Biased Agonists of the Type 1 Angiotensin II Receptor Promote Distinct Subcellular β-Arrestin Conformations.
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2025-10
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Abstract
G protein-coupled receptors (GPCRs) are central to cellular signaling and therapeutic targeting. Ligands that activate the same GPCR can selectively activate some signaling pathways over others, a phenomenon termed biased agonism. Additionally, the same ligand and receptor complex can elicit distinct signaling profiles in different subcellular locations (location bias). Here, we examine how various biased agonists influence the recruitment of β-arrestins 1 and 2 induced by the angiotensin II type 1 receptor at the receptor, plasma membrane, and early endosomes. We also assessed β-arrestin conformational states at the receptor and plasma membrane. Using split luciferase and BRET assays, we demonstrate that angiotensin II, its G protein-biased analogs (TRV055, TRV056), and its β-arrestin-biased analogs (TRV023, TRV026, TRV027, TRV034) functionally stratify into two clusters. G protein-biased agonists and AngII predominantly favor a receptor-β-arrestin core complex conformation driven by engagement of the β-arrestin finger loop with the receptor core. In contrast, β-arrestin-biased agonists promote a tail complex configuration of receptor-associated β-arrestins. However, the conformations of β-arrestins monitored at the plasma membrane were found to be unaffected by ligand bias. Furthermore, balanced and G protein-biased ligands induced higher levels of ERK activation in subcellular locations (nucleus, cytosol, and early endosomes) over the β-arrestin-biased ligands, but equal ERK activity at the plasma membrane. Our findings highlight the interplay between ligand and location biases in dictating GPCR signaling, revealing new insights into the molecular mechanisms driving selective signal propagation.
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Chundi, Anand, Uyen Pham, Srikrishna Darbha and Sudarshan Rajagopal (2025). Biased Agonists of the Type 1 Angiotensin II Receptor Promote Distinct Subcellular β-Arrestin Conformations. Biochemistry, 64(19). pp. 4206–4216. 10.1021/acs.biochem.4c00884 Retrieved from https://hdl.handle.net/10161/34346.
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Sudarshan Rajagopal
I am a physician-scientist with a research focus on G protein-coupled receptor signaling in inflammation and vascular disease and a clinical focus on pulmonary vascular disease, as I serve as Co-Director of the Duke Pulmonary Vascular Disease Center. My research spans the spectrum from clinical research in pulmonary vascular disease, to translational research in cardiovascular disease, to the basic science of receptor signaling.
Our basic science research focuses on understanding and untapping the signaling potential of G protein-coupled receptors (GPCRs) to regulate inflammation in vascular disease. GPCRs are the most common transmembrane receptors in the human genome (over 800 members) and are some of the most successful targets for drug therapies. While it has been known for some time that these receptors signal through multiple downstream effectors (such as heterotrimeric G proteins and multifunctional beta arrestin adapter proteins), over the past decade it has been better appreciated that these receptors are capable of signaling with different efficacies to these effectors, a phenomenon referred to as “biased agonism”. Ligands can be biased, by activating different pathways from one another, and receptors can be biased, by signaling to a limited number of pathways that are normally available to them. Moreover, this phenomenon also appears to be common to other transmembrane and nuclear receptors. While a growing number of biased agonists acting at multiple receptors have been identified, there is still little known regarding the mechanisms underlying biased signaling and its physiologic impact. We use multiple approaches to probe these signaling mechanisms, including in-house pharmacological assays, advanced phosphoproteomics and single cell RNA sequencing.
Our translational research is focused on studying signaling in different forms of pulmonary hypertension (PH), a disease of the pulmonary vasculature that results in right heart failure. We have identified novel molecular mechanisms that contribute to the development of pulmonary arterial hypertension (PAH), a disease of the pulmonary arterioles. We have also used single cell RNA sequencing to identify the cell types and signaling pathways that contribute to chronic thromboembolic pulmonary hypertension (CTEPH).
Lastly, our clinical research program focuses on the application of novel imaging technologies for diagnosis, prognosis and management of PH. Most notably, this includes the application of hyperpolarized Xenon MRI, in collaboration with Dr. Bastiaan Driehuys in the Department of Radiology, to characterizing the physiological basis of gas exchange and hemodynamic abnormalities across all forms of PH. In collaboration with Dr. Fawaz Alenezi, we have applied advanced echo approaches for the management of PH.
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