Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase synthesis in Syrian hamster C100 cells by mevinolin, 25-hydroxycholesterol, and mevalonate: the role of posttranscriptional control.
C100 is a baby hamster kidney cell line that expresses high levels of HMG-CoA reductase relative to its parental cell line SV28. In this study the effects of the oxysterol 25-hydroxycholesterol and mevalonate on the mRNA level and rate of synthesis for HMG-CoA reductase were evaluated in C100 cells treated with mevinolin, a competitive inhibitor of HMG-CoA reductase. The addition of 25-hydroxycholesterol to the cell culture medium resulted in a fourfold decrease in both the rate of synthesis and mRNA level for HMG-CoA reductase. Mevalonate at a concentration of 0.4 mM, when added to mevinolin-treated C100 cells, produced no apparent reduction in HMG-CoA reductase mRNA levels and only a small (25%) decline in HMG-CoA synthesis. Mevalonate (0.4 mM) added to 25-hydroxycholesterol-treated cells resulted in no further reduction in the HMG-CoA reductase mRNA level when compared to cells treated with 25-hydroxycholesterol alone, but produced an additional 30-fold decrease in the rate of HMG-CoA reductase synthesis. Degradation of HMG-CoA reductase was rapid in the presence (t1/2 = 1.34 h) or absence (t1/2 = 1.17 h) of mevinolin and was not changed significantly by adding either 25-hydroxycholesterol, alone (t1/2 = 1.30 h) or both 25-hydroxycholesterol and mevalonate (t1/2 = 1.30 h) to mevinolin-treated cells. This study demonstrates that mevalonate and 25-hydroxycholesterol act synergistically in the presence of mevinolin to achieve a greater degree of suppression in the rate of HMG-CoA reductase synthesis than can be accounted for by their individual effects on HMG-CoA reductase mRNA. In addition, the data suggest that mevalonate affects the synthesis of HMG-CoA reductase at a yet unidentified posttranscriptional control site.
Peffley
D M
DM
University of Tennessee, Memphis, Health Science Center, Department of Pharmacology 38163.
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D006224:Cricetinae; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006888:Hydroxycholesterols / Q000494:pharmacology*; D006903:Hydroxymethylglutaryl CoA Reductases / Q000096:biosynthesis* / Q000235:genetics; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007668:Kidney; D008148:Lovastatin / Q000494:pharmacology*; D008647:Mesocricetus; D008798:Mevalonic Acid / Q000494:pharmacology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects
D006888:Hydroxycholesterols; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D012333:RNA, Messenger; C007997:25-hydroxycholesterol; D008148:Lovastatin; D006903:Hydroxymethylglutaryl CoA Reductases; D008798:Mevalonic Acid