Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.1.1.3 (HSD)
3,464 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

11Beta-hydroxysteroid dehydrogenase (11beta-HSD) is thought to confer aldosterone specificity to mineralocorticoid target cells by protecting the mineralocorticoid receptor (MR) from occupancy by endogenous glucocorticoids. In aldosterone target cells the type 2 11beta-HSD is present, which, in contrast to the type 1 11beta-HSD, has very high affinity for its substrate, is unidirectional and prefers NAD as cofactor. cDNAs encoding 11beta-HSD2 have been recently cloned from different species, and the cell-specific expression of its mRNA and protein were determined. 11Beta-HSD2 is expressed in every aldosterone target tissue. Northern analysis revealed that the rabbit 11beta-HSD2 is expressed at high levels in the renal collecting duct and at much lower levels in the colon. RT-PCR experiments demonstrated that 11beta-HSD2 mRNA is present only in aldosterone target cells within the kidney. We determined the subcellular localization of the rabbit 11beta-HSD2 using a chimera encoding 11beta-HSD2 and the green fluorescent protein (GFP). This construct was stably transfected into CHO and MDCK cells. The expressed 11beta-HSD2/GFP protein retained high enzymatic activity, and its characteristics were undistinguishable from those of the native enzyme. The intracellular localization of this protein was determined by fluorescence microscopy. 11Beta-HSD2-associated fluorescence was observed as a reticular network over the cytoplasm whereas the plasma membrane and the nucleus were negative, suggesting endoplasmic reticulum (ER) localization. Co-staining with markers for ER proteins, the Golgi membrane, mitochondria and nucleus confirmed that 11beta-HSD2 is localized exclusively to the ER. To determine what structural motifs are responsible for the ER localization, we generated deletion mutants missing the C-terminal 42 and 118 amino acids, and fused them to GFP. Similarly as with the intact 11beta-HSD2, these mutants localized exclusively to the ER. Both C-terminal deletion mutants completely lost dehydrogenase activity, independently whether activity was determined in intact cells or homogenates. These results indicate that 11beta-HSD2 has a novel ER retrieval signal which is not localized to the C-terminal region. In addition, the C-terminal 118 amino acids are essential for NAD-dependent 11beta-HSD activity.
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PMID:The role of 11beta-hydroxysteroid dehydrogenase in steroid hormone specificity. 969 85

11 Beta-hydroxysteroid dehydrogenase (11 beta-HSD) catalyses the interconversion of active corticosterone and inert 11-dehydrocorticosterone. The recently discovered type 2 isozyme (11 beta-HSD-2) is a high affinity, NAD-dependent, exclusive 11 beta-dehydrogenase, which rapidly inactivates glucocorticoids. Thus the enzyme generates aldosterone-selectivity for intrinsically non-selective mineralocorticoid receptors in vivo as well as excluding glucocorticoids from glucocorticoid receptors, the latter being particularly important during development. Aldosterone exerts selective central effects upon salt appetite and blood pressure whilst glucocorticoids have potent effects upon postnatal neurogenesis and brain remodelling. We examined 11 beta-HSD-2 expression during postnatal ontogeny and in adult rat brain. High 11 beta-HSD-2 mRNA expression was found specifically in the postnatal thalamus and the external granule cell layer of the cerebellum. Expression peaked at the end of the first postnatal week and declined rapidly thereafter. Postnatal brain showed considerable activity of high affinity 11 beta-HSD-2 which paralleled expression of 11 beta-HSD-2 messenger ribonucleic acid (mRNA). Adult brain showed high 11 beta-HSD-2 mRNA expression limited to the subcommissural organ, with lower expression in the ventromedial nucleus of the hypothalamus, amygdala, locus coeruleus and nucleus tractus solitarius. These discrete areas are compatible with proposed selective central actions of aldosterone on blood pressure (subcommissural organ, nucleus tractus solitarius) and salt appetite (ventromedial nucleus, amygdala). In contrast, early postnatal 11 beta-HSD-2 coincides with glucocorticoid receptor rather than mineralocorticoid receptor expression, and areas of expression are among the regions where glucocorticoids have been demonstrated to have profound effects upon neuronal division, growth and maturation.
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PMID:11 Beta-hydroxysteroid dehydrogenase type 2 in the postnatal and adult rat brain. 979 98

Although oxidation of cortisol or corticosterone by 11beta-hydroxysteroid dehydrogenase (11beta-HSD) represents the physiological mechanism conferring specificity for aldosterone on the mineralocorticoid receptor in mineralocorticoid target tissues, little attention has been paid until now to the expression and activity of this enzyme in human adrenals. We have shown that human adrenal cortex expresses 11beta-HSD type 2 (11beta-HSD2) gene, and found a marked 11beta-HSD2 activity in microsomal preparations obtained from slices of decapsulated normal human adrenal cortices. Under basal conditions, adrenal slices secreted, in addition to cortisol and corticosterone (B), sizeable amounts of cortisone and 11-dehydrocorticosterone (DH-B), the inactive forms to which the former glucocorticoids are converted by 11beta-HSD. Addition of the 11beta-HSD inhibitor glycyrrhetinic acid elicited a moderate rise in the production of cortisol and B and suppressed that of cortisone and DH-B. ACTH and angiotensin II evoked a marked rise in the secretion of cortisol and B, but unexpectedly depressed the release of cortisone and DH-B. ACTH also lowered the capacity of adrenal slices to convert [3H]cortisol to [3H]cortisone. This last effect of ACTH was concentration-dependently abolished by both aminoglutethimide and cyanoketone, which blocks early steps of steroid synthesis, but not by metyrapone, an inhibitor of 11beta-hydroxylase. Collectively, these findings indicate that the human adrenal cortex possesses an active 11beta-HSD2 engaged in the inactivation of newly formed glucocorticoids. The activity of this enzyme is negatively modulated by the main agonists of glucocorticoid secretion through an indirect mechanism, probably involving the rise in the intra-adrenal concentration of non-11beta-hydroxylated steroid hormones.
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PMID:11beta-hydroxysteroid dehydrogenase expression and activity in the human adrenal cortex. 980 62

In mammalian tissues, at least two isozymes of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) catalyze the interconversion of hormonally active C11-hydroxylated corticosteroids (cortisol, corticosterone) and their inactive C11-keto metabolites (cortisone, 11-dehydrocorticosterone). The type 1 and type 2 11 beta-HSD isozymes share only 14% homology and are separate gene products with different physiological roles, regulation, and tissue distribution. 11 beta-HSD2 is a high affinity NAD-dependent dehydrogenase that protects the mineralocorticoid receptor from glucocorticoid excess; mutations in the HSD11B2 gene explain an inherited form of hypertension, the syndrome of apparent mineralocorticoid excess in which cortisol acts as a potent mineralocorticoid. By contrast, 11 beta-HSD1 acts predominantly as a reductase in vivo, facilitating glucocorticoid hormone action in key target tissues such as liver and adipose tissue. Over the 10 years, 11 beta-HSD has progressed from an enzyme merely involved in the peripheral metabolism of cortisol to a crucial pre-receptor signaling pathway in the analysis of corticosteroid hormone action. This review details the enzymology, molecular biology, distribution, regulation, and function of the 11 beta-HSD isozymes and highlights the clinical consequences of altered enzyme expression.
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PMID:11 beta-Hydroxysteroid dehydrogenase. 1023 52

The enzyme 11 beta HSD catalyzes the interconversion of the biologically active cortisol and the biologically inactive cortisone. There are two distinct isozymes: 11 beta HSD type 1 is mainly expressed in liver and is a bidirectional enzyme, with both dehydrogenase and reductase activity. 11 beta HSD type 2 is mainly expressed in kidney and is a unidirectional enzyme with only dehydrogenase activity. 11 beta HSD type 2 protects the mineralocorticoid receptor from being activated by cortisol. Thus, specificity of this receptor in vivo is enzyme and not receptor mediated. The syndrome of apparent mineralocorticoid excess is caused by a congenital deficiency of 11 beta HSD type 2. Liquorice-induced hypertension is an example of an acquired defect in dehydrogenase activity of 11 beta HSD, caused by glycyrrhetinic acid. 11 beta HSD may play a role in the pathogenesis of 'essential' hypertension, obesity and type 1 diabetes mellitus. Angiotensin-converting enzyme inhibitors enhance dehydrogenase activity of 11 beta HSD, which may contribute to their natriuretic effect.
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PMID:[11 beta-hydroxysteroid-dehydrogenase: characteristics and the clinical significance of a key enzyme in cortisol metabolism]. 1032 Dec 59

Studies in vitro and in vivo have shown that corticosteroids play an important role in bone physiology and pathophysiology. It is now established that corticosteroid hormone action is regulated, in part, at the pre-receptor level through the expression of isozymes of 11beta-hydroxysteroid dehydrogenase (11beta-HSD), which are responsible for the interconversion of hormonally active cortisol to cortisone. In this report we demonstrate 11beta-HSD activity in human osteoblast (OB) cells. Osteosarcoma-derived OB cell lines TE-85, MG-63 and SaOS-2 and fibrosarcoma Hs913T cells express the type 2 isoform of 11beta-HSD, as determined by reverse transcription polymerase chain reaction (RT-PCR) and specific enzyme assays. Enzyme activity was shown to be strictly NAD dependent with a Km of approximately 71 nM; 11beta-HSD type 1 mRNA expression and enzyme activity were not detected. All four cell lines expressed mRNA for the glucocorticoid receptor (GR) and mineralocorticoid receptor, but specific binding was only detectable with radiolabelled dexamethasone (Kd=10 nM) and not aldosterone. MG-63 cells had two to three times more GR than the other OB cells, which correlated with the higher levels of 11beta-HSD 2 activity in these cells. In contrast to the osteosarcoma cell studies, RT-PCR analysis of primary cultures of human OB cells revealed the presence of mRNA for 11beta-HSD 1 as well as 11beta-HSD 2. However, enzyme activity in these cells remained predominantly oxidative, i.e. inactivation of cortisol to cortisone (147 pmol/h per mg protein at 500 nM cortisol) was greater than cortisone to cortisol (10.3 pmol/h per mg protein at 250 nM cortisone). Data from normal human OB and osteosarcoma cells demonstrate the presence of an endogenous mechanism for inactivation of glucocorticoids in OB cells. We postulate that expression of the type 1 and type 2 isoforms of 11beta-HSD in human bone plays an important role in normal bone homeostasis, and may be implicated in the pathogenesis of steroid-induced osteoporosis.
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PMID:Characterization of 11beta-hydroxysteroid dehydrogenase activity and corticosteroid receptor expression in human osteosarcoma cell lines. 1033 48

11beta-Hydroxysteroid dehydrogenases (11beta-HSD) interconvert cortisol, the physiological glucocorticoid, and its inactive metabolite cortisone in humans. The diminished dehydrogenase activity (cortisol to cortisone) has been demonstrated in patients with essential hypertension and in resistance vessels of genetically hypertensive rats. 11beta-Hydroxysteroid dehydrogenase type 2 (11beta-HSD2) catalyzes only 11beta-dehydrogenation. However, a functional relationship between diminished vascular 11beta-HSD2 activity and elevated blood pressure has been unclear. In this study we showed the expression and enzyme activity of 11beta-HSD2 and 11beta-HSD type 1 (which is mainly oxoreductase, converting cortisone to cortisol) in human vascular smooth muscle cells. Glucocorticoids and mineralocorticoids increase vascular tone by upregulating the receptors of pressor hormones such as angiotensin II. We found that physiological concentrations of cortisol-induced increase in angiotensin II binding were significantly enhanced by the inhibition of 11beta-HSD2 activity with an antisense DNA complementary to 11beta-HSD2 mRNA, and the enhancement was partially but significantly abolished by a selective aldosterone receptor antagonist. This may indicate that impaired 11beta-HSD2 activity in vascular wall results in increased vascular tone by the contribution of cortisol, which acts as a mineralocorticoid. In congenital 11beta-HSD deficiency and after administration of 11beta-HSD inhibitors, suppression of 11beta-HSD2 activity in the kidney has been believed to cause renal mineralocorticoid excess, resulting in sodium retention and hypertension. In the present study we provide evidence for a mechanism that could link impaired vascular 11beta-HSD2 activity, increased vascular tone, and elevated blood pressure without invoking renal sodium retention.
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PMID:11beta-hydroxysteroid dehydrogenase in cultured human vascular cells. Possible role in the development of hypertension. 1033 8

Local tissue concentrations of glucocorticoids are modulated by the enzyme 11beta-hydroxysteroid dehydrogenase which interconverts cortisol and the inactive glucocorticoid cortisone in man, and corticosterone and 11-dehydrocorticosterone in rodents. The type I isoform (11beta-HSD1) is a bidirectional enzyme but acts predominantly as a oxidoreductase to form the active glucocorticoids cortisol or corticosterone, while the type II enzyme (11beta-HSD2) acts unidirectionally producing inactive 11-keto metabolites. There are no known clinical conditions associated with 11beta-HSD1 deficiency, but gene deletion experiments in the mouse indicate that this enzyme is important both for the maintenance of normal serum glucocorticoid levels, and in the activation of key hepatic gluconeogenic enzymes. Other important sites of action include omental fat, the ovary, brain and vasculature. Congenital defects in the 11beta-HSD2 enzyme have been shown to account for the syndrome of apparent mineralocorticoid excess (AME), a low renin severe form of hypertension resulting from the overstimulation of the non-selective mineralocorticoid receptor by cortisol in the distal tubule of the kidney. Inactivation of the 11beta-HSD2 gene in mice results in a phenotype with similar features to AME. In addition, these mice show high neonatal mortality associated with marked colonic distention, and remarkable hypertrophy and hyperplasia of the distal tubule epithelia. 11Beta-HSD2 also plays an important role in decreasing the exposure of the fetus to the high levels of maternal glucocorticoids. Recent work suggests a role for 11beta-HSD2 in non-mineralocorticoid target tissues where it would modulate glucocorticoid access to the glucocorticoid receptor, in invasive breast cancer and as a mechanism providing ligand for the putative 11-dehydrocorticosterone receptor. While previous homologies between members of the SCAD superfamily have been of the order of 20-30% phylogenetic analysis of a new branch of retinol dehydrogenases indicates identities of > 60% and overlapping substrate specificities. The availability of crystal structures of family members has allowed the mapping of conserved 11beta-HSD domains A-D to a cleft in the protein structure (cofactor binding domain), two parallel beta-sheets, and an alpha-helix (active site), respectively.
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PMID:The type I and type II 11beta-hydroxysteroid dehydrogenase enzymes. 1041 17

The 11beta-hydroxysteroid dehydrogenase (11beta-HSD) protects the testis from the inhibitory effects of corticosterone on testosterone (T) production. The objectives of the present studies were to determine the effects of deoxycorticosterone (DOC) and its mechanism of actions on testicular 11beta-HSD activity and plasma T levels after 7 days of treatment. The results revealed that at the end of 7 days treatment, DOC significantly increased testicular 11beta-HSD activity and plasma T levels in normal rats. However, the time course showed that high plasma T levels lowered 11beta-HSD activity on day 14 and by 21 days both the levels normalized. In adrenalectomized (ADX) rats, only the enzyme activity increased significantly but not plasma T levels. Spironolactone, a competitive inhibitor of mineralocorticoid receptor (MR), did not change testicular 11beta-HSD activity in both normal and DOC treated rats suggesting that DOC did not act through MR in increasing 11beta-HSD activity. On the other hand, spironolactone significantly decreased plasma T levels in DOC treated rats. Progesterone (P), a competitive inhibitor of glucocorticoid receptors (GR) or corticosterone significantly suppressed testicular enzyme activity and plasma T levels in DOC treated normal rats. Carbenoxolone which is an inhibitor of 11beta-HSD activity significantly depressed testicular 11beta-HSD activity and plasma T levels in DOC treated normal rats. This paper suggests that DOC increased testicular 11beta-HSD activity through GR; whilst increase in plasma T levels required functioning adrenal glands. The testicular 11beta-HSD is one of the regulators of T levels and vice versa.
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PMID:Novel effects of deoxycorticosterone on testicular 11beta-hydroxysteroid dehydrogenase activity and plasma testosterone levels in normal and adrenalectomized rats. 1048 40

Salt-sensitive subjects (SS) increase their blood pressure with increasing salt intake. Because steroid hormones modulate renal sodium retention, we hypothesize that the activity of the 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) enzyme is impaired in SS subjects as compared with salt-resistant (SR) subjects. The 11betaHSD2 enzyme inactivates 11-hydroxy steroids in the kidney, thus protecting the nonselective mineralocorticoid receptor from occupation by glucocorticoids. We performed an association study using a recently identified single AluI polymorphism in exon 3 and a polymorphic microsatellite marker of the HSD11B2 gene in 149 normotensive white males (37 SS and 112 SR). The activity of the enzyme 11betaHSD2 was assessed by determining the urinary ratio of cortisol (THF+5alphaTHF) to cortisone (THE) metabolites by gas chromatography in all the 37 SS subjects and in 37 age- and body habitus-matched SR volunteers. Mean (THF+5alphaTHF)/THE ratio was markedly elevated in SS subjects compared with SR subjects (1.51 +/- 0.34 vs. 1.08 +/- 0.26, P < 0.00001), indicating enhanced access of glucocorticoids to the mineralocorticoid receptor in SS subjects. In 58% of SS subjects this ratio was higher than the maximum levels in SR subjects. The salt-induced elevation in arterial pressure increased with increasing (THF+5alphaTHF)/THE ratio (r2 = 0.51, P < 0.0001). A total of 12 alleles of the polymorphic microsatellite marker were detected. Homozygosity for the allele A7 was higher in SS subjects than in SR subjects (41 vs. 28%, P < 0.005), whereas the occurrence of the allele A7 with allele A8 was lower in SS subjects than in SR subjects (8 vs. 15%, P < 0.03). The prevalence of salt sensitivity was 35% in subjects with allele A7/A7, whereas salt sensitivity was present in only 9% of the subjects with allele A7/A8. The (THF+5alphaTHF)/THE ratio was higher in subjects homozygous for the A7 microsatellite allele as compared with the corresponding control subjects. The prevalence of the AluI allele was 8.0% in SR subjects and 5.4% in SS subjects and did not correlate with blood pressure. The decreased activity of the 11betaHSD2 in SS subjects indicates that this enzyme is involved in salt-sensitive blood pressure response in humans. The association of a polymorphic microsatellite marker of the gene with a reduced 11betaHSD2 activity suggests that variants of the HSD 11B2 gene contribute to enhanced blood pressure response to salt in humans.
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PMID:Molecular basis of human salt sensitivity: the role of the 11beta-hydroxysteroid dehydrogenase type 2. 1113 65


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