The human angiotensin II type 1 receptor+1166 A/C polymorphism attenuates MicroRNA-155 binding

The adverse effects of angiotensin II (Ang II) are primarily mediated through the Ang II type 1 receptor (AT(1)R). A silent polymorphism ( + 1166 A/C) in the human AT(1)R gene has been associated with cardiovascular disease, possibly as a result of enhanced AT(1)R activity. Because this polymorphism occurs in the 3'-untranslated region of the human AT(1)R gene, the biological importance of this mutation has always been questionable. Computer alignment demonstrated that the + 1166 A/C polymorphism occurred in a cis-regulatory site, which is recognized by a specific microRNA (miRNA), miR-155. miRNAs are non-coding RNAs that silence gene expression by base-pairing with complementary sequences in the 3'-untranslated region of target RNAs. When the + 1166 C-allele is present, base-pairing complementarity is interrupted, and the ability of miR-155 to interact with the cis-regulatory site is decreased. As a result, miR-155 no longer attenuates translation as efficiently as demonstrated by luciferase reporter and Ang II radioreceptor binding assays. In situ hybridization experiments demonstrated that mature miR-155 is abundantly expressed in the same cell types as the AT(1)R (e.g. endothelial and vascular smooth muscle). Finally, when human primary vascular smooth muscle cells were transfected with an antisense miR-155 inhibitor, endogenous human AT(1)R expression and Ang II-induced ERK1/2 activation were significantly increased. Taken together, our study demonstrates that the AT(1)R and miR-155 are co-expressed and that miR-155 translationally represses the expression of AT(1)R in vivo. Therefore, our study provides the first feasible biochemical mechanism by which the + 1166 A/C polymorphism can lead to increased AT(1)R densities and possibly cardiovascular disease.