1
|
Abstract
Pannexin 1 (PANX1) is an ATP-permeable channel with critical roles in a variety of physiological functions such as blood pressure regulation1, apoptotic cell clearance2 and human oocyte development3. Here we present several structures of human PANX1 in a heptameric assembly at resolutions of up to 2.8 angström, including an apo state, a caspase-7-cleaved state and a carbenoxolone-bound state. We reveal a gating mechanism that involves two ion-conducting pathways. Under normal cellular conditions, the intracellular entry of the wide main pore is physically plugged by the C-terminal tail. Small anions are conducted through narrow tunnels in the intracellular domain. These tunnels connect to the main pore and are gated by a long linker between the N-terminal helix and the first transmembrane helix. During apoptosis, the C-terminal tail is cleaved by caspase, allowing the release of ATP through the main pore. We identified a carbenoxolone-binding site embraced by W74 in the extracellular entrance and a role for carbenoxolone as a channel blocker. We identified a gap-junction-like structure using a glycosylation-deficient mutant, N255A. Our studies provide a solid foundation for understanding the molecular mechanisms underlying the channel gating and inhibition of PANX1 and related large-pore channels.
Collapse
Affiliation(s)
- Zheng Ruan
- Van Andel Institute, Grand Rapids, MI, USA
| | | | - Juan Du
- Van Andel Institute, Grand Rapids, MI, USA.
| | - Wei Lü
- Van Andel Institute, Grand Rapids, MI, USA.
| |
Collapse
|
2
|
Tykarska E, Gdaniec M. Solid-state supramolecular architecture of carbenoxolone – comparative studies with glycyrrhetinic and glycyrrhizic acids. Acta Crystallogr B Struct Sci Cryst Eng Mater 2015; 71:25-33. [PMID: 25643713 DOI: 10.1107/s2052520614026419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/01/2014] [Indexed: 06/04/2023]
Abstract
Carbenoxolone (CBXH2), a pharmaceutically relevant derivative of glycyrrhetinic acid, was studied by X-ray crystallography. The crystal structures of its unsolvated form, propionic acid and dimethoxyethane solvates and a solvated cocrystal of the free acid with its monobasic sodium salt CBXH2·CBXHNa·(butan-2-one)2·2H2O reveal that the recurring motif of supramolecular architecture in all crystal forms is a one-dimensional ribbon with closely packed triterpene fragments. It does not result from strong specific interactions but solely from van der Waals interactions. The ribbons are further arranged into diverse layer-type aggregates with a hydrophobic interior (triterpene skeletons) and hydrophilic surfaces covered with carboxylic/carboxylate groups. Solvent molecules included at the interface between the layers influence hydrogen-bonding interactions between the carbenoxolone molecules and organization of the ribbons within the layer. Comparison of crystal structures of carbenoxolone, glycyrrhizic acid and its aglycone-glycyrrhetinic acid have shown the impact of the size and hydrophilic character of the substituent at the triterpene C3 atom on the supramolecular architecture of these three closely related molecules.
Collapse
Affiliation(s)
- Ewa Tykarska
- Department of Chemical Technology of Drugs, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznań, Poland
| | - Maria Gdaniec
- Faculty of Chemistry, A. Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland
| |
Collapse
|
3
|
Kuzma-Kuzniarska M, Yapp C, Pearson-Jones TW, Jones AK, Hulley PA. Functional assessment of gap junctions in monolayer and three-dimensional cultures of human tendon cells using fluorescence recovery after photobleaching. J Biomed Opt 2014; 19:15001. [PMID: 24390370 PMCID: PMC4019415 DOI: 10.1117/1.jbo.19.1.015001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 11/11/2013] [Accepted: 12/03/2013] [Indexed: 06/03/2023]
Abstract
Gap junction-mediated intercellular communication influences a variety of cellular activities. In tendons, gap junctions modulate collagen production, are involved in strain-induced cell death, and are involved in the response to mechanical stimulation. The aim of the present study was to investigate gap junction-mediated intercellular communication in healthy human tendon-derived cells using fluorescence recovery after photobleaching (FRAP). The FRAP is a noninvasive technique that allows quantitative measurement of gap junction function in living cells. It is based on diffusion-dependent redistribution of a gap junction-permeable fluorescent dye. Using FRAP, we showed that human tenocytes form functional gap junctions in monolayer and three-dimensional (3-D) collagen I culture. Fluorescently labeled tenocytes following photobleaching rapidly reacquired the fluorescent dye from neighboring cells, while HeLa cells, which do not communicate by gap junctions, remained bleached. Furthermore, both 18 β-glycyrrhetinic acid and carbenoxolone, standard inhibitors of gap junction activity, impaired fluorescence recovery in tendon cells. In both monolayer and 3-D cultures, intercellular communication in isolated cells was significantly decreased when compared with cells forming many cell-to-cell contacts. In this study, we used FRAP as a tool to quantify and experimentally manipulate the function of gap junctions in human tenocytes in both two-dimensional (2-D) and 3-D cultures.
Collapse
Affiliation(s)
- Maria Kuzma-Kuzniarska
- University of Oxford, Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Oxford OX3 7LD, United Kingdom
| | - Clarence Yapp
- University of Oxford, Structural Genomics Consortium, Oxford OX3 7DQ, United Kingdom
| | - Thomas W. Pearson-Jones
- University of Oxford, Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Oxford OX3 7LD, United Kingdom
| | - Andrew K. Jones
- Oxford Brookes University, Faculty of Health and Life Sciences, Department of Biological and Medical Sciences Oxford OX3 0BP, United Kingdom
| | - Philippa A. Hulley
- University of Oxford, Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Oxford OX3 7LD, United Kingdom
| |
Collapse
|
4
|
Takeuchi H, Mizoguchi H, Doi Y, Jin S, Noda M, Liang J, Li H, Zhou Y, Mori R, Yasuoka S, Li E, Parajuli B, Kawanokuchi J, Sonobe Y, Sato J, Yamanaka K, Sobue G, Mizuno T, Suzumura A. Blockade of gap junction hemichannel suppresses disease progression in mouse models of amyotrophic lateral sclerosis and Alzheimer's disease. PLoS One 2011; 6:e21108. [PMID: 21712989 PMCID: PMC3119678 DOI: 10.1371/journal.pone.0021108] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 05/18/2011] [Indexed: 12/13/2022] Open
Abstract
Background Glutamate released by activated microglia induces excitotoxic neuronal death, which likely contributes to non-cell autonomous neuronal death in neurodegenerative diseases, including amyotrophic lateral sclerosis and Alzheimer's disease. Although both blockade of glutamate receptors and inhibition of microglial activation are the therapeutic candidates for these neurodegenerative diseases, glutamate receptor blockers also perturbed physiological and essential glutamate signals, and inhibitors of microglial activation suppressed both neurotoxic/neuroprotective roles of microglia and hardly affected disease progression. We previously demonstrated that activated microglia release a large amount of glutamate specifically through gap junction hemichannel. Hence, blockade of gap junction hemichannel may be potentially beneficial in treatment of neurodegenerative diseases. Methods and Findings In this study, we generated a novel blood-brain barrier permeable gap junction hemichannel blocker based on glycyrrhetinic acid. We found that pharmacologic blockade of gap junction hemichannel inhibited excessive glutamate release from activated microglia in vitro and in vivo without producing notable toxicity. Blocking gap junction hemichannel significantly suppressed neuronal loss of the spinal cord and extended survival in transgenic mice carrying human superoxide dismutase 1 with G93A or G37R mutation as an amyotrophic lateral sclerosis mouse model. Moreover, blockade of gap junction hemichannel also significantly improved memory impairments without altering amyloid β deposition in double transgenic mice expressing human amyloid precursor protein with K595N and M596L mutations and presenilin 1 with A264E mutation as an Alzheimer's disease mouse model. Conclusions Our results suggest that gap junction hemichannel blockers may represent a new therapeutic strategy to target neurotoxic microglia specifically and prevent microglia-mediated neuronal death in various neurodegenerative diseases.
Collapse
Affiliation(s)
- Hideyuki Takeuchi
- Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Blum A, Favia AD, Maser E. 11beta-Hydroxysteroid dehydrogenase type 1 inhibitors with oleanan and ursan scaffolds. Mol Cell Endocrinol 2009; 301:132-6. [PMID: 18822345 DOI: 10.1016/j.mce.2008.08.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Revised: 08/15/2008] [Accepted: 08/25/2008] [Indexed: 11/26/2022]
Abstract
The enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts cortisone to the active glucocorticoid cortisol, thereby acting as a cellular switch to mediate glucocorticoid action in many tissues. Several studies have indicated that 11beta-HSD1 plays a crucial role in the onset of type 2 diabetes and central obesity. As a consequence, selective inhibition of 11beta-HSD1 in humans might become a new and promising approach for lowering blood glucose concentrations and for counteracting the accumulation of visceral fat and its related metabolic abnormalities in type 2 diabetes. In this study, we present the synthesis and the biological evaluation of ursan or oleanan type triterpenoids which may act as selective 11beta-HSD1 inhibitors in liver as well as in peripheral tissues, like adipocytes and muscle cells. In order to rationalise the outcomes of the inhibition data, docking simulations of the ligands were performed on the experimentally determined structure of 11beta-HSD1. Furthermore, we discuss the structural determinants that confer enzymatic specificity. From our investigation, valuable information has been obtained to design selective 11beta-HSD1 blockers based on the oleanan and ursan scaffold.
Collapse
Affiliation(s)
- Andreas Blum
- Institute of Toxicology and Pharmacology for Natural Scientists, University Medical School Schleswig-Holstein, Kiel, Germany
| | | | | |
Collapse
|
6
|
Zhou JJ, Jiang YX, Jin SJ, Tao LJ, Liu LJ. [Studies on analgesic effects and sites of oxymatrine-carbenoxolone sodium complex]. Zhongguo Zhong Yao Za Zhi 2008; 33:822-824. [PMID: 18589792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
OBJECTIVE To study the analgesic effects and sites of oxymatrine-carbenoxolone sodium complex (OCSC). METHOD Adopting formalin test, warm water tail-flick test and intracerebroventricularly (icv) injection to observe the analgesic effects of OCSC in mice. RESULT Intraperitoneally injecting (ip) OCSC (75, 150 mg x kg(-1)) remarkedly inhibited the pain of mice in the formalin test and prolonged latent phases of tail-shrinking of mice, icy OCSC (1.875, 3.75, 7.5 mg x kg(-1)) significantly prolonged latent phases of tail-shrinking of mice, it had dose-dependent effect with concentration. CONCLUSION The result indicated that OCSC has obvious analgesic effects and its mechanism may be involved in central nervous system (CNS).
Collapse
Affiliation(s)
- Jun-Jun Zhou
- Department of Pharmacology, Ningxia Medical College, Yinchuan 750004, China
| | | | | | | | | |
Collapse
|
7
|
Su X, Vicker N, Lawrence H, Smith A, Purohit A, Reed MJ, Potter BVL. Inhibition of human and rat 11beta-hydroxysteroid dehydrogenase type 1 by 18beta-glycyrrhetinic acid derivatives. J Steroid Biochem Mol Biol 2007; 104:312-20. [PMID: 17493801 DOI: 10.1016/j.jsbmb.2007.03.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) plays an important role in regulating the cortisol availability to bind to corticosteroid receptors within specific tissue. Recent advances in understanding the molecular mechanisms of metabolic syndrome indicate that elevation of cortisol levels within specific tissues through the action of 11beta-HSD1 could contribute to the pathogenesis of this disease. Therefore, selective inhibitors of 11beta-HSD1 have been investigated as potential treatments for metabolic diseases, such as diabetes mellitus type 2 or obesity. Here we report the discovery and synthesis of some 18beta-glycyrrhetinic acid (18beta-GA) derivatives (2-5) and their inhibitory activities against rat hepatic11beta-HSD1 and rat renal 11beta-HSD2. Once the selectivity over the rat type 2 enzyme was established, these compounds' ability to inhibit human 11beta-HSD1 was also evaluated using both radioimmunoassay (RIA) and homogeneous time resolved fluorescence (HTRF) methods. The 11-modified 18beta-GA derivatives 2 and 3 with apparent selectivity for rat 11beta-HSD1 showed a high percentage inhibition for human microsomal 11beta-HSD1 at 10 microM and exhibited IC50 values of 400 and 1100 nM, respectively. The side chain modified 18beta-GA derivatives 4 and 5, although showing selectivity for rat 11beta-HSD1 inhibited human microsomal 11beta-HSD1 with IC50 values in the low micromolar range.
Collapse
Affiliation(s)
- Xiangdong Su
- Medicinal Chemistry, Department of Pharmacy and Pharmacology and Sterix Ltd., University of Bath, Bath BA2 7AY, UK
| | | | | | | | | | | | | |
Collapse
|
8
|
Richards S, Sorensen B, Jae HS, Winn M, Chen Y, Wang J, Fung S, Monzon K, Frevert EU, Jacobson P, Sham H, Link JT. Discovery of potent and selective inhibitors of 11beta-HSD1 for the treatment of metabolic syndrome. Bioorg Med Chem Lett 2006; 16:6241-5. [PMID: 17000111 DOI: 10.1016/j.bmcl.2006.09.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 09/04/2006] [Accepted: 09/07/2006] [Indexed: 10/24/2022]
Abstract
High throughput screening efforts have identified a novel class of dichloroaniline amide 11beta-HSD1 inhibitors. SAR studies initiated from dichloroaniline 4 focused on retaining the potency and selectivity profile of the lead.
Collapse
Affiliation(s)
- Steven Richards
- Metabolic Disease Research, GPRD, Abbott Laboratories, 100 Abbott Park Rd., Abbott Park, IL 60064, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Cherian PP, Siller-Jackson AJ, Gu S, Wang X, Bonewald LF, Sprague E, Jiang JX. Mechanical strain opens connexin 43 hemichannels in osteocytes: a novel mechanism for the release of prostaglandin. Mol Biol Cell 2005; 16:3100-6. [PMID: 15843434 PMCID: PMC1165395 DOI: 10.1091/mbc.e04-10-0912] [Citation(s) in RCA: 372] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mechanosensing bone osteocytes express large amounts of connexin (Cx)43, the component of gap junctions; yet, gap junctions are only active at the small tips of their dendritic processes, suggesting another function for Cx43. Both primary osteocytes and the osteocyte-like MLO-Y4 cells respond to fluid flow shear stress by releasing intracellular prostaglandin E2 (PGE2). Cells plated at lower densities release more PGE2 than cells plated at higher densities. This response was significantly reduced by antisense to Cx43 and by the gap junction and hemichannel inhibitors 18 beta-glycyrrhetinic acid and carbenoxolone, even in cells without physical contact, suggesting the involvement of Cx43-hemichannels. Inhibitors of other channels, such as the purinergic receptor P2X7 and the prostaglandin transporter PGT, had no effect on PGE2 release. Cell surface biotinylation analysis showed that surface expression of Cx43 was increased by shear stress. Together, these results suggest fluid flow shear stress induces the translocation of Cx43 to the membrane surface and that unapposed hemichannels formed by Cx43 serve as a novel portal for the release of PGE2 in response to mechanical strain.
Collapse
Affiliation(s)
- Priscilla P Cherian
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
| | | | | | | | | | | | | |
Collapse
|
10
|
Hu HY, Horton JK, Gryk MR, Prasad R, Naron JM, Sun DA, Hecht SM, Wilson SH, Mullen GP. Identification of small molecule synthetic inhibitors of DNA polymerase beta by NMR chemical shift mapping. J Biol Chem 2004; 279:39736-44. [PMID: 15258144 DOI: 10.1074/jbc.m402842200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA polymerase beta (beta-pol) plays a central role in repair of damaged DNA bases by base excision repair (BER) pathways. A predominant phenotype of beta-pol null mouse fibroblasts is hypersensitivity to the DNA-methylating agent methyl methanesulfonate. Residues in the 8-kDa domain of beta-pol that seem to interact with a known natural product beta-pol inhibitor, koetjapic acid, were identified by NMR chemical shift mapping. The data implicate the binding pocket as the hydrophobic cleft between helix-2 and helix-4, which provides the DNA binding and deoxyribose phosphate lyase activities of the enzyme. Nine structurally related synthetic compounds, containing aromatic or other hydrophobic groups in combination with two carboxylate groups, were then tested. They were found to bind to the same or a very similar region on the surface of the enzyme. The ability of these compounds to potentiate methyl methanesulfonate cytotoxicity, an indicator of cellular BER capacity, in wild-type and beta-pol null mouse fibroblasts, was next ascertained. The most active and beta-pol-specific of these agents, pamoic acid, was further characterized and found to be an inhibitor of the deoxyribose phosphate lyase and DNA polymerase activities of purified beta-pol on a BER substrate. Our results illustrate that NMR-based mapping techniques can be used in the design of small molecule enzyme inhibitors including those with potential use in a clinical setting.
Collapse
Affiliation(s)
- Hong-Yu Hu
- Department of Biochemistry, University of Connecticut Health Center, Farmington, Connecticut 06032, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Ozog MA, Siushansian R, Naus CCG. Blocked gap junctional coupling increases glutamate-induced neurotoxicity in neuron-astrocyte co-cultures. J Neuropathol Exp Neurol 2002; 61:132-41. [PMID: 11855382 DOI: 10.1093/jnen/61.2.132] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Gap junctional communication is likely one means by which neurons can endure glutamate cytotoxicity associated with CNS insults (i.e. ischemia). To examine this neuroprotective role of gap junctions, we employed gap junctional blockers to neuronal and astrocytic co-cultures during exposure to a high concentration of extracellular glutamate. Co-cultures were treated with the blocking agents carbenoxolone (CBX; 25 microM), 18alpha-glycyrrhetinic acid (AGA; 10 microM), vehicle or the inactive blocking analogue glycyrrhizic acid (GZA; 25 microM). Twenty-four hours following the insult, cell mortality was analyzed and quantified by the release of lactate dehydrogenase (LDH) into the media, the cells' inability to exclude propidium iodide, and terminal dUTP nick end labeling (TUNEL). Measurement of LDH release revealed that the glutamate insult was detrimental to the co-cultures when gap junctions were blocked with CBX and AGA. Based on propidium iodide and TUNEL labeling, the glutamate insult caused significant cell death compared to sham vehicle and mortality was amplified in the presence of CBX and AGA. Since blockers were not themselves toxic and did not affect astrocytic uptake of glutamate, it is likely that blocked gap junctions lead to the increased glutamate cytotoxicity. These findings support the hypothesis that gap junctions play a neuroprotective role against glutamate cytotoxicity.
Collapse
Affiliation(s)
- Mark A Ozog
- Department of Anatomy & Cell Biology, The University of Western Ontario, London, Canada
| | | | | |
Collapse
|
12
|
Tolstikov GA, Baltina LA, Shul'ts EE, Pokrovskił AG. [Glycyrrhizic acid]. Bioorg Khim 1997; 23:691-709. [PMID: 9441592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The specific properties, chemical transformations, and biological activity of glycyrrhizic acid and its derivatives are discussed. Particular attention is paid to investigations that hold promise for the development of important drugs for clinical use.
Collapse
|
13
|
Ghosh D, Wawrzak Z, Pletnev V, Erman M, Duax WL, Pangborn W, Zhu DW, Labrie F, Lin SX. Molecular mechanism of inhibition of steroid dehydrogenases by licorice-derived steroid analogs in modulation of steroid receptor function. Ann N Y Acad Sci 1995; 761:341-3. [PMID: 7625731 DOI: 10.1111/j.1749-6632.1995.tb31388.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- D Ghosh
- Medical Foundation of Buffalo, New York 14203, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Abstract
Endogenous glucocorticoids (GC) can be metabolized through the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD); in the rat, corticosterone (B) is converted to its inactive metabolite 11-dehydrocorticosterone (A). Since increased tissue concentrations of GCs may affect blood pressure by potentiating the vasoactive effects of alpha-adrenergic agonists and possibly other pressors, we studied the metabolism of corticosterone in freshly dissected aortae and cultured vascular smooth muscle cells (VSMC). Incubations were generally conducted for 60 min with 10(-8) M steroid; steroids were isolated and identified by HPLC. In aortic minces stripped of endothelium, the oxo-reductase reaction of A back to B was nearly 4 times greater than the dehydrogenase reaction of B to A (2.8 +/- 0.5 x 10(-11) versus 7.3 +/- 1.0 x 10(-12) mol/mg protein). This pattern was also seen in cultured VSMC during growth and quiescent states (growth A to B 3.2 +/- 0.4 x 10(-12) versus B to A 9.7 +/- 0.9 x 10(-13) mol/mg protein; quiescent A to B 8.8 +/- 0.1 x 10(-12) versus B to A 1.2 +/- 0.2 x 10(-12) mol/mg protein). Enzyme activity in either direction was less during growth, correlating with a decrease in mRNA for 11 beta-OHSD. In cell homogenates containing 200 microM NADP(H), the enzyme functioned equally in either direction at pH 7.4 with an apparent Km for corticosterone of approximately 2 x 10(-7) M. Carbenoxolone, an inhibitor of 11 beta-OHSD, suppressed the dehydrogenase reaction to a greater degree than the reverse oxo-reductase reaction.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- A S Brem
- Department of Pediatrics (Nephrology), Rhode Island Hospital, Providence 02903, USA
| | | | | | | |
Collapse
|
15
|
Ghosh D, Erman M, Wawrzak Z, Duax WL, Pangborn W. Mechanism of inhibition of 3 alpha, 20 beta-hydroxysteroid dehydrogenase by a licorice-derived steroidal inhibitor. Structure 1994; 2:973-80. [PMID: 7866748 DOI: 10.1016/s0969-2126(94)00099-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Bacterial 3 alpha, 20 beta-hydroxysteroid dehydrogenase (3 alpha, 20 beta-HSD) reversibly oxidizes the 3 alpha and 20 beta hydroxyl groups of androstanes and pregnanes and uses nicotinamide adenine dinucleotide as a cofactor. 3 alpha, 20 beta-HSD belongs to a family of short-chain dehydrogenases that has a highly conserved Tyr-X-X-X-Lys sequence. The family includes mammalian enzymes involved in hypertension, digestion, fertility and spermatogenesis. Several members of the enzyme family, including 3 alpha, 20 beta-HSD, are competitively inhibited by glycyrrhizic acid, a steroidal compound found in licorice, and its derivative, carbenoxolone, an anti-inflammatory glucocorticoid. RESULTS The three-dimensional structure of the enzyme-carbenoxolone complex has been determined and refined at 2.2 A resolution to a crystallographic R-factor of 19.4%. The hemisuccinate side chain of carbenoxolone makes a hydrogen bond with the hydroxyl group of the conserved residue Tyr152 and occupies the position of the nicotinamide ring of the cofactor. The occupancies of the inhibitor in four independent catalytic sites refine to 100%, 95%, 54% and 36%. CONCLUSIONS The steroid binds at the catalytic site in a mode much like the previously proposed mode of binding of the substrate cortisone. No bound cofactor molecules were found. The varying occupancy of steroid molecules observed in the four catalytic sites is either due to packing differences or indicates a cooperative effect among the four sites. The observed binding accounts for the inhibition of 3 alpha, 20 beta-HSD.
Collapse
Affiliation(s)
- D Ghosh
- Hauptman-Woodward Medical Research Institute, Buffalo, NY 14203-1196
| | | | | | | | | |
Collapse
|