The research of the Rajagopal lab 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.
Much of our research focuses on the chemokine system, which consists of approximately twenty receptors and fifty ligands that display considerable promiscuity with each other in the regulation of immune cell function in inflammatory diseases. Research from our group and others have shown that many of these ligands act as biased agonists when signaling through the same receptor. We use models of inflammation such as contact hypersensitivity and pulmonary arterial hypertension (PAH). PAH is a disease of the pulmonary arterioles that results in right heart failure and most of its treatments target signaling by GPCRs. We use multiple approaches to probe these signaling mechanisms, including in-house pharmacological assays, advanced phosphoproteomics and single cell RNA sequencing.
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