G Protein-coupled Research Articles

Sphingosine 1-phosphate receptor subtype 1 (S1P1) activity in the course of Alzheimer's disease

Some specific lipid molecules in the brain act as signaling molecules, neurotransmitters, or neuromodulators, by binding to specific G protein-coupled receptors (GPCR) for neurolipids. One such receptor, sphingosine 1-phosphate receptor subtype 1 (S1P1), is coupled to Gi/o proteins and is involved in cell proliferation, growth, and neuroprotection. S1P1 constitutes an interesting target for neurodegenerative diseases like multiple sclerosis and Alzheimer's disease (AD), in which changes in the sphingolipid metabolism have been observed. This study analyzes S1P1 receptor-mediated activity in healthy brains and during AD progression using postmortem samples from controls and patients at different Braak's stages. Additionally, the distribution of S1P1 receptor activity in human brains is compared to that in commonly used rodent models, rats and mice, through functional autoradiography, measuring [35S]GTPγS binding stimulated by the S1P1 receptor selective agonist CYM-5442 to obtain the distribution of functional activity of S1P1 receptors.S1P1 receptor-mediated activity, along with that of the cannabinoid CB1 receptor, is one of the highest recorded for any GPCR in many gray matter areas of the brain, reaching maximum values in the cerebellar cortex, specific areas of the hippocampus and the basal forebrain. S1P1 signaling is crucial in areas that regulate learning, memory, motor control, and nociception, such as the basal forebrain and basal ganglia. In AD, S1P1 receptor activity is increased in the inner layers of the frontal cortex and underlying cortical white matter at early stages, but decreases in the hippocampus in advanced stages, indicating ongoing brain impairment. Importantly, we identified significant correlations between S1P1 receptor activity and Braak stages, suggesting that S1P1 receptor dysfunction is associated to disease progression, particularly in memory-related regions. The S1P signaling via S1P1 receptor is a promising neurological target due to its role in key neurophysiological functions and its potential to modify the progression of neurodegenerative diseases. Finally, rats are suggested as a preferred experimental model for studying S1P1 receptor-mediated responses in the human brain.

Local and Remote Chemogenetic Suppression of Hippocampal Seizures in Rats.

Innovative treatments of refractory epilepsy are widely desired, for which chemogenetic technology can provide region- and cell-type-specific modulation with relative noninvasiveness. We aimed to explore the specific applications of chemogenetics for locally and remotely networks controlling hippocampal seizures. A virus coding for a modified human Gi-coupled M4 muscarinic receptor (hM4Di) on pyramidal cells was injected into either the right hippocampal CA3 or the bilateral anterior nucleus of the thalamus (ANT) in rats. After one month, seizures were induced by 4-aminopyridine (4-AP) injection into the right CA3. Simultaneously, clozapine-N-oxide (CNO) (2.5 mg/kg) or clozapine (0.1 mg/kg), the specific ligands acting on hM4Di, were injected intraperitoneally. We also set up hM4Di control and clozapine control groups to eliminate the influence of viral transfection and the ligand alone on the experimental results. For both local and remote controls, the mean seizure duration was significantly reduced upon ligand application in the experimental groups. Seizure frequency, on the other hand, only showed a significant decrease in local control, with a lower frequency in the clozapine group than in the CNO group. Both the effects of CNO and clozapine were time-dependent, and clozapine was faster than CNO in local seizure control. This study shows the potency of chemogenetics to attenuate hippocampal seizures locally or remotely by activating the transfected hM4Di receptor with CNO or clozapine. ANT is suggested as a potentially safe chemogenetic application target in the epileptic network for focal hippocampal seizures.

Transactivation of the EGF receptor as a novel desensitization mechanism for G protein-coupled receptors, illustrated by dopamine D2-like and β2 adrenergic receptors

Transactivation of epidermal growth factor receptors (EGFR) provides intricate control over multiple regulatory cellular processes that merge the diversity of G protein-coupled receptors (GPCRs) with the robust signaling capacities of receptor tyrosine kinases. Contrary to the typical assertions, our findings demonstrate that EGFR transactivation contributes to the desensitization of GPCRs. Repeated agonist stimulation of certain GPCRs enhanced EGFR transactivation, triggering a series of cellular events associated with GPCR desensitization. This effect was observed in receptors undergoing desensitization (D3R, K149C-D2R, β2AR) but not in those resistant to desensitization (D2R, C147K-D3R, D4R, β2AR mutants lacking GRK2 or GRK6 phosphorylation sites). The EGFR inhibitor AG1478 prevented both desensitization and the associated cellular events. Similarly, these cellular events were also observed when cells were treated with EGF, but only in GPCRs that undergo desensitization. These findings suggest that EGFR transactivation diversifies pathways involved in ERK activation through the EGFR signaling system and also mediates GPCR desensitization. Alongside the widely accepted steric hindrance model, these findings offer new insights into understanding the mechanisms of GPCR desensitization, which occurs through complex cellular processes.

Structural Basis for Chemerin Recognition and Signaling Through Its Receptors

Chemerin is a chemotactic adipokine that participates in a multitude of physiological processes, including adipogenesis, leukocyte chemotaxis, and neuroinflammation. Chemerin exerts biological functions through binding to one or more of its G protein-coupled receptors (GPCRs), namely chemokine-like receptor 1 (CMKLR1), G protein-coupled receptor 1 (GPR1), and CC-motif receptor-like 2 (CCRL2). Of these receptors, CMKLR1 and GPR1 have been confirmed as signaling receptors of chemerin, whereas CCRL2 serves as a chemerin-binding protein without transmembrane signaling. High-resolution structures of two chemerin receptors are now available thanks to recent advancements in structure biology. This review focuses on the structural perspectives of the chemerin receptors with an emphasis on the structure–activity correlation, including key components of the two receptors for ligand recognition and conformational changes induced by chemerin and its derivative peptides for G protein activation. There are also comparisons between the two chemerin receptors and selected GPCRs with peptide ligands for better appreciation of the shared and distinct features of the chemerin receptors in ligand recognition and transmembrane signaling, and in the evolution of this subclass of GPCRs.

Mechanistic exploration of bioactive constituents in Gnetum gnemon for GPCR-related cancer treatment through network pharmacology and molecular docking

G Protein-Coupled Receptors (GPCRs) are integral membrane proteins that have gained considerable attention as drug targets, particularly in cancer treatment. In this study, we explored the capacity of bioactive compounds derived from Gnetum gnemon (GG) for the development of of pharmaceuticals targeting GPCRs within the context of cancer therapy. Integrated approach combined network pharmacology and molecular docking to identify and validate the underlying pharmacological mechanisms. We retrieved targets for GG-derived compounds and GPCRs-related cancer from databases. Subsequently, we established a protein-protein interaction (PPI) network by mapping the shared targets. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were employed to predict the mechanism of action of these targets. Molecular docking was conducted to validate our findings. We identified a total of 265 targets associated with GG-derived bioactive compounds for the treatment of GPCRs-related cancer. Functional enrichment analysis revealed the promising therapeutic effects of these targets on GPCRs-related cancer pathways. The PPI network analysis identified hub targets, including MAPK3, SRC, EGFR, STAT3, ESR1, MTOR, CCND1, and PPARG, which demonstrate as treatment targets for GPCRs-related cancer using GG-derived compounds. Additionally, molecular docking experiments demonstrated the strong binding affinity of gnetin A, gnetin C, (-)-viniferin, and resveratrol dimer, thus inhibiting MAPK3, SRC, EGFR, and MTOR. Survival analysis established the clinical prognostic relevance of identified hub genes in cancer. This study presents a novel approach for comprehending the therapeutic mechanisms of GG-derived active compounds and thereby paving the way for their prospective clinical applications in the field of cancer treatment.

Bitter taste receptors as sensors of gut luminal contents.

Taste is important in the selection of food and is orchestrated by a group of distinct receptors, the taste G protein-coupled receptors (GPCRs). Taste 1 receptors (Tas1rs in mice and TAS1Rs in humans; also known as T1Rs) detect sweet and umami tastes, and taste 2 receptors (Tas2rs in mice and TAS2Rs in humans; also known as T2Rs) detect bitterness. These receptors are also expressed in extraoral sites, including the gastrointestinal mucosa. Tas2rs/TAS2Rs have gained interest as potential targets to prevent or treat metabolic disorders. These bitter taste receptors are expressed in functionally distinct types of gastrointestinal mucosal cells, including enteroendocrine cells, which, upon stimulation, increase intracellular Ca2+ and release signalling molecules that regulate gut chemosensory processes critical for digestion and absorption of nutrients, for neutralization and expulsion of harmful substances, and for metabolic regulation. Expression of Tas2rs/TAS2Rs in gut mucosa is upregulated by high-fat diets, and intraluminal bitter 'tastants' affect gastrointestinal functions and ingestive behaviour through local and gut-brain axis signalling. Tas2rs/TAS2Rs are also found in Paneth and goblet cells, which release antimicrobial peptides and glycoproteins, and in tuft cells, which trigger type 2 immune response against parasites, thus providing a direct line of defence against pathogens. This Review will focus on gut Tas2r/TAS2R distribution, signalling and regulation in enteroendocrine cells, supporting their role as chemosensors of luminal content that serve distinct functions as regulators of body homeostasis and immune response.

Treatment of Post-COVID-19 POTS by inhibiting FcRn: a phase 2 randomized, placebo controlled, double-blind, proof of concept study with efgartigimod

Abstract Background While the underlying pathophysiology is unknown, post–COVID-19 postural orthostatic tachycardia syndrome (POTS) may be related to immune dysfunction and autoimmunity precipitated by SARS-CoV-2 infection. Various autoantibodies, including those targeting G-protein coupled receptors (GPCRs), have been observed in patients with POTS. Binding of these autoantibodies to adrenergic receptors, which are prototypical GPCRs, has been hypothesized to modulate receptor activity, increase sympathetic tone, and cause tachycardia. Moreover, IgG anti-GPCR autoantibodies, acting as partial agonists, are thought to decrease the effect of peripheral vasomotor control, leading to an increased sympathetic response to upright posture that can result in postural tachycardia in the absence of hypotension. Purpose We hypothesize that a reduction in autoantibody levels by efgartigimod, a FcRn-antagonist, will ameliorate the underlying immune-mediated pathogenesis and lead to clinical improvements in patients who developed POTS following COVID-19 infection. We propose a phase II multicenter, randomized, placebo-controlled, double-blind, proof-of-mechanism study initiated to evaluate the safety and efficacy of efgartigimod in adults with post–COVID-19 POTS. Methods Adult patients diagnosed with new-onset of POTS following SARS-CoV-2 infection are eligible for participation in the study. Prior COVID-19 must be confirmed by documentation of historical PCR test, and POTS diagnosis must meet consensus criteria. Study subjects must have moderate to severe autonomic symptoms (COMPASS-31 score ≥ 35 points at screening). Approximately 42 patients will be randomly allocated (2:1) to receive weekly intravenous efgartigimod or placebo for 24 weeks. At the end of the treatment period, participants who complete the study may roll over into an open-label extension (OLE). The co-primary endpoints are change from baseline to week 24 in the COMPASS-31 and Malmo POTS Symptom Score as well as safety and tolerability outcomes. Key secondary endpoints include assessments of disease activity, fatigue, cognitive function, walking capacity and quantitative autonomic testing. Additional exploratory endpoints include intraepidermal small fiber densities (optional), sudomotor innervation (optional) and peripheral blood biomarkers to define histopathological and immune determinants associated with treatment response. Conclusions This phase II study of efgartigimod will evaluate the effect of FcRn inhibition on disease pathology and the potential for therapeutic benefit in patients with post–COVID-19 POTS.

VPS26 Moonlights as a β-Arrestin-like Adapter for a 7-Transmembrane RGS Protein in Arabidopsis thaliana.

Extracellular signals perceived by 7-transmembrane (7TM)-spanning receptors initiate desensitization that involves the removal of these receptors from the plasma membrane. Agonist binding often evokes phosphorylation in the flexible C-terminal region and/or intracellular loop 3 of many 7TM G-protein-coupled receptors in animal cells, which consequently recruits a cytoplasmic intermediate adaptor, β-arrestin, resulting in clathrin-mediated endocytosis (CME) and downstream signaling such as transcriptional changes. Some 7TM receptors undergo CME without recruiting β-arrestin, but it is not clear how. Arrestins are not encoded in the Arabidopsis thaliana genome, yet Arabidopsis cells have a well-characterized signal-induced CME of a 7TM protein, designated Regulator of G Signaling 1 (AtRGS1). Here we show that a component of the retromer complex, Vacuolar Protein Sorting-Associated 26 (VPS26), binds the phosphorylated C-terminal region of AtRGS1 as a VPS26A/B heterodimer to form a complex that is required for downstream signaling. We propose that VPS26 moonlights as an arrestin-like adaptor in the CME of AtRGS1.

Identification and Functional Analysis of Git3 G Protein-Coupled Receptors in Ganoderma boninense PER71

G protein-coupled receptors (GPCRs) are integral components of eukaryotic heterotrimeric G proteins, playing crucial roles in detecting extracellular signals and initiating the activity of signaling proteins within cells to activate cellular responses to these signals. The objectives of this study are to identify and characterize the function of Git3, a Class III GPCR protein, in the oil palm pathogen Ganoderma boninense. To identify the potential genes encoded for GPCR in this fungus, intensive data mining on the genome and transcriptome data has been carried out. A total of six classes of GPCRs have been identified. These include Class II pheromone detectors, Class III carbon detectors, Class IV nitrogen detectors, Class VII proteins similar to glycosyltransferase, Class VIII proteins similar to hemolysin, and Class X protein receptors. Among these, the Class III protein Git3, postulated to be involved in glucose sensing and fungal pathogenicity, was selected for gene knockdown using RNA interference (RNAi). A plasmid, designated pUChph-GIT3, was constructed, to target git3 silencing by incorporating a hygromycin resistance gene cassette and antisense sequences of git3. Transformation of G. boninense PER71 with pUChph-GIT3 produced five potential Δgit3 gene-silenced mutants. PCR analysis confirmed the integration of the RNAi expression cassette into the fungal genome. Quantitative PCR (qPCR) analysis revealed significant reductions in git3 expression in three G. boninense mutants, M42, M66, and M5 by 47%, 23%, and 13%, respectively. The Disease Severity Index (DSI) indicated slower disease progression in oil palm plantlets infected with Δgit3 mutants compared to those infected with wild-type G. boninense PER71. In conclusion, this study successfully isolated and characterized the git3 GPCR from G. boninense and demonstrated that it might play a role during the early stages of infection, as the mutants were able to slow the progression of infection in oil palm plantlets.

The role of Gαq in regulating NLRP3 inflammasome activation.

G proteins are a class of important signal transducers in mammalians. G proteins can corpoarated with G proteincoupled receptors (GPCRs) and transmit signals from extracellular stimuli into intracellular response, which will regulate a series of biological functions. G-proteins are heterotrimeric proteins composed of Gα, Gβ, and Gγ subunits. Based on structural and functional similarity of their α-subunits, G proteins are typically grouped into four classes (Gi, Gs, Gq/11, and G12/13). The Gq/11 subfamily consists of Gq, G11, G14, and G15/16 proteins. Gαq is the α-subunit of Gq protein and encoded by GNAQ. Our previous studies revealed that Gαq play an important role in regulating T cell survival and T cell differentiation. Inflammasomes are multiprotein complexes that play a critical role in modulating innate inflammatory response. NLRP3 inflammasome is currently the most extensively studied inflammasome. We found that Gαq suppressed NLRP3 inflammasome activation in macrophage, Gαq also suppressed NLRP3 inflammasome activation in a LPS-induced sepsis mouse model. Gαq can locate to mitochondria and Gαq was required for the maintenance of mitochondrial homeostasis. Gαq regulated NLRP3 inflammasome activation by modulating mitochondrial reactive oxygen species (mtROS). We found that Gαq suppressed NLRP3 inflammasome activation in macrophage, Gαq also suppressed NLRP3 inflammasome activation in a LPS-induced sepsis mouse model. Gαq can locate to mitochondria and Gαq was required for the maintenance of mitochondrial homeostasis. Gαq regulated NLRP3 inflammasome activation by modulating mitochondrial reactive oxygen species (mtROS). Our results indicate that Gαq regulates NLRP3 inflammasome activation by modulating mitochondrial ROS production. Our research provides new mechanistic insight into the activation of NLRP3 inflammasome. As it has been proved that NLRP3 inflammasome plays an important role in the pathogenesis many diseases such as Alzheimer's disease, cancer, and inflammatory bowel disease, Gαq might become a novel drug target for these diseases in future.

The Research Progress of Metformin Regulation of Metabolic Reprogramming in Malignant Tumors.

Metabolism reprogramming is a crucial hallmark of malignant tumors. Tumor cells demonstrateenhanced metabolic efficiency, converting nutrient inputs into glucose, amino acids, and lipids essential for theirmalignant proliferation and progression. Metformin, a commonly prescribed medication for type 2 diabetes mellitus,has garnered attention for its potential anticancer effects beyond its established hypoglycemic benefits. This review adopts a comprehensive approach to delineate the mechanisms underlying metabolite abnormalities within the primary metabolic processes of malignant tumors. This review examines the abnormal activation of G protein-coupled receptors (GPCRs) in these metabolic pathways, encompassing aerobic glycolysis with increased lactate production in glucose metabolism, heightened lipid synthesis and cholesterol accumulation in lipid metabolism, and glutamine activation alongside abnormal protein post-translational modifications in amino acid and protein metabolism. Furthermore, the intricate metabolic pathways and molecular mechanisms through which metformin exerts its anticancer effects are synthesized and analyzed, particularly its impacts on AMP-activated protein kinase activation and the mTOR pathway. The analysis reveals a multifaceted understanding of how metformin can modulate tumor metabolism, targeting key nodes in metabolic reprogramming essential for tumor growth and progression. The review compiles evidence that supports metformin's potential as an adjuvant therapy for malignant tumors, highlighting its capacity to interfere with critical metabolic pathways. In conclusion, this review offers a comprehensive overview of the plausible mechanisms mediating metformin's influence on tumor metabolism, fostering a deeper comprehension of its anticancer mechanisms. By expanding the clinical horizons of metformin and providing insight into metabolism-targeted tumor therapies, this review lays the groundwork for future research endeavors aimed at refining and advancing metabolic intervention strategies for cancer treatment.

Generation of CRISPR/Cas9 modified human iPSC line with correction of heterozygous mutation in exon 6 of the CaSR gene.

The calcium-sensing receptor (CaSR) gene encodes a cell membrane G protein-coupled receptor (GPCR) which has a key role in maintaining the extracellular Ca2+ homeostasis. We aimed at correcting the compound heterozygous mutation in the 6th [c.1656delA, p.I554SfsX73] and 7th [c.2217T > A, p.C739X] exons of the CASR gene which the original patient-derived iPSC line had. The mutation is associated with neonatal severe primary hyperparathyroidism of the patient. We generated and characterized a CRISP/Cas9-edited hiPSC line with the restored sequence in the sixth exon of the CASR gene, bearing only heterozygous mutation in the 7th exon. The results showed that the new genetically modified cell line has karyotype without abnormalities, typical hiPSCs morphology, characteristic expression of pluripotency markers, and ability to develop into three germ layers, and differentiates in chondrogenic, adipogenic, osteogenic directions. This new cell line will complement the existing pool of CaSR-mutated cell lines, a valuable resource for in-depth understanding of neonatal severe primary hyperparathyroidism. This will allow further exploration of the application of pharmacological drugs in the context of personalized medicine to correct Ca-homeostasis disorders.

Characterization, expressional and evolutionary analysis of five fish-specific CCRs (CCR4La, CCR4Lc, CCR12a1, CCR12a2, and CCR12b) in largemouth bass (Micropterus salmoides)

CC chemokine receptors (CCRs), the numbers of the G protein-coupled receptor (GPCR) superfamily, had crucial roles in treating infection, inflammation, and tissue damage by binding to their ligands. In this study, five fish-specific CCRs, namely CCR4La, CCR4Lc, CCR12a1, CCR12a2, and CCR12b, were identified in largemouth bass (Micropterus salmoides). The correction of nomenclatures of these CCRs were confirmed by phylogenetic analysis, structural analysis and genomic synteny analysis. Following 1×106 CFU/mL and 1×107 CFU/mL Edwardsiella piscicida infection, these five CCRs were significantly induced in spleen of largemouth bass, indicating their important roles in the immune response against bacterial infection. Selection pressure analysis revealed that CCR4La, CCR4Lc, CCR12a1, and CCR12a2 underwent negative selection pressure, whereas CCR12b experienced positive selection pressure. Robust selection site detection methods identified that positive selected sites of CCR4La, CCR4Lc, CCR12a1, and CCR12a2 mainly distributed in their extracellular regions, which involved in ligand binding and pathogen interaction. Similarly, the positive selected sites of CCR12b were also located in its extracellular regions. The accuracy of the pressure selected sites were also validated by molecular docking analysis. The potential ligands for these five CCRs were identified by molecular docking analysis, with finding that CCL3 and CCL5 might be the ligands of largemouth bass CCR4La/Lc, and CCL5, CCL8, CCL7, CCL13 and CCL26 might be that of largemouth bass CCR12a1/a2/b. Our results provided basis for elucidating the functions of chemokine-receptor complex in largemouth bass.

Comparative Study of Allosteric GPCR Binding Sites and Their Ligandability Potential.

The steadily growing number of experimental G-protein-coupled receptor (GPCR) structures has revealed diverse locations of allosteric modulation, and yet few drugs target them. This gap highlights the need for a deeper understanding of allosteric modulation in GPCR drug discovery. The current work introduces a systematic annotation scheme to structurally classify GPCR binding sites based on receptor class, transmembrane helix contacts, and, for membrane-facing sites, membrane sublocation. This GPCR specific annotation scheme was applied to 107 GPCR structures bound by small molecules contributing to 24 distinct allosteric binding sites for comparative evaluation of three binding site detection methods (BioGPS, SiteMap, and FTMap). BioGPS identified the most in 22 of 24 sites. In addition, our property analysis showed that extrahelical allosteric ligands and binding sites represent a distinct chemical space characterized by shallow pockets with low volume, and the corresponding allosteric ligands showed an enrichment of halogens. Furthermore, we demonstrated that combining receptor and ligand similarity can be a viable method for ligandability assessment. One challenge regarding site prediction is the ligand shaping effect on the observed binding site, especially for extrahelical sites where the ligand-induced effect was most pronounced. To our knowledge, this is the first study presenting a binding site annotation scheme standardized for GPCRs, and it allows a comparison of allosteric binding sites across different receptors in an objective way. The insight from this study provides a framework for future GPCR binding site studies and highlights the potential of targeting allosteric sites for drug development.

Insight into structural properties of viral G protein-coupled receptors and their role in the viral infection: IUPHAR Review 41.

G protein-coupled receptors (GPCRs) are pivotal in cellular signalling and drug targeting. Herpesviruses encode GPCRs (vGPCRs) to manipulate cellular signalling, thereby regulating various aspects of the virus life cycle, such as viral spreading and immune evasion.vGPCRs mimic host chemokine receptors, often with broader signalling and high constitutive activity. This review focuses on the recent advancements in structural knowledge about vGPCRs, with an emphasis on molecular mechanisms of action and ligand binding. The structures of US27 and US28 from human cytomegalovirus (HCMV) are compared to their closest human homologue, CX3CR1. Contrasting US27 and US28, the homotrimeric UL78 structure (HCMV) reveals more distance to chemokine receptors. Open reading frame 74 (ORF74; Kaposi's sarcoma-associated herpesvirus) is compared to CXCRs, whereas BILF1 (Epstein-Barr virus) is discussed as a putative lipid receptor. Furthermore, the rolesof vGPCRs in latency and lytic replication, reactivation, dissemination and immune evasion arereviewed, together with their potential as drug targets for virus infections and virus-related diseases.

Fusarium graminearum Ste2 and Ste3 Receptors Undergo Peroxidase-Induced Heterodimerization when Expressed Heterologously in Saccharomyces cerevisiae.

Fusarium graminearum FgSte2 and FgSte3 are G-protein coupled receptors (GPCRs) shown to play roles in hyphal chemotropism and fungal plant pathogenesis in response to activity arising from host-secreted peroxidases. Here, we follow up on the observation that chemotropism is dependent on both FgSte2 and FgSte3 being present; testing the possibility that this might be due to formation of an FgSte2-FgSte3 heterodimer. Bioluminescence resonance energy transfer (BRET) analyses were conducted in Saccharomyces cerevisiae, where the addition of horse radish peroxidase (HRP) was found to increase the transfer of energy from the inducibly-expressed FgSte3-Nano luciferase donor, to the constitutively-expressed FgSte2-yellow fluorescent protein (YFP) acceptor, compared to controls. A partial response was also detected when an HRP-derived ligand-containing extract was enriched from F. graminearum spores and applied instead of HRP. In contrast, substitution with pheromones or an unrelated bovine GPCR, rhodopsin-YFP used as acceptor, eliminated all BRET responses. Interaction results were validated by affinity pulldown and receptor expression was validated by confocal immunofluorescence microscopy. Taken together these findings demonstrate the formation of HRP and HRP-derived ligand stimulated heterodimers between FgSte2 and FgSte3. Outcomes are discussed from the context of the roles of ligands and reactive oxygen species in GPCR dimerization.

Activation of Gs signaling in mouse enteroendocrine K-cells greatly improves obesity- and diabetes-related metabolic deficits.

Following a meal, glucagon-like peptide-1 (GLP1) and glucose-dependent insulinotropic polypeptide (GIP), the two major incretins promoting insulin release, are secreted from specialized enteroendocrine cells (L- and K-cells, respectively). Although GIP is the dominant incretin in humans, the detailed molecular mechanisms governing its release remain to be explored. GIP secretion is regulated by the activity of G protein-coupled receptors (GPCRs) expressed by K-cells. GPCRs couple to one or more specific classes of heterotrimeric G proteins. In the present study, we focused on the potential metabolic roles of K-cell Gs. First, we generated a mouse model that allowed us to selectively stimulate K-cell Gs signaling. Second, we generated a mouse strain harboring an inactivating mutation of Gnas, the gene encoding the alpha-subunit of Gs, selectively in K-cells. Metabolic phenotyping studies showed that acute or chronic stimulation of K-cell Gs signaling greatly improved impaired glucose homeostasis in obese mice and in a mouse model of type 2 diabetes, due to enhanced GIP secretion. In contrast, K-cell-specific Gnas knockout mice displayed markedly reduced plasma GIP levels. These data strongly suggest that strategies aimed at enhancing K-cell Gs signaling may prove useful for the treatment of diabetes and related metabolic diseases.

The pyruvate–GPR31 axis promotes transepithelial dendrite formation in human intestinal dendritic cells

The intestinal lumen is rich in gut microbial metabolites that serve as signaling molecules for gut immune cells. G-protein-coupled receptors (GPCRs) sense metabolites and can act as key mediators that translate gut luminal signals into host immune responses. However, the impacts of gut microbe-GPCR interactions on human physiology have not been fully elucidated. Here, we show that GPR31, which is activated by the gut bacterial metabolite pyruvate, is specifically expressed on type 1 conventional dendritic cells (cDC1s) in the lamina propria of the human intestine. Using human induced pluripotent stem cell-derived cDC1s and a monolayer human gut organoid coculture system, we show that cDC1s extend their dendrites toward pyruvate on the luminal side, forming transepithelial dendrites (TED). Accordingly, GPR31 activation via pyruvate enhances the fundamental function of cDC1 by allowing efficient uptake of gut luminal antigens, such as dietary compounds and bacterial particles through TED formation. Our results highlight the role of GPCRs in tuning the human gut immune system according to local metabolic cues.

CXC chemokine receptor 4 - mediated immune modulation and tumor microenvironment heterogeneity in gastric cancer: Utilizing multi-omics approaches to identify potential therapeutic targets.

G-protein-coupled receptors (GPRs) are critical regulators of various biological behaviors, and their role in gastric cancer (GC) progression is gaining increasing attention. Among them, the immune regulatory mechanisms mediated by chemokine receptor 4 (CXCR4) remain insufficiently understood. This study aims to explore the immune regulatory functions of CXCR4 and the heterogeneity of the tumor microenvironment (TME) by examining GPR-related gene expression in GC. Through multi-omics approaches, including spatial transcriptomics and single-cell RNA sequencing, we investigated the oncogenic mechanisms of CXCR4, particularly its role in T cell immune exhaustion. In vitro experiments, including ELISA, PCR, CCK8 assays, cell scratch assays, and colony formation assays, were used to validate the role of CXCR4 in the migration and invasion of AGS and SNU-1 cell lines. CXCR4 silencing using siRNA further demonstrated its regulatory effects on these cellular processes. Our results revealed a strong correlation between elevated CXCR4 expression and increased exhaustion of regulatory T cells (Tregs) in the TME. Furthermore, heightened CXCR4 expression was linked to increased TME heterogeneity, driven by oxidative stress and activation of the NF-κB pathway, promoting immune evasion and tumor progression. Silencing CXCR4 significantly inhibited the invasive and proliferative abilities of AGS and SNU-1 cells, while also reducing the expression of pro-inflammatory cytokines IL-1β and interleukin-6, thus alleviating chronic inflammation and improving TME conditions. In conclusion, our comprehensive investigation highlights CXCR4 as a key mediator of TME dynamics and immune modulation in GC. Targeting CXCR4 presents a promising therapeutic strategy to slow tumor progression by reducing Tregs-mediated immune exhaustion and TME heterogeneity, positioning it as a novel therapeutic target in GC treatment.

Orphan GPCRs in Neurodegenerative Disorders: Integrating Structural Biology and Drug Discovery Approaches.

Neurodegenerative disorders, particularly Alzheimer's and Parkinson's diseases, continue to challenge modern medicine despite therapeutic advances. Orphan G-protein-coupled receptors (GPCRs) have emerged as promising targets in the central nervous system, offering new avenues for drug development. This review focuses on the structural biology of orphan GPCRs implicated in these disorders, providing a comprehensive analysis of their molecular architecture and functional mechanisms. We examine recent breakthroughs in structural determination techniques, such as cryo-electron microscopy and X-ray crystallography, which have elucidated the intricate conformations of these receptors. The review highlights how structural insights inform our understanding of orphan GPCR activation, ligand binding and signaling pathways. By integrating structural data with molecular pharmacology, we explore the potential of structure-guided approaches in developing targeted therapeutics toward orphan GPCRs. This structural-biology-centered perspective aims to deepen our comprehension of orphan GPCRs and guide future drug discovery efforts in neurodegenerative disorders.