Regulation of Rat Liver β-Hydroxy-β-Methylglutaryl-CoA Reductase Activity by Cholesterol

Higgins, Malcolm J. P.; Rudney, Harry

doi:10.1038/newbio246060a0

Cited by 83 publications

(27 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, the liver microsomes from the cholesterol-fed rats contained HMG-CoA reductase enzyme that was approximately 0.41 as active as enzyme from the microsomes of untreated animals. Studies from other laboratories are consistent with the conclusion that cholesterol feeding may suppress HMG-CoA reductase activity by decreasing the quantity of enzyme protein present (8,11,14,39,40) or by inhibition of existing enzyme (8,11,14).…”

supporting

confidence: 74%

“…The mechanism whereby cholesterol feeding reduces the quantity of HMG-CoA reductase present is probably related to a diminished synthesis of HMG-CoA reductase enzyme by the liver (8,11,39,40).…”

mentioning

confidence: 99%

“…Evidence from several laboratories suggests that HMG-CoA reductase may be regulated both by changes in enzyme concentration (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) and by changes in enzyme activity .…”

mentioning

confidence: 99%

See 2 more Smart Citations

Immunotitration of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in various physiological states.

Hardgrave¹,

Heller²,

Herrera³

et al. 1979

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The immunotitration of 3-hydroxy-3-methyl- Evidence from several laboratories suggests that HMG-CoA reductase may be regulated both by changes in enzyme concentration (3-13) and by changes in enzyme activity .The present article describes studies of rat liver HMG-CoA reductase by the technique of immunotitration of enzyme activity with HMG-CoA reductase antiserum. This procedure, which can be carried out by using either crude unpurified or purified biological preparations, allows a rapid quantitative estimate of the regulation achieved by changes in enzyme concentration and the regulation achieved by changes in enzyme activity. The following physiological states were investigated: (i) diurnal rhythm, (ii) cholestyramine feeding, and (iii) cholesterol feeding. The results show that the major change observed in the diurnal rhythm is a change in the concentration of HMG-CoA reductase enzyme molecules, whereas, for both cholestyramine feeding and for cholesterol feeding, significant changes occur in both enzyme activity and enzyme concentration.MATERIALS AND METHODS Materials. The materials used in this paper were obtained from described sources (13,34).HMG-CoA Reductase Antiserum. HMG-CoA reductase antiserum was prepared by injecting rabbits with purified rat liver HMG-CoA reductase as described (34). Ouchterlony immunodiffusion experiments with solubilized HMG-CoA reductase and HMG-CoA reductase antiserum showed a single precipitation line (12).The specific activity of the purified HMG-CoA reductase utilized as the antigen was approximately 500 nmol of mevalonate formed/(min-mg of protein). Because other investigators have obtained purified HMG-CoA reductase with a higher specific activity (35), the possibility exists, in spite of the finding of a single precipitation line by immunodiffusion (12), that the antigen was not completely homogeneous. In part, this may be due to the presence of both active and inactive forms of HMG-CoA reductase. Support for this concept has been presented by Klinsek et al. (35). Even if the purified HMG-CoA reductase utilized as antigen were not completely homogeneous, the inactivation of HMG-CoA reductase activity by HMG-CoA reductase antiserum is still a valid approach to detect relative changes in enzyme concentration and enzyme activity. Titrations conducted with rabbit serum from control animals (animals that were not immunized with HMG-CoA reductase) did not show inactivation of HMG-CoA reductase activity.Animals. Male Sprague-Dawley rats were used. All rats were maintained on the following cycle: 3:30 a.m. to 3:30 p.m., dark; 3:30 p.m. to 3:30 a.m., light. The rats were maintained on this cycle for 2 weeks prior to sacrifice. The animals were killed at 9:30 a.m. (mid-dark) Abbreviations: HMG-CoA, 3-hydroxy-3-methylglutaryl-coenzyme A; D 4.5, 4.5 hr after the beginning of the dark period; L 4.5, 4.5 hr after the beginning of the light period; Ec, relative enzyme concentration; EA, relative enzyme activity.

show abstract

supporting

confidence: 74%

mentioning

confidence: 99%

See 1 more Smart Citation

Immunotitration of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in various physiological states.

Hardgrave¹,

Heller²,

Herrera³

et al. 1979

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Diminution of the 8S band, similar to that indicated by the broken line in Fig. 3A (20 jig/ml) of unlabeled cholesterol or 25-hydroxycholesterol ( Fig. 3 B and D (1977) tosolic proteins, the greatest proportion of which exhibited a sedimentation coefficient of about 5 S. The protein nature of the cytosolic components in both the 5S and 8S bands is indicated by their lability to heat.…”

mentioning

confidence: 77%

“…Diurnal alterations in hepatic HMG-CoA reductase activity and induction of the enzyme activity by cholestyramine feeding or by injecting Triton WR 1339 involve alterations in the rate of enzyme synthesis (16)(17)(18)(19). On the other hand, dietary cholesterol may result in inactivation of the enzyme as well as suppression of its synthesis (20). Because inhibitory sterols do not affect HMG-CoA reductase activity directly-i.e., when they are added to an enzyme reaction mixture (1-3)-it seems likely that they repress the synthesis of the enzyme or else they inactivate it through some indirect mechanism as has been suggested by Bell et al (10).…”

mentioning

confidence: 99%

Binding of 25-hydroxycholesterol and cholesterol to different cytoplasmic proteins

Kandutsch

Chen

Shown

1977

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

Regulation of sterol synthesis in cultured cells by oxygenated derivatives of cholesterol

1975

View full text Add to dashboard Cite

Sterol synthesis in liver in vivo is regulated at the site of the reaction catalyzed by 3-hydroxy-3-methylglutaryl-CoA reductase through a feedback system thought to involve either cholesterol or one or more of the products of its metabolism. Cholesterol feeding results in repression of the synthesis of the enzyme, but inactivation of the enzyme seems to precede repressroblasts is not inhibited by purified exogenous cholesterol. However, derivatives of cholesterol produced by the introduction of a ketone or hydroxyl function in the 7, 20, 22 or 25 positions effectively inhibit sterol synthesis by specifically depressing the level of HMG CoA reductase activity. As a result of this specific effect prolonged incubation of an inhibitory sterol with growing L cells results in depletion of cellular sterol. Growth of the culture then ceases and the cells die unless an appropriate sterol or a sterol precursor is supplied in the medium. The inhibitory sterols, 25-hydroxycholesterol and 7-ketocholesterol appear to be taken up by L cells through processes that involve their specific interactions with saturable cellular receptors. The uptake of cholesterol by L cells appears to be by a different process--possibly through physical diffusion.

show abstract

Regulation of Rat Liver β-Hydroxy-β-Methylglutaryl-CoA Reductase Activity by Cholesterol

Cited by 83 publications

References 12 publications

Immunotitration of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in various physiological states.

Immunotitration of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in various physiological states.

Binding of 25-hydroxycholesterol and cholesterol to different cytoplasmic proteins

Regulation of sterol synthesis in cultured cells by oxygenated derivatives of cholesterol

Contact Info

Product

Resources

About