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Atherosclerosis-associated cardiovascular disease is one of the main causes of death and disability among patients with diabetes mellitus. However, little is known about the impact of S-nitrosylation in diabetes-accelerated atherosclerosis. Here, we show increased levels of S-nitrosylation of guanine nucleotide-binding protein G(i) subunit alpha-2 (SNO-GNAI2) at Cysteine 66 in coronary artery samples from diabetic patients with atherosclerosis, consistently with results from mice. Mechanistically, SNO-GNAI2 acted by coupling with CXCR5 to dephosphorylate the Hippo pathway kinase LATS1, thereby leading to nuclear translocation of YAP and promoting an inflammatory response in endothelial cells. Furthermore, Cys-mutant GNAI2 refractory to S-nitrosylation abrogated GNAI2-CXCR5 coupling, alleviated atherosclerosis in diabetic mice, restored Hippo activity, and reduced endothelial inflammation. In addition, we showed that melatonin treatment restored endothelial function and protected against diabetes-accelerated atherosclerosis by preventing GNAI2 S-nitrosylation. In conclusion, SNO-GNAI2 drives diabetes-accelerated atherosclerosis by coupling with CXCR5 and activating YAP-dependent endothelial inflammation, and reducing SNO-GNAI2 is an efficient strategy for alleviating diabetes-accelerated atherosclerosis. S-nitrosylation can influence many pathophysiological processes. Here the authors show that the coupling efficiency of GNAI2 with CXCR5 is enhanced by S-nitrosylation of GNAI2, leading to Hippo-YAP dysfunction in endothelium, and plays a role in diabetes-accelerated atherosclerosis.

In the clades of animals that diverged from the bony fish, a group of Mas-related G-protein-coupled receptors (MRGPRs) evolved that have an active role in itch and allergic signals 1 , 2 . As an MRGPR, MRGPRX2 is known to sense basic secretagogues (agents that promote secretion) and is involved in itch signals and eliciting pseudoallergic reactions 3 – 6 . MRGPRX2 has been targeted by drug development efforts to prevent the side effects induced by certain drugs or to treat allergic diseases. Here we report a set of cryo-electron microscopy structures of the MRGPRX2–G i1 trimer in complex with polycationic compound 48/80 or with inflammatory peptides. The structures of the MRGPRX2–G i1 complex exhibited shallow, solvent-exposed ligand-binding pockets. We identified key common structural features of MRGPRX2 and describe a consensus motif for peptidic allergens. Beneath the ligand-binding pocket, the unusual kink formation at transmembrane domain 6 (TM6) and the replacement of the general toggle switch from Trp 6.48 to Gly 6.48 (superscript annotations as per Ballesteros–Weinstein nomenclature) suggest a distinct activation process. We characterized the interfaces of MRGPRX2 and the G i trimer, and mapped the residues associated with key single-nucleotide polymorphisms on both the ligand and G-protein interfaces of MRGPRX2. Collectively, our results provide a structural basis for the sensing of cationic allergens by MRGPRX2, potentially facilitating the rational design of therapies to prevent unwanted pseudoallergic reactions. Cryo-electron microscopy structures of the MRGPRX2–G i1 trimer in complex with polycationic compound 48/80 or inflammatory peptides provide insights into the sensing of cationic allergens by MRGPRX2, potentially facilitating the design of therapies to prevent unwanted pseudoallergic reactions.

The G-protein-coupled bile acid receptor (GPBAR) conveys the cross-membrane signalling of a vast variety of bile acids and is a signalling hub in the liver–bile acid–microbiota–metabolism axis 1 – 3 . Here we report the cryo-electron microscopy structures of GPBAR–G s complexes stabilized by either the high-affinity P395 4 or the semisynthesized bile acid derivative INT-777 1 , 3 at 3 Å resolution. These structures revealed a large oval pocket that contains several polar groups positioned to accommodate the amphipathic cholic core of bile acids, a fingerprint of key residues to recognize diverse bile acids in the orthosteric site, a putative second bile acid-binding site with allosteric properties and structural features that contribute to bias properties. Moreover, GPBAR undertakes an atypical mode of activation and G protein coupling that features a different set of key residues connecting the ligand-binding pocket to the G s -coupling site, and a specific interaction motif that is localized in intracellular loop 3. Overall, our study not only reveals unique structural features of GPBAR that are involved in bile acid recognition and allosteric effects, but also suggests the presence of distinct connecting mechanisms between the ligand-binding pocket and the G-protein-binding site in the G-protein-coupled receptor superfamily. Using cryo-electron microscopy, the authors report the structures of G-protein-coupled bile acid receptor–G s complexes and reveal the structural basis of bile acid recognition.

Adhesion G-protein-coupled receptors (GPCRs) are a major family of GPCRs, but limited knowledge of their ligand regulation or structure is available 1 – 3 . Here we report that glucocorticoid stress hormones activate adhesion G-protein-coupled receptor G3 (ADGRG3; also known as GPR97) 4 – 6 , a prototypical adhesion GPCR. The cryo-electron microscopy structures of GPR97–G o complexes bound to the anti-inflammatory drug beclomethasone or the steroid hormone cortisol revealed that glucocorticoids bind to a pocket within the transmembrane domain. The steroidal core of glucocorticoids is packed against the ‘toggle switch’ residue W 6.53 , which senses the binding of a ligand and induces activation of the receptor. Active GPR97 uses a quaternary core and HLY motif to fasten the seven-transmembrane bundle and to mediate G protein coupling. The cytoplasmic side of GPR97 has an open cavity, where all three intracellular loops interact with the G o protein, contributing to the high basal activity of GRP97. Palmitoylation at the cytosolic tail of the G o protein was found to be essential for efficient engagement with GPR97 but is not observed in other solved GPCR complex structures. Our work provides a structural basis for ligand binding to the seven-transmembrane domain of an adhesion GPCR and subsequent G protein coupling. The authors report on the structure of a glucocorticoid-bound adhesion G-protein-coupled receptor–G protein complex.

Arrestins recognize different receptor phosphorylation patterns and convert this information to selective arrestin functions to expand the functional diversity of the G protein-coupled receptor (GPCR) superfamilies. However, the principles governing arrestin-phospho-receptor interactions, as well as the contribution of each single phospho-interaction to selective arrestin structural and functional states, are undefined. Here, we determined the crystal structures of arrestin2 in complex with four different phosphopeptides derived from the vasopressin receptor-2 (V2R) C-tail. A comparison of these four crystal structures with previously solved Arrestin2 structures demonstrated that a single phospho-interaction change results in measurable conformational changes at remote sites in the complex. This conformational bias introduced by specific phosphorylation patterns was further inspected by FRET and 1 H NMR spectrum analysis facilitated via genetic code expansion. Moreover, an interdependent phospho-binding mechanism of phospho-receptor-arrestin interactions between different phospho-interaction sites was unexpectedly revealed. Taken together, our results provide evidence showing that phospho-interaction changes at different arrestin sites can elicit changes in affinity and structural states at remote sites, which correlate with selective arrestin functions. The interaction between a GPCR, such as the vasopressin receptor-2 (V2R), and arrestin depends on the receptors’ phosphorylation pattern. Here authors use FRET and NMR to analyze the phosphorylation patterns of the V2R-arrestin complex and show that phospho-interactions are the key determinants of selective arrestin conformational states and correlated functions.

Odorants are detected as smell in the nasal epithelium of mammals by two G-protein-coupled receptor families, the odorant receptors and the trace amine-associated receptors 1 , 2 (TAARs). TAARs emerged following the divergence of jawed and jawless fish, and comprise a large monophyletic family of receptors that recognize volatile amine odorants to elicit both intraspecific and interspecific innate behaviours such as attraction and aversion 3 – 5 . Here we report cryo-electron microscopy structures of mouse TAAR9 (mTAAR9) and mTAAR9–G s or mTAAR9–G olf trimers in complex with β-phenylethylamine, N , N -dimethylcyclohexylamine or spermidine. The mTAAR9 structures contain a deep and tight ligand-binding pocket decorated with a conserved D 3.32 W 6.48 Y 7.43 motif, which is essential for amine odorant recognition. In the mTAAR9 structure, a unique disulfide bond connecting the N terminus to ECL2 is required for agonist-induced receptor activation. We identify key structural motifs of TAAR family members for detecting monoamines and polyamines and the shared sequence of different TAAR members that are responsible for recognition of the same odour chemical. We elucidate the molecular basis of mTAAR9 coupling to G s and G olf by structural characterization and mutational analysis. Collectively, our results provide a structural basis for odorant detection, receptor activation and G olf coupling of an amine olfactory receptor. Cryo-electron microscopy structures of mouse trace amine-associated receptor 9 reveals structural motifs involved in odorant ligand recognition, including a unique disulfide bond linking the N terminus to extracellular loop 2.

Adhesion G protein-coupled receptors (aGPCRs) constitute an evolutionarily ancient family of receptors that often undergo autoproteolysis to produce α and β subunits 1 – 3 . A tethered agonism mediated by the ‘Stachel sequence’ of the β subunit has been proposed to have central roles in aGPCR activation 4 – 6 . Here we present three cryo-electron microscopy structures of aGPCRs coupled to the G s heterotrimer. Two of these aGPCRs are activated by tethered Stachel sequences—the ADGRG2-β–G s complex and the ADGRG4-β–G s complex (in which β indicates the β subunit of the aGPCR)—and the other is the full-length ADGRG2 in complex with the exogenous ADGRG2 Stachel-sequence-derived peptide agonist IP15 (ADGRG2(FL)–IP15–G s ). The Stachel sequences of both ADGRG2-β and ADGRG4-β assume a U shape and insert deeply into the seven-transmembrane bundles. Constituting the FXφφφXφ motif (in which φ represents a hydrophobic residue), five residues of ADGRG2-β or ADGRG4-β extend like fingers to mediate binding to the seven-transmembrane domain and activation of the receptor. The structure of the ADGRG2(FL)–IP15–G s complex reveals the structural basis for the improved binding affinity of IP15 compared with VPM–p15 and indicates that rational design of peptidic agonists could be achieved by exploiting aGPCR-β structures. By converting the ‘finger residues’ to acidic residues, we develop a method to generate peptidic antagonists towards several aGPCRs. Collectively, our study provides structural and biochemical insights into the tethered activation mechanism of aGPCRs. Cryo-electron microscopy structures of three adhesion G protein-coupled receptors (aGPCRs) complexes provide insight into the tethered activation mechanism of aGPCRs and show the potential for rational design of agonists.

Adhesion G-protein-coupled receptors (aGPCRs) are important for organogenesis, neurodevelopment, reproduction and other processes 1 – 6 . Many aGPCRs are activated by a conserved internal (tethered) agonist sequence known as the Stachel sequence 7 – 12 . Here, we report the cryogenic electron microscopy (cryo-EM) structures of two aGPCRs in complex with G s : GPR133 and GPR114. The structures indicate that the Stachel sequences of both receptors assume an α-helical–bulge–β-sheet structure and insert into a binding site formed by the transmembrane domain (TMD). A hydrophobic interaction motif (HIM) within the Stachel sequence mediates most of the intramolecular interactions with the TMD. Combined with the cryo-EM structures, biochemical characterization of the HIM motif provides insight into the cross-reactivity and selectivity of the Stachel sequences. Two interconnected mechanisms, the sensing of Stachel sequences by the conserved ‘toggle switch’ W 6.53 and the constitution of a hydrogen-bond network formed by Q 7.49 /Y 7.49 and the P 6.47 /V 6.47 φφG 6.50 motif (φ indicates a hydrophobic residue), are important in Stachel sequence-mediated receptor activation and G s coupling. Notably, this network stabilizes kink formation in TM helices 6 and 7 (TM6 and TM7, respectively). A common G s -binding interface is observed between the two aGPCRs, and GPR114 has an extended TM7 that forms unique interactions with G s . Our structures reveal the detailed mechanisms of aGPCR activation by Stachel sequences and their G s coupling. Adhesion GPCRs involved in cell and matrix interactions signal through a distinct self-cleavage, self-activation mechanism.

As a critical subfamily of G protein-coupled receptors (GPCRs), chemokine receptors (CCRs) play pivotal regulatory roles in immune cell migration, inflammatory modulation, tissue regeneration, and tumor microenvironment (TME) remodeling. By specifically recognizing chemokine ligands, CCRs orchestrate immune cell trafficking and tissue positioning, with functional dysregulation implicated in infectious diseases, autoimmune disorders, neurodegenerative pathologies, and cancer. These receptors thus represent promising therapeutic targets. Recent breakthroughs in cryo-electron microscopy (cryo-EM) and computational chemistry have enabled high-resolution structural analysis and dynamic conformational modeling of CCRs, establishing a robust foundation for structure-based drug design (SBDD). This review synthesizes current advances in CCR biology, structural mechanisms, disease involvement, and targeted drug development, providing theoretical insights and technical frameworks for future research.

Arrestins were initially identified for their role in homologous desensitization and internalization of G protein–coupled receptors. Receptor-bound arrestins also initiate signaling by interacting with other signaling proteins. Arrestins scaffold MAPK signaling cascades, MAPK kinase kinase (MAP3K), MAPK kinase (MAP2K), and MAPK. In particular, arrestins facilitate ERK1/2 activation by scaffolding ERK1/2 (MAPK), MEK1 (MAP2K), and Raf (MAPK3). However, the structural mechanism underlying this scaffolding remains unknown. Here, we investigated the mechanism of arrestin-2 scaffolding of cRaf, MEK1, and ERK2 using hydrogen/deuterium exchange–mass spectrometry, tryptophan-induced bimane fluorescence quenching, and NMR. We found that basal and active arrestin-2 interacted with cRaf, while only active arrestin-2 interacted with MEK1 and ERK2. The ATP binding status of MEK1 or ERK2 affected arrestin-2 binding; ATP-bound MEK1 interacted with arrestin-2, whereas only empty ERK2 bound arrestin-2. Analysis of the binding interfaces suggested that the relative positions of cRaf, MEK1, and ERK2 on arrestin-2 likely facilitate sequential phosphorylation in the signal transduction cascade.