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ELife Oct 2023The vasopressin type 2 receptor (VR) is an essential G protein-coupled receptor (GPCR) in renal regulation of water homeostasis. Upon stimulation, the VR activates Gα...
The vasopressin type 2 receptor (VR) is an essential G protein-coupled receptor (GPCR) in renal regulation of water homeostasis. Upon stimulation, the VR activates Gα and Gα, which is followed by robust recruitment of β-arrestins and receptor internalization into endosomes. Unlike canonical GPCR signaling, the β-arrestin association with the VR does not terminate Gα activation, and thus, Gα-mediated signaling is sustained while the receptor is internalized. Here, we demonstrate that this VR ability to co-interact with G protein/β-arrestin and promote endosomal G protein signaling is not restricted to Gα, but also involves Gα. Furthermore, our data imply that β-arrestins potentiate Gα/Gα activation at endosomes rather than terminating their signaling. Surprisingly, we found that the VR internalizes and promote endosomal G protein activation independent of β-arrestins to a minor degree. These new observations challenge the current model of endosomal GPCR signaling and suggest that this event can occur in both β-arrestin-dependent and -independent manners.
Topics: beta-Arrestins; Receptors, Vasopressin; Arrestins; beta-Arrestin 1; Endosomes; GTP-Binding Proteins; Vasopressins
PubMed: 37855711
DOI: 10.7554/eLife.87754 -
Nature Communications Jul 2023Urocortin 2 (UCN2) acts as a ligand for the G protein-coupled receptor corticotropin-releasing hormone receptor 2 (CRHR2). UCN2 has been reported to improve or worsen...
Urocortin 2 (UCN2) acts as a ligand for the G protein-coupled receptor corticotropin-releasing hormone receptor 2 (CRHR2). UCN2 has been reported to improve or worsen insulin sensitivity and glucose tolerance in vivo. Here we show that acute dosing of UCN2 induces systemic insulin resistance in male mice and skeletal muscle. Inversely, chronic elevation of UCN2 by injection with adenovirus encoding UCN2 resolves metabolic complications, improving glucose tolerance. CRHR2 recruits Gs in response to low concentrations of UCN2, as well as Gi and β-Arrestin at high concentrations of UCN2. Pre-treating cells and skeletal muscle ex vivo with UCN2 leads to internalization of CRHR2, dampened ligand-dependent increases in cAMP, and blunted reductions in insulin signaling. These results provide mechanistic insights into how UCN2 regulates insulin sensitivity and glucose metabolism in skeletal muscle and in vivo. Importantly, a working model was derived from these results that unifies the contradictory metabolic effects of UCN2.
Topics: Animals; Male; Mice; Corticotropin-Releasing Hormone; Glucose; Insulin; Insulin Resistance; Ligands; Receptors, Corticotropin-Releasing Hormone; Urocortins
PubMed: 37402735
DOI: 10.1038/s41467-023-39597-w -
British Journal of Pharmacology May 2024GPR84 is an understudied rhodopsin-like class A G protein-coupled receptor, which is arousing particular interest from a therapeutic perspective. Not least this reflects... (Review)
Review
GPR84 is an understudied rhodopsin-like class A G protein-coupled receptor, which is arousing particular interest from a therapeutic perspective. Not least this reflects that gpr84 expression is significantly up-regulated following acute inflammatory stimuli and in inflammatory diseases, and that receptor activation plays a role in regulating pro-inflammatory responses and migration of cells of the innate immune system such as neutrophils, monocytes, macrophages and microglia. Although most physiological responses of GPR84 reflect receptor coupling to G-proteins, several studies indicate that agonist-activated GPR84 can recruit arrestin adaptor proteins and this regulates receptor internalisation and desensitisation. To date, little is known on the patterns of either basal or ligand regulated GPR84 phosphorylation and how these might control these processes. Here, we consider what is known about the regulation of GPR84 signalling with a focus on how G protein receptor kinase-mediated phosphorylation regulates arrestin protein recruitment and receptor function. LINKED ARTICLES: This article is part of a themed issue GPR84 Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.10/issuetoc.
Topics: Arrestin; Macrophages; Phosphorylation; Receptors, G-Protein-Coupled; Signal Transduction; Humans
PubMed: 37085331
DOI: 10.1111/bph.16098 -
Proceedings of the National Academy of... Aug 2023Catecholamine-stimulated β-adrenergic receptor (βAR) signaling via the canonical G-adenylyl cyclase-cAMP-PKA pathway regulates numerous physiological functions,...
Catecholamine-stimulated β-adrenergic receptor (βAR) signaling via the canonical G-adenylyl cyclase-cAMP-PKA pathway regulates numerous physiological functions, including the therapeutic effects of exogenous β-agonists in the treatment of airway disease. βAR signaling is tightly regulated by GRKs and β-arrestins, which together promote βAR desensitization and internalization as well as downstream signaling, often antithetical to the canonical pathway. Thus, the ability to βAR signaling toward the G pathway while avoiding β-arrestin-mediated effects may provide a strategy to improve the functional consequences of βAR activation. Since attempts to develop G-biased agonists and allosteric modulators for the βAR have been largely unsuccessful, here we screened small molecule libraries for allosteric modulators that selectively inhibit β-arrestin recruitment to the receptor. This screen identified several compounds that met this profile, and, of these, a difluorophenyl quinazoline (DFPQ) derivative was found to be a selective negative allosteric modulator of β-arrestin recruitment to the βAR while having no effect on βAR coupling to G. DFPQ effectively inhibits agonist-promoted phosphorylation and internalization of the βAR and protects against the functional desensitization of β-agonist mediated regulation in cell and tissue models. The effects of DFPQ were also specific to the βAR with minimal effects on the βAR. Modeling, mutagenesis, and medicinal chemistry studies support DFPQ derivatives binding to an intracellular membrane-facing region of the βAR, including residues within transmembrane domains 3 and 4 and intracellular loop 2. DFPQ thus represents a class of biased allosteric modulators that targets an allosteric site of the βAR.
Topics: beta-Arrestins; Arrestin; Signal Transduction; beta-Arrestin 1; Receptors, Adrenergic; Receptors, Adrenergic, beta-2
PubMed: 37490535
DOI: 10.1073/pnas.2302668120 -
Proceedings of the National Academy of... Oct 2023β-arrestins are multivalent adaptor proteins that bind active phosphorylated G protein-coupled receptors (GPCRs) to inhibit G protein signaling, mediate receptor...
β-arrestins are multivalent adaptor proteins that bind active phosphorylated G protein-coupled receptors (GPCRs) to inhibit G protein signaling, mediate receptor internalization, and initiate alternative signaling events. β-arrestins link agonist-stimulated GPCRs to downstream signaling partners, such as the c-Raf-MEK1-ERK1/2 cascade leading to ERK1/2 activation. β-arrestins have been thought to transduce signals solely via passive scaffolding by facilitating the assembly of multiprotein signaling complexes. Recently, however, β-arrestin 1 and 2 were shown to activate two downstream signaling effectors, c-Src and c-Raf, allosterically. Over the last two decades, ERK1/2 have been the most intensely studied signaling proteins scaffolded by β-arrestins. Here, we demonstrate that β-arrestins play an active role in allosterically modulating ERK kinase activity in vitro and within intact cells. Specifically, we show that β-arrestins and their GPCR-mediated active states allosterically enhance ERK2 autophosphorylation and phosphorylation of a downstream ERK2 substrate, and we elucidate the mechanism by which β-arrestins do so. Furthermore, we find that allosteric stimulation of dually phosphorylated ERK2 by active-state β-arrestin 2 is more robust than by active-state β-arrestin 1, highlighting differential capacities of β-arrestin isoforms to regulate effector signaling pathways downstream of GPCRs. In summary, our study provides strong evidence for a new paradigm in which β-arrestins function as active "catalytic" scaffolds to allosterically unlock the enzymatic activity of signaling components downstream of GPCR activation.
Topics: beta-Arrestins; beta-Arrestin 1; Arrestins; Allosteric Regulation; Signal Transduction; Receptors, G-Protein-Coupled; Phosphorylation; beta-Arrestin 2
PubMed: 37844230
DOI: 10.1073/pnas.2303794120 -
Assessment of the potential of novel and classical opioids to induce respiratory depression in mice.British Journal of Pharmacology Dec 2023Opioid-induced respiratory depression limits the use of μ-opioid receptor agonists in clinical settings and is the main cause of opioid overdose fatalities. The...
BACKGROUND AND PURPOSE
Opioid-induced respiratory depression limits the use of μ-opioid receptor agonists in clinical settings and is the main cause of opioid overdose fatalities. The relative potential of different opioid agonists to induce respiratory depression at doses exceeding those producing analgesia is understudied despite its relevance to assessments of opioid safety. Here we evaluated the respiratory depressant and anti-nociceptive effects of three novel opioids and relate these measurements to their in vitro efficacy.
EXPERIMENTAL APPROACH
Respiration was measured in awake, freely moving male CD-1 mice using whole body plethysmography. Anti-nociception was measured using the hot plate test. Morphine, oliceridine and tianeptine were administered intraperitoneally, whereas methadone, oxycodone and SR-17018 were administered orally. Receptor activation and arrestin-3 recruitment were measured in HEK293 cells using BRET assays.
KEY RESULTS
Across the dose ranges examined, all opioids studied depressed respiration in a dose-dependent manner, with similar effects at the highest doses, and with tianeptine and oliceridine showing reduced duration of effect, when compared with morphine, oxycodone, methadone and SR-17018. When administered at doses that induced similar respiratory depression, all opioids induced similar anti-nociception, with tianeptine and oliceridine again showing reduced duration of effect. These data were consistent with the in vitro agonist activity of the tested compounds.
CONCLUSION AND IMPLICATIONS
In addition to providing effective anti-nociception, the novel opioids, oliceridine, tianeptine and SR-17018 depress respiration in male mice. However, the different potencies and kinetics of effect between these novel opioids may be relevant to their therapeutic application in different clinical settings.
Topics: Male; Humans; Animals; Mice; Analgesics, Opioid; Oxycodone; HEK293 Cells; Morphine; Respiratory Insufficiency; Methadone
PubMed: 37489013
DOI: 10.1111/bph.16199 -
Cell Reports Nov 2023Glioblastoma (GBM) is the most common and aggressive primary brain malignancy. Adhesion G protein-coupled receptors (aGPCRs) have attracted interest for their potential...
Glioblastoma (GBM) is the most common and aggressive primary brain malignancy. Adhesion G protein-coupled receptors (aGPCRs) have attracted interest for their potential as treatment targets. Here, we show that CD97 (ADGRE5) is the most promising aGPCR target in GBM, by virtue of its de novo expression compared to healthy brain tissue. CD97 knockdown or knockout significantly reduces the tumor initiation capacity of patient-derived GBM cultures (PDGCs) in vitro and in vivo. We find that CD97 promotes glycolytic metabolism via the mitogen-activated protein kinase (MAPK) pathway, which depends on phosphorylation of its C terminus and recruitment of β-arrestin. We also demonstrate that THY1/CD90 is a likely CD97 ligand in GBM. Lastly, we show that an anti-CD97 antibody-drug conjugate selectively kills tumor cells in vitro. Our studies identify CD97 as a regulator of tumor metabolism, elucidate mechanisms of receptor activation and signaling, and provide strong scientific rationale for developing biologics to target it therapeutically in GBM.
Topics: Humans; Glioblastoma; Phosphorylation; Receptors, G-Protein-Coupled; Signal Transduction
PubMed: 37938973
DOI: 10.1016/j.celrep.2023.113374 -
Nature Communications Jul 2023Representing the most attractive and successful druggable receptors of the proteome, GPCRs regulate a myriad of physiological and pathophysiological functions. Although...
Representing the most attractive and successful druggable receptors of the proteome, GPCRs regulate a myriad of physiological and pathophysiological functions. Although over half of present pharmaceuticals target GPCRs, the advancement of drug discovery is hampered by a lack of adequate screening tools, the majority of which are limited to probing agonist-induced G-protein and β-arrestin-2-mediated events as a measure of receptor activation. Here, we develop Tango-Trio, a comprehensive cell-based high-throughput platform comprising cumate-inducible expression of transducers, capable of the parallelized profiling of both basal and agonist-dependent GPCR activities. We capture the functional diversity of GPCRs, reporting β-arrestin-1/2 couplings, selectivities, and receptor internalization signatures across the GPCRome. Moreover, we present the construction of cumate-induced basal activation curves at approximately 200 receptors, including over 50 orphans. Overall, Tango-Trio's robustness is well-suited for the functional characterization and screening of GPCRs, especially for parallel interrogation, and is a valuable addition to the pharmacological toolbox.
Topics: Receptors, G-Protein-Coupled; Ligands; Signal Transduction; beta-Arrestin 2; Drug Discovery; beta-Arrestins
PubMed: 37407564
DOI: 10.1038/s41467-023-39132-x -
Science Signaling Aug 2023G protein-coupled receptors engage both G proteins and β-arrestins, and their coupling can be biased by ligands and mutations. Here, to resolve structural elements and...
G protein-coupled receptors engage both G proteins and β-arrestins, and their coupling can be biased by ligands and mutations. Here, to resolve structural elements and mechanisms underlying effector coupling to the angiotensin II (AngII) type 1 receptor (AT1R), we combined alanine scanning mutagenesis of the entire sequence of the receptor with pharmacological profiling of Gα and β-arrestin engagement to mutant receptors and molecular dynamics simulations. We showed that Gα coupling to AT1R involved a large number of residues spread across the receptor, whereas fewer structural regions of the receptor contributed to β-arrestin coupling regulation. Residue stretches in transmembrane domain 4 conferred β-arrestin bias and represented an important structural element in AT1R for functional selectivity. Furthermore, we identified allosteric small-molecule binding sites that were enclosed by communities of residues that produced biased signaling when mutated. Last, we showed that allosteric communication within AT1R emanating from the Gα coupling site spread beyond the orthosteric AngII-binding site and across different regions of the receptor, including currently unresolved structural regions. Our findings reveal structural elements and mechanisms within AT1R that bias Gα and β-arrestin coupling and that could be harnessed to design biased receptors for research purposes and to develop allosteric modulators.
Topics: beta-Arrestins; Receptor, Angiotensin, Type 1; beta-Arrestin 1; Signal Transduction; GTP-Binding Proteins; Angiotensin II
PubMed: 37552769
DOI: 10.1126/scisignal.adf2173 -
Molecular Pharmacology Oct 2023Atypical chemokine receptor 3 (ACKR3) is an arrestin-biased receptor that regulates extracellular chemokine levels through scavenging. The scavenging process restricts...
Atypical chemokine receptor 3 (ACKR3) is an arrestin-biased receptor that regulates extracellular chemokine levels through scavenging. The scavenging process restricts the availability of the chemokine agonist CXCL12 for the G protein-coupled receptor (GPCR) CXCR4 and requires phosphorylation of the ACKR3 C-terminus by GPCR kinases (GRKs). ACKR3 is phosphorylated by GRK2 and GRK5, but the mechanisms by which these kinases regulate the receptor are unresolved. Here we determined that GRK5 phosphorylation of ACKR3 results in more efficient chemokine scavenging and -arrestin recruitment than phosphorylation by GRK2 in HEK293 cells. However, co-activation of CXCR4-enhanced ACKR3 phosphorylation by GRK2 through the liberation of G, an accessory protein required for efficient GRK2 activity. The results suggest that ACKR3 "senses" CXCR4 activation through a GRK2-dependent crosstalk mechanism, which enables CXCR4 to influence the efficiency of CXCL12 scavenging and -arrestin recruitment to ACKR3. Surprisingly, we also found that despite the requirement for phosphorylation and the fact that most ligands promote -arrestin recruitment, -arrestins are dispensable for ACKR3 internalization and scavenging, suggesting a yet-to-be-determined function for these adapter proteins. Since ACKR3 is also a receptor for CXCL11 and opioid peptides, these data suggest that such crosstalk may also be operative in cells with CXCR3 and opioid receptor co-expression. Additionally, kinase-mediated receptor cross-regulation may be relevant to other atypical and G protein-coupled receptors that share common ligands. SIGNIFICANCE STATEMENT: The atypical receptor ACKR3 indirectly regulates CXCR4-mediated cell migration by scavenging their shared agonist CXCL12. Here, we show that scavenging and -arrestin recruitment by ACKR3 are primarily dependent on phosphorylation by GRK5. However, we also show that CXCR4 co-activation enhances the contribution of GRK2 by liberating G. This phosphorylation crosstalk may represent a common feedback mechanism between atypical and G protein-coupled receptors with shared ligands for regulating the efficiency of scavenging or other atypical receptor functions.
Topics: Humans; beta-Arrestins; Chemokine CXCL12; G-Protein-Coupled Receptor Kinases; HEK293 Cells; Ligands; Phosphorylation; Protein Binding; Receptors, CXCR4
PubMed: 37474305
DOI: 10.1124/molpharm.123.000710