Browsing by Author "Choi, Issac"

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    Beta-Arrestins and Receptor Signaling in the Vascular Endothelium.
    (Biomolecules, 2020-12-23) Lee, Claudia; Viswanathan, Gayathri; Choi, Issac; Jassal, Chanpreet; Kohlmann, Taylor; Rajagopal, Sudarshan
    The vascular endothelium is the innermost layer of blood vessels and is a key regulator of vascular tone. Endothelial function is controlled by receptor signaling through G protein-coupled receptors, receptor tyrosine kinases and receptor serine-threonine kinases. The β-arrestins, multifunctional adapter proteins, have the potential to regulate all of these receptor families, although it is unclear as to whether they serve to integrate signaling across all of these different axes. Notably, the β-arrestins have been shown to regulate signaling by a number of receptors important in endothelial function, such as chemokine receptors and receptors for vasoactive substances such as angiotensin II, endothelin-1 and prostaglandins. β-arrestin-mediated signaling pathways have been shown to play central roles in pathways that control vasodilation, cell proliferation, migration, and immune function. At this time, the physiological impact of this signaling has not been studied in detail, but a deeper understanding of it could lead to the development of novel therapies for the treatment of vascular disease.
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    Biased agonists of the chemokine receptor CXCR3 differentially signal through Gαi:β-arrestin complexes.
    (Science signaling, 2022-03-22) Zheng, Kevin; Smith, Jeffrey S; Eiger, Dylan S; Warman, Anmol; Choi, Issac; Honeycutt, Christopher C; Boldizsar, Noelia; Gundry, Jaimee N; Pack, Thomas F; Inoue, Asuka; Caron, Marc G; Rajagopal, Sudarshan
    G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors and signal through the proximal effectors, G proteins and β-arrestins, to influence nearly every biological process. The G protein and β-arrestin signaling pathways have largely been considered separable; however, direct interactions between Gα proteins and β-arrestins have been described that appear to be part of a distinct GPCR signaling pathway. Within these complexes, Gαi/o, but not other Gα protein subtypes, directly interacts with β-arrestin, regardless of the canonical Gα protein that is coupled to the GPCR. Here, we report that the endogenous biased chemokine agonists of CXCR3 (CXCL9, CXCL10, and CXCL11), together with two small-molecule biased agonists, differentially formed Gαi:β-arrestin complexes. Formation of the Gαi:β-arrestin complexes did not correlate well with either G protein activation or β-arrestin recruitment. β-arrestin biosensors demonstrated that ligands that promoted Gαi:β-arrestin complex formation generated similar β-arrestin conformations. We also found that Gαi:β-arrestin complexes did not couple to the mitogen-activated protein kinase ERK, as is observed with other receptors such as the V2 vasopressin receptor, but did couple with the clathrin adaptor protein AP-2, which suggests context-dependent signaling by these complexes. These findings reinforce the notion that Gαi:β-arrestin complex formation is a distinct GPCR signaling pathway and enhance our understanding of the spectrum of biased agonism.