Regulation of squalene epoxidase in HepG2 cells.
Regulation of squalene epoxidase in the cholesterol biosynthetic pathway was studied in a human hepatoma cell line, HepG2 cells. Since the squalene epoxidase activity in cell homogenates was found to be stimulated by the addition of Triton X-100, enzyme activity was determined in the presence of thi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Elsevier
1990-11-01
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| Series: | Journal of Lipid Research |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0022227520422734 |
| _version_ | 1818590509905477632 |
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| author | Y Hidaka T Satoh T Kamei |
| author_facet | Y Hidaka T Satoh T Kamei |
| author_sort | Y Hidaka |
| collection | DOAJ |
| description | Regulation of squalene epoxidase in the cholesterol biosynthetic pathway was studied in a human hepatoma cell line, HepG2 cells. Since the squalene epoxidase activity in cell homogenates was found to be stimulated by the addition of Triton X-100, enzyme activity was determined in the presence of this detergent. Incubation of HepG2 cells for 18 h with L-654,969, a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, increased squalene epoxidase activity dose-dependently. On the other hand, low density lipoprotein (LDL) and 25-hydroxy-cholesterol decreased the enzyme activity. These results demonstrate that squalene epoxidase is regulated by the concentrations of endogenous and exogenous sterols. The affinity of the enzyme for squalene was not changed by treatment with L-654,969. Cytosolic (S105) fractions, prepared from HepG2 cells treated with or without L-654,969, had no effect on microsomal squalene epoxidase activity of HepG2 cells, in contrast to the stimulating effect of S105 fractions from rat liver homogenate. Mevalonate, LDL, and oxysterol treatment abolished the effect of L-654,969. Simultaneous addition of cycloheximide and actinomycin D also prevented enzyme induction in HepG2 cells. From these results, the change in squalene epoxidase activity is thought to be caused by the change in the amount of enzyme protein. It is further suggested that squalene epoxidase activity is suppressed only by sterols, not by nonsterol derivative(s) of mevalonate, in contrast to the regulation of HMG-CoA reductase. |
| first_indexed | 2024-12-16T09:57:41Z |
| format | Article |
| id | doaj.art-e4028204c9164f53948a9b6d17c4a731 |
| institution | Directory Open Access Journal |
| issn | 0022-2275 |
| language | English |
| last_indexed | 2024-12-16T09:57:41Z |
| publishDate | 1990-11-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Lipid Research |
| spelling | doaj.art-e4028204c9164f53948a9b6d17c4a7312022-12-21T22:35:53ZengElsevierJournal of Lipid Research0022-22751990-11-01311120872094Regulation of squalene epoxidase in HepG2 cells.Y Hidaka0T Satoh1T Kamei2Central Research Laboratories, Banyu Pharmaceutical Co., Ltd., Tokyo, Japan.Central Research Laboratories, Banyu Pharmaceutical Co., Ltd., Tokyo, Japan.Central Research Laboratories, Banyu Pharmaceutical Co., Ltd., Tokyo, Japan.Regulation of squalene epoxidase in the cholesterol biosynthetic pathway was studied in a human hepatoma cell line, HepG2 cells. Since the squalene epoxidase activity in cell homogenates was found to be stimulated by the addition of Triton X-100, enzyme activity was determined in the presence of this detergent. Incubation of HepG2 cells for 18 h with L-654,969, a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, increased squalene epoxidase activity dose-dependently. On the other hand, low density lipoprotein (LDL) and 25-hydroxy-cholesterol decreased the enzyme activity. These results demonstrate that squalene epoxidase is regulated by the concentrations of endogenous and exogenous sterols. The affinity of the enzyme for squalene was not changed by treatment with L-654,969. Cytosolic (S105) fractions, prepared from HepG2 cells treated with or without L-654,969, had no effect on microsomal squalene epoxidase activity of HepG2 cells, in contrast to the stimulating effect of S105 fractions from rat liver homogenate. Mevalonate, LDL, and oxysterol treatment abolished the effect of L-654,969. Simultaneous addition of cycloheximide and actinomycin D also prevented enzyme induction in HepG2 cells. From these results, the change in squalene epoxidase activity is thought to be caused by the change in the amount of enzyme protein. It is further suggested that squalene epoxidase activity is suppressed only by sterols, not by nonsterol derivative(s) of mevalonate, in contrast to the regulation of HMG-CoA reductase.http://www.sciencedirect.com/science/article/pii/S0022227520422734 |
| spellingShingle | Y Hidaka T Satoh T Kamei Regulation of squalene epoxidase in HepG2 cells. Journal of Lipid Research |
| title | Regulation of squalene epoxidase in HepG2 cells. |
| title_full | Regulation of squalene epoxidase in HepG2 cells. |
| title_fullStr | Regulation of squalene epoxidase in HepG2 cells. |
| title_full_unstemmed | Regulation of squalene epoxidase in HepG2 cells. |
| title_short | Regulation of squalene epoxidase in HepG2 cells. |
| title_sort | regulation of squalene epoxidase in hepg2 cells |
| url | http://www.sciencedirect.com/science/article/pii/S0022227520422734 |
| work_keys_str_mv | AT yhidaka regulationofsqualeneepoxidaseinhepg2cells AT tsatoh regulationofsqualeneepoxidaseinhepg2cells AT tkamei regulationofsqualeneepoxidaseinhepg2cells |