epidermal-growth-factor and mevastatin

The effect of growth factors such as fibroblast growth factor on the production of a basement lamina by cultured endothelial cells has been investigated. The ability of these cells to grow and differentiate properly correlated with their ability to produce a basement lamina. The effect of such a substrate on the growth, differentiation, and aging of cells in vitro, as well as its use for the long-term culture of either normal diploid cells or tumor cells, is reviewed.

Topics: Animals; Basement Membrane; Cell Adhesion; Cell Differentiation; Cell Division; Cell Survival; Endothelium; Epidermal Growth Factor; Fibroblast Growth Factors; Growth Substances; Humans; Hydroxymethylglutaryl CoA Reductases; Lipoproteins; Lovastatin; Naphthalenes; Neurons; Peptides

We have used compactin, an inhibitor of mevalonate biosynthesis, to block p21ras posttranslational modification and membrane association in PC12 cells. Previous studies have demonstrated a requirement for isoprenylation for mitogenic effects of activated p21ras in mammalian cells and for function of RAS gene products in yeast. Immunoprecipitation of [35S]methionine-labeled p21ras from PC12 cell homogenates confirmed that the processed p21ras species is missing from compactin-treated PC12 cells. Immunoprecipitation from particulate and cytosolic fractions of PC12 cells confirmed that compactin blocks p21ras membrane association: p21ras is confined to the cytosol fraction. Induction of neuronal differentiation and ornithine decarboxylase (ODCase) transcription by oncogenic p21N-ras does not occur in compactin-treated cells indicating that activity of oncogenic p21N-ras expressed in PC12 cells is abolished by compactin treatment. Thus, p21ras isoprenylation or association with the membrane appears to be required for early responses and neuronal differentiation attributable to p21ras activation. In contrast, blockade of p21ras isoprenylation and membrane association by compactin treatment did not significantly reduce PC12 cell responses to NGF. Responses examined included rapid phosphorylation of tyrosine hydroxylase, rapid induction of ODCase expression, survival in serum-free medium and neuronal differentiation. Compactin blocked growth factor-induced rapid changes in cell surface morphology but did so whether this response was induced by NGF or by EGF. These results indicate that functional p21ras is not necessary for responses to NGF which in turn implies that if a ras-dependent NGF signal transduction pathway exists, as has been previously suggested, at least one additional ras-independent pathway must also be present.

Topics: Animals; Cell Differentiation; Cytosol; Dexamethasone; DNA Probes; Epidermal Growth Factor; Gene Expression; Genes, ras; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Lovastatin; Nerve Growth Factors; Neurons; Ornithine Decarboxylase; PC12 Cells; Phosphoproteins; Polyisoprenyl Phosphates; Protein Processing, Post-Translational; Proto-Oncogene Proteins p21(ras); RNA, Neoplasm; Signal Transduction

EGF stimulates adrenal steroidogenesis in ewes and in ovine adrenal slices. In vitro, The stimulation is blocked by the cholesterol synthesis inhibitors compactin and AY 9944. EGF stimulates the incorporation of [14C]acetate into cholesterol. EGF increases the activity of the rate limiting enzyme in cholesterol biosynthesis, HMG CoA reductase. EGF has no effect on the levels of any intermediates involved in the conversion of pregnenolone to cortisol, although ACTH produced changes consistent with 17 alpha-hydroxylase activation. We propose that EGF increases adrenal cortisol synthesis in vitro by a stimulation of cholesterol precursor biosynthesis mediated through activation of HMG CoA reductase.

Topics: Adrenal Cortex; Adrenocorticotropic Hormone; Animals; Cholesterol; Epidermal Growth Factor; Female; Hydrocortisone; Hydroxymethylglutaryl-CoA Reductase Inhibitors; In Vitro Techniques; Lovastatin; Mice; Naphthalenes; Pregnenolone