Rat Pregnane X Receptor: Molecular Cloning, Tissue Distribution, and Xenobiotic Regulation

Zhang, He; LeCulyse, Edward; Liu, Lan; Hu, Maowen; Matoney, Lynn; Zhu, Weizhu; Yan, Bingfang

doi:10.1006/abbi.1999.1307

Cited by 177 publications

(118 citation statements)

References 32 publications

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“…2 and 4) at the doses given, suggesting that Oatp2 is a target of the recently cloned rat PXR (rPXR-1). 43 That PCN appears to be a more effective inducer of Oatp2 than PB further implicates the PXR pathway in activation of the Oatp2 gene, because PCN is a much more potent and efficacious ligand of mouse PXR as compared with PB. 42 However, the fact that PB also activates the CAR pathway leaves open the possibility that both the PXR-and CAR-mediated pathways are involved in the response of Oatp2 to PCN and PB.…”

Section: Discussionmentioning

confidence: 99%

Differential effects of microsomal enzyme–inducing chemicals on the hepatic expression of rat organic anion transporters, OATP1 and OATP2

Rausch‐Derra

2001

Hepatology

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The organic anion transporting polypeptides, Oatp1 (Slc21a1) and Oatp2 (Slc21a5), mediate hepatic uptake of cardiac glycosides. Previously, we demonstrated that chemicals that increase cytochrome P450s differentially affect hepatic uptake of cardiac glycosides. We postulated that increased uptake of cardiac glycosides observed after pretreatment of animals with phenobarbital (PB) and pregnenolone-16␣-carbonitrile ( Hepatic clearance and biliary excretion of drugs and their metabolites can occur through passive transport or through active transport (carrier-mediated) systems. Previous studies from this laboratory described a phenomenon in which pretreatment of animals with chemicals known to differentially increase specific microsomal cytochrome P450 enzymes also enhanced both hepatic plasma clearance and biliary excretion of a number of choleophiles, including cardiac glycosides. [1][2][3][4] Specifically, pretreatment of rats with two compounds known classically to activate CYP2B and CYP3A transcription, the barbiturate phenobarbital (PB) and the synthetic steroid pregenenolone-16␣-carbonitrile (PCN), respectively, resulted in the decreased plasma half-life, increased hepatic clearance, and decreased toxicity of cardiac glycosides. In contrast, pretreatment of rats with chemicals known to act through the aryl hydrocarbon receptor resulted in a slight suppression of cardiac glycoside plasma clearance by the liver. 2 Further studies demonstrated that PCN increased the maximal velocity and affinity of ouabain uptake into hepatocytes, 3 suggesting that this chemical altered the hepatocellular capacity and affinity for choleophilic substrates. In subsequent studies, an energydependent, Na ϩ -independent carrier-mediated transport system for ouabain was identified. This Na ϩ -independent transport system was sensitive to inhibition by neutral (e.g., digoxin), acidic (e.g., taurocholate), and basic (e.g., quinine) compounds. 4 Together, these findings suggested that a multispecific, Na ϩ -independent hepatic transport system existed, which could be positively modulated by microsomal enzymeinducing chemicals, specifically PB and PCN.Since these earlier reports, 1-4 specific mediators of this hepatic Na ϩ -independent transport system have been cloned and characterized, and consist of several members of the rat organic anion transporting polypeptide (Oatp) family. The primary forms expressed in rat liver include, Oatp1 (gene symbol: Slc21a1), Oatp2 (Slc21a5), and liver-specific transporter 1 (rlst-1) or Oatp4 (Slc21a10). In rat liver, the organic anion transporting polypeptides, Oatp1, 5 Oatp2, 6,7 and rlst-1/ Oatp4, 8-10 transport a number of conjugated and unconjugated xenobiotics and endobiotics in a charge-independent manner. The substrates for this family of transporters include: the cardiac glycosides, the statin class of lipid-lowering drugs, human immunodeficiency virus-protease inhibitors, bile acids, eicosanoids, thyroid hormone and thyroid hormone conjugates, steroid hormone conjugates, and numerous peptidede...

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Section: Discussionmentioning

confidence: 99%

Differential effects of microsomal enzyme–inducing chemicals on the hepatic expression of rat organic anion transporters, OATP1 and OATP2

Rausch‐Derra

2001

Hepatology

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“…In case of human and rat, three main bands have been previously reported in experiments utilizing in vitro transcription-translation approach. Of the three bands reported, one was larger and the other was smaller in size with respect to the major 50-51 kDa band [1,24]. Recently, in case of another nuclear hormone receptor, i.e., human GR, eight isoforms for GR have been reported [15,16].…”

Section: Fig 8 (A)mentioning

confidence: 97%

Purification of full-length human Pregnane and Xenobiotic Receptor: polyclonal antibody preparation for immunological characterization

et al. 2005

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Pregnane and Xenobiotic Receptor (PXR; or Steroid and Xenobiotic Receptor, SXR), a new member of the nuclear receptor superfamily, is thought to modulate a network of genes that are involved in xenobiotic metabolism and elimination. To further explore the role of PXR in body's homeostatic mechanisms, we for the first time, report successful prokaryotic expression and purification of full-length PXR and preparation of polyclonal antibody against the whole protein. The full-length cDNA encoding a 434 amino acids protein was sub-cloned into prokaryotic expression vector, pET-30b and transformed into E. coli BL21(DE3) cells for efficient over expression. The inclusion body fraction, containing the expressed recombinant protein, was purified first by solubilizing in sarcosine extraction buffer and then by affinity column chromatography using Ni-NTA His-Bind matrix. The efficacy of anti-PXR antibody was confirmed by immunocytology, Western blot analysis, EMSA and immunohistochemistry. The antibody obtained was capable of detecting human and mouse PXR with high specificity and sensitivity. Immunofluorescence staining of COS-1 cells transfected with human or mouse PXR showed a clear nuclear localization. Results from immunohistochemistry showed that level of PXR in liver sections is immunologically detectable in the nuclei. Similar to exogenously transfected PXR, Western blot analysis of cell extract from HepG2 and COLO320DM cells revealed a major protein band for endogenous PXR having the expected molecular weight of 50 kDa. Relevance of other immunodetectable bands with reference to PXR isoforms and current testimony are evaluated. Advantages of antibody raised against full-length PXR protein for functional characterization of receptor is discussed and its application for clinical purposes is envisaged.

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“…1-4) support a novel mechanism for SNURF-mediated coactivation of ER␣. We recently showed that the N-terminal region of SNURF (amino acids [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] is required for nonspecific DNA binding (95), and deletion of this domain also resulted in loss of ER␣ coactivation (Fig. 4A).…”

Section: Fig 4 Multiple Regions On Snurf Are Required For Coactivatmentioning

confidence: 99%

“…The orphan pregnane (steroid) X receptor, constitutive androstane receptor, and peroxisome proliferator-activated receptor ␣ bind structurally diverse steroidal compounds, drugs, and xenobiotics and induce members of the CYP2, CYP3, and CYP4 family of P450 isoenzymes (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). NRs share common structural features or domains, and these have been extensively characterized for most ligand-activated NRs (1)(2)(3)(4)(5)(6).…”

mentioning

confidence: 99%

Cooperative Coactivation of Estrogen Receptor α in ZR-75 Human Breast Cancer Cells by SNURF and TATA-binding Protein

Saville

Poukka

Wormke

et al. 2002

Journal of Biological Chemistry

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SNURF is a small RING finger protein that binds the zinc finger region of steroid hormone receptors and enhances Sp1-and androgen receptor-mediated transcription in COS and CV-1 cells. In this study, we show that SNURF coactivates both wild-type estrogen receptor ␣ (ER␣) (4-fold)-and HE19 (ER␣ deletion of activation function 1 (AF1)) (210-fold)-mediated activation of an estrogen-responsive element promoter in ZR-75 cells. In mammalian two-hybrid assays in ZR-75 cells SNURF interactions were estrogen (E2)-dependent and were not observed with the antiestrogen ICI 182,780. ER␣ interacted with multiple regions of SNURF; SNURF interactions with ER␣ were dependent on AF2, and D538N, E542Q, and D545N mutations in helix 12 abrogated both SNURF-ER␣ binding and coactivation. Moreover, peptide fusion proteins that inhibit interactions between helix 12 of ER␣ with LXXLL box-containing proteins also blocked ER␣ coactivation by SNURF. However, cotransfection of SNURF with prototypical steroid receptor coactivators 1, 2, and 3 that contain LXXLL box motifs did not enhance E2 responsiveness, whereas TATA-binding protein (TBP) and SNURF cooperatively coactivated ER␣-mediated transactivation. The results are consistent with a unique model for cooperative coactivation of ER␣ that requires ligand binding, repositioning of helix 12, recruitment of TBP, and interaction with SNURF, which binds both ER␣ and TBP. The nuclear receptor (NR)1 superfamily of transcription factors includes the steroid/thyroid hormone, retinoid, and vitamin D receptors and a growing number of orphan receptors for which endogenous ligands have not yet been identified (1-6). The orphan pregnane (steroid) X receptor, constitutive androstane receptor, and peroxisome proliferator-activated receptor ␣ bind structurally diverse steroidal compounds, drugs, and xenobiotics and induce members of the CYP2, CYP3, and CYP4 family of P450 isoenzymes (7-19). NRs share common structural features or domains, and these have been extensively characterized for most ligand-activated NRs (1-6). For example, the two forms of the estrogen receptor (ER␣ and ER␤) contain a highly conserved DNA binding domain C (DBD) (97% homology for human ERs) in the central portion of both proteins (20 -23). Similarities between the DBDs of NRs are due to their zinc finger motifs, which directly bind DNA; however, despite these similarities, subtle structural differences are important for sequence-specific interactions of these transcription factors (2). The N-terminal and C-terminal domains (A/B and E/F for the ER) of NRs contain activation function 1 (AF1) and AF2, respectively, and the ligand binding domain is also located in AF2. The expression and functions of AF1/AF2 are highly variable among NRs; however, for some NRs, such as the androgen receptor (AR), both domains interact to enhance transcriptional activation.Several different classes of proteins interact with NRs to enhance or inhibit their activity as trans-acting factors, and these interacting proteins include coactivators, cointegrato...

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Rat Pregnane X Receptor: Molecular Cloning, Tissue Distribution, and Xenobiotic Regulation

Cited by 177 publications

References 32 publications

Differential effects of microsomal enzyme–inducing chemicals on the hepatic expression of rat organic anion transporters, OATP1 and OATP2

Differential effects of microsomal enzyme–inducing chemicals on the hepatic expression of rat organic anion transporters, OATP1 and OATP2

Purification of full-length human Pregnane and Xenobiotic Receptor: polyclonal antibody preparation for immunological characterization

Cooperative Coactivation of Estrogen Receptor α in ZR-75 Human Breast Cancer Cells by SNURF and TATA-binding Protein

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