The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Thomas A. Kocarek - One of the best experts on this subject based on the ideXlab platform.
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Age- and sex-dependent expression of multiple murine hepatic Hydroxysteroid Sulfotransferase (SULT2A) genes
Biochemical pharmacology, 2008Co-Authors: Thomas A. Kocarek, Hai-lin Fang, Zhengbo Duanmu, Melissa Runge-morrisAbstract:Hydroxysteroid Sulfotransferase (SULT2A) enzymes play important roles in hepatic steroid and xenobiotic metabolism. Unlike humans, which express one SULT2A, inspection of mouse genome information indicated the presence of seven SULT2A genes within a cluster on chromosome 7. The age- and sex-dependent expressions of the seven murine SULT2A family members were characterized in the livers of C57BL/6 mice using real-time RT-PCR. The transcripts for three of the SULT2A forms (NCBI reference/model sequences XM_001471624, NM_009286 and NM_001111296) were abundant in pre-pubertal male and female mouse liver but were essentially silenced in the livers of adult male mice. The mRNAs of three other SULT2A forms (NM_001101534, XM_894052 and NM_001081325) were also expressed in pre-pubertal male and female mouse liver, but at markedly reduced levels relative to those of the abundant forms. The mRNA levels of these lower-abundance forms were further suppressed in adult animals. A seventh SULT2A mRNA (XM_983034) was expressed in adult male and female mouse liver, but was not detected in pre-pubertal mouse liver of either sex. Full-length amplifications with primers targeting untranslated regions confirmed that all SULT2A forms were expressed. However, while the XM_001471624, NM_001111296, NM_001101534, XM_894052 and NM_001081325 transcripts were detected at their predicted sizes, the NM_009286 and XM_983034 transcripts each lacked two predicted exons. These results demonstrate that seven murine SULT2As display different profiles of age- and sex-dependent hepatic expression.
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Regulation of Human Hepatic Hydroxysteroid Sulfotransferase Gene Expression by the Peroxisome Proliferator-Activated Receptor α Transcription Factor
Molecular pharmacology, 2005Co-Authors: Hai-lin Fang, Charles N Falany, Thomas A. Kocarek, Stephen C. Strom, Hongbo Cai, Melissa Runge-morrisAbstract:Human Hydroxysteroid Sulfotransferase or (HUMAN)SULT2A1 catalyzes the sulfonation of procarcinogen xenobiotics, Hydroxysteroids, and bile acids and plays a dynamic role in hepatic cholesterol homeostasis. The treatment of primary cultured human hepatocytes with a peroxisome proliferator-activated receptor α (PPARα)-activating concentration of ciprofibrate (10-4 M) increased (HUMAN)SULT2A1 mRNA, immunoreactive protein, and enzymatic activity levels by ∼2-fold. By contrast, expression of (RAT)SULT2A3, the rat counterpart to (HUMAN)SULT2A1, was induced by treatment of primary hepatocyte cultures with an activator of the pregnane X receptor, but not PPARα. In HepG2 cells, transient transfection analyses of luciferase reporter constructs containing upstream regions of the (HUMAN)SULT2A1 gene implicated a candidate peroxisome proliferator response element (PPRE) at nucleotides (nt) -5949 to -5929 relative to the transcription start site. Site-directed mutagenesis and electrophoretic mobility shift assay studies confirmed that this distal PPRE (dPPRE), a direct repeat nuclear receptor motif containing one intervening nt, represented a functional PPRE. Chromatin immunoprecipitation analysis indicated that the (HUMAN)SULT2A1 dPPRE was also a functional element in the context of the human genome. These data support a major role for the PPARα transcription factor in the regulation of hepatic (HUMAN)SULT2A1. Results also indicate that important species differences govern the transactivation of SULT2A gene transcription by nuclear receptors.
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Regulation of human hepatic Hydroxysteroid Sulfotransferase gene expression by the peroxisome proliferatoractivated receptor alpha transcription
2005Co-Authors: Hai-lin Fang, Charles N Falany, Thomas A. Kocarek, Stephen C. Strom, Hongbo Cai, Melissa Runge-morrisAbstract:Human Hydroxysteroid Sulfotransferase or (HUMAN)SULT2A1 catalyzes the sulfonation of procarcinogen xenobiotics, hy-droxysteroids, and bile acids and plays a dynamic role in hepatic cholesterol homeostasis. The treatment of primary cultured human hepatocytes with a peroxisome proliferator-activated receptor (PPAR)-activating concentration of cip-rofibrate (104 M) increased (HUMAN)SULT2A1 mRNA, immu-noreactive protein, and enzymatic activity levels by 2-fold. By contrast, expression of (RAT)SULT2A3, the rat counterpart to (HUMAN)SULT2A1, was induced by treatment of primary he-patocyte cultures with an activator of the pregnane X receptor, but not PPAR. In HepG2 cells, transient transfection analyses of luciferase reporter constructs containing upstream regions of the (HUMAN)SULT2A1 gene implicated a candidate peroxi
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Regulation of glucocorticoidinducible Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription in primary cultured rat hepatocytes: Role of CCAAT/enhancer-binding protein liver-enriched transcription factors. Drug Metab. Dispos
2005Co-Authors: Hai-lin Fang, Thomas A. Kocarek, Zhengbo Duanmu, Masumeh Abdolalipour, Jeffrey R. Smigelski, Amy Weckle, Melissa Runge-morrisAbstract:The mechanism responsible for glucocorticoid receptor (GR)-me-diated induction of rat hepatic Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription was investigated. We previ-ously reported that the region of the SULT2A-40/41 5-flanking region delimited by 158 to 77 nucleotides relative to the tran-scription start site was sufficient to support GR-inducible expres-sion. This region of the SULT2A-40/41 gene does not contain a consensus glucocorticoid receptor-responsive element, but does contain two consensus sites for liver-enriched CCAAT/enhancer-binding protein (C/EBP) transcription factors. In the present study, incubation of primary cultured rat hepatocytes with a GR-activat-ing concentration (107 M) of a potent glucocorticoid, dexameth-asone or triamcinolone acetonide (TA), rapidly produced increases in C/EBP and C/EBP nuclear protein contents, as measured by Western blot or in vitro DNA-binding activity analysis, that pre
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regulation of glucocorticoid inducible Hydroxysteroid Sulfotransferase sult2a 40 41 gene transcription in primary cultured rat hepatocytes role of ccaat enhancer binding protein liver enriched transcription factors
Drug Metabolism and Disposition, 2005Co-Authors: Hai-lin Fang, Thomas A. Kocarek, Zhengbo Duanmu, Masumeh Abdolalipour, Jeffrey R. Smigelski, Amy Weckle, Melissa RungemorrisAbstract:The mechanism responsible for glucocorticoid receptor (GR)-mediated induction of rat hepatic Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription was investigated. We previously reported that the region of the SULT2A-40/41 5′-flanking region delimited by -158 to -77 nucleotides relative to the transcription start site was sufficient to support GR-inducible expression. This region of the SULT2A-40/41 gene does not contain a consensus glucocorticoid receptor-responsive element, but does contain two consensus sites for liver-enriched CCAAT/enhancer-binding protein (C/EBP) transcription factors. In the present study, incubation of primary cultured rat hepatocytes with a GR-activating concentration (10-7 M) of a potent glucocorticoid, dexamethasone or triamcinolone acetonide (TA), rapidly produced increases in C/EBPα and C/EBPβ nuclear protein contents, as measured by Western blot or in vitro DNA-binding activity analysis, that preceded increases in SULT2A-40/41 mRNA and protein levels. Transient cotransfection of SULT2A-40/41 reporter plasmids with a dominant negative C/EBP expression plasmid completely blocked TA-inducible SULT2A-40/41 reporter gene expression. Linker scanning and site-directed mutagenesis of the proximal SULT2A-40/41 5′-flanking region, complemented by in vitro DNA-binding analyses, indicated that the more distal C/EBP site was important for controlling SULT2A-40/41 promoter activity. These data support a role for GR-inducible C/EBPα and C/EBPβ expression in the transactivation of hepatic SULT2A-40/41 expression.
Melissa Runge-morris - One of the best experts on this subject based on the ideXlab platform.
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Age- and sex-dependent expression of multiple murine hepatic Hydroxysteroid Sulfotransferase (SULT2A) genes
Biochemical pharmacology, 2008Co-Authors: Thomas A. Kocarek, Hai-lin Fang, Zhengbo Duanmu, Melissa Runge-morrisAbstract:Hydroxysteroid Sulfotransferase (SULT2A) enzymes play important roles in hepatic steroid and xenobiotic metabolism. Unlike humans, which express one SULT2A, inspection of mouse genome information indicated the presence of seven SULT2A genes within a cluster on chromosome 7. The age- and sex-dependent expressions of the seven murine SULT2A family members were characterized in the livers of C57BL/6 mice using real-time RT-PCR. The transcripts for three of the SULT2A forms (NCBI reference/model sequences XM_001471624, NM_009286 and NM_001111296) were abundant in pre-pubertal male and female mouse liver but were essentially silenced in the livers of adult male mice. The mRNAs of three other SULT2A forms (NM_001101534, XM_894052 and NM_001081325) were also expressed in pre-pubertal male and female mouse liver, but at markedly reduced levels relative to those of the abundant forms. The mRNA levels of these lower-abundance forms were further suppressed in adult animals. A seventh SULT2A mRNA (XM_983034) was expressed in adult male and female mouse liver, but was not detected in pre-pubertal mouse liver of either sex. Full-length amplifications with primers targeting untranslated regions confirmed that all SULT2A forms were expressed. However, while the XM_001471624, NM_001111296, NM_001101534, XM_894052 and NM_001081325 transcripts were detected at their predicted sizes, the NM_009286 and XM_983034 transcripts each lacked two predicted exons. These results demonstrate that seven murine SULT2As display different profiles of age- and sex-dependent hepatic expression.
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Regulation of Human Hepatic Hydroxysteroid Sulfotransferase Gene Expression by the Peroxisome Proliferator-Activated Receptor α Transcription Factor
Molecular pharmacology, 2005Co-Authors: Hai-lin Fang, Charles N Falany, Thomas A. Kocarek, Stephen C. Strom, Hongbo Cai, Melissa Runge-morrisAbstract:Human Hydroxysteroid Sulfotransferase or (HUMAN)SULT2A1 catalyzes the sulfonation of procarcinogen xenobiotics, Hydroxysteroids, and bile acids and plays a dynamic role in hepatic cholesterol homeostasis. The treatment of primary cultured human hepatocytes with a peroxisome proliferator-activated receptor α (PPARα)-activating concentration of ciprofibrate (10-4 M) increased (HUMAN)SULT2A1 mRNA, immunoreactive protein, and enzymatic activity levels by ∼2-fold. By contrast, expression of (RAT)SULT2A3, the rat counterpart to (HUMAN)SULT2A1, was induced by treatment of primary hepatocyte cultures with an activator of the pregnane X receptor, but not PPARα. In HepG2 cells, transient transfection analyses of luciferase reporter constructs containing upstream regions of the (HUMAN)SULT2A1 gene implicated a candidate peroxisome proliferator response element (PPRE) at nucleotides (nt) -5949 to -5929 relative to the transcription start site. Site-directed mutagenesis and electrophoretic mobility shift assay studies confirmed that this distal PPRE (dPPRE), a direct repeat nuclear receptor motif containing one intervening nt, represented a functional PPRE. Chromatin immunoprecipitation analysis indicated that the (HUMAN)SULT2A1 dPPRE was also a functional element in the context of the human genome. These data support a major role for the PPARα transcription factor in the regulation of hepatic (HUMAN)SULT2A1. Results also indicate that important species differences govern the transactivation of SULT2A gene transcription by nuclear receptors.
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Regulation of human hepatic Hydroxysteroid Sulfotransferase gene expression by the peroxisome proliferatoractivated receptor alpha transcription
2005Co-Authors: Hai-lin Fang, Charles N Falany, Thomas A. Kocarek, Stephen C. Strom, Hongbo Cai, Melissa Runge-morrisAbstract:Human Hydroxysteroid Sulfotransferase or (HUMAN)SULT2A1 catalyzes the sulfonation of procarcinogen xenobiotics, hy-droxysteroids, and bile acids and plays a dynamic role in hepatic cholesterol homeostasis. The treatment of primary cultured human hepatocytes with a peroxisome proliferator-activated receptor (PPAR)-activating concentration of cip-rofibrate (104 M) increased (HUMAN)SULT2A1 mRNA, immu-noreactive protein, and enzymatic activity levels by 2-fold. By contrast, expression of (RAT)SULT2A3, the rat counterpart to (HUMAN)SULT2A1, was induced by treatment of primary he-patocyte cultures with an activator of the pregnane X receptor, but not PPAR. In HepG2 cells, transient transfection analyses of luciferase reporter constructs containing upstream regions of the (HUMAN)SULT2A1 gene implicated a candidate peroxi
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Regulation of glucocorticoidinducible Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription in primary cultured rat hepatocytes: Role of CCAAT/enhancer-binding protein liver-enriched transcription factors. Drug Metab. Dispos
2005Co-Authors: Hai-lin Fang, Thomas A. Kocarek, Zhengbo Duanmu, Masumeh Abdolalipour, Jeffrey R. Smigelski, Amy Weckle, Melissa Runge-morrisAbstract:The mechanism responsible for glucocorticoid receptor (GR)-me-diated induction of rat hepatic Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription was investigated. We previ-ously reported that the region of the SULT2A-40/41 5-flanking region delimited by 158 to 77 nucleotides relative to the tran-scription start site was sufficient to support GR-inducible expres-sion. This region of the SULT2A-40/41 gene does not contain a consensus glucocorticoid receptor-responsive element, but does contain two consensus sites for liver-enriched CCAAT/enhancer-binding protein (C/EBP) transcription factors. In the present study, incubation of primary cultured rat hepatocytes with a GR-activat-ing concentration (107 M) of a potent glucocorticoid, dexameth-asone or triamcinolone acetonide (TA), rapidly produced increases in C/EBP and C/EBP nuclear protein contents, as measured by Western blot or in vitro DNA-binding activity analysis, that pre
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Regulation of glucocorticoid-inducible Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription in primary cultured rat hepatocytes: role of CCAAT/enhancer-binding protein liver-enriched transcription factors.
Drug metabolism and disposition: the biological fate of chemicals, 2004Co-Authors: Hai-lin Fang, Thomas A. Kocarek, Zhengbo Duanmu, Masumeh Abdolalipour, Jeffrey R. Smigelski, Amy Weckle, Melissa Runge-morrisAbstract:The mechanism responsible for glucocorticoid receptor (GR)-mediated induction of rat hepatic Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription was investigated. We previously reported that the region of the SULT2A-40/41 5′-flanking region delimited by -158 to -77 nucleotides relative to the transcription start site was sufficient to support GR-inducible expression. This region of the SULT2A-40/41 gene does not contain a consensus glucocorticoid receptor-responsive element, but does contain two consensus sites for liver-enriched CCAAT/enhancer-binding protein (C/EBP) transcription factors. In the present study, incubation of primary cultured rat hepatocytes with a GR-activating concentration (10-7 M) of a potent glucocorticoid, dexamethasone or triamcinolone acetonide (TA), rapidly produced increases in C/EBPα and C/EBPβ nuclear protein contents, as measured by Western blot or in vitro DNA-binding activity analysis, that preceded increases in SULT2A-40/41 mRNA and protein levels. Transient cotransfection of SULT2A-40/41 reporter plasmids with a dominant negative C/EBP expression plasmid completely blocked TA-inducible SULT2A-40/41 reporter gene expression. Linker scanning and site-directed mutagenesis of the proximal SULT2A-40/41 5′-flanking region, complemented by in vitro DNA-binding analyses, indicated that the more distal C/EBP site was important for controlling SULT2A-40/41 promoter activity. These data support a role for GR-inducible C/EBPα and C/EBPβ expression in the transactivation of hepatic SULT2A-40/41 expression.
Michael W Duffel - One of the best experts on this subject based on the ideXlab platform.
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hydroxylated and sulfated metabolites of commonly occurring airborne polychlorinated biphenyls inhibit human steroid Sulfotransferases sult1e1 and sult2a1
Environmental Toxicology and Pharmacology, 2018Co-Authors: Victoria S Parker, Edwin J Squirewell, Hans-joachim Lehmler, Larry W. Robertson, Michael W DuffelAbstract:Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that are associated with varied adverse health effects. Lower chlorinated PCBs are prevalent in indoor and outdoor air and can be metabolized to their hydroxylated derivatives (OH-PCBs) followed by sulfation to form PCB sulfates. Sulfation is also a means of signal termination for steroid hormones. The human estrogen Sulfotransferase (SULT1E1) and alcohol/Hydroxysteroid Sulfotransferase (SULT2A1) catalyze the formation of steroid sulfates that are inactive at steroid hormone receptors. We investigated the inhibition of SULT1E1 (IC50s ranging from 7.2 nM to greater than 10 μM) and SULT2A1 (IC50s from 1.3 μM to over 100 μM) by five lower-chlorinated OH-PCBs and their corresponding PCB sulfates relevant to airborne PCB-exposure. Several congeners of lower chlorinated OH-PCBs relevant to airborne PCB exposures were potent inhibitors of SULT1E1 and SULT2A1 and thus have the potential to disrupt regulation of intracellular concentrations of the receptor-active steroid substrates for these enzymes.
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Endoxifen and Other Metabolites of Tamoxifen Inhibit Human Hydroxysteroid Sulfotransferase 2A1 (hSULT2A1)
Drug metabolism and disposition: the biological fate of chemicals, 2014Co-Authors: Edwin J Squirewell, Xiaoyan Qin, Michael W DuffelAbstract:Although tamoxifen is a successful agent for treatment and prevention of estrogen-dependent breast cancer, its use has been limited by the low incidence of endometrial cancer. Human Hydroxysteroid Sulfotransferase 2A1 (hSULT2A1) catalyzes the formation of an α-sulfooxy metabolite of tamoxifen that is reactive toward DNA, and this has been implicated in its carcinogenicity. Also, hSULT2A1 functions in the metabolism of steroid hormones such as dehydroepiandrosterone (DHEA) and pregnenolone (PREG). These roles of hSULT2A1 in steroid hormone metabolism and in generating a reactive metabolite of tamoxifen led us to examine its interactions with tamoxifen and several of its major metabolites. We hypothesized that metabolites of tamoxifen may regulate the catalytic activity of hSULT2A1, either through direct inhibition or through serving as alternate substrates for the enzyme. We found that 4-hydroxy-N-desmethyltamoxifen (endoxifen) is a potent inhibitor of hSULT2A1-catalyzed sulfation of PREG and DHEA, with Ki values of 3.5 and 2.8 μM, respectively. In the hSULT2A1-catalyzed sulfation of PREG, 4-hydroxytamoxifen (4-OHTAM) and N-desmethyltamoxifen (N-desTAM) exhibited Ki values of 12.7 and 9.8 μM, respectively, whereas corresponding Ki values of 19.4 and 17.2 μM were observed with DHEA as substrate. A Ki value of 9.1 μM was observed for tamoxifen-N-oxide with DHEA as substrate, and this increased to 16.9 μM for the hSULT2A1-catalyzed sulfation of PREG. Three metabolites were substrates for hSULT2A1, with relative sulfation rates of 4-OHTAM > N-desTAM > > endoxifen. These results may be useful in interpreting ongoing clinical trials of endoxifen and in improving the design of related molecules.
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Binding Interactions of Hydroxylated Polychlorinated Biphenyls (OHPCBs) with Human Hydroxysteroid Sulfotransferase hSULT2A1
Chemico-biological interactions, 2014Co-Authors: Edugie J. Ekuase, Larry W. Robertson, Hans-joachim Lehmler, Michael W DuffelAbstract:Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and exposure to PCBs and their hydroxylated metabolites (OHPCBs) has been associated with various adverse health effects. The mammalian cytosolic Sulfotransferases (SULTs) catalyze the sulfation of OHPCBs, and the interaction of OHPCBs with both the SULT1 and SULT2 families of these enzymes has received attention both with respect to metabolic disposition of these molecules and the potential mechanisms for their roles in endocrine disruption. We have previously shown that OHPCBs interact with human Hydroxysteroid Sulfotransferase hSULT2A1, an enzyme that catalyzes the sulfation of dehydroepiandrosterone (DHEA), other alcohol-containing steroids, bile acids, and many xenobiotics. The objective of our current studies is to investigate the mechanism of inhibition of hSULT2A1 by OHPCBs by combining inhibition kinetics with determination of equilibrium binding constants and molecular modeling of potential interactions. Examination of the effects of fifteen OHPCBs on the sulfation of DHEA catalyzed by hSULT2A1 showed predominantly noncompetitive inhibition patterns. This was observed for OHPCBs that were substrates for sulfation reactions catalyzed by the enzyme as well as those that solely inhibited the sulfation of DHEA. Equilibrium binding experiments and molecular modeling studies indicated that the OHPCBs bind at the binding site for DHEA on the enzyme, and that the observed noncompetitive patterns of inhibition are consistent with binding in more than one orientation to more than one enzyme complex. These results have implications for the roles of SULTs in the toxicology of OHPCBs, while also providing molecular probes of the complexity of substrate/inhibitor interactions with hSULT2A1.
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Chlorinated Biphenyl Quinones and Phenyl-2,5-benzoquinone Differentially Modify the Catalytic Activity of Human Hydroxysteroid Sulfotransferase hSULT2A1
Chemical research in toxicology, 2013Co-Authors: Xiaoyan Qin, Larry W. Robertson, Hans-joachim Lehmler, Lynn M. Teesch, Michael W DuffelAbstract:Human Hydroxysteroid Sulfotransferase (hSULT2A1) catalyzes the sulfation of a broad range of environmental chemicals, drugs, and other xenobiotics in addition to endogenous compounds that include Hydroxysteroids and bile acids. Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and oxidized metabolites of PCBs may play significant roles in the etiology of their adverse health effects. Quinones derived from the oxidative metabolism of PCBs (PCB-quinones) react with nucleophilic sites in proteins and also undergo redox cycling to generate reactive oxygen species. This, along with the sensitivity of hSULT2A1 to oxidative modification at cysteine residues, led us to hypothesize that electrophilic PCB-quinones react with hSULT2A1 to alter its catalytic function. Thus, we examined the effects of four phenylbenzoquinones on the ability of hSULT2A1 to catalyze the sulfation of the endogenous substrate, dehydroepiandrosterone (DHEA). The quinones studied were 2′-chlorophenyl-2,5-benzoquino...
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Structure-activity relationships for hydroxylated polychlorinated biphenyls as inhibitors of the sulfation of dehydroepiandrosterone catalyzed by human Hydroxysteroid Sulfotransferase SULT2A1.
Chemical research in toxicology, 2011Co-Authors: Edugie J. Ekuase, Larry W. Robertson, Hans-joachim Lehmler, Yungang Liu, Michael W DuffelAbstract:Polychlorinated biphenyls (PCBs) are persistent worldwide pollutants that are of concern due to their bioaccumulation and health effects. Metabolic oxidation of PCBs results in the formation of hydroxylated metabolites (OHPCBs). Among their biological effects, OHPCBs have been shown to alter the metabolism of endocrine hormones, including inhibition of mammalian cytosolic Sulfotransferases (SULTs) that are responsible for the inactivation of thyroid hormones and phenolic steroids (i.e., hSULT1A1, hSULT1B1, and hSULT1E1). OHPCBs also interact with a human Hydroxysteroid Sulfotransferase that plays a role in the sulfation of endogenous alcohol-containing steroid hormones and bile acids (i.e., hSULT2A1). The objectives of our current study were to examine the effects of a series of OHPCB congeners on the activity of hSULT2A1 and to develop a three-dimensional quantitative structure-activity relationship (3D-QSAR) model for OHPCBs as inhibitors of the enzyme. A total of 15 OHPCBs were examined, and the sulfation of 1 μM [(3)H] dehydroepiandrosterone (DHEA) was utilized as a model reaction catalyzed by the enzyme. All 15 OHPCBs inhibited the sulfation of DHEA, with IC(50) values ranging from 0.6 μM to 96 μM, and eight of these OHPCBs were also substrates for the enzyme. Comparative molecular field analysis (CoMFA) provided a predictive 3D-QSAR model with a q(2) value of 0.697 and an r(2) value of 0.949. The OHPCBs that had the highest potency as inhibitors of DHEA sulfation were those with a 3, 5-dichloro-4-hydroxy substitution pattern on the biphenyl ring system, and these congeners were also substrates for sulfation catalyzed by hSULT2A1.
Charles A. Strott - One of the best experts on this subject based on the ideXlab platform.
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Crystal structure of human cholesterol Sulfotransferase (SULT2B1b) in the presence of pregnenolone and 3'-phosphoadenosine 5'-phosphate. Rationale for specificity differences between prototypical SULT2A1 and the SULT2BG1 isoforms.
The Journal of biological chemistry, 2003Co-Authors: Karen A. Lee, Young C. Lee, Hirotoshi Fuda, Charles A. Strott, Masahiko Negishi, Lars C. PedersenAbstract:Abstract The gene for human Hydroxysteroid Sulfotransferase (SULT2B1) encodes two peptides, SULT2B1a and SULT2B1b, that differ only at their amino termini. SULT2B1b has a predilection for cholesterol but is also capable of sulfonating pregnenolone, whereas SULT2B1a preferentially sulfonates pregnenolone and only minimally sulfonates cholesterol. We have determined the crystal structure of SULT2B1a and SULT2B1b bound to the substrate donor product 3′-phosphoadenosine 5′-phosphate at 2.9 and 2.4 A, respectively, as well as SULT2B1b in the presence of the acceptor substrate pregnenolone at 2.3 A. These structures reveal a different catalytic binding orientation for the substrate from a previously determined structure of Hydroxysteroid Sulfotransferase (SULT2A1) binding dehydroepiandrosterone. In addition, the amino-terminal helix comprising residues Asp19 to Lys26, which determines the specificity difference between the SULT2B1 isoforms, becomes ordered upon pregnenolone binding, covering the substrate binding pocket.
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conservation of the Hydroxysteroid Sulfotransferase sult2b1 gene structure in the mouse pre and postnatal expression kinetic analysis of isoforms and comparison with prototypical sult2a1
Endocrinology, 2003Co-Authors: Chikara Shimizu, Hirotoshi Fuda, Hidekatsu Yanai, Charles A. StrottAbstract:A novel mouse Hydroxysteroid Sulfotransferase cDNA has been cloned, and organization of its gene structure has been determined. The new mouse Sulfotransferase, SULT2B1a, and its closely related isoform, SULT2B1b, are derived from a single SULT2B1 gene as a result of an alternative exon I and differential splicing. Thus, the only structural distinction between the two SULT2B1 isoforms is at their amino-terminal ends. Importantly, in contrast to the prototypical mouse Hydroxysteroid Sulfotransferase SULT2A1, the SULT2B1 isoforms have a predilection for cholesterol. Real-time RT-PCR reveals that the SULT2B1a isoform is most abundantly expressed in the brain and spinal cord, whereas SULT2B1b and SULT2A1 are weakly, if at all, expressed in the central nervous system. On the other hand, the SULT2B1b isoform is the most prominent Hydroxysteroid Sulfotransferase expressed in skin, whereas SULT2A1 is strikingly expressed in the liver. The substrate specificities and differential expression patterns of the three SU...
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Mutational analysis of human Hydroxysteroid Sulfotransferase SULT2B1 isoforms reveals that exon 1B of the SULT2B1 gene produces cholesterol Sulfotransferase, whereas exon 1A yields pregnenolone Sulfotransferase.
Journal of Biological Chemistry, 2002Co-Authors: Hirotoshi Fuda, Norman B. Javitt, Young C. Lee, Chikara Shimizu, Charles A. StrottAbstract:Abstract As a result of an alternative exon 1, the gene for human Hydroxysteroid Sulfotransferase (SULTB1) encodes for two peptides differing only at their amino termini. The SULT2B1b isoform preferentially sulfonates cholesterol. Conversely, the SULT2B1a isoform avidly sulfonates pregnenolone but not cholesterol. The outstanding structural feature that distinguishes the SULT2B1 isoforms from the prototypical SULT2A1 isozyme is the presence of extended amino- and carboxyl-terminal ends in the former. Investigating the functional significance of this unique characteristic reveals that removal of 53 amino acids from the relatively long carboxyl-terminal end that is common to both SULT2B1 isoforms has no effect on the catalytic activity of either isoform. On the other hand, removal of 23 amino acids from the amino-terminal end that is unique to SULT2B1b results in loss of cholesterol Sulfotransferase activity, whereas removal of 8 amino acids from the amino-terminal end that is unique to SULT2B1a has no effect on pregnenolone Sulfotransferase activity. Deletion analysis along with site-directed mutagenesis of SULT2B1b reveal that the amino acid segment 19–23 residues from the amino terminus and particularly isoleucines at positions 21 and 23 are crucial for cholesterol catalysis. In the gene for SULT2B1, exon 1B encodes for only the unique amino-terminal region of SULT2B1b; however, exon 1A encodes for the unique amino-terminal end of SULT2B1a plus an additional 48 amino acids. Thus, if the gene forSULT2B1 employs exon 1B, cholesterol Sulfotransferase is synthesized, whereas if exon 1A is used, pregnenolone Sulfotransferase is produced.
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Cholesterol and Hydroxycholesterol Sulfotransferases: Identification, Distinction from Dehydroepiandrosterone Sulfotransferase, and Differential Tissue Expression
Endocrinology, 2001Co-Authors: Norman B. Javitt, Young C. Lee, Chikara Shimizu, Hirotoshi Fuda, Charles A. StrottAbstract:In humans, the biotransformation of cholesterol and its hydroxylated metabolites (oxysterols) by sulfonation is a fundamental process of great importance. Nevertheless, the Sulfotransferase enzyme(s) that carries out this function has never been clearly identified. Cholesterol is a relatively poor substrate for the previously cloned Hydroxysteroid Sulfotransferase (HST), i.e. dehydroepiandrosterone (DHEA) Sulfotransferase (HST1). Recently, cloning of a single human gene that encodes for two proteins related to HST1 was reported. These newly cloned Sulfotransferases (HST2a and HST2b), while exhibiting sequence similarity to other members of the soluble Sulfotransferase superfamily, also contain unique structural features. This latter aspect prompted an examination of their substrate specificity for comparison with HST1. Thus, HST1, HST2a, and HST2b were overexpressed as fusion proteins and purified. Furthermore, a novel procedure for the isolation of cholesterol and oxysterol sulfonates was developed that ...
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Testosterone Sulfotransferase: Evidence in the guinea pig that this reaction is carried out by 3α-Hydroxysteroid Sulfotransferase
Steroids, 1999Co-Authors: Byoung C. Park, Young C. Lee, Charles A. StrottAbstract:Abstract During the course of isolating, characterizing, and cloning estrogen and 3-Hydroxysteroid Sulfotransferases from the guinea pig adrenal gland, it was noted that cytosolic preparations from this tissue would also sulfonate testosterone. Therefore, we set out to isolate and clone the enzyme that performs this reaction. Testosterone Sulfotransferase (TST) was isolated from the guinea pig adrenal by using the standard procedures of ion exchange, affinity, and high-performance liquid chromatography. When purified, TST was examined by liquid-phase nondenaturing isoelectric focusing, it was found that the TST activity profile completely overlapped with the activity profile of the 3α-Hydroxysteroid Sulfotransferase (3αHST) isoform, but not the 3β-Hydroxysteroid Sulfotransferase (3βHST) isoform. This finding was further investigated by overexpressing the cDNAs for 3αHST and 3βHST in Escherichia coli and examining the expressed proteins for TST activity. This experiment confirmed that 3αHST does indeed function as a TST. In addition, 3αHST was also found to sulfonate estradiol but not estrone, a finding that further suggested that 3αHST may function as a general 17β-Hydroxysteroid Sulfotransferase.
Melissa Rungemorris - One of the best experts on this subject based on the ideXlab platform.
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regulation of glucocorticoid inducible Hydroxysteroid Sulfotransferase sult2a 40 41 gene transcription in primary cultured rat hepatocytes role of ccaat enhancer binding protein liver enriched transcription factors
Drug Metabolism and Disposition, 2005Co-Authors: Hai-lin Fang, Thomas A. Kocarek, Zhengbo Duanmu, Masumeh Abdolalipour, Jeffrey R. Smigelski, Amy Weckle, Melissa RungemorrisAbstract:The mechanism responsible for glucocorticoid receptor (GR)-mediated induction of rat hepatic Hydroxysteroid Sulfotransferase (SULT2A-40/41) gene transcription was investigated. We previously reported that the region of the SULT2A-40/41 5′-flanking region delimited by -158 to -77 nucleotides relative to the transcription start site was sufficient to support GR-inducible expression. This region of the SULT2A-40/41 gene does not contain a consensus glucocorticoid receptor-responsive element, but does contain two consensus sites for liver-enriched CCAAT/enhancer-binding protein (C/EBP) transcription factors. In the present study, incubation of primary cultured rat hepatocytes with a GR-activating concentration (10-7 M) of a potent glucocorticoid, dexamethasone or triamcinolone acetonide (TA), rapidly produced increases in C/EBPα and C/EBPβ nuclear protein contents, as measured by Western blot or in vitro DNA-binding activity analysis, that preceded increases in SULT2A-40/41 mRNA and protein levels. Transient cotransfection of SULT2A-40/41 reporter plasmids with a dominant negative C/EBP expression plasmid completely blocked TA-inducible SULT2A-40/41 reporter gene expression. Linker scanning and site-directed mutagenesis of the proximal SULT2A-40/41 5′-flanking region, complemented by in vitro DNA-binding analyses, indicated that the more distal C/EBP site was important for controlling SULT2A-40/41 promoter activity. These data support a role for GR-inducible C/EBPα and C/EBPβ expression in the transactivation of hepatic SULT2A-40/41 expression.
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regulation of rat hepatic Hydroxysteroid Sulfotransferase sult2 40 41 gene expression by glucocorticoids evidence for a dual mechanism of transcriptional control
Molecular Pharmacology, 1999Co-Authors: Melissa Rungemorris, Thomas A. KocarekAbstract:Glucocorticoid-inducible Hydroxysteroid Sulfotransferase (SULT2-40/41) gene transcription was investigated in primary cultured rat hepatocytes transiently transfected with a series of SULT2-40/41 5′-flanking region-luciferase reporter constructs, with emphasis on examining the functional role of an inverted repeat-0 nuclear receptor motif (IR0). Treatment of transfected cultures with any of four glucocorticoids activated luciferase expression from a construct containing 1938 base pairs (bp) of the SULT2-40/41 gene 5′-flanking sequence, whereas deletion of bp −227 to −158 (containing the IR0 motif) largely abolished the effect. On closer analysis, treatment of hepatocyte cultures with either of the potent glucocorticoids dexamethasone [strong cytochrome P-450 3A (CYP3A) inducer] or triamcinolone acetonide (weak CYP3A inducer) produced dose-dependent increases in luciferase activity when hepatocytes were transiently transfected with a construct containing as little as 158 bp of 5′-flanking sequence or containing a mutated IR0 motif. The dexamethasone dose-dependent increase in luciferase activity continued through a dose of 10−6 M when the transfected construct contained the IR0 motif, but was maximal at 10−7 M when the transfected construct lacked the IR0 motif. In contrast, triamcinolone acetonide-induced luciferase activity was maximal at a dose of 10−7 M, irrespective of the presence or absence of the IR0 motif. Coincubation of transfected hepatocytes with 10−8 M dexamethasone and the antiglucocorticoid RU486 inhibited luciferase expression. Luciferase induction by the prototypical CYP3A inducer pregnenolone 16α-carbonitrile was restricted to constructs containing the IR0 motif. These data suggest that glucocorticoid-inducible SULT2-40/41 gene expression occurs through a dual mechanism, whose components possibly involve the glucocorticoid receptor and the pregnane X receptor.