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Pharmacological Reviews Jul 2017The visual/-arrestins, a small family of proteins originally described for their role in the desensitization and intracellular trafficking of G protein-coupled receptors... (Review)
Review
The visual/-arrestins, a small family of proteins originally described for their role in the desensitization and intracellular trafficking of G protein-coupled receptors (GPCRs), have emerged as key regulators of multiple signaling pathways. Evolutionarily related to a larger group of regulatory scaffolds that share a common arrestin fold, the visual/-arrestins acquired the capacity to detect and bind activated GPCRs on the plasma membrane, which enables them to control GPCR desensitization, internalization, and intracellular trafficking. By acting as scaffolds that bind key pathway intermediates, visual/-arrestins both influence the tonic level of pathway activity in cells and, in some cases, serve as ligand-regulated scaffolds for GPCR-mediated signaling. Growing evidence supports the physiologic and pathophysiologic roles of arrestins and underscores their potential as therapeutic targets. Circumventing arrestin-dependent GPCR desensitization may alleviate the problem of tachyphylaxis to drugs that target GPCRs, and find application in the management of chronic pain, asthma, and psychiatric illness. As signaling scaffolds, arrestins are also central regulators of pathways controlling cell growth, migration, and survival, suggesting that manipulating their scaffolding functions may be beneficial in inflammatory diseases, fibrosis, and cancer. In this review we examine the structure-function relationships that enable arrestins to perform their diverse roles, addressing arrestin structure at the molecular level, the relationship between arrestin conformation and function, and sites of interaction between arrestins, GPCRs, and nonreceptor-binding partners. We conclude with a discussion of arrestins as therapeutic targets and the settings in which manipulating arrestin function might be of clinical benefit.
Topics: Animals; Arrestin; Humans; Models, Molecular; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestins
PubMed: 28626043
DOI: 10.1124/pr.116.013367 -
Nature Communications Nov 2022Communication across membranes controls critical cellular processes and is achieved by receptors translating extracellular signals into selective cytoplasmic responses....
Communication across membranes controls critical cellular processes and is achieved by receptors translating extracellular signals into selective cytoplasmic responses. While receptor tertiary structures can be readily characterized, receptor associations into quaternary structures are challenging to study and their implications in signal transduction remain poorly understood. Here, we report a computational approach for predicting receptor self-associations, and designing receptor oligomers with various quaternary structures and signaling properties. Using this approach, we designed chemokine receptor CXCR4 dimers with reprogrammed binding interactions, conformations, and abilities to activate distinct intracellular signaling proteins. In agreement with our predictions, the designed CXCR4s dimerized through distinct conformations and displayed different quaternary structural changes upon activation. Consistent with the active state models, all engineered CXCR4 oligomers activated the G protein Gi, but only specific dimer structures also recruited β-arrestins. Overall, we demonstrate that quaternary structures represent an important unforeseen mechanism of receptor biased signaling and reveal the existence of a bias switch at the dimer interface of several G protein-coupled receptors including CXCR4, mu-Opioid and type-2 Vasopressin receptors that selectively control the activation of G proteins vs β-arrestin-mediated pathways. The approach should prove useful for predicting and designing receptor associations to uncover and reprogram selective cellular signaling functions.
Topics: Arrestins; beta-Arrestins; Signal Transduction; Receptors, G-Protein-Coupled; GTP-Binding Proteins
PubMed: 36369272
DOI: 10.1038/s41467-022-34382-7 -
Nature Communications Dec 2023Serotonergic psychedelics possess considerable therapeutic potential. Although 5-HT receptor activation mediates psychedelic effects, prototypical psychedelics activate...
Serotonergic psychedelics possess considerable therapeutic potential. Although 5-HT receptor activation mediates psychedelic effects, prototypical psychedelics activate both 5-HT-Gq/11 and β-arrestin2 transducers, making their respective roles unclear. To elucidate this, we develop a series of 5-HT-selective ligands with varying Gq efficacies, including β-arrestin-biased ligands. We show that 5-HT-Gq but not 5-HT-β-arrestin2 recruitment efficacy predicts psychedelic potential, assessed using head-twitch response (HTR) magnitude in male mice. We further show that disrupting Gq-PLC signaling attenuates the HTR and a threshold level of Gq activation is required to induce psychedelic-like effects, consistent with the fact that certain 5-HT partial agonists (e.g., lisuride) are non-psychedelic. Understanding the role of 5-HT Gq-efficacy in psychedelic-like psychopharmacology permits rational development of non-psychedelic 5-HT agonists. We also demonstrate that β-arrestin-biased 5-HT receptor agonists block psychedelic effects and induce receptor downregulation and tachyphylaxis. Overall, 5-HT receptor Gq-signaling can be fine-tuned to generate ligands distinct from classical psychedelics.
Topics: Male; Animals; Mice; Hallucinogens; Receptor, Serotonin, 5-HT2A; Serotonin; Signal Transduction; beta-Arrestins; Ligands
PubMed: 38102107
DOI: 10.1038/s41467-023-44016-1 -
Progress in Molecular Biology and... 2019Arrestins play a key role in homologous desensitization of G protein-coupled receptors (GPCRs) and regulate several other vital signaling pathways in cells. Considering... (Review)
Review
Arrestins play a key role in homologous desensitization of G protein-coupled receptors (GPCRs) and regulate several other vital signaling pathways in cells. Considering the critical roles of these proteins in cellular signaling, surprisingly few disease-causing mutations in human arrestins were described. Most of these are loss-of-function mutations of visual arrestin-1 that cause excessive rhodopsin signaling and hence night blindness. Only one dominant arrestin-1 mutation was discovered so far. It reduces the thermal stability of the protein, which likely results in photoreceptor death via unfolded protein response. In case of the two nonvisual arrestins, only polymorphisms were described, some of which appear to be associated with neurological disorders and altered response to certain treatments. Structure-function studies revealed several ways of enhancing arrestins' ability to quench GPCR signaling. These enhanced arrestins have potential as tools for gene therapy of disorders associated with excessive signaling of mutant GPCRs.
Topics: Animals; Arrestin; Disease; Eye; Humans; Mammals; Models, Biological; Mutation
PubMed: 30711028
DOI: 10.1016/bs.pmbts.2018.09.004 -
Biomolecules Dec 2020The vascular endothelium is the innermost layer of blood vessels and is a key regulator of vascular tone. Endothelial function is controlled by receptor signaling... (Review)
Review
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.
Topics: Blood Vessels; Endothelium, Vascular; Humans; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestins
PubMed: 33374806
DOI: 10.3390/biom11010009 -
Hypertension (Dallas, Tex. : 1979) Nov 2022GPCRs (G protein-coupled receptors) are implicated in blood pressure (BP) and fluid intake regulation. There is a developing concept that these effects are mediated by...
BACKGROUND
GPCRs (G protein-coupled receptors) are implicated in blood pressure (BP) and fluid intake regulation. There is a developing concept that these effects are mediated by both canonical G protein signaling and noncanonical β-arrestin mediated signaling, but the contributions of each remain largely unexplored. Here, we hypothesized that β-arrestin contributes to fluid homeostasis and blood pressure (BP) regulation in deoxycorticosterone acetate (DOCA) salt hypertension, a prototypical model of salt-sensitive hypertension.
METHODS
Global β-arrestin1 () and β-arrestin2 () knockout mice were employed to evaluate drinking behavior, and BP was evaluated in -knockout mice. Age- and sex-matched C57BL/6 mice served as controls. We measured intake of water and different sodium chloride solutions and BP employing a 2-bottle choice paradigm with and without DOCA.
RESULTS
Without DOCA (baseline), -knockout mice exhibited a significant elevation in saline intake with no change in water intake. With DOCA treatment, -knockout mice exhibited a significant increase in both saline and water intake. Although -knockout mice exhibited hypernatremia at baseline conditions, we did not find significant changes in total body sodium stores or sodium palatability. In a separate cohort, BP was measured via telemetry in -knockout and C57BL/6 mice with and without DOCA. -knockout did not exhibit significant differences in BP before DOCA treatment when provided water alone, or when provided a choice of water and saline. However, -knockout exhibited an increased pressor response to DOCA-salt.
CONCLUSIONS
These findings suggest that in salt-sensitive hypertension, ARRB2, but not ARRB1 (β-arrestin 1), might counterbalance the canonical signaling of GPCRs.
Topics: Animals; Mice; Blood Pressure; Desoxycorticosterone Acetate; beta-Arrestin 2; Mice, Inbred C57BL; Hypertension; Sodium Chloride, Dietary; Sodium Chloride; Sodium; beta-Arrestins; Mice, Knockout; Homeostasis; Water; Desoxycorticosterone
PubMed: 36215165
DOI: 10.1161/HYPERTENSIONAHA.122.19863 -
Proceedings of the National Academy of... Apr 2021β-arrestins regulate many cellular functions including intracellular signaling and desensitization of G protein-coupled receptors (GPCRs). Previous studies show that...
β-arrestins regulate many cellular functions including intracellular signaling and desensitization of G protein-coupled receptors (GPCRs). Previous studies show that β-arrestin signaling and receptor endocytosis are modulated by the plasma membrane phosphoinositide lipid phosphatidylinositol-(4, 5)-bisphosphate (PI(4,5)P). We found that β-arrestin also helped promote synthesis of PI(4,5)P and up-regulated GPCR endocytosis. We studied these questions with the G-coupled protease-activated receptor 2 (PAR2), which activates phospholipase C, desensitizes quickly, and undergoes extensive endocytosis. Phosphoinositides were monitored and controlled in live cells using lipid-specific fluorescent probes and genetic tools. Applying PAR2 agonist initiated depletion of PI(4,5)P, which then recovered during rapid receptor desensitization, giving way to endocytosis. This endocytosis could be reduced by various manipulations that depleted phosphoinositides again right after phosphoinositide recovery: PI(4)P, a precusor of PI(4,5)P could be depleted at either the Golgi or the plasma membrane (PM) using a recruitable lipid 4-phosphatase enzyme and PI(4,5)P could be depleted at the PM using a recruitable 5-phosphatase. Endocytosis required the phosphoinositides. Knock-down of β-arrestin revealed that endogenous β-arrestin normally doubles the rate of PIP5-kinase (PIP5K) after PAR2 desensitization, boosting PI(4,5)P-dependent formation of clathrin-coated pits (CCPs) at the PM. Desensitized PAR2 receptors were swiftly immobilized when they encountered CCPs, showing a dwell time of ∼90 s, 100 times longer than for unactivated receptors. PAR2/β-arrestin complexes eventually accumulated around the edges or across the surface of CCPs promoting transient binding of PIP5K-Iγ. Taken together, β-arrestins can coordinate potentiation of PIP5K activity at CCPs to induce local PI(4,5)P generation that promotes recruitment of PI(4,5)P-dependent endocytic machinery.
Topics: Arrestins; Cell Membrane; Clathrin; Endocytosis; HEK293 Cells; Humans; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Phosphorylation; Protein Binding; Receptor, PAR-2; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestin 1; beta-Arrestins
PubMed: 33879605
DOI: 10.1073/pnas.2011023118 -
Frontiers in Immunology 2022The chemokine receptor CXCR3 plays a critical role in immune cell recruitment and activation. CXCR3 exists as two main isoforms, CXCR3-A and CXCR3-B, resulting from...
The chemokine receptor CXCR3 plays a critical role in immune cell recruitment and activation. CXCR3 exists as two main isoforms, CXCR3-A and CXCR3-B, resulting from alternative splicing. Although the two isoforms differ only by the presence of an N-terminal extension in CXCR3-B, they have been attributed divergent functional effects on cell migration and proliferation. CXCR3-B is the more enigmatic isoform and the mechanisms underlying its function and signaling remain elusive. We therefore undertook an in-depth cellular and molecular comparative study of CXCR3-A and CXCR3-B, investigating their activation at different levels of the signaling cascades, including G protein coupling, β-arrestin recruitment and modulation of secondary messengers as well as their downstream gene response elements. We also compared the subcellular localization of the two isoforms and their trafficking under resting and stimulated conditions along with their ability to internalize CXCR3-related chemokines. Here, we show that the N-terminal extension of CXCR3-B drastically affects receptor features, modifying its cellular localization and preventing G protein coupling, while preserving β-arrestin recruitment and chemokine uptake capacities. Moreover, we demonstrate that gradual truncation of the N terminus leads to progressive recovery of surface expression and G protein coupling. Our study clarifies the molecular basis underlying the divergent effects of CXCR3 isoforms, and emphasizes the β-arrestin-bias and the atypical nature of CXCR3-B.
Topics: Alternative Splicing; Chemokine CXCL11; Chemokines; Signal Transduction; beta-Arrestins
PubMed: 35720349
DOI: 10.3389/fimmu.2022.868579 -
Journal of Cardiovascular Pharmacology Sep 2017β-arrestin1 (or arrestin2) and β-arrestin2 (or arrestin3) are ubiquitously expressed cytosolic adaptor proteins that were originally discovered for their inhibitory... (Review)
Review
β-arrestin1 (or arrestin2) and β-arrestin2 (or arrestin3) are ubiquitously expressed cytosolic adaptor proteins that were originally discovered for their inhibitory role in G protein-coupled receptor (GPCR) signaling through heterotrimeric G proteins. However, further biochemical characterization revealed that β-arrestins do not just "block" the activated GPCRs, but trigger endocytosis and kinase activation leading to specific signaling pathways that can be localized on endosomes. The signaling pathways initiated by β-arrestins were also found to be independent of G protein activation by GPCRs. The discovery of ligands that blocked G protein activation but promoted β-arrestin binding, or vice-versa, suggested the exciting possibility of selectively activating intracellular signaling pathways. In addition, it is becoming increasingly evident that β-arrestin-dependent signaling is extremely diverse and provokes distinct cellular responses through different GPCRs even when the same effector kinase is involved. In this review, we summarize various signaling pathways mediated by β-arrestins and highlight the physiologic effects of β-arrestin-dependent signaling.
Topics: Animals; Endocytosis; Humans; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestins
PubMed: 28328745
DOI: 10.1097/FJC.0000000000000482 -
The Journal of Biological Chemistry Sep 2022G protein-coupled receptor (GPCR) kinases (GRKs) and arrestins interact with agonist-bound GPCRs to promote receptor desensitization and downregulation. They also... (Review)
Review
G protein-coupled receptor (GPCR) kinases (GRKs) and arrestins interact with agonist-bound GPCRs to promote receptor desensitization and downregulation. They also trigger signaling cascades distinct from those of heterotrimeric G proteins. Biased agonists for GPCRs that favor either heterotrimeric G protein or GRK/arrestin signaling are of profound pharmacological interest because they could usher in a new generation of drugs with greatly reduced side effects. One mechanism by which biased agonism might occur is by stabilizing receptor conformations that preferentially bind to GRKs and/or arrestins. In this review, we explore this idea by comparing structures of GPCRs bound to heterotrimeric G proteins with those of the same GPCRs in complex with arrestins and GRKs. The arrestin and GRK complexes all exhibit high conformational heterogeneity, which is likely a consequence of their unusual ability to adapt and bind to hundreds of different GPCRs. This dynamic behavior, along with the experimental tactics required to stabilize GPCR complexes for biophysical analysis, confounds these comparisons, but some possible molecular mechanisms of bias are beginning to emerge. We also examine if and how the recent structures advance our understanding of how arrestins parse the "phosphorylation barcodes" installed in the intracellular loops and tails of GPCRs by GRKs. In the future, structural analyses of arrestins in complex with intact receptors that have well-defined native phosphorylation barcodes, such as those installed by the two nonvisual subfamilies of GRKs, will be particularly illuminating.
Topics: Arrestins; G-Protein-Coupled Receptor Kinases; Humans; Phosphorylation; Receptors, G-Protein-Coupled; Signal Transduction
PubMed: 35863432
DOI: 10.1016/j.jbc.2022.102279