Classical Steroidogenic Tissues Research Articles

The significance of CYP11A1 expression in skin physiology and pathology

CYP11A1, a member of the cytochrome P450 family, plays several key roles in the human body. It catalyzes the first and rate-limiting step in steroidogenesis, converting cholesterol to pregnenolone. Aside from the classical steroidogenic tissues such as the adrenals, gonads and placenta, CYP11A1 has also been found in the brain, gastrointestinal tract, immune systems, and finally the skin. CYP11A1 activity in the skin is regulated predominately by StAR protein and hence cholesterol levels in the mitochondria. However, UVB, UVC, CRH, ACTH, cAMP, and cytokines IL-1, IL-6 and TNFα can also regulate its expression and activity. Indeed, CYP11A1 plays several critical roles in the skin through its initiation of local steroidogenesis and specific metabolism of vitamin D, lumisterol, and 7-dehydrocholesterol. Products of these pathways regulate the protective barrier and skin immune functions in a context-dependent fashion through interactions with a number of receptors. Disturbances in CYP11A1 activity can lead to skin pathology.

Differential regulation of the human CYP11A1 promoter in mouse brain and adrenals

CYP11A1 encodes the first enzyme of steroid biosynthesis, cytochrome P450scc. The expression of CYP11A1 in the nervous system allows neurosteroids to be synthesized de novo. In the classic steroidogenic tissues, adrenals and gonads, the key regulator controlling CYP11A1 expression is steroidogenic factor-1 (SF-1), but the transcriptional regulation of CYP11A1 in the brain is unclear. We recently used the 4.4-kb regulatory region of the human CYP11A1 gene to drive Cre recombinase expression in the diencephalon and midbrain. In this study, we characterized the regional-specific expression of Cre reporter in the SCC-Cre transgenic brain using a transient Cre/ROSA26R transgenic system. Mutation of either the upstream or proximal SF-1 binding site did not affect brain CYP11A1 promoter activity. The upstream SF-1 binding site, however, is required for CYP11A1 promoter function in the embryonic adrenals. The 3.8-kb promoter, like the 4.4-kb length promoter, directed Cre expression in the diencephalon, midbrain and olfactory epithelium, whereas Cre expression controlled by the 2.7-kb promoter was only observed in the caudal part of midbrain. This suggests that the 5'-flanking region between 3.8 and 2.7 kb contains a crucial element for activation of CYP11A1 promoter in the diencephalon, olfactory epithelium and the anterior part of midbrain. Thus we have identified regions of the promoter that control CYP11A1 expression in the brain and embryonic adrenals.

Advances in Development of Inhibitors of 17β-Hydroxysteroid Dehydrogenases

The 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) are involved in the regulation of estrogens and androgens by catalyzing the reduction of 17-ketosteroids or the oxidation of 17beta hydroxysteroids. The enzyme activities associated with the different 17beta-HSD isoforms are widespread in human tissues, not only in classic steroidogenic tissues but also in a large series of peripheral intracrine tissues. Being involved at the end of steroidogenesis, the numerous members of 17beta-HSD family constitute interesting therapeutic targets for controlling the concentration of estrogens and androgens. Thus, inhibitors of reductive 17beta-HSD isoforms are attractive to block the formation of hydroxysteroids that stimulate estrogeno-sensitive pathologies (breast, ovarian, and endometrium cancers) and androgeno-sensitive pathologies (prostate cancer, benign prostatic hyperplasia, acne, and hirsutism). The inhibitors could be used to block the degradation of estradiol, an attractive strategy for treating osteoporosis and Alzheimer's disease. In addition to their classical use as anti-cancer agents and therapeutic agents, inhibitors of 17beta-HSDs are also useful tools to elucidate the role of these enzymes in particular biological systems. The present review article gives a description of novel inhibitors of 17beta-HSDs that were published in 2003-2006.

CAMP‐Induced Expression of the Orphan Nuclear Receptor Nur77 in MA‐10 Leydig Cells Involves a CaMKI Pathway

The Nur77 (Nr4a1) gene, encoding the orphan nuclear receptor NUR77 (NR4A1), is an immediate early response gene whose expression is rapidly induced by a variety of physiologic stimuli. Nur77 is expressed in several organs, including the classic steroidogenic tissues: gonads and adrenal. In MA-10 Leydig cells, NUR77 has been shown to regulate expression of several genes involved in steroidogenesis and male sex differentiation. In Leydig cells, androgen biosynthesis is controlled primarily by the pituitary gonadotropin luteinizing hormone (LH) acting via its receptor (LH-R), which in turn activates the adenylate cyclase/cyclic adenosine monophosphate (cAMP) signaling pathway. Even though Nur77 expression is induced both at the mRNA and protein levels in response to LH/forskolin/cAMP in Leydig cells, the mechanisms involved remain largely unknown. Here, we report that cAMP-mediated induction of Nur77 expression at the protein, mRNA, and promoter levels in MA-10 cells involves different mechanisms. We found that increased NUR77 protein requires transcription and translation, whereas increased Nur77 mRNA does not require de novo protein synthesis, and would therefore rely on transcription factors already present in the cell. In addition, our detailed analysis of the Nur77 promoter in MA-10 cells revealed that distinct regulatory elements are involved in basal and cAMP-induced Nur77 transcription. Finally, we found that maximal cAMP-mediated increase in Nur77 promoter activity involves a Ca(2+)/calmodulin kinase (CaMK)-dependent pathway and that Ca(2+)/calmodulin kinase I regulates Nur77 promoter activity in Leydig cells. Thus, our findings demonstrate the involvement of various mechanisms in the regulation of Nur77 expression in MA-10 Leydig cells, including a previously uncharacterized CaMK pathway.

Neurosteroids: the StAR protein in the brain.

The nervous system is a well-known target for steroid hormones, as these hormones regulate brain functions that include neuronal survival and differentiation, myelination, neurogenesis, plasticity and repair after injury. Furthermore, the brain is also a steroidogenic tissue because it possesses the enzymes required to metabolize the common precursor, cholesterol, into steroids, named 'neurosteroids'. The rate-limiting step in the synthesis of steroid hormones is the access of cholesterol, accumulated in the outer mitochondrial membrane, to the first steroidogenic enzyme, P450scc (cholesterol side-chain cleavage enzyme), located in the inner mitochondrial membrane. In the ovary and the adrenal gland, which comprise classic steroidogenic tissues, this process requires the steroidogenic acute regulatory protein (StAR) to facilitate the shuttle of cholesterol through the intermembrane space. The mechanism used by the brain to regulate the first stage of steroidogenesis remains unknown. Recently, several groups have investigated the potential presence of StAR in the nervous tissue and have concluded that StAR is widely expressed throughout the brain, although restricted to specific cell populations. New results concerning localization, regulation and possible functions of StAR in the brain are discussed.

Inhibitors of 17 beta-hydroxysteroid dehydrogenases.

The 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) play an important role in the regulation of steroid hormones, such as estrogens and androgens, by catalysing the reduction of 17-ketosteroids or the oxidation of 17beta-hydroxysteroids using NAD(P)H or NAD(P)(+) as cofactor. The enzyme activities associated with the different 17beta-HSD isoforms are widespread in human tissues, not only in classic steroidogenic tissues, such as the testis, ovary, and placenta, but also in a large series of peripheral intracrine tissues. In the nineties, several new types of 17beta-HSD were reported, indicating that a fine regulation is carried out. More importantly, each type of 17beta-HSD has a selective substrate affinity, directional (reductive or oxidative) activity in intact cells, and a particular tissue distribution. These findings are important for understanding the mode of action of the 17beta-HSD family. From a therapeutic point of view, this means that selectivity of drug action could be achieved by targeting a particular 17beta-HSD isozyme. Consequently, each study that leads to better knowledge of the inhibition of 17beta-HSDs deserves attention from scientists working in this and related fields. Being involved in the last step of the biosynthesis of sex steroids from cholesterol, the 17beta-HSD family constitutes an interesting target for controlling the concentration of estrogens and androgens. Thus, inhibitors of 17beta-HSDs are useful tools to elucidate the role of these enzymes in particular biological systems or for a therapeutic purpose, especially to block the formation of active hydroxysteroids that stimulate estrogeno-sensitive pathologies (breast, ovarian, and endometrium cancers) and androgeno-sensitive pathologies (prostate cancer, benign prostatic hyperplasia, acne, hirsutism, etc). Few review articles have however focussed on 17beta-HSD inhibitors although this family of steroidogenic enzymes includes interesting therapeutic targets for the control of several diseases. Furthermore, inhibitors of 17beta-HSDs constitute a growing field in biomedical research and there is a need for an exhaustive review on this topic. In addition to giving an up-to-date description of inhibitors of all 17beta-HSD isoforms (types 1-8), the present review will also address, when possible, the isoform selectivity and residual estrogenic or androgenic activity often associated with steroidal inhibitors.

Biosynthesis of neurosteroids and regulation of their sysnthesis

The brain, like the gonads, adrenal glands, and placenta, is a steroidogenic organ. The steroids synthesized by the brain and by the nervous system, given the name neurosteroids, have a wide variety of diverse functions. In general, they mediate their actions not through classic steroid hormone nuclear receptors but through ion-gated neurotransmitter receptors. This chapter summarizes the biochemistry of the enzymes involved in the biosynthesis of neurosteroids, their localization during development and in adulthood, and the regulation of their expression, highlighting both similarities and differences between expression in the brain and in classic steroidogenic tissues.

Immunohistochemical Study of 3.BETA.-Hydroxysteroid Dehydrogenase /.DELTA.5-.DELTA.4 Isomerase in the Rat Cardiovascular System.

The enzyme complex 3beta-hydroxysteroid dehydrogenase (3beta-HSD) is involved in the biosynthesis of all classes of active steroids. It is known that the enzymatic activity of 3beta-HSD is present not only in classical steroidogenic tissues, but also in many peripheral tissues including cardiac tissue. To determine whether 3beta-HSD is present in rat non-steroidogenic tissues, we examined cardiovascular tissues including the ventricle, atrium, aortic arch, abdominal aorta, and inferior vena cava by immunohistochemistry and Western blotting using polyclonal antibody raised against a synthetic peptide of human placental 3beta-HSD. By Western blotting, protein bands immunoreactive for anti-3beta-HSD were detected at molecular weights of 42 and 37 kDa in both the ventricle and atrium, whereas only a 37 kDa band was recognized in both the aortic arch and abdominal aorta. By immunohistochemistry, immunoreactivity for 3beta,-HSD was detected in both the ventricular and atrial cardiocytes, while immunostaining was also found, though faintly, in the smooth muscles of the aortic arch, abdominal aorta, and inferior vena cava. These results suggest that cardiocytes may synthesize the steroidogenic 3beta,-HSD enzyme.

Molecular Cloning, Nucleotide Sequence and Tissue Distribution of Equine Testicular 3.BETA.-Hydroxysteroid Dehydrogenase/.DELTA.5-.DELTA.4 Isomerase Messenger Ribonucleic Acid.

Complementary DNA (cDNA) clones encoding equine testicular steroidogenic enzyme 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) have been isolated from equine testicular cDNA library. Polymerase chain reaction (PCR) with 3β-HSD specific primers was performed with equine testicular cDNA, and PCR fragment was used as a probe for screening of equine testicular λ ZAP II phage cDNA library. Positive clones were excised into plasmid vector pBluescript and determined their nucleotide sequences. Total 1651 bp of the cDNA sequence was consisted with 112 bp of 5' flanking untranslated sequence, 1122 bp open reading frame encodes 373 amino acids, and putative poly-adenylation signal “AATAAA” at 385 bp downstream of the stop codon. The nucleotide and the deduced amino acid sequence of equine 3β-HSD were very similar to the known mammalian 3β-HSD sequences. From the deduced amino acid sequence, equine testicular 3β-HSD may be concluded to catalyze 3β-dehydrogenation and Δ-isomerization, but 3-ketoreduction as well as murine isoforms. As the clone was used in Northern blot analysis of equine tissues, the expression of equine 3β-HSD mRNA was prominent in the classical steroidogenic tissues including placenta.

Synergistic Activation of the Human Type II 3β-Hydroxysteroid Dehydrogenase/Δ5-Δ4 Isomerase Promoter by the Transcription Factor Steroidogenic Factor-1/Adrenal 4-binding Protein and Phorbol Ester

Steroidogenic factor-1/adrenal 4-binding protein (SF-1/Ad4BP) is an orphan nuclear receptor/transcription factor known to regulate the P450 steroid hydroxylases; however, mechanisms that regulate the activity of SF-1/Ad4BP are not well defined. In addition, little is known about the mechanisms that regulate the human steroidogenic enzyme, type II 3beta-hydroxysteroid dehydrogenase (3beta-HSD II), the major gonadal and adrenal isoform. Regulation of the 3beta-HSD II promoter was examined using human adrenal cortical (H295R; steroidogenic) and cervical (HeLa; non-steroidogenic) carcinoma cells. H295R cells were transfected with a series of 5' deletions of 1251 base pairs (bp) of the 3beta-HSD II 5'-flanking region fused to a chloramphenicol acetyltransferase (CAT) reporter gene followed by treatment with or without phorbol ester (phorbol 12-myristate 13-acetate; PMA). CAT assay data indicated that the region from -101 to -52 bp of the promoter was required for PMA-induced expression. A putative SF-1/Ad4BP regulatory element, TCAAGGTAA, was identified by sequence homology at -64 to -56 bp of the promoter. Cotransfection of HeLa cells with the -101 3beta-HSD-CAT construct and an expression vector for SF-1/Ad4BP increased CAT activity 49-fold. Subsequent treatment with PMA induced an unexpected synergistic increase in transcriptional activity 540-fold over basal. Mutation of the putative response element (TCAAGGTAA to TCAATTTAA) abolished SF-1-induced CAT activity and the synergistic response to PMA. Gel mobility shift assays confirmed that SF-1/Ad4BP interacts with the putative element and transcripts for SF-1/Ad4BP were detected in H295R cells by Northern analysis. These data are the first to demonstrate 1) regulation of a non-cytochrome P450 steroidogenic enzyme promoter by SF-1/Ad4BP, 2) a powerful synergistic effect of PMA on SF-1/Ad4BP-induced transcription, and 3) the importance of the SF-1/Ad4BP regulatory element in the regulation of the 3beta-HSD II promoter.

The multiple murine 3β-hydroxysteroid dehydrogenase isoforms: Structure, function, and tissue- and developmentally specific expression

The enzyme 3β-hydroxysteroid dehydrogenase (3β-HSD) is essential for the biosynthesis of all active steroid hormones. To date five distinct isoforms have been identified in the mouse. The different isoforms are indicated by roman numerals (I–V) in the chronological order in which they have been isolated. The different isoforms are expressed in a tissue- and developmentally specific manner and fall into two functionally distinct groups. 3β-HSD I, II, and III function as NAD +-dependent dehydrogenase/isomerases, and IV and V function as NADPH-dependent 3-keto steroid reductases. These latter two isoforms, therefore, are not involved in the biosynthesis of steroid hormones, but most likely in the inactivation of steroid hormones. In the adult mouse 3β-HSD I is expressed in the classical steroidogenic tissues, the adrenal glands and the gonads. 3β-HSD II and III are expressed in the liver and kidney, with III being the major isoform expressed in the adult liver. 3β-HSD IV is expressed almost exclusively in the kidney of both sexes, and expression of 3β-HSD V is observed only in the male liver starting late in puberty. In the fetal liver of both sexes, 3β-HSD I is the major or only isoform expressed at 13.5 days postconception and remains the major isoform until the day of birth, after which 3β-HSD III becomes the major isoform. Expression of 3β-HSD I in the liver decreases after birth and ceases by day 20 postnatally. Thus the liver expresses four distinct isoforms of 3β-HSD, I, II, III, and V, at different times during development. The mouse 3β-HSD genes, Hsd3b, have been mapped to a small region on mouse chromosome 3. Analysis of two yeast artificial chromosome (YAC) libraries identified one clone that contains the entire Hsd3b locus within a 1400-kb insert. Hybridization by Southern blot analysis of restriction-enzyme-digested YAC DNA using an 18-base oligonucleotide that hybridizes without mismatch to all known Hsd3b sequences indicates that there are a total of seven Hsd3b genes or pseudogenes in the mouse genome. Further analysis of mouse genomic DNA by pulse field gel electrophoresis suggests that all of the Hsd3b gene family is found within a 400-kb fragment.

Transcriptional regulation of P450scc gene expression in neural and steroidogenic cells: implications for regulation of neurosteroidogenesis.

Regulation of steroidogenesis in classic endocrine tissues is mediated by transcriptional regulation of the P450scc gene, which encodes the first and rate-limiting cholesterol side-chain cleavage enzyme. We previously showed that P450scc messenger RNA is regionally expressed in the adult rat brain, primary glial cultures, and C6 glioma cells. Expression of P450scc in the brain results in the de novo synthesis of neurosteroids, a class of steroid hormones that are active at gamma-aminobutyric acidA and N-methyl-D-aspartate receptors. We determined whether P450scc expression is transcriptionally regulated in neural cells, using the same DNA sequences and nuclear proteins as classic steroidogenic adrenal and Leydig cells. The transcriptional activity of deletional mutants of 2.5 kilobases of the 5'-flanking regulatory region of the rat P450scc gene cloned into a luciferase reporter gene was assessed in mouse adrenocortical Y-1, mouse Leydig MA-10, rat C6 glioma, rat GC somatotrope, and mouse GT1-7 neurosecretory cell lines. P450scc was transcriptionally regulated in Y-1, MA-10, and C6 glioma cells, but not in GC or GT1-7 cells. In one region (-94/-35), putative steroidogenic factor-1-binding sites appeared to be critical for the basal transcriptional activity and cAMP responsiveness in steroidogenic Y-1 and MA-10 cells, but had no function in rat C6 cells. DNA sequences between -94/-130 mediated both basal and cAMP-inducible transcriptional activity in C6 cells. Gel mobility shift assays showed that one nuclear protein binding to DNA sequences between -54 and -35 was abundant in MA-10 and Y-1 cells, but was absent from C6 cells, whereas another nuclear protein, binding to DNA sequences between -94 and -130 was abundant in C6 cells, but was rare in MA-10 cells and absent from Y-1 and other adrenocortical cells. Although the DNA sequence between -94 and -130 contains an Sp1 site, Sp1 did not bind to this site. Nevertheless, this GC-rich region was critical for nuclear protein binding and for basal and cAMP-induced transcriptional regulation in both C6 and MA-10 cells. These observations demonstrate that the rat P450scc gene is transcriptionally regulated in glioma cells, but its regulation in glial cells involves a DNA element different from those used in classic steroidogenic tissues. The results further suggest that steroidogenic factor-1 is not involved in regulating neurosteroidogenesis.

Expression of cytochrome P450 side-chain cleavage enzyme and 3 beta-hydroxysteroid dehydrogenase in the rat central nervous system: a study by polymerase chain reaction and in situ hybridization.

In examining steroid synthesis in the CNS, expression of the mRNAs encoding for cytochrome P450 side-chain cleavage enzyme (P450scc) and 3 beta-hydroxy-steroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) has been studied in the rat brain. P450scc transforms cholesterol into pregnenolone and 3 beta-HSD transforms pregnenolone into progesterone. PCR was used to amplify cDNA sequences from total RNA extracts. Classical steroidogenic tissues, like adrenal and testis, as well as the non-steroidogenic tissue lung have been used as controls. The expression of P450scc and 3 beta-HSD have been demonstrated by PCR in cortex, cerebellum, and spinal cord. In addition, primary cultures of rat cerebellar glial cells and rat cerebellar granule cells were found to express P450scc and 3 beta-HSD at comparable levels. Furthermore, three of the four known isoenzymes of 3 beta-HSD were identified, as determined using selective PCR primers coupled with discriminative restriction enzymes and sequencing analysis of the amplified brain products. Using RNA probes, in situ hybridization indicated that P450scc and 3 beta-HSD are expressed throughout the brain at a low level and mainly in white matter. Enrichment of glial cell cultures in oligodendrocytes, however, does not increase the relative abundance of P450scc and 3 beta-HSD mRNA detected by PCR. This discrepancy suggests that the developmental state of cultured cells and their intercellular environment may be critical for regulating the expression of these enzymes. These findings support the proposal that the brain apparently has the capacity to synthesize progesterone from cholesterol, through pregnenolone, but that the expression of these enzymes appears to be quite low.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of the ferredoxin component of renal hydroxylases at transcriptional and postranslational levels and of the protein inhibitor of cyclic AMP-dependent kinase.

We have studied two proteins potentially involved in the regulation of the 25-OH-D-1-hydroxylase, which is located in the renal mitochondria and which is responsible for the production of the steroid hormone 1,25(OH)2D3. The endogenous inhibitor of cyclic AMP-dependent protein kinase, PKI, is down regulated by 1,25(OH)2D3. Having cloned and sequenced PKI cDNA, we studied its message levels and found them to be regulated by 1,25(OH)2D3 tissue specifically in the kidney and in kidney cell culture. In other experiments we over expressed the ferredoxin component of the 1-hydroxylase and found it to be physically and chemically indistinguishable from those of classic steroidogenic tissues. The mRNA encoding the ferredoxin component is up-regulated by chronic vitamin D deficiency, which at the same time leads to sustained elevation in 1-hydroxylase activity; no short term effect of 1,25(OH)2D3 on ferredoxin mRNA in kidney cell culture could be demonstrated. Finally, there was an association between decreased phosphorylation of ferredoxin and decreased 1-hydroxylase activity brought about by treatment of cultured kidney cells with TPA. Control of the renal signaling events involved in the production of 1,25(OH)2D3 remains a fruitful area of investigation in the field of the metabolism and actions of vitamin D and its metabolites.

Synthesis of 16-(bromoalkyl)-estradiols having inhibitory effect on human placental estradiol 17β-hydroxysteroid dehydrogenase (17-β-HSD type 1)

The activity of 17β-HSD type 1, the enzyme that converts estrone into its more potent metabolite estradiol, has been demonstrated in all classical steroidogenic tissues and almost all peripheral tissues from both rat and human. Since 17β-HSD is one of the most important enzymes involved in active steroid hormone formation, its inactivation could be a clinical approach to the treatment of hormono-dependent diseases like breast cancer. Herein we report the synthesis of 16-(bromoalkyl)-estradiols and their potency to inhibit the human placenta cytosolic estradiol 17β-HSD (type 1). Synthetic analogues possess various side chain lengths and orientation (α or β) at position 16 of the steroidal D ring. The most potent inhibitory effect was observed when the length of the side chain was 3 or 4 carbons. However, the 16β-(bromopropyl)-estradiol easily undergoes cyclization and its effect on 17β-HSD is lost. Consequently, 16α-(bromopropyl)-E 2, 16α-(bromobutyl)-E 2, and 16β-(bromobutyl)-E 2 were the best inhibitors discussed in this paper.

11 Structure, regulation and role of 3β-hydroxysteroid dehydrogenase, 17β-hydroxysteroid dehydrogenase and aromatase enzymes in the formation of sex steroids in classical and peripheral intracrine tissues

In addition to the classical steroidogenic tissues, namely the ovaries, testes, adrenals and placenta, a large series of human peripheral tissues possess all the enzymatic systems required for the formation of active androgens and oestrogens from a relatively large supply of precursor steroids provided by the adrenals. This chapter describes the structure, function, tissue-specific expression and regulation of the 3 beta-HSD and 17 beta-HSD gene families as well as some information about the aromatase gene. While, so far, most therapeutic approaches have been aimed and limited at controlling steroid formation by the classical steroidogenic tissues, it is clear that major efforts should now be turned towards intracrinology in order to understand better the physiological mechanisms controlling local steroid formation in peripheral target tissues and thus be in a position to develop novel therapeutic approaches that take into account the high proportion of steroids that are made locally and are responsible for the growth and function of normal as well as cancerous tissue.

Structure and tissue-specific expression of a novel member of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) family. The exclusive 3 beta-HSD gene expression in the skin.

Structures of cDNA clones encoding three members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) family were characterized. To search for potential new types of 3 beta-HSD, rat types I and II 3 beta-HSD cDNAs were used as probes to screen a rat genomic DNA library. Among the clones isolated, one encodes a novel predicted rat 3 beta-HSD isoenzyme, chronologically designated type IV. The corresponding full-length cDNA was thereafter isolated by selective polymerase chain reaction amplification from rat ovary and day-15 placenta cDNA libraries. The rat type IV 3 beta-HSD cDNA encodes a predicted 372-amino acid protein of 41,854 daltons, which shares 90.9, 87.9, and 78.8% sequence identity with rat types I, II, and III proteins, respectively. Ribonuclease protection assay reveals that type IV 3 beta-HSD is the sole 3 beta-HSD mRNA species detectable in the skin and represents the predominant species in the placenta while being also detectable in the ovary and, to a lower degree, in the adrenal gland. Transient expression of type IV cDNA in SW-13 cells indicates 3 beta-HSD activity similar to that of rat type I 3 beta-HSD. The presence of multiple 3 beta-HSD genes should permit differential and tissue-specific regulation of this rate-limiting enzymatic activity essential in the biosynthesis of all classes of steroid hormones in both classical steroidogenic and intracrine peripheral tissues.

Characterization of macaque 3β-hydroxy-5-ene steroid dehydrogenase/Δ 5-Δ 4 isomerase: structure and expression in steroidogenic and peripheral tissues in primate

The conversion of 3β-hydroxy-5-ene steroids by the enzyme complex 3β-hydroxysteroid dehydrogenase/Δ 5-Δ 4 isomerase (3β-HSD) is an obligatory step in the biosynthesis of all classes of hormonal steroids in classical steroidogenic as well as in peripheral tissues. To develop a model more closely related to the human, we have isolated and characterized cDNA clones encoding macaque 3β-HSD by screening a rhesus monkey ovary κgt11 cDNA library using a human 3β-HSD cDNA probe. Nucleotide sequence of 1629 bp from overlapping cDNA clones predicts a protein of 372 amino acids with a calculated molecular mass of 41,874 (excluding the first Met). The deduced amino acid sequence of macaque 3β-HSD displays 79.4% and 93.9% similarity with that of bovine and human 3β-HSD, respectively. RNA blot analysis performed under high stringency conditions of macaque poly(A) + RNA samples using full-length 32P-labeled macaque 3β-HSD cDNA revealed the presence of an approximately 1.7 kb mRNA species in classical steroidogenic tissues, namely the ovary, testis and adrenal glands as well as in several peripheral tissues including the liver, kidney and epididymis. Computer analysis of the deduced macaque 3/gb-HSD protein sequence predicts the presence of an NH 2-terminal membrane-associated segment as well as four additional membrane-spanning segments, thus suggesting that 3β-HSD is an integral protein. The availability of macaque cDNA should permit detailed studies concerning the tissue-specific expression as well as the hormonal regulation of 3β-HSD mRNA in classical steroidogenic glands as well as in peripheral tissues which are an important site of Steroidogenesis in primates.