Steroidogenic acute regulatory protein (StAR) is a 30-kDa protein involved in the transport of cholesterol to the inner mitochondrial membrane and thus plays a key role in steroid biosynthesis. To clarify the implications of this protein in neurosteroid biosynthesis, we examined the possible expression of a StAR transcript in the adult rat CNS and detected it. cDNA cloning and sequencing analysis revealed that two forms of StAR mRNAs are expressed in the brain in the same manner as in the adrenal gland, indicating that they are fully functional and not minor gene transcripts. An RNase protection assay quantitatively revealed that the amount of the rat StAR transcript in brain was two to three orders of magnitude lower than that in the adrenal gland. An in situ hybridization study, involving antisense riboprobes, revealed that StAR transcripts were abundant in the cerebral cortex, hippocampus, dentate gyrus, olfactory bulb, cerebellar granular layer, and Purkinje cells. Furthermore, other steroidogenic enzymes, side-chain cleavage cytochrome P-45O~~(CYP XIA1) and 3/3-hydroxysteroid dehydrogenase/z~isomerase (EC 1.1.1 .145), were found tobe coexpressed in the hippocampus, dentate gyrus, cerebellar granular layer, and Purkinje cells. These findings strongly indicate that neurosteroids are synthesized in a region-specific manner in the brain. Key Words: Steroidogenic acute regulatory protein -Brain-Neurosteroid-In situ hybridization -Ribonuclease protection assay-Cholesterol side-chain cleavage enzyme.

BiochemistryRole of steroid 11,6-hydroxylase and steroid 18-hydroxylase in the biosynthesis of glucocorticoids and mineralocorticoids in humans (cortisol (9) recently isolated aldosterone synthase cytochrome P-450 (P-450ado), which is induced in Na+-depleted K+-replete rat adrenal cortex (10,11), and demonstrated that rat P-450ado catalyzes three successive monooxygenation reactions of DOC to form aldosterone as a final product, whereas rat P-45011p does not substantially catalyze the reaction to form aldosterone. In regard to aldosterone biosynthesis in the human adrenal cortex, it has been postulated for a long time (12)(13)(14)

We have established a new purification procedure of cytochrome b 561 from bovine adrenomedullary chromaffin vesicles. The heme content analysis of the purified sample indicated the presence of 1.7 molecules of heme B/cytochrome b 561 molecule. EPR spectroscopy of the purified enzyme in oxidized state showed that there were three types of low spin heme species. Two of them showed usual EPR signals at g z ‫؍‬ 3.14 and g z ‫؍‬ 2.84 arising from the same heme and were interconvertible depending on pH. The other species showed a highly anisotropic low spin signal at g z ‫؍‬ 3.70, with a lower redox potential than the others, and a temperature-sensitive character. These properties are very similar to low potential cytochrome b (b L or b 566 ) of the mitochondrial complex III, indicating that the g z ‫؍‬ 3.70 species is derived from a heme component different from the one that shows the usual low spin EPR signals. Based on our new structural model, these two heme B prosthetic groups are likely to be located on both sides of the membranes in close contact with the ascorbic acid-and semidehydroascorbic acid-binding sites, respectively, to facilitate the electron transfer across the membranes. This molecular architecture may provide a structural basis for the transmembrane electron transfer catalyzed by this hemoprotein.

We examined the genotypes of the aldehyde dehydrogenase (ALDH)-2, alcohol dehydrogenase (ADH)-2, ADH3, and P-4502E1 loci of 53 alcoholics and 97 nonalcoholics. All of the subjects fulfilled the DSM-III-R criteria for alcohol dependence. The control group consisted of 97 subjects who were either hospital staff or students. We also compared the frequencies of homozygous ALDH2*1/1 and heterozygous ALDH2*1/2 genotypes in alcoholics. Our study revealed differences in the allelic frequencies of the ALDH2, ADH2, and ADH3 loci between alcoholics and nonalcoholics. For alcoholics with both homozygous ALDH2*1/1 and heterozygous ALDH2*1/2 genotypes, it was found that ADH2 and ADH3 played important rates. Alcoholics with the heterozygous ALDH2*1/2 genotype showed a significantly higher frequency of ADH2*1/1 than ones with the homozygous ALDH2*1/1 genotype. We assume ADH2*1 plays an important role in the development of alcoholism in alcoholics with the heterozygous ALDH2*1/2 genotype.

No abstract