Mouse OCTN2 is directly regulated by peroxisome proliferator-activated receptor alpha (PPARalpha) via a PPRE located in the first intron.
Recent studies provided strong evidence to suggest that organic cation transporter 2 (OCTN2) is a direct target gene of peroxisome proliferator-activated receptor alpha (PPARalpha). However, subsequent studies failed to demonstrate a functional peroxisome proliferator response element (PPRE) in the promoter region of the OCTN2 gene. In the present study we hypothesized that the OCTN2 gene is transcriptionally induced by PPARalpha via a functional PPRE located in the first intron. In silico-analysis of the first intron of mouse OCTN2 revealed 11 putative PPRE with high similarity to the consensus PPRE. In addition, reporter gene assays using a mouse OCTN2 intron reporter construct containing a cluster of three partially overlapping PPRE (PPREint-1-8-10) revealed a marked response to exogenous mouse PPARalpha/RXRalpha and subsequent stimulation with PPARalpha agonist WY-14,643. Introduction of a selective mutation in either PPRE8 or PPRE10 in the PPREint-1-8-10 reporter constructs caused a substantial loss of the responsiveness to PPARalpha activation, but a selective mutation in PPRE1 resulted in a complete loss of responsiveness to PPARalpha activation. Moreover, gel shift assays revealed binding of PPARalpha/RXRalpha heterodimer to the PPRE1 of mouse OCTN2 first intron. In conclusion, the present study shows that mouse OCTN2 is a direct target gene of PPARalpha and that transcriptional upregulation of OCTN2 by PPARalpha is likely mediated via PPRE1 in its first intron.
Wen
Gaiping
G
Institute of Agricultural and Nutritional Sciences, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 2, 06120 Halle (Saale), Germany.
Ringseis
Robert
R
Eder
Klaus
K
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D007438:Introns; D008113:Liver Neoplasms; D051379:Mice; D027701:Organic Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D047493:PPAR alpha / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D020218:Response Elements / Q000235:genetics*; D000074058:Solute Carrier Family 22 Member 5; D015533:Transcriptional Activation; D015854:Up-Regulation
D027701:Organic Cation Transport Proteins; D047493:PPAR alpha; C492019:Slc22a5 protein, mouse; D000074058:Solute Carrier Family 22 Member 5