1996 Volume 19 Issue 4 Pages 271-279
The rat angiotensin II type 2 receptor (AT2-R) gene was isolated, and cis-regulatory regions in its 5"- flanking area were analyzed. Primer extension and RNase protection analyses revealed a single transcriptional initiation site at the position 24bp downstream of the TATA box. The 5′-flanking region of AT2-R contained several cis-regulatory elements, such as AP-1, AP-2, C/EBP, NF-1, NF-IL6, NE-κB, and glucocorticoid- and cAMP-responsive elements (CRE). The treatment of PC12 cells with dibutyryl cAMP caused a marked decrease (90%) in the AT2-R mRNA level, which was blocked by the inhibitor of protein kinase A and did not require new protein synthesis. The protein level was also reduced 84% after a 24-h exposure to cAMP and the binding affinity was unchanged. The half-life of the AT2-R mRNA decreased -66% by cAMP as compared with control (18.4±0.4h). Deletion and mutation analyses of the 5′-flanking region (1.2Kb) revealed that there were one negative (-1, 199 to -739) and two positive cis-regulatory regions (-739 to -436 and -59 to +45), and that the CRE motif located at -426 repressed (-23%) the promoter activity of the rat AT2-R gene. The region between -59 and +45 containing TATA box and AP-2 site accounted for 70% of the promoter activity. These findings indicate that the promoter activity of the rat AT2-R gene is modulated by several cis-regulatory regions and that cAMP markedly downregulates the expression of the AT2-R mainly by inducing AT2-R mRNA destabilization rather than CRE-mediated inhibition of the gene transcription. Thus, humoral factors that transduce cAMP as an intracellular signal may modulate AT2-R-mediated function of Ang II by reducing AT2-R expression. (Hypertens Res 1996; 19: 271-279)
