Mitochondrial processing of bovine adrenal steroidogenic acute regulatory protein.

Steroidogenic acute regulatory (StAR) protein is an important regulatory protein in steroidogenesis and rapidly undergoes proteolysis after import into the mitochondria. In this study, we determined the proteolytic cleavage sites and investigated the effects on the stimulation of steroidogenic activity of the blockage of these sites by mutation. The cleaved StAR proteins, which were purified using an anti-StAR immobilized column, reacted with antiserum against the StAR C-terminal oligopeptide.

Novel signaling stimulated by arsenite increases cholesterol metabolism through increases in unphosphorylated steroidogenic acute regulatory (StAR) protein.

Cholesterol metabolism to pregnenolone is dependent on the steroidogenic acute regulatory protein (StAR), which activates mitochondrial transfer of cholesterol to cytochrome CYP450scc. In mouse Y-1 adrenal cells and testis MA10 cells stimulation by 8-Bromo-cAMP (Br-cAMP) is augmented by a novel signaling initiated by low concentrations of arsenite (3-20 microM) and anisomycin (0.2 microM), a more selective stress agent.

Multiple contributions from long-chain fatty acid metabolism in Y-1 and MA-10 cells.

Acute steroidogenesis in either Y-1 or MA-10 cells is sensitive to different effects of fatty acids compare to a chronic stimulation. A 3-h stimulation of StAR expression in both cell types was completely blocked by NDGA and AA861, each functioning as lipoxygenase inhibitors. However, the acute 15-min stimulation in Y-1 cells was inhibited by these agents by distinct mechanisms.

[Content and transportation of Ca(2+) to hepatocytes and lipid content of liver cell membrane structure in experimental diabetes in the rat].

It is proved that at experimental diabetes the calcium content in hepatocytes is disturbed. This disorder is mostly shown in increase of calcium content in hepatocytes and in decrease of accumulation of these ions in mitochondrias. One of the possible reasons of changes at this pathology is the change of lipid content of hepatocytes, mitochondrias and microsomes.

Mitochondrial processing of newly synthesized steroidogenic acute regulatory protein (StAR), but not total StAR, mediates cholesterol transfer to cytochrome P450 side chain cleavage enzyme in adrenal cells.

The metabolism of cholesterol by cytochrome P450 side chain cleavage enzyme is hormonally regulated in steroidogenic tissues via intramitochondrial cholesterol transport. The mediating steroidogenic acute regulatory protein (StAR) is synthesized as a 37-kDa (p37) precursor that is phosphorylated by protein kinase A and cleaved within the mitochondria to generate 30-kDa forms (p30, pp30). The effectiveness of modified recombinant StAR forms in COS-1 cells without mitochondrial import has led to a prevailing view that cholesterol transport is mediated by p37 StAR via activity on the outer mitochondrial membrane.