Role of biosynthesis of cholesterol and isoprenoid derivatives in regulation of G1 progression and cell proliferation of 3T6 cells.
The growth of 3T6-cells was rapidly decreased, although not completely stopped, as a consequence of treatment of the cell cultures with serum-free medium. By analyzing the cell cycle traverse it was found that the decrease in growth rate was attributable to a 6-8-h delay in progression through the proximal part of G1. These effects of serum depletion on cell-cycle traverse and cell proliferation were compared with simultaneous effects on the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and the biosynthesis of cholesterol and the two isoprenoid derivatives coenzyme Q and dolichol. The activity of HMG CoA reductase was unaffected during the first 8 h of serum depletion and depressed by approximately 50% during the next 16 h. In contrast, the rate of coenzyme Q and dolichol synthesis, as related to cholesterol synthesis, was substantially decreased, and within 4 h after shift to serum-free medium both were reduced by 70-80%. As distinguished from dolichol synthesis, the synthesis of coenzyme Q was even decreased following exposures of the cell cultures to cholesterol-poor serum. This indicates that the rate of coenzyme Q synthesis is dependent on the concentration of serum cholesterol, whereas rate of dolichol synthesis is stimulated by some other serum factor(s). In addition, supplementation with dolichol to serum-depleted cells partially normalized G1 traverse and DNA synthesis, whereas cholesterol or coenzyme Q was ineffective. Taken together, the results suggest that a certain level of de novo synthesis of dolichol is required to maintain normal cell-cycle traverse and growth of 3T6 cells.
Larsson
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Department of Tumor Pathology, Karolinska Institutet, Stockholm, Sweden.
D000818:Animals; D002455:Cell Division; D002460:Cell Line; D002784:Cholesterol / Q000096:biosynthesis*; D003470:Culture Media; D004261:DNA Replication; D004224:Diterpenes / Q000096:biosynthesis*; D004286:Dolichols / Q000096:biosynthesis*; D005434:Flow Cytometry; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007399:Interphase; D008798:Mevalonic Acid / Q000378:metabolism; D014451:Ubiquinone / Q000096:biosynthesis*
D003470:Culture Media; D004224:Diterpenes; D004286:Dolichols; D014451:Ubiquinone; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D008798:Mevalonic Acid