Further characterization of a somatic cell mutant defective in regulation of 3-hydroxy-3-methylglutaryl coenzyme a reductase

Peffley, Dennis M.; Miyake, Jon H.; Leonard, Sherry; Gunten, Charles von; Sinensky, Michael

doi:10.1007/bf01535308

Cited by 20 publications

(17 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6; Table 3). These findings support previous studies (12,25,31) which demonstrate that transcriptional and posttranscriptional control of cholesterol metabolism are achieved by genetically distinct mechanisms.…”

Section: Resultssupporting

confidence: 93%

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

Evans¹,

Metherall²

1993

Mol. Cell. Biol.

View full text Add to dashboard Cite

Cholesterol biosynthesis and uptake are controlled by a classic end product-feedback mechanism whereby elevated cellular sterol levels suppress transcription of the genes encoding 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, HMG-CoA reductase, and the low-density lipoprotein receptor. The 5'-flanking region of each gene contains a common cis-acting element, designated the sterol regulatory element (SRE) cells is limited to transcriptional regulation, since posttranscriptional mechanisms of sterol-mediated regulation were intact: the cells retained the ability to posttranscriptionally suppress HMG-CoA reductase activity and to stimulate acyl-CoA:cholesterol acyltransferase activity. These results suggest that SRD-6 cells lack a factor required for SRE-dependent transcriptional activation. We contrast these cells with a previously isolated oxysterol-resistant cell line (SRD-2) that lacks a factor required for SRE-dependent transcriptional suppression and propose a model for the role of these genetically defined factors in sterol-mediated transcriptional regulation.Mammalian cells demonstrate exquisite control over the level of free cholesterol within the cell (reviewed in reference 17). This control is achieved through the concerted action of a number of mechanisms, including the coordinate transcriptional suppression of the genes encoding 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, HMG-CoA reductase, and the low-density lipoprotein (LDL) receptor. HMG-CoA synthase and HMG-CoA reductase are the first two committed steps in the pathway of cholesterol biosynthesis, and transcriptional suppression of these genes decreases the rate of cholesterol synthesis. The LDL receptor mediates endocytosis of cholesterol-rich lipoprotein particles such as LDL, and transcriptional suppression of the LDL receptor results in a decreased rate of cholesterol uptake. Transcriptional suppression of these three genes appears to be mediated through a common cis-acting sequence, termed the sterol regulatory element (SRE), that resides in the 5'-flanking region of each gene. A protein that interacts with the SRE of the LDL receptor promoter has recently been identified and purified (1,40 levels rise, the rate of degradation of HMG-CoA reductase is enhanced. This increased degradation requires the membrane-spanning domain of the protein, which anchors it to the endoplasmic reticulum (14). This increased degradation results in decreased HMG-CoA reductase activity and a consequent decrease in the rate of cholesterol synthesis. Sterols also inhibit translation of HMG-CoA reductase mRNA (28), which further decreases the rate of cholesterol synthesis. In addition, sterols stimulate acyl-CoA:cholesterol acyltransferase (ACAT) activity by a mechanism that does not require new protein synthesis (4, 16). ACAT resides in the endoplasmic reticulum and catalyzes the transfer of long-chain fatty acyl residues from acyl-CoA to the 3-hydroxyl group of cholesterol to form cholesteryl esters. While free cholesterol can be deleter...

show abstract

Section: Resultssupporting

confidence: 93%

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

Evans¹,

Metherall²

1993

Mol. Cell. Biol.

View full text Add to dashboard Cite

show abstract

“…Other authors found that mevalonate is required to allow sterol-mediated HMG-CoA reductase degradation (7,42). This discrepancy might be due to differences between the CHO and Hep G2 cell lineages similar to those observed between CHO and C100 cells (43).…”

Section: Table IImentioning

confidence: 88%

The Novel Cholesterol-lowering Drug SR-12813 Inhibits Cholesterol Synthesis via an Increased Degradation of 3-Hydroxy-3-methylglutaryl-coenzyme A Reductase

Berkhout

Simon

Patel

et al. 1996

Journal of Biological Chemistry

View full text Add to dashboard Cite

SR-12813 (tetra-ethyl 2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethenyl-1, 1-bisphosphonate) lowers plasma cholesterol in five species. In this paper we investigate the underlying mechanism using Hep G2 cells. SR-12813 inhibited incorporation of tritiated water into cholesterol with an IC50 of 1.2 microM but had no effect on fatty acid synthesis. Furthermore, SR-12813 reduced cellular 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity with an IC50 of 0.85 microM. The inhibition of HMG-CoA reductase activity was rapid with a T1/2 of 10 min. After a 16-h incubation with SR-12813, mRNA levels of HMG-CoA reductase and low density lipoprotein (LDL) receptor were increased. The increased expression of LDL receptor translated into a higher LDL uptake, which can explain the primary hypocholesterolemic effect of SR-12813 in vivo. Western blot analysis indicated that the amount of HMG-CoA reductase protein rapidly decreased in the presence of SR-12813. Pulse-chase experiments with [35S]methionine showed that the T1/2 of HMG-CoA reductase degradation decreased in the presence of SR-12813 from 90 to 20 min. Pre-incubation with 50 microM of lovastatin did not prevent the effects of SR-12813 on HMG-CoA reductase degradation, indicating that the compound does not need mevalonate-derived regulators for its action. It is concluded that SR-12813 inhibits cholesterol synthesis mainly by an enhanced degradation of HMG-CoA reductase.

show abstract

“…HMG CoA reductase is the rate-limiting enzyme of mevalonate biosynthesis as well as the most highly regulated enzyme in this series (55)(56)(57). The multivalent regulation of HMG CoA reductase (56) integrates activities at the transcriptional (55-70), post-transcriptional (55,(59)(60)(61)(62)(63)(64)(71)(72)(73)(74), and post-translational (55,61,(71)(72)(73)(74)(75)(76)(77)(78)(79)(80)(81)(82)(83) levels. Sterolmediated regulation of transcription, the dominant regulatory site in sterologenic tissues, is mediated through the sterol regulatory element, (SRE), a promoter-enhancer octanucleotide sequence, GTGCGGTG, located in the 5Ј flanking region of the reductase gene (55,66,68).…”

mentioning

confidence: 99%

“…The posttranslational control of HMG CoA reductase activity, a secondary level of control called into play when cellular isoprenoid requirements are satisfied, is mediated by a nonlysosomal cysteine protease (81)(82)(83). This protease activity, a process accelerated by sterols and a mevalonate-derived nonsterol product (60)(61)(62)(63)(74)(75)(76)(77)(78)(79)(80)(81)(82), has high specificity for the 97-kDA HMG CoA reductase with intact hydrophobic domains in the endoplasmic reticulum. If membrane domains are deleted, neither sterols nor the mevalonatederived nonsterol product affects reductase turnover (79).…”

mentioning

confidence: 99%

Isoprenoid‐Mediated Inhibition of Mevalonate Synthesis: Potential Application to Cancer

Elson

Peffley

Hentosh

et al. 1999

Proc Soc Exp Biol Med

View full text Add to dashboard Cite

Pure and mixed isoprenoid end products of plant mevalonate metabolism trigger actions that suppress 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase activity. These actions modulate HMG CoA reductase mRNA translation and the proteolytic degradation of HMG CoA reductase. Such post-transcriptional events, we propose, are activated directly by acyclic isoprenoids and indirectly by cyclic isoprenoids. Isoprenoids, acting secondarily to the dominant transcriptional effector of sterologenesis, modestly lower cholesterol levels, if and only if, sterologenesis is not repressed by a saturating imput of dietary cholesterol. An anomaly associated with tumor growth-a sterol feedback-resistant HMG CoA reductase activity-ensures a pool of sterologenic pathway intermediates. Such intermediates provide lipophilic anchors essential for membrane attachment and biological activity of growth hormone receptors, nuclear lamins A and B, and oncogenic ras. Tumor HMG CoA reductase retains high sensitivity to the isoprenoid-mediated secondary regulation. Repression of mevalonate synthesis by plant-derived isoprenoids reduces ras and lamin B processing, arrests cells in G1, and initiates cellular apoptosis. This unique tumor cell-specific sensitivity allows isoprenoids to be used for tumor therapy, an application emulating that of the statins, but one free of adverse effects. When evaluated at levels provided by a typical diet, isoprenoids individually have no impact on cholesterol synthesis and tumor growth. Nonetheless, isoprenoid-mediated activities are additive, and, sometimes synergistic. Therefore, the combined actions of the estimated 23,000 isoprenoid constituents of plant materials, acting in concert with other chemopreventive phytochemicals, may explain the lowered cancer risk associated with a diet rich in plant products. In contrast, that lowering of cancer risk does not correspond to supplemental intake of other dietary factors associated with fruits, vegetables, and cereal grains, namely fiber, beta-carotene, vitamin C, and vitamin E, and only weakly to supplemental folate.

show abstract

Further characterization of a somatic cell mutant defective in regulation of 3-hydroxy-3-methylglutaryl coenzyme a reductase

Cited by 20 publications

References 37 publications

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

The Novel Cholesterol-lowering Drug SR-12813 Inhibits Cholesterol Synthesis via an Increased Degradation of 3-Hydroxy-3-methylglutaryl-coenzyme A Reductase

Isoprenoid‐Mediated Inhibition of Mevalonate Synthesis: Potential Application to Cancer

Contact Info

Product

Resources

About