Pregnane x receptor is a ligand-activated transcription element that regulates drug-inducible
Pregnane x receptor is a ligand-activated transcription element that regulates drug-inducible manifestation of several key cytochrome P450 enzymes and drug transporter proteins in liver and intestine inside a species-specific manner. gene activation in mouse hepatocytes. Conversely cyclic AMP-dependent protein kinase signaling has a repressive effect upon pregnane x receptor-mediated gene activation in rat and human being hepatocytes. We display that the human being pregnane x receptor protein can serve as an effective substrate for catalytically active cyclic AMP-dependent protein kinase shows that human being pregnane x receptor is present like a phosphoprotein and that activation of cyclic AMP-dependent protein kinase signaling modulates the phosphorylation status of pregnane x receptor. Activation of cyclic AMP-dependent protein kinase signaling also modulates the relationships of pregnane x receptor with protein cofactors. Our results define the species-specific effect of cyclic AMP-dependent protein kinase signaling on pregnane x receptor and provide a molecular explanation of cyclic AMP-dependent protein kinase-mediated repression of human being pregnane x receptor activity. Taken together our results identify a novel mode of rules of pregnane x receptor activity and focus on prominent functional variations in the process across varieties. The nuclear hormone receptor pregnane x receptor (PXR2; NR1I2) regulates drug-inducible gene manifestation in liver and intestine (1). BMS-794833 PXR is definitely BMS-794833 activated by a vast array of compounds including particular steroids and bile acids a plethora of naturally occurring compounds specific antibiotics antifungal medicines polychlorinated binphenyls organochloride pesticides and phenobarbital (PB) (2). The prototypical marker of PXR activation and best-characterized PXR target gene in mammals encodes particular members of the CYP3A family of cytochrome P450 (CYP) drug-metabolizing enzymes (3 4 It is now obvious that PXR-mediated gene BMS-794833 activation coordinately regulates a group of genes that encode CYP proteins and additional drug-metabolizing enzymes as well as drug transporter proteins in liver and intestine (5). Hence PXR-mediated gene activation generates profound up-regulation of the rate of metabolism transport and removal of potentially harmful chemicals including many steroids xenobiotics cholesterol metabolites and additional compounds from the body. Ligand-mediated activation of PXR happens inside a species-specific manner (6). Probably one of the most effective activators of human being PXR is the macrocyclic antibiotic rifampicin. Interestingly rifampicin does not appreciably activate mouse PXR. Conversely pregnenolone 16α-carbonitrile (PCN) is an efficacious activator of mouse PXR but offers only minimal effect on human being PXR. The species-specific induction of gene manifestation can be fully accounted for by development of the ligand-binding pocket of this nuclear receptor from mice to humans. We while others have shown this experimentally using novel lines of PXR knock-out mice crossed with additional novel lines of transgenic mice expressing the Rabbit polyclonal to ANKRD33. human being PXR protein (7-10). Although much is known concerning the identity of target genes and ligands for this nuclear receptor very little is known concerning the transmission transduction pathways that interface with the PXR protein. The primary target of intracellular cAMP is definitely cAMP-dependent protein kinase (PKA) (11). Several physiological stimuli such as β-adrenergic activation during fasting and caloric restriction as well as acute swelling produce raises in BMS-794833 the intracellular concentration of cAMP in BMS-794833 hepatocytes. The PKA transmission transduction pathway is also involved in the phosphorylation of target proteins through indirect connection with the classical mitogen-activated protein kinase signaling pathway (12). You will find conflicting reports in the literature regarding the effect of PKA signaling on drug-inducible and gene manifestation in hepatocytes. Using main ethnicities of rat hepatocytes Sidhu and Omiecinski (13) clearly shown that PB-mediated induction of and manifestation is definitely inhibited by treatment with cAMP analogues. Conversely the same laboratory reported that forskolin treatment generates increased manifestation of in rat hepatocytes; however induction was self-employed of cAMP and PKA signaling (14). The molecular basis for this difference was conclusively shown when two organizations individually found that.