Adenosine deaminases acting on RNA modulate the expression of the human pregnane X receptor. (April 2021)

• Record Type: Journal Article
• Authors: Takemoto, Seiya; Nakano, Masataka; Nozaki, Kaori; Fukami, Tatsuki; Nakajima, Miki
• Is Part Of: Drug metabolism and pharmacokinetics. Volume 37(2021)
• Publication Date: 2021-04
• Subjects: Drug metabolism -- A-to-I RNA editing -- Post-transcriptional regulation -- Nuclear receptor -- Cytochrome P450; ADAR adenosine deaminase acting on RNA -- A-to-I adenosine-to-inosine -- CAR constitutive androstane receptor -- C/EBP CCAAT/enhancer binding proteins -- CYP3A4 cytochrome P450 3A4 -- DR3 direct repeat separated by three nucleotides -- dsRNA double-stranded RNA -- ER6 everted repeat separated by six nucleotide -- HNF hepatocyte nuclear factors -- LCA lithocholic acid -- miRNA microRNA -- PCR polymerase chain reaction -- PXR pregnane X receptor -- RT-PCR reverse-transcription PCR -- RXRα retinoid X receptor α -- siADAR siRNA for human ADAR -- siControl siRNA for negative control -- siPXR siRNA for human PXR -- siRNA small interfering RNA -- TBP TATA box binding protein -- UGT UDP-glucuronosyltransferase -- 3′-UTR 3′-untranslated region; Drugs -- Metabolism -- Periodicals; Pharmacokinetics -- Periodicals; 615.7
• DOI: 10.1016/j.dmpk.2020.11.002
• Languages: English
• ISSNs: 1347-4367

Abstract

Abstract: The pregnane X receptor (PXR) is one of the major transcription factors that regulate the expression of different drug-metabolizing enzymes and transporters. Adenosine-to-inosine RNA editing, the most frequent nucleotide conversion on RNA, which is catalyzed by adenosine deaminase acting on RNA (ADAR) enzymes, may modulate gene expression and function. Here, we investigated the potential regulation of human PXR expression by adenosine-to-inosine RNA editing. Knockdown of ADAR1 increased PXR mRNA level, and the knockdown of ADAR1 or ADAR2 significantly increased PXR protein level in HepaRG cells. In HepG2 cells, the knockdown of ADAR1 or ADAR2 significantly increased PXR mRNA and protein levels. The increase in the PXR protein by ADAR1 knockdown resulted in increased cytochrome P450 3A4 (CYP3A4) transactivity and CYP3A4 and UDP-glucuronosyltransferase 1A1 (UGT1A1) expression. A reporter assay revealed that the 3′-untranslated region (UTR) of PXR mRNA, especially from +3371 to +3440, is responsible for the ADAR-mediated post-transcriptional control of PXR expression, despite the lack of RNA edited sites in this region. Collectively, we found that PXR is negatively regulated by ADAR1 via an indirect mechanism, which facilitates the degradation of PXR mRNA. We could demonstrate that ADAR1 can cause interindividual variability in hepatic drug metabolism potencies.