SAT-033 Studying Cell-Context Specific Effects on the Function of the AT1R in iPSCs and Their Differentiated Derivatives

Abstract

Cardiovascular homeostasis is tightly regulated by numerous neurohormonal mediators such as the renin-angiotensin system which plays an important role in the maintenance of blood pressure. Central to this system is the peptide hormone angiotensin II (Ang II) whose signals are transduced via the AT1 receptor (AT1R), an important member of the superfamily of G protein-coupled receptors (GPCRs). Ang II binding results in receptor activation characterized by structural re-arrangements within the receptor structure and the subsequent activation of its cognate G protein partners. GPCRs are allosteric in nature and their biological activity is highly dependent on the cell context in which they are expressed1. Changes in the cellular background such as the differential availability of G proteins and effector molecules including putative dimer partners can affect receptor conformation and function. As such, we are interested in understanding how AT1R conformation and signaling are modulated by the cell context in which it is expressed1. In the past, studies that aimed at understanding signaling downstream of GPCRs mostly relied on heterologous expression systems such as HEK 293 cells because of their ease of culture. Such studies led to a ‘one size fits all’ notion that our findings could be reasonably extrapolated to guide drug discovery platforms relevant for human disease. However, it is clear that with the high rate of drug attrition, we need more physiologically relevant cellular models for studies of molecular signal transduction events to be translatable. With this in mind, we are generating iPSCs that stably express a panel of conformation-sensitive biosensors that reliably report on the conformational changes in the AT1R1,2. Our biosensors use resonance energy transfer between a bioluminescent donor and a fluorescent acceptor (FlAsH) where agonist-mediated conformational changes can be recorded1. Here, we will investigate how the conformation of the AT1R changes when expressed in AT1R-relevant cell types such as iPSC-derived cardiomyocytes and vascular smooth muscle cells. We will investigate how our conformational profiles differ in different iPSC-derived cell types in response to AT1R-specific agonists. Our goal is to gain a better mechanistic understanding of how cells are differentially wired leading to cell-specific conformational and signaling responses. We hope our results can guide rational drug design to better target the AT1R and other GPCRs. 1Devost D., et al (2017). Journal of Biological Chemistry, jbc-M116. 2Pei Y., et al (2015). Scientific reports, 5, 9205.