Activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase does not respond to ubiquinone uptake in cultured cells

Induction of differentiation in neuro-2A cells by the monoterpene perillyl alcohol

The monoterpenes limonene and perillyl alcohol have been shown to induce the complete regression of rat mammary carcinomas by what appears to be a cytostatic and differentiation process. In order to evaluate the differentiating effects of the monoterpenes we tested the ability of perillyl alcohol to induce differentiation in a well-characterized neuroblastoma cell model. Perillyl alcohol was found to be a potent inducer of the neuroblastoma-derived cell line Neuro-2A. Several cellular effects of monoterpenes were ruled out as contributing to Neuro-2A differentiation including its cytostatic effect and its ability to inhibit ubiquinone (CoQ) syntheses.

Feedback-type inhibition of activity of 3-hydroxy-3-methylglutaryl coenzyme a reductase by ubiquinone

Accompanying the decrease in serum cholesterol and increase in concentration of ubiquinone in liver and its microsomes, the activity, but not the protein, of HMG-CoA reductase decreased in ubiquinone-supplemented rats. A soluble 58-kDa preparation of HMG-CoA reductase was partially inhibited on addition of ubiquinone indicating a possible feedback type of action.

Regulation of the mevalonate pathway

The mevalonate pathway produces isoprenoids that are vital for diverse cellular functions, ranging from cholesterol synthesis to growth control. Several mechanisms for feedback regulation of low-density-lipoprotein receptors and of two enzymes involved in mevalonate biosynthesis ensure the production of sufficient mevalonate for several end-products. Manipulation of this regulatory system could be useful in treating certain forms of cancer as well as heart disease.