments demonstrated greatly enhanced production and more rapid reduction of intracellular procollagen molecules in the 1,25-(OH)2 D3-treated cells as compared to the nontreated case. After a chase for 1 h, labeled procollagen was reduced by nine-tenths in 1,25-(OH)2 D3-treated cells, while half of the radioactivity still remained in nontreated cells. The expression rate of type I collagen, which was examined by pulse label experiment, was elevated in association with an increase in the mRNA coding for the type I collagen alpha 1 chain by 1,25-(OH)2 D3 treatment. However, the amount of intracellular procollagen present after 4 h continuous labeling was almost the same, independent of the 1,25-(OH)2 D3 treatment. Thus, we conclude that strage of the molecule was not affected. The results therefore suggest an increase in both the synthesis and secretion of type I collagen. The 1,25-(OH)2 D3 treatment was also found to induce the alpha subunit of prolyl 4-hydroxylase and to be associated with an elevated level of hydroxyproline in the procollagen. Moreover, gelatinase B-resistant procollagen molecules, indicative of intracellular procollagen molecules in the stable triple helical form, were detected only in the 1,25-(OH)2 D3-treated cells. These data suggest more efficient proline hydroxylation is involved in rapid secretion of procollagen after hormone administration. The present evidence points to posttranslational control of procollagen synthesis.
Kojima
T
T
Department of Orthopaedic Surgery, Nagoya University School of Medicine, Japan.
Kozaki
K
K
Saga
S
S
Hashizume
Y
Y
Ishiguro
N
N
Iwata
H
H
Miyaishi
O
O
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D017364:Collagenases / Q000378:metabolism; D006801:Humans; D006900:Hydroxylation; D007700:Kinetics; D020780:Matrix Metalloproteinase 9; D051379:Mice; D012516:Osteosarcoma / Q000378:metabolism*; D010641:Phenotype; D011347:Procollagen / Q000096:biosynthesis*; D011393:Procollagen-Proline Dioxygenase / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D014407:Tumor Cells, Cultured
D011347:Procollagen; D011392:Proline; D011393:Procollagen-Proline Dioxygenase; D017364:Collagenases; D020780:Matrix Metalloproteinase 9; D002117:Calcitriol