Angiotensin II type 2 (AT(2)R) or bradykinin B-2 (B2R) receptor activation enhances NO production. Recently, we demonstrated enhancement of NO production when AT(2)R and B2R are simultaneously activated in vivo. However, the mechanism involved in this enhancement is unknown. Using confocal fluorescence resonance energy transfer microscopy, we report the distance between the AT(2)R and B2R in PC12W cell membranes to be 50 +/- 5 angstrom, providing evidence and quantification of receptor heterodimerization as the mechanism for enhancing NO production. The rate of AT(2)R-B2R heterodimer formation is largely a function of the degree of AT(2)R-B2R expression. The physical association between the dimerized receptors initiates changes in intracellular phosphoprotein signaling activities leading to phosphorylation of c-Jun terminal kinase, phosphotyrosine phosphatase, inhibitory protein kappa B alpha, and activating transcription factor 2; dephosphorylation of p38 and p42/44 mitogen-activated protein kinase and signal transducer inhibitor of transcription 3; and enhancing production of NO and cGMP. Controlling the expression of AT(2)R-B2R, consequently influencing their biologically active dimerization, presents a potential therapeutic target for the treatment of hypertension and other cardiovascular and renal disorders.
