Novel AT1R-Allosteric Ligands Mask the Preeclampsia Auto-antibody Epitope and Decrease Angiotensin-induced Vasoconstriction
Maternal blood pressure regulation by the hormone angiotensin II (AngII) sustains fetal growth through feto-placental circulation. AngII binding to orthosteric pocket in the angiotensin type 1 receptor (AT1R) induces G protein and {beta}-arrestin signaling. AT1R blocking drugs and {beta}-arrestin biased ligands also bind to the orthosteric pocket but evoke different inactive and active states1-6. AT1R-directed auto-antibodies observed in preeclampsia bound outside the orthosteric pocket to extracellular loop-2 (ECL2) of AT1R7-9. How auto-antibodies modulate AT1R activity causing preeclampsia pathogenesis is unknown. Here we report a druggable cryptic allosteric pocket encompassing the preeclampsia epitope on ECL2. Using structure based high-throughput small molecule screening we discovered 18 ligands specific for AT1Rs allosteric pocket. After procuring these ligands we validated inhibition of preeclampsia epitope-specific antibody binding. We characterize their inhibitory effect on antibody and AngII-signaling in cells and vasoconstriction ex vivo. These novel AT1R allosteric ligands, thus act as dual action negative modulators of auto-antibody action and vasoconstriction. Our study demonstrates that positive allosteric modulator action of auto-antibody causes a disease linked to AT1R. We anticipate our findings to kindle structure-based discovery of AT1R allosteric ligands for intervention in maladies such as preeclampsia7-10, rejection of organ transplants11, vasodilatory shock12, 13 and metabolic syndrome14.