Novel kinin B₁ receptor splice variant and 5'UTR regulatory elements are responsible for cell specific B₁ receptor expression.

Abstract

The kinin B₁ receptor (B₁R) is rapidly upregulated after tissue trauma or inflammation and is involved in cancer and inflammatory diseases such as asthma. However, the role of the: promoter; a postulated alternative promoter; and spliced variants in airway epithelial and other lung cells are poorly understood. We identified, in various lung cell lines and leucocytes, a novel, naturally occurring splice variant (SV) of human B₁R gene with a shorter 5'untranslated region. This novel SV is ≈35% less stable than the wild-type (WT) transcript in lung adenocarcinoma cells (H2126), but does not influence translation efficiency. Cell-specific differences in splice variant expression were observed post des[Arg10]-kallidin stimulation with delayed upregulation of SV compared to WT suggesting potentially different regulatory responses to inflammation. Although an alternative promoter was not identified in our cell-lines, several cell-specific regulatory elements within the postulated alternative promoter region (negative response element (NRE) -1020 to -766 bp in H2126; positive response element (PRE) -766 to -410 bp in 16HBE; -410 to +1 region acts as a PRE in H2126 and NRE in 16HBE cells) were found. These findings reveal complex regulation of B₁R receptor expression in pulmonary cells which may allow future therapeutic manipulation in chronic pulmonary inflammation and cancer.