Molecular structure and expression of rat bradykinin B2 receptor gene. Evidence for alternative splicing.
Bradykinin is a potent vasodilatory peptide hormone involved in a broad range of physiological actions. While it acts through at least two types of receptors which are named B1 and B2, most of its effects are mediated via activation of the B2 receptor. The gene for this receptor was isolated from a rat genomic library and shown to span more than 28 kilobases, including four introns. The relative positions of the exons were mapped and all exons, intron-exon boundaries, and 5'- and 3'-flanking regions were sequenced. While the 5'-untranslated region of the mRNA is distributed on all four exons, the coding and the 3'-untranslated region are located entirely on the fourth exon. Characterization of the region upstream to the transcriptional start site detected by primer extension analysis shows that the bradykinin B2 receptor promoter contains no typical TATA or CCAAT boxes. Nevertheless, the promoter sequence was shown to be functional in NG108-15 cells transfected with a construct bearing 1.1 kilobases of 5'-flanking sequence fused to a luciferase reporter gene. Reverse transcription-polymerase chain reaction analysis detected two different bradykinin B2 receptor mRNAs containing or lacking exon 3 in all rat tissues tested, providing evidence for alternative splicing of the 5'-untranslated sequence.