Bone Gla Protein Messenger Ribonucleic Acid is Regulated by Both 1,25-Dihydroxyvitamin D3and 3′,5′-Cyclic Adenosine Monophosphate in Rat Osteosarcoma Cells

Publisher Website
Google Scholar
Abstract
1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] regulates the synthesis of bone .gamma.-carboxyglutamic acid (Gla) protein (BGP) by osteoblastic cells. In this study we examined the effect of cAMP, alone and inc ombination with 1,25-(OH)2D3, on the regulation of BGP mRNA levels in ROS 17/2 rat osteosarcoma cells. Elevation of intracellular cAMP levels by cAMP analogs or by isobutylmethylxanthine (IBMX), forskolin, or PTH, resulted in increased BGP mRNA levels and BGP secretion after 1 day of treatment. The effects of these agents were additive with 1,25-(OH)2D3 in stimulating BGP gene expression. After 4 days of treatment, pertussis toxin (PT) and 1,25-(OH)2D3 were synergistic in stimulating BGP mRNA, and the effect of PT couble be mimicked by (Bu)2cAMP, IBMX, forskolin, cholera toxin, and to a lesser extent by PTH. THe effect of 1-day treatment with cAMP alone and the synergistic effect with 1,25(OH)2D3 on the stimulation of BGP mRNA were dependent on cell density, while basal and 1,25(OH)2D3-stimulated synthesis were not. Cyclic AMP inhibited ROS 17/2 cell growth after 1 day of treatment, an effect that was also dependent on intial cell density. After 4 days of treatment, 1,25-(OH)2D3, cAMP, and PT all demonstrated inhibition of cell growth. When cells were treated with actinomycin D, both 1,25(OH)2D3 and cAMP stimulation of BGP mRNA were blocked, in addition, neither agent was effective in enhancing BGP mRNA stability when prestimulated cells were exposed to actinomycin D. These results suggest that cAMP may play a role in the regulation of BGP gene expression at the level of transcription, and the additive effects observed with cAMP and 1,25-(OH)2D3 suggest that these two agents are acting through different mechanisms.

This publication has 0 references indexed in Scilit: