Abstract
The bradykinin B1 receptor (BKB1R) gene is expressed in selected tissues such as lung and kidney. In these tissues it is expressed at a very low level until induced by inflammatory mediators. Our aim has been to understand the mechanism of this regulatory process. A human BKB1R minigene was constructed. It contained a 1.8 kb promoter, the entire exon I, 1.5 kb of intron I, the entire exon II and intron II, and the luciferase gene as a reporter. Transient transfection of the minigene into SV40‐transformed IMR90 cells (IMRSV) resulted in a promoter activity which was activated by the mediators, lipopolysaccharide and (LPS) desArg^10^‐kallidin. In contrast, these mediators did not induce the activity of the 1.8 kb promoter construct alone. Thus, motifs exclusive of the promoter such as 5′‐UTR and/or intron regions are required for mediator‐induced expression of this gene. Promoter activities of both the minigene and the 1.8 kb promoter construct were enhanced in a dose‐dependent manner upon cotransfection with c‐Jun. Furthermore, cotransfecting c‐Jun with the minigene achieved the maximal promoter activity with no further increase in response to mediators. Conversely, the induction of the minigene promoter activity by mediators was abolished upon cotransfection with a dominant negative mutant of c‐Jun. Other experiments suggest that multiple AP‐1 sites are interactive with the c‐Jun upregulation of this gene. Taken together, these results point to c‐Jun as a key intermediary in the activation of the expression of this gene by mediators. However, participation of motifs outside of the promoter are necessary to obtain this inducible expression. J. Cell. Biochem. 82: 163–170, 2001. © 2001 Wiley‐Liss, Inc.