Search Results (863)

The chemical constituents and neuroprotective potential of Schizophyllum commune remain insufficiently characterized. Therefore, we isolated and identified five secondary metabolites (A–E) from S. commune, and investigated their neuroprotective activities and underlying mechanisms. Compound C showed the most significant protective effect against H₂O₂-induced cytotoxicity in C17.2 neural stem cells. Spectroscopy was used to structurally characterize the isolated compounds. Using RNA sequencing (RNA-seq), compound C was found to significantly modulate genes associated with G protein-coupled receptor (GPCR)-related signaling pathways and neuroactive ligand–receptor interactions. Differentially expressed genes, including Adora2a, S1pr1, Adm, Tbxa2r, and Grin3b, were validated using quantitative real-time PCR. They are associated with GPCR-related signaling and neurotransmission pathways, consistent with the RNA-seq data. As indicated by the functional enrichment analysis, compound C may regulate neuronal stress responses through GPCR-associated signaling networks. In the Western blot, compound C markedly attenuated H₂O₂-induced protein kinase A (PKA) C phosphorylation without altering total PKA C expression, suggesting that modulation of the cAMP/PKA signaling pathway may contribute to the neuroprotective effects of compound C. Collectively, compound C may exert neuroprotective effects against oxidative stress-induced neuronal injury, potentially through the modulation of GPCR-mediated PKA signaling. S. commune is a promising natural bioactive compound source for further development in neuroprotective research. Full article

APLNR is a therapeutically important G protein-coupled receptor (GPCR) implicated in cardiovascular and metabolic regulation; however, how agonist binding reorganizes receptor dynamics to promote signaling competence remains poorly understood. Here, we used the small-molecule agonist CMF-019 as a representative ligand and integrated Gaussian accelerated molecular dynamics (GaMD), Markov state models (MSMs), and neural relational inference (NRI) to characterize the conformational dynamics, kinetic organization, and allosteric communication of APLNR in apo and CMF-019-bound states. We found that CMF-019 binding altered structural flexibility in extracellular and intracellular regions while modifying collective motions within the transmembrane core, indicating a transition toward a more signaling-permissive dynamic state. MSM analyses further revealed that CMF-019 binding redistributed APLNR toward activation-related intermediate conformations and accelerated transitions among metastable states. Mechanistically, NRI uncovered extensive rewiring of the receptor communication network, in which CMF-019 binding strengthened transmembrane coupling and redirected signal propagation toward more convergent signaling routes linked to intracellular functional regions. Together, these findings suggest that CMF-019 promotes APLNR signaling competence through integrated kinetic and allosteric remodeling, revealing a dynamic mechanism by which an agonist can reorganize receptor communication prior to downstream coupling. Full article

Glaesserella parasuis (G. parasuis) is a major respiratory pathogen in piglets, but the regulatory mechanisms underlying its induced pulmonary inflammation remain poorly understood. In this study, whole-transcriptome sequencing was carried out on lung tissues from colostrum-deprived piglets with mild and severe serotype 5 G. parasuis infection and healthy controls. Differential expression (DE) analysis revealed 299 nominally DE mRNAs and 408 nominally DE lncRNAs in the mild group, increasing to 625 and 1193, respectively, in the severe group. Ingenuity Pathway Analysis identified the S100 family signaling pathway as a core inflammatory module predicted to be activated across both infection grades, with its transcriptional involvement expanding from 8 genes in mild infection to 42 genes in severe infection. Notably, G-protein-coupled receptors (GPCRs) accounted for nearly half (19/42) of the S100-associated DE genes in severe infection, covering multiple functional categories including chemokine receptors, lipid mediator receptors, and metabotropic receptors, suggesting systemic activation of the GPCR family in severe inflammation. Weighted gene co-expression network analysis identified multiple lncRNA candidates, among which two—LOC110256217 and LOC110259349—showed severity-associated connectivity patterns and were selected for further validation. Following G. parasuis infection, time-series RT-qPCR in 3D4/21 cells confirmed their co-expression with corresponding mRNAs and revealed distinct temporal patterns, suggesting their potential differential involvement at early and late stages of the inflammatory response. Collectively, these findings identify a putative lncRNA-S100-GPCR-associated inflammatory module linked to pulmonary inflammation in G. parasuis infection, providing a transcriptomic resource and candidate lncRNA-mRNA pairs for further functional studies and investigation into host resilience. Given the limited sample size (n = 3 per group), these findings should be considered exploratory and warrant validation in larger cohorts. Full article

Background: Paclitaxel is a cornerstone chemotherapeutic agent widely used in breast cancer treatment, primarily through the stabilization of microtubule dynamics. Beyond its canonical tubulin-targeting activity, increasing evidence suggests that paclitaxel may engage additional molecular targets, contributing to its complex pharmacological profile. In this study, an integrated computational workflow was applied to evaluate the structural compatibility between paclitaxel and the neurokinin-2 receptor (NK2R), a G protein-coupled receptor involved in tumor-associated inflammatory and proliferative signaling pathways. Physicochemical profiling and target prediction were performed using SwissADME and SwissTargetPrediction, followed by molecular docking and molecular dynamics simulations using AutoDock Vina and GROMACS 2024.1. Paclitaxel exhibited physicochemical properties consistent with transient interactions in hydrophobic transmembrane environments. Docking analysis identified a plausible binding mode within the NK2R transmembrane cavity, primarily stabilized by hydrophobic contacts. Molecular dynamics simulations over 100 ns revealed stable ligand occupancy and overall complex stability, while MM-PBSA calculations indicated a favorable transient association. The predicted interaction is consistent with secondary or non-canonical receptor engagement. While NK2R is not established as a pharmacological target of paclitaxel, the results support the structural feasibility of a previously uncharacterized receptor interaction and provide a reproducible computational framework for exploring GPCR-associated effects of cytotoxic agents. Full article

G protein-coupled receptors (GPCRs) are dynamic allosteric proteins whose signaling properties are governed by reciprocal communication between extracellular ligand-binding sites and intracellular transducer interfaces. Although classical pharmacological models established the concept that ligand binding and G protein coupling are thermodynamically linked, recent structural, biophysical, and computational studies have revealed a far more complex picture in which GPCRs exist as ensembles of interconverting conformational states. Accumulating evidence indicates that G proteins function not only as downstream signaling effectors but also as endogenous allosteric modulators. By reshaping receptor conformational landscapes, G protein coupling can influence the structure and dynamics of orthosteric ligand-binding pockets, thereby regulating ligand affinity, binding kinetics, and receptor selectivity. These findings support a bidirectional model of GPCR signaling in which information is transmitted not only from ligand-binding sites to intracellular signaling partners but also in the reverse direction through receptor-wide allosteric networks. Disease-associated mutations of endothelin A receptor (ETAR) provide in vivo evidence that structural perturbations located far from orthosteric ligand-binding sites can alter ligand recognition through long-range allosteric communication. In addition, emerging studies of positive allosteric modulators demonstrate the therapeutic potential of selectively stabilizing ligand–receptor–G protein complexes. These observations suggest that ligand recognition, receptor activation, and transducer coupling should be viewed as integrated properties of a dynamic receptor–ligand–transducer ensemble. This perspective provides a conceptual framework that links classical GPCR pharmacology, structural biology, disease mechanisms, and next-generation drug discovery. Full article

Depression is a leading cause of disability worldwide, and currently available antidepressants are limited by delayed therapeutic onset, inadequate efficacy in some patients, and adverse effects. G protein-coupled receptors (GPCRs), the largest family of membrane receptors in the central nervous system, regulate neurotransmission, neuroplasticity, neuroinflammation, stress responses, and reward processing, and are therefore important targets for antidepressant drug development. Natural products are a rich source of structurally diverse bioactive compounds, many of which show antidepressant-like effects through the modulation of GPCR-mediated signaling pathways. In this narrative review, we summarize the roles of major GPCR families implicated in depression and provide an updated overview of natural products that modulate these receptors. We particularly emphasize receptor-specific mechanisms, downstream signaling networks, and the pharmacological actions of representative natural compounds. We also highlight emerging concepts in GPCR biology, including receptor heteromerization, signaling bias, and allosteric modulation, that may create new opportunities for antidepressant discovery. Finally, we discuss current challenges related to target validation, pharmacokinetics, and clinical translation. Collectively, these insights support further investigation of natural product-derived GPCR modulators as potential leads for next-generation antidepressant development. Full article

Sustained neurohormonal stress, adverse myocardial remodeling, and inflammation are major components of heart failure (HF) progression. Alterations in circulating neurohormonal signaling are directly sensed by the β-adrenergic receptor (βAR), a system mainly responsible for chronotropic and inotropic cardiac responses. βARs are regulated by G-protein-coupled receptor (GPCR) kinase 2 (GRK2). Within this context, decades of study have unraveled mechanistic details on how GRK2 canonically imposes a “brake” on βARs and other GPCR-mediated signaling. Notably, an expanding body of evidence demonstrates that GRK2 functions in a highly compartment- and cell-dependent manner, with roles extending far beyond GPCR regulation. These noncanonical activities span metabolic control, maintenance of organelle integrity, and regulation of inter-cellular signaling networks, particularly those governing immune–vascular interactions. In this review, we will discuss recent advances in our understanding of the cell-specific functions of GRK2, its emerging biological roles in cardiac diseases, and the opportunities these findings present for advancing mechanistic insights in cardio-oncology. We propose that the therapeutic value of GRK2 is directly dependent on a deeper understanding of its noncanonical functions in a compartment- and cell-specific manner within a disease-specific context. Full article

The spatial organisation of plasma membrane proteins such as G protein-coupled receptors (GPCRs) plays a critical role in regulating cell signalling, function, and ultimately cell fate. Resolving this organisation requires techniques capable of probing dynamics at the single-molecule level with high spatial and temporal resolution. In this study, we employ the complementary fluorescence fluctuation spectroscopy approaches, Fluorescence Correlation Spectroscopy (FCS), Photon Counting Histogram Analysis (PCH), Raster Image Correlation Spectroscopy (RICS) and Number and Brightness Analysis (N&B), in conjunction with Fluorescence Recovery After Photobleaching (FRAP), to investigate the membrane organisation of the C-X-C chemokine receptor 4 (CXCR4), a GPCR known to undergo ligand-induced reorganisation. At the nanoscale, FCS highlighted opposing effects on diffusion after agonist (CXCL12) and inverse agonist (IT1t) treatment, whilst RICS also showed ligand-mediated changes in particle number. Both single-point and image-based brightness analyses (PCH and N&B) showed increased brightness after CXCL12 treatment, consistent with the pre-internalisation clustering of CXCR4. At the microscale, FRAP showed an increase in immobile CXCR4, not visible to FFS approaches, following CXCL12 stimulation. This integrated approach, performed on a single commercial confocal microscope, provides valuable insight into the reorganisation of CXCR4 in the plasma membrane over a range of temporal and spatial scales, which are not detectable using standard imaging. Full article

Cheonggukjang (CGJ) exerts anti-obesity and lipid-lowering effects; however, its effects on gut microbiota-derived short-chain fatty acid (SCFA) production, adipose G protein-coupled receptor (GPCR) expression, and the mechanistic associations between them have not been investigated. Thus, the current study aimed to investigate these relationships in relation to lipid metabolism in white adipose tissue (WAT). Two distinct CGJ samples were administered to high-fat/high-cholesterol diet-induced (HCFD) obese mice. CGJ slightly lowered body weight gain and significantly improved dyslipidemia and hepatic lipid accumulation, also improving WAT lipid metabolism-related gene expression. Additionally, CGJ reversed gut microbiota dysbiosis, increased the abundance of genera associated with SCFA production, and increased colonic SCFA levels. Adipose Gpr41 and Gpr109a expressions were upregulated, and their mRNA levels were strongly correlated with systemic lipid indicators and WAT lipid-metabolism genes. To the best of our knowledge, this is the first study to provide evidence that CGJ modulates gut microbiota-derived SCFA levels and elevates adipose GPCR gene expression, suggesting that CGJ may exert anti-obesity and lipid-metabolism-alleviating effects through the gut microbiota–SCFA–adipose GPCR–WAT lipid metabolism axis. Full article

G protein-coupled receptors (GPCRs) are present in all kingdoms of life. GPCRs are the largest family of signaling proteins in animals, including humans. Numerous lines of indirect evidence suggest that eukaryotic light-sensitive rhodopsins (usually called type II), as well as other structurally similar non-visual GPCRs, trace their origins from prokaryotic rhodopsins (type I), possibly via receptors in unicellular eukaryotes that have a similar transmembrane core, even though existing sequence analysis software cannot detect homology. Bacterial and archaeal rhodopsins share the same overall design with eukaryotic GPCRs: a flexible core consisting of seven transmembrane α-helices with an extracellular N-terminus, an intracellular C-terminus, and three loops on each side of the membrane. Both families include many hundreds of members and apparently have expanded for billions of years, which makes the results of direct comparisons of the sequence and structure of these groups of proteins inconclusive. The distribution of residues with aromatic and ionizable side chains in prokaryotic rhodopsins and eukaryotic GPCRs was found to be similar. Established similarities suggest that shared origins are possible but do not unambiguously prove this hypothesis. Full article

G protein-coupled receptors (GPCRs) are among the most common drug targets, with numerous agonists and antagonists approved for clinical use. More recently, it has been appreciated that drugs can also modulate the action of natural agonists of these receptors, thus providing unique clinical advantages. Here, we describe the identification and characterization of a small molecule positive allosteric modulator (PAM) of secretin action at the class B G protein-coupled secretin receptor. This phenyl(trifluoromethyl)-pyrimidine can occupy the secretin receptor without stimulating its internalization, yet priming it to enhance both the potency and efficacy of the action of natural secretin. This is also shown to exhibit its effects on cells expressing low numbers of these receptors, without enhancing the effects of other structurally related hormones acting at other class B GPCRs. The mechanism responsible for this PAM effect is the slowing of the off-rate of receptor-bound secretin. This compound can serve as a lead to the development of other drugs that enhance the action of natural endogenous secretin and can be utilized to explore the potential therapeutic utility of such compounds. Full article

Cyclic adenosine monophosphate (cAMP) is a ubiquitous second messenger downstream of G protein-coupled receptors (GPCRs) and a central regulator of cellular signaling. Genetically encoded exchange proteins directly activated by cAMP (Epac)-based Förster resonance energy transfer (FRET) biosensors enable real-time monitoring of cAMP dynamics in living cells, but commonly used cyan/yellow FRET pairs require short-wavelength excitation, limiting compatibility with multiplex imaging and blue-light optogenetic tools such as bacterial photoactivated adenylyl cyclases (bPACs). Here, we engineered and systematically characterized four red-shifted Epac-based single-chain FRET cAMP sensors combining yellow or orange FRET donors with red fluorescent FRET acceptors. Using ratiometric live-cell imaging, we quantified stimulus-evoked FRET responses and identified Epac_red4 as the best-performing variant, showing an approximately 55% decrease in normalized FRET after forskolin stimulation. Epac_red4 also reliably detected G_i/o-mediated decreases in cAMP following μ-opioid receptor activation. Brief 405 nm light pulses induced graded and reversible cAMP elevations using the low dark-activity variant bPAC-F198Y. Furthermore, Epac_red4 enabled analysis of cAMP recovery kinetics during phosphodiesterase inhibition and multiplex imaging of cAMP and intracellular Ca²⁺ using Fura-2 with minimal spectral and pH-related interference under physiological imaging conditions. Together, Epac_red4 represents a robust red-shifted cAMP sensor for optogenetic and multiplex signaling studies. Full article

The glucagon-like peptide-1 receptor (GLP-1R) is a class B G protein-coupled receptor (GPCR) central to metabolic regulation, and its potential modulation by dietary phytochemicals is increasingly recognized as physiologically relevant. Understanding how such compounds interact with GLP-1R is important for clarifying mechanisms that may contribute to gut-to-brain signaling. In this study, we examined three structurally related dietary ginsenosides, Rg1, Rg2, and Rg3, as potential modulators of GLP-1R using luciferase reporter assays and computational analyses. Despite sharing similar molecular weights, a common dammarane scaffold, and comparable sugar moieties, the three ginsenosides displayed distinct effects on GLP-1R activity: Rg2 and Rg3 potently reduced receptor activation in a dose-dependent manner when co-administered with Exendin-4, whereas Rg1 had minimal effect. Computational screening of the GLP-1R structure for binding sites identified a putative extracellular pocket on the protein that can accommodate these compounds, while molecular docking and binding free energy calculations provided predicted affinities qualitatively reflecting the phytochemicals’ experimental activities. These findings point to a plausible extracellular mechanism through which dietary ginsenosides may influence GLP-1R responsiveness at the intestinal interface. Our results point to the possibility that non-absorbed phytochemicals can differentially modulate gut-expressed receptors, suggesting a novel pathway for dietary signaling relevant to ethnopharmacology and metabolic health. Full article

Background/Objectives: Signaling mediators of PPARγ influence pathways involved in adipogenesis, lipid storage, inflammation, energy-related processes, and glucose utilization. Recent research indicates that PPARγ coregulators, recruited or released during ligand binding, govern specific gene pathways. It was recently discovered that Gα_q, a heterotrimeric G protein subunit, also signals to PPARγ and may significantly affect adipogenesis and glucose sensitivity. Methods: To explore Gα_q’s role in adipocytes, we generated CRISPR-mediated Gα_q (Gnaq) knockout (Gnaq KO) and scramble control cells from 3T3-L1 preadipocytes. Results: The absence of Gα_q resulted in increased lipid accumulation and elevated serine 273 (but not serine 112) phosphorylation of PPARγ. Gα_q deficiency also decreased mitochondrial abundance and respiration in response to PPARγ ligands such as rosiglitazone, pioglitazone, and troglitazone. RNA sequencing comparing differentiated Gnaq KO and control adipocytes identified over 800 differentially expressed genes, including those associated with enhanced lipid metabolism and reduced inflammation. Corresponding PamGene kinome profiling showed increased serine/threonine kinase activity and decreased phosphotyrosine kinase signaling in Gnaq KO adipocytes. Conclusions: These findings support Gα_q as a regulator of adipocyte function, linking kinase signaling pathways to PPARγ-mediated transcription. This research provides mechanistic insights into targeting Gα_q as a potential treatment for individuals with obesity and metabolic disorders. Full article

Background: Dysregulated G protein-coupled receptor (GPCR) signaling is increasingly implicated as an important driver for oncogenesis. Uveal melanoma (UM) represents a highly metastatic intraocular malignancy primarily driven by activating mutations in G protein family members Gαq/11. Although Tebentafusp, the first FDA-approved bi-specific T-cell engager for UM, improves survival, its activity is restricted to specific human leukocyte antigen (HLA) alleles, highlighting the need to identify broadly expressed targetable proteins for immunotherapeutic strategies. Here we aimed to define surfaceome and phospho-signaling signatures associated with oncogenic Gαq-signaling. Methods: Heterologous and UM in vitro systems were used to interrogate Gαq-driven changes. HEK293T cells were transfected with wild-type Gαq or the oncogenic Gαq (R183Q) mutant, with surface marker profiles quantified by flow cytometry. Complementary immunophenotyping was performed in the Gαq-mutant UM cell line MP46 and Gα11-mutant line MP41. Kinase phosphorylation was assessed in control and Gαq mutant conditions followed by effect size estimation (Hedges’ g), Welch’s t-test, principal component analysis, and Spearman correlation-based network analysis of surface and phosphoprotein readouts. Results: Hyperactive Gαq in HEK293T cells induced graded remodeling of surface protein profiles, including reduced CD56 (NCAM) and CD49c (ITGA3) expression. Similarly, in UM models, MP46 versus MP41 had limited expression of CD56 and CD49c. Moreover, phospho kinase profiling and network analysis identified altered surface-phosphoprotein relationships, including a CD56-p70 S6 kinase association. Conclusions: These data provide new insights into Gαq-driven modulators of UM phenotype of relevance for studies of tumor–microenvironment interaction and metastasis. Full article