Alteration of the kinetics of type I procollagen synthesis in human osteosarcoma cells by 1,25-dihydroxyvitamin D3

✍ Scribed by Toshihisa Kojima; Ken-ichi Kozaki; Shinsuke Saga; Yoshio Hashizume; Naoki Ishiguro; Hisashi Iwata; Osamu Miyaishi

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 113 KB
• Volume: 65
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(19970615)65:4<542::aid-jcb9>3.0.co;2-o

✦ Synopsis

The kinetics of type I procollagen synthesis in a human osteosarcoma cell line, MG 63, were investigated after treatment with 1,25-dihydroxyvitamin D 3 (1,25-(OH) 2 D 3 ), 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 D 3 -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 D 3 -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 a1 chain by 1,25-(OH) 2 D 3 treatment. However, the amount of intracellular procollagen present after 4 h continuous labeling was almost the same, independent of the 1,25-(OH) 2 D 3 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 D 3 treatment was also found to induce the a 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 D 3 -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.