UNIPROT:P41181 - FACTA Search

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Query: UNIPROT:P41181 (collecting duct)
5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Eleven-beta-hydroxysteroid dehydrogenase (11 beta OHSD) protects the aldosterone receptor (MR) against its occupancy by glucocorticoid hormones. We examined the intrarenal distribution of 11 beta OHSD, as compared to that of MR. MR were localized in histological sections from rabbit kidney, using immunohistochemical methods with an anti-MR monoclonal antibody. 11 beta OHSD activity was measured in isolated tubular segments from rabbit, rat and mouse kidneys. Tubules were incubated in the presence of tritiated corticosterone (3H-B:2 x 10(-8)M). Then the rate of degradation of 3H-B into 3H-11-dehydrocorticosterone (3H-A) was determined by HPLC. MR was immunodetected in the distal tubule and the collecting duct. No positive staining was present in the proximal tubule. The conversion rate of 3H-B into 3H-A was high (approximately 80%) in the distal and collecting tubule. It was low in the proximal tubule (less than 15%) except in the rat (approximately 50%). These results indicate that MR and 11OHSD are colocalized along the mammalian nephron. This colocalization constitutes a strong argument in favor of the MR-protective role of 11 beta OHSD, and of a role of a defect of this enzyme in the genesis of some types of arterial hypertension.
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PMID:[A new regulatory mechanism of the action of corticosteroid hormones: cellular 11beta-hydroxycorticosteroid dehydrogenase]. 150 75

Aldosterone selectivity in mineralocorticoid target tissues has been suggested to be due to 11 beta-hydroxysteroid dehydrogenase (11-OHSD), which, by inactivating the endogenous glucocorticoids cortisol and corticosterone (CS), would allow aldosterone to bind to the mineralocorticoid receptor that has equal affinity for aldosterone and natural glucocorticoids. However, a recent immunohistochemical study failed to colocalize 11-OHSD and mineralocorticoid receptors in the kidney. The goal of this study was to determine 1) whether metabolism of CS occurs in the renal target cells of aldosterone, i.e. in cortical collecting duct cells, and 2) if it does so, whether this activity is sufficient to reduce intracellular CS levels to allow binding of aldosterone to the mineralocorticoid receptor. Cortical collecting duct cells were isolated by solid phase immunoadsorption, with a cell purity of approximately 98%. Metabolism of CS was studied in both freshly isolated cells and primary cultures grown as monolayers on permeable supports. Freshly isolated cells rapidly converted CS to 11-dehydro-CS, which was the only major metabolite detected. In intact collecting duct cells 11-OHSD had an apparent Km for CS of approximately 60 nM, a value more than 100-fold lower than the Km of 11-OHSD in the rat liver, and a maximum velocity of approximately 1.7 x 10(-14) mol/min.1000 cells. In cultured cells, when [3H]CS was applied to one side of the monolayer, almost all radioactivity on the opposite side was 11-dehydro-CS. The cells were able to almost completely metabolize CS passing through them for up to a concentration of 2.5 x 10(-7) M. Carbenoxolone, an inhibitor of 11-OHSD, reduced CS degradation by 88%. Neither freshly isolated nor cultured collecting duct cells converted [3H]11-dehydro-CS back to CS in a significant amount (less than 1%). These data provide functional evidence for 11-OHSD activity in renal aldosterone target cells and indicate that this enzyme might be a collecting duct-specific isoform of 11-OHSD which can sufficiently reduce intracellular CS concentrations to contribute to the apparent mineralocorticoid selectivity of the collecting duct.
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PMID:11 beta-Hydroxysteroid dehydrogenase activity in the renal target cells of aldosterone. 205 80

Enzymatic properties of the enzyme 11 beta-hydroxysteroid dehydrogenase (11-HSD), which confers mineralocorticoid selectivity, have been explored in the aldosterone-sensitive collecting duct (CCD) and the aldosterone-insensitive Pars Recta (PR) of the rat kidney. After incubation of freshly isolated tubular segments with [3H]corticosterone (3H-B) or [3H]dehydrocorticosterone (3H-A), the rate of transformation of 3H-B into 3H-A (dehydrogenase activity), or the reverse reaction (reductase activity) were measured by HPLC, Vmax for dehydrogenase activity was found to be 8- to 10-fold higher in CCD than PR. The enzyme functions over a very wide range (0.1-5000 nM) of corticosterone concentration. In CCD, enzyme kinetics suggest either the presence of two 11-HSD forms, differing by their affinity for corticosterone, or complex kinetics. Addition of NAD or NADP to permeabilized tubules revealed that dehydrogenase activity is NAD-dependent in CCD and NADP-dependent in PR. Cofactor addition was ineffective in intact tubules. CCD exhibited an exclusive dehydrogenase activity, whereas in PR dehydrogenase and reductase activity were found. No regulation of dehydrogenase activity could be evidenced in adrenalectomized rats receiving or not aldosterone, corticosterone or dexamethasone, for 2 h, 3 days or 4 days. We conclude that 11-HSD in the CCD and PR differs by its Vmax and cofactor dependence. Corticosteroid hormones do not influence 11-HSD activity.
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PMID:Characteristics and regulation of 11 beta-hydroxysteroid dehydrogenase of proximal and distal nephron. 772 21

11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) is thought to confer aldosterone specificity to mineralocorticoid target cells by protecting the mineralocorticoid receptor from occupancy by endogenous glucocorticoids. We have recently described a novel isoform of 11-OHSD in the renal aldosterone target cells (11 beta-OHSD/CD) that differs from the previously characterized isoform (11 beta-OHSD-1). Unlike 11-OHSD-1, the collecting duct enzyme catalyzes irreversible dehydrogenation, has a very high affinity for its substrate, and is tissue-specific. We report here the isolation, sequence, and characterization of a complementary DNA (cDNA) encoding the rabbit collecting duct 11 beta-OHSD/CD or 11 beta-OHSD type 2. The cDNA, isolated using expression screening in Xenopus oocytes, is 1.9 kilobases in length and encodes a protein of 406 amino acids with a predicted molecular mass of 44,130 daltons. The cloned enzyme has a Michaelis constant (Km) for corticosterone of 6.6 +/- 3 nM, catalyzes exclusively dehydrogenation, and uses only NAD as cofactor. The cloned enzyme shows 85% and 75% amino acid identity to the recently cloned human type 2 11 beta-OHSD and sheep kidney 11 beta-OHSD, respectively, whereas the overall homology to rat liver 11 beta-OHSD-1 is less than 20% The messenger RNA for this 11 beta-OHSD is expressed at very high levels in the renal collecting duct and at much lower levels in the colon. The intrarenal distribution was determined by reverse-transcription polymerase chain reaction in isolated nephron segments or cell types. The messenger RNA is present only in aldosterone target cells within the kidney, at highest levels in principal cells, at lower levels in intercalated cells, and in inner medullary cells. These data suggest that the 11 beta-OHSD cDNA from rabbit collecting duct cells encodes the enzyme that confers aldosterone selectivity to mineralocorticoid target cells.
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PMID:Expression cloning of the aldosterone target cell-specific 11 beta-hydroxysteroid dehydrogenase from rabbit collecting duct cells. 775 Apr 80

In addition to mineralocorticoid and glucocorticoid receptors, the kidney contains a third high affinity binding site for endogenous glucocorticoids, the type III receptor. These binding sites have been localized to the collecting duct, but their biological function has not yet been identified. We have used immunodissected rabbit cortical collecting duct (CCD) cells to further characterize these binding sites. Experiments using intact cells revealed very high levels of [3H]corticosterone (CS) binding (2.99 +/- 0.38 x 10(6) sites/cell), about 100-fold higher than the number of mineralocorticoid or glucocorticoid receptors in CCD cells. Among the two cell types of the collecting duct, principal cells, the putative targets of aldosterone, contain approximately 10 times more CS-binding sites than intercalated cells. The Kd of the binding sites for CS averaged 54.3 +/- 3.48 nM at 0 C. The relative affinity of unlabeled steroids for the binding sites is CS > carbenoxolone congruent to glycyrrhetinic acid > or = 11-dehydrocorticosterone (11-DHCS) > cortisol congruent to cortisone > deoxycorticosterone > progesterone. Synthetic glucocorticoids (dexamethasone, RU 28362, and RU 486) and aldosterone did not compete for [3H]CS binding. Based on their preferential localization to CCD cells, which are the main targets of aldosterone, we hypothesized that these CS-binding sites are involved in conferring aldosterone specificity on mineralocorticoid receptors in these cells. As 11 beta-hydroxysteroid dehydrogenase (11-OHSD) is thought to play a key role in this process, we studied the relationship between CS-binding sites and the collecting duct isoform of this enzyme (11-OHSD/CD) in purified CCD cells. Freshly isolated cells rapidly converted [3H]CS to 11-DHCS with an apparent Km of about 50 nM, a value close to the Kd of the CS-binding sites for CS in these cells. The rank order of potency of unlabeled steroids to decrease the conversion of [3H]CS to [3H]11-DHCS was identical to their relative affinity for the CS-binding sites. Also, there is a close correlation (r = 0.783; P < 0.0001) between the activity of 11-OHSD and the number of CS-binding sites in different CCD preparations. Based on the similarities between the abundant CS-binding sites and avid CS metabolism in CCD cells, we suggest that these binding sites belong to the collecting duct isoform of 11-OHSD, which, by decreasing the intracellular levels of active glucocorticoids, plays an important role in conferring aldosterone selectivity on mineralocorticoid receptors in CCD cells.
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PMID:Is the renal type III corticosteroid-binding site the collecting duct-specific isoform of 11 beta-hydroxysteroid dehydrogenase? 813 30

The purpose of this paper it to briefly review recent work from our laboratory dealing with the form of 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) present in renal aldosterone target cells. It is well established that aldosterone is the physiological mineralocorticoid hormone. The observation that mineralocorticoid receptors have equal affinity for aldosterone and endogenous glucocorticoids, coupled with the fact that circulating levels of glucocorticoids are much higher than those of aldosterone, raises the question of how aldosterone can fulfill its function. To explain this paradox, it was hypothesized that in mineralocorticoid target tissues 11 beta-OHSD rapidly inactivates glucocorticoids (but not aldosterone), thereby decreasing intracellular glucocorticoid levels, so that aldosterone can exert specific regulation via the mineralocorticoid receptor. However, the only form of this enzyme which has been cloned thus far might not be the enzyme which is able to confer aldosterone selectivity on the mineralocorticoid receptor. On the other hand, a new form of 11 beta-OHSD (11 beta-OHSD/CD) that we have discovered in renal collecting duct cells possesses all the properties necessary for protecting the mineralocorticoid receptor: very high affinity for endogenous glucocorticoids, high abundance in target cells, and irreversible dehydrogenase activity. Our hypothesis is that 11 beta-OHSD/CD is the enzyme that ensures aldosterone selectivity in mineralocorticoid target cells, and that is the product of a gene different from the one previously cloned.
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PMID:11 beta-Hydroxysteroid dehydrogenase in renal collecting duct cells. 819 37

The type 1 and type 2 isoforms of human 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) play a crucial role, respectively, in modulating glucocorticoid and mineralocorticoid hormone action. Deficiency of the 11 beta-HSD2 isoform, as described in the syndrome of apparent mineralocorticoid excess and following liquorice (glycyrrhetinic acid) or carbenoxolone ingestion, results in hypertension in which cortisol acts as a potent mineralocorticoid. Several studies have addressed the effects of progesterone, glycyrrhetinic acid, and their derivatives on 11 beta-HSD activity, but these were largely undertaken before the characterization of the 11 beta-HSD isoforms. The aim of this study was to evaluate the localization of 11 beta-HSD2 in human kidney and to study the effects of progesterone, glycyrrhetinic acid, and their related compounds on stable transfectants of the human 11 beta-HSD isoforms. Using an in-house sheep antibody against human 11 beta-HSD2, immunoperoxidase studies localized 11 beta-HSD2 to renal cortical and medullary collecting ducts. Glomeruli, vascular structures, loops of Henle, and proximal tubules were all negative. Confocal laser microscopy studies indicated both a cytoplasmic and nuclear localization for the enzyme within renal collecting ducts. The nuclear staining, which was intranuclear and was not associated with the nuclear membrane, accounted for 40% of the total cellular 11 beta-HSD2 immunoreactivity. Kinetic analysis of 11 beta-HSD activity in fetal kidney 293 cells stably transfected with h11 beta-HSD1/pcDNA3 or 11 beta-HSD2/pCR3, indicated, respectively, low-affinity dehydrogenase/oxoreductase activity (Km for F, 1.8 microM; Km for E, 270 nM) and high-affinity dehydrogenase activity (Km for F, 190 nM). The reductase activity of 11 beta-HSD1 was inhibited by 11 alpha-hydroxyprogesterone > carbenoxolone = glycyrrhetinic acid = progesterone > 11 beta-hydroxyprogesterone. The dehydrogenase activity of 11 beta-HSD2 was inhibited 11 alpha-hydroxyprogesterone = 11 beta-hydroxyprogesterone > glycyrrhetinic acid > carbenoxolone = progesterone. 11 beta-HSD2, expressed in the renal collecting duct, serves to protect the mineralocorticoid receptor (MR) in an autocrine fashion. The demonstration of a nuclear localization for what was thought to be principally a microsomal enzyme suggests that interaction between the MR and its ligand (either aldosterone or cortisol) may be a nuclear rather than a cytoplasmic event. The inhibitory effects of progesterone, glycyrrhetinic acid, and related compounds on 11 beta-HSD1 and 2 were similar, and it remains to be seen what implication these findings have for 11 beta-HSD1 action in tissues such as the liver and gonad and renal 11 beta-HSD2 activity in relation to sodium homeostasis and blood pressure control.
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PMID:Human 11 beta-hydroxysteroid dehydrogenase: studies on the stably transfected isoforms and localization of the type 2 isozyme within renal tissue. 902 19

Type 2 11beta-hydroxysteroid dehydrogenase (11betaHSD2) plays a key role in conferring aldosterone selectivity on the mineralocorticoid receptor (MR) by inactivating intracellular glucocorticoids before they can occupy the MR. 11betaHSD2 is a microsomal enzyme expressed in aldosterone target cells, although its subcellular distribution is still unclear. The goal of this study was to determine the subcellular localization of the endogenous 11betaHSD2 in renal aldosterone target cells. We generated an antibody against rabbit 11betaHSD2 and used it in combination with a nuclear marker and confocal laser scanning microscopy. On Western blots the antibody recognized a single band of approximately 41 kDa in the renal cortical collecting duct, outer medullary collecting duct, submandibular gland and adrenal cortex, whereas the colon, liver, renal medulla, and heart were negative. Immunohistochemistry showed specific reaction in the known aldosterone target cells of the kidney (connecting tubule, cortical collecting duct, and outer medullary collecting duct) with no signals over glomeruli, proximal nephron segments, and blood vessels. Staining for 11betaHSD2 was very weak in rabbit colon, and no immunoreactivity could be detected in the heart and brain. Confocal microscopy of kidney sections costained with the 11betaHSD2 antibody and the nuclear marker propidium iodide demonstrated that 11betaHSD2 is in the cytoplasmic compartment with no evidence for nuclear localization. Subcellular localization of 11betaHSD2 to a cytoplasmic compartment seems ideal for fulfilling its biological function, i.e. the efficient inactivation of intracellular glucocorticoids before they occupy MRs, which are predominantly cytoplasmic in the absence of hormone.
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PMID:Extranuclear localization of endogenous 11beta-hydroxysteroid dehydrogenase-2 in aldosterone target cells. 960 6

Mineralocorticoid hormones regulate salt transport along the distal nephron by binding to intracellular receptors and activating gene transcription. Previous experiments showed that systemic aldosterone infusions stimulate thiazide-sensitive Na and Cl transport by distal convoluted tubule (DCT) cells; this effect could have been direct or secondary to systemic hormonal effects. Aldosterone target tissues express both mineralocorticoid receptors and the metabolic enzyme 11beta-hydroxysteroid dehydrogenase type 2. Mineralocorticoid receptors have been localized to the DCT in some experiments, but not in others. Expression of 11beta-hydroxysteroid dehydrogenase type 2 by DCT cells has not been investigated. The present experiments were designed to test the hypothesis that rat DCT cells are targets of aldosterone action. Patterns of mineralocorticoid receptor, 11beta-hydroxysteroid dehydrogenase, thiazide-sensitive Na-Cl cotransporter, and Na/Ca exchanger expression along the distal tubule were examined. A polyclonal antibody was generated to localize the thiazide-sensitive Na-Cl cotransporter. Thiazide-sensitive Na-Cl cotransporter and 11beta-hydroxysteroid dehydrogenase expression were examined using both in situ hybridization and immunocytochemistry; Na/Ca exchanger and mineralocorticoid receptor expression were examined by immunocytochemistry. The results indicate that 11beta-hydroxysteroid dehydrogenase is expressed by DCT cells, as well as connecting tubule cells and principal cells of the collecting duct; expression levels are low near the junction with the thick ascending limb and rise near the transition to the connecting tubule. Mineralocorticoid receptors are expressed by DCT cells, as well as along the thick ascending limb, connecting tubule, and collecting duct. The results indicate that components of the mineralocorticoid receptor system are expressed by DCT cells, suggesting that these cells are targets of aldosterone action.
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PMID:11Beta-hydroxysteroid dehydrogenase, mineralocorticoid receptor, and thiazide-sensitive Na-Cl cotransporter expression by distal tubules. 969 56

Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from glucocorticoid binding by an enzyme, 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2). To study the role of 11 beta-HSD2 in acid-base homeostasis, 11 beta-HSD2 activity was measured in rat IMCD-enriched cell suspensions. Homogenates of cell suspensions were incubated in buffers ranging in pH from 6.00 to 8.15 in the presence of 1 microCi of 3H-corticosterone (CS) and 400 microM NAD+. Enzyme activity was expressed as the amount of 3H-CS converted to 3H-11-dehydrocorticosterone (DHCS). IMCD 11 beta-HSD2 activity at pH 6.5 was 49% of activity at pH 7.5; 22.5 versus 11.0 fmol/microgram of protein per h. Experiments also were performed on intact cell suspensions at pH 7.5 and 6.5. There was a 42% inhibition in the IMCD cell suspension conversion rate of 3H-CS to 3H-11-DHCS at pH 6.5; 13.1 versus 7.6 fmol/microgram per h (P < 0.005). In cell suspensions at pH 7.5, 1-day acid loading caused a 26% inhibition in conversion rate, 13.2 versus 9.9 fmol/microgram per h (P < 0.05), when compared with controls. These results suggest that during acute metabolic acidosis, IMCD 11 beta-HSD2 is inhibited and may allow access to the mineralocorticoid receptors by glucocorticoids.
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PMID:Inhibition of IMCD 11 beta-hydroxysteroid dehydrogenase type 2 by low pH and acute acid loading. 1049 81

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