Structure-Guided Analysis of Mechanisms of AT1R Functions



 DESCRIPTION (provided by applicant): The AngII type 1 receptor (AT1R) is widely known to be the master regulator of normal cardiovascular physiology. In a variety of diseases chronic stimulation of AT1R causes organ damage due to AngII-induced abnormal growth, adhesion, migration and inflammatory gene expression in cells. AT1R blockers (ARBs) effectively control hypertension but their efficacy in preventing organ damage varies widely due to unknown mechanism. Efforts have been made in several laboratories to elucidate the molecular basis of pleotropic AT1R signaling process. We have focused our research on structure, conformation and pharmacological mechanisms governing AT1R. We were the first to show ligand-independent and biased signaling in AT1R, leading to the concept of ligand modulation of subset of AT1R functions. We have recently elucidated first 3D-structure of an ARB-bound human AT1R, as an important step for beginning structure-based studies of this antihypertensive drug-target. With this new knowledge, we will address unresolved questions including: (i) how functional efficacy of clinically used drugs targeting AT1R is determined by different ligand sub-pockets within the receptor? (ii) How does a putative filamin-A binding motif embedded in AT1R operates in regulating cytoskeletal dynamics and cell adhesion properties? (iii) What aspect of activation and regulation of AT1R functions is altered by naturally occurring structural variations in AT1R? Our preliminary studies provide insight regarding (i) AT1R-ligand sub-pockets influencing differential efficacies of ARBs; (ii) AngII-induced engagement of filamin by AT1R which may be a novel pathway leading to adhesion- dependent cell functions; and (iii) possible structural effects of human AT1R variants naturally occurring in population. Our specific goals for this application are: (Aim 1) to test the hypothesis that efficacy of structuraly different ARBs in clinical practice is determined by different ligand sub-pockets found in the AT1R 3D-structure. (Aim 2) to test the hypothesis that AngII-induced AT1R interaction with filamin is regulated by a novel protein- protein interaction mechanism. (Aim 3) to test the hypothesis that AT1R variants reported in human population studies alter coupling between functional domains. We will use state-of-the-art molecular, biophysical, cell biology and in vivo techniques in our preclinical studies to advance our understanding of long unresolved issues in AT1R biology. Our findings are easily translatable to the clinic and may facilitate the development of novel therapeutics.