Seven-transmembrane receptors

Activation and signaling characteristics of the hydroxy-carboxylic acid 3 receptor identified in human neutrophils through a microfluidic flow cell technique

Human neutrophils express numerous G protein-coupled receptors (GPCRs) of importance for immune regulation. However, several functionally characterized neutrophil GPCRs, are not included within the human neutrophil proteome. To identify GPCRs not previously demonstrated to be expressed in human neutrophils, we utilized a microfluidic flow cell technique in conjunction with subcellular granule fractionation and liquid chromatography-tandem mass spectrometry (LC-MS/MS). This approach led to the identification of hydroxy-carboxylic acid 3 receptor (HCA3R, also known as GPR109B) as a novel component of the human neutrophil proteome. The β-oxidation intermediate 3-hydroxy-octanoic acid (3-OH-C8) is the primary endogenous agonist of the HCA3R and expressed at high levels in adipocytes where it exerts anti-lipolytic effects. However, literature describing the role and function of HCA3R in human neutrophils is scarce. We show that 3-OH-C8, as well as the synthetic HCA3R agonist IBC 293, activate human neutrophils determined as an increase in the intracellular concentration of free calcium ions ([Ca2+]i) and activation of the NADPH oxidase. However, in contrast to the rise in [Ca2+]i, which could be triggered in naïve neutrophils, pre-treatment of neutrophils was required for the HCA3R agonists to activate the NADPH oxidase. That is, the HCA3R-mediated NADPH oxidase activation occurred only in neutrophils pre-treated with either an actin cytoskeleton disrupter or an allosteric modulator targeting the GPCR termed free fatty acid receptor 2 (FFA2R). Our findings demonstrate that HCA3R is not only a new member of the human neutrophil proteome but also exhibits functional activity with complex signaling pathways when stimulated with endogenous and synthetic HCA3R agonists.

Advancing targeted therapies in pancreatic cancer: Leveraging molecular abberrations for therapeutic success

Pancreatic cancer is one of the most deadly with poor prognosis and overall survival rate due to the dense stroma in the tumors which often is challenging for the delivery of drug to penetrate deep inside the tumor bed and usually results in the progression of cancer. The conventional treatment such as chemotherapy, radiotherapy or surgery shows a minimal benefit in the survival due to the drug resistance, poor penetration, less radiosensitivity or recurrence of tumor. There is an urgent demand to develop molecular-level targeted therapies to achieve therapeutic efficacy in the pancreatic ductal adenocarcinoma (PDAC) patients. The precision oncology focuses on the unique attributes of the patient such as epigenome, proteome, genome, microbiome, lifestyle and diet habits which contributes to promote oncogenesis. The targeted therapy helps to target the mutated proteins responsible for controlling growth, division and metastasis of tumor in the cancer cells. It is very important to consider all the attributes of the patient to provide the suitable personalized treatment to avoid any severe side effects. In this review, we have laid emphasis on the precision medicine; the utmost priority is to improve the survival of cancer patients by targeting molecular mutations through transmembrane proteins, inhibitors, signaling pathways, immunotherapy, gene therapy or the use of nanocarriers for the delivery at the tumor site. It will become beneficial therapeutic window to be considered for the advanced stage pancreatic cancer patients to prolong their survival rate.

Intracellular GPCR modulators enable precision pharmacology

G-protein-coupled receptors (GPCRs) have proven to be the most successful target class for drug discovery but their complicated signal transduction pathways cause difficulties for drug development. Recently, ligands have been identified that engage an intracellular binding site which promotes pathway biased signal in cooperation with orthosteric ligands. Here, we explore the topic of biased signaling and intracellular modulators to understand their application for precision pharmacology of Class A or Rhodopsin-Like GPCRs.

Loss of expression and function of Gβγ by GNB1 encephalopathy-associated L95P mutation of the Gβ1 subunit

Background

G-proteins areindispensable regulators of cellular signaling, with G-protein-gated inwardly rectifying potassium channels (GIRK) as key effectors. GNB1 encephalopathy (GNB1E) is a congenital neurological syndrome resulting from mutations in the GNB1 gene, encoding the Gβ1 subunit of G-proteins trimer (Gαβγ). GNB1E manifests as a global developmental delay, accompanied by tonus disturbances, ataxia, and epilepsy.

Methods

We utilized the Xenopus laevis oocyte heterologous expression system to investigate the impact of the L95P mutation in Gβ1 (Gβ1-L95P) on the activation of neuronal GIRK channels GIRK2 and GIRK1/2. Mutant and wild-type (WT) Gβ1 RNAs were co-injected with RNAs encoding the Gγ2 and GIRK channel subunits. The expression levels of both Gβ1 and the channel proteins, as well as the channel activity, were systematically monitored. Additionally, rigid-body docking was used to model the GIRK1/2-Gβγ complex, evaluating L95P's effect on channel-Gβγ interaction, Gβγ stability, and Gβγ-effector affinity.

Results

. Gβ1-L95P exhibited reduced protein expression compared to WT. Even after RNA adjustments to restore comparable membrane localization, the mutant failed to effectively activate GIRK2 and GIRK1/2. Structural analysis revealed that L95 was not consistent in the Gβγ-effector interface. Thermodynamic calculations suggested that the mutation primarily destabilized Gβ1 and Gβ1-effector complex.

Conclusion

Gβ1-L95P leads to both reduced protein expression and impaired function in the GIRK-Gβγ interaction system. The later effect can be attributed to the changes associated with protein misfolding.

Proximity-induced membrane protein degradation for cancer therapies

The selective modulation of membrane proteins presents a significant challenge in drug development, particularly in cancer therapies. However, conventional small molecules and biologics often face significant hurdles in effectively targeting membrane-bound proteins, largely due to the structural complexity of these proteins and their involvement in intricate cellular processes. In light of these limitations, proximity-induced protein modulation has recently emerged as a transformative approach. It leverages molecule-induced proximity strategies to commandeer endogenous cellular machinery for precise protein manipulation. One of these modulatory strategies is protein degradation, wherein membrane-targeting degraders derived from proximity-induction approaches offer a unique therapeutic avenue by inducing the irreversible removal of key oncogenic and immune-regulatory proteins to combat cancer. This review explores the fundamental principles underlying proximity-driven membrane protein degradation, highlighting key strategies such as LYTACs, PROTABs, TransTACs, and IFLD that are reshaping targeted cancer therapy. We discuss recent technological advancements in the application of proximity-induced degraders across breast cancer, lung cancer, immunotherapy, and other malignancies, underscoring how these innovative approaches have demonstrated significant therapeutic potential. Lastly, while these emerging technologies offer significant promise, they still face substantial limitations, including drug delivery, selectivity, and resistance mechanisms that need to be addressed to achieve successful clinical translation.

Chemical, Sensory Variations in Black Teas from Six Tea Cultivars in Jingshan, China

The development of black tea quality is the outcome of the synergistic interaction between tea cultivars and the ecological environment of the production area, including factors such as climate, soil, and cultivation practices. Nevertheless, within a specific geographical region, systematic analysis of the environmental regulation mechanisms governing processing adaptability and quality formation among different cultivars remains insufficient. This study evaluated six Camellia sinensis cultivars from the Jingshan region of Hangzhou, China, integrating non-targeted metabolomics, sensory profiling, bioassays, and molecular docking to elucidate cultivar-specific quality attributes. Non-volatile metabolomics identified 84 metabolites linked to color and taste, including amino acids, catechins, flavonoid glycosides, and phenolic acids. Sensory and metabolite correlations revealed that amino acids enhanced brightness and imparted fresh-sweet flavors, while catechins contributed to bitterness and astringency. Specific metabolites, such as 4-hydroxybenzoyl glucose and feruloyl quinic acid, modulated color luminance. Volatile analysis identified 13 aroma-active compounds (OAV ≥ 1), with 1-octen-3-ol, phenylacetaldehyde, and linalool endowing JK with distinct floral-fruity notes. Molecular docking further demonstrated interactions between these volatiles and olfactory receptors (e.g., OR1A1 and OR2J2), providing mechanistic insights into aroma perception. These findings establish a robust link between cultivar-driven metabolic profiles in black tea, offering actionable criteria for cultivar selection and quality optimization in regional tea production.

The single-cell atlas of short-chain fatty acid receptors in human and mice hearts

Introduction

The gut microbiota metabolite, short-chain fatty acids (SCFAs), can protect against multiple cardiovascular diseases, while the molecular targets and underlying mechanisms need to be elucidated. One of the primary mechanisms of SCFA benefits was the direct activation of a group of G-protein-coupled receptors (GPCRs), termed free fatty acid receptors (FFARs), the FFAR2 (GPR43), and FFAR3 (GPR41). At present, the distribution of FFAR2/3 in cardiac cells has not been entirely clarified.

Methods

Using 18 public single-cell RNA-seq and single-nuclear RNA-seq data of human and mouse hearts, we illustrate the entire atlas of FFAR2/3 distribution in different regions and cell types in normal and infarcted hearts.

Results and discussion

We present the atlas of FFAR2/3 in the whole human body, normal and infarcted hearts at single-cell resolution. We also illustrated the entire atlas of FFAR2/3 in normal/ischemic hearts of newborn and adult mice by combining public and newly built sc/snRNA-seq datasets. These findings provide valuable information on the possible effect of SCFAs via FFAR2/3 in the heart and valuable references for future studies.

A time window for memory consolidation during NREM sleep revealed by cAMP oscillation

Memory formation requires specific neural activity in coordination with intracellular signaling mediated by second messengers such as cyclic adenosine monophosphate (cAMP). However, the real-time dynamics of cAMP remain largely unknown. Here, using a genetically encoded cAMP sensor with high temporal resolution, we found neural-activity-dependent rapid cAMP elevation during learning. Interestingly, in slow-wave sleep, during which memory consolidation occurs, the cAMP level in mice was anti-correlated with neural activity and exhibited norepinephrine β1 receptor-dependent infra-slow oscillations that were synchronized across the hippocampus and cortex. Furthermore, the hippocampal-cortical interactions increased during the narrow time-window of the peak cAMP level; suppressing hippocampal activity specifically during this window impaired spatial memory consolidation. Thus, hippocampal-dependent memory consolidation occurs within a specific time window of high cAMP activity during slow-wave sleep.

LTB4 is converted into a potent human neutrophil NADPH oxidase activator via a receptor transactivation mechanism in which the BLT1 receptor activates the free fatty acid receptor 2

The endogenous neutrophil chemoattractant leukotriene B4 (LTB4) is a biased signalling agonist that potently increases the intracellular concentration of free calcium ions ([Ca2+]i), but alone is a weak activator of the neutrophil superoxide anion (O2-)-generating NADPH oxidase. However, in this study we show that an allosteric modulator of the free fatty acid 2 receptor (FFA2R) converts LTB4 into a potent NADPH oxidase activating agonist. While an allosteric modulation of FFA2R was required for LTB4 receptor 1 (BLT1R)-mediated activation of the NADPH oxidase, the LTB4-induced increase in [Ca2+]i was not affected by the modulator. Thus, the biased BLT1R signalling pattern was altered in the presence of the allosteric FFA2R modulator, being biased with a preference towards the signals that activate the NADPH oxidase relative to an increase in [Ca2+]i. Both BLT1R and FFA2R belong to the family of G protein-coupled receptors (GPCRs), and our results show that a communication between the activated BLT1R and the allosterically modulated FFA2Rs generates signals that induce NADPH oxidase activity. This is consistent with a previously described receptor transactivation (crosstalk) model whereby the function of one neutrophil GPCR can be regulated by receptor downstream signals generated by another GPCR. Furthermore, the finding that an allosteric FFA2R modulator sensitises not only the response induced by orthosteric FFA2R agonists but also the response induced by LTB4, violates the receptor restriction properties that normally define the selectivity of allosteric GPCR modulators.

Unraveling GPCRs Allosteric Modulation. Cannabinoid 1 Receptor as a Case Study

G-protein-coupled receptors (GPCRs) constitute one of the most prominent families of integral membrane receptor proteins that mediate most transmembrane signaling processes. Malfunction of these signal transduction processes is one of the underlying causes of many human pathologies (Parkinson's, Huntington's, heart diseases, etc), provoking that GPCRs are the largest family of druggable proteins. However, these receptors have been targeted traditionally by orthosteric ligands, which usually causes side effects due to the simultaneous targeting of homologous receptor subtypes. Allosteric modulation offers a promising alternative approach to circumvent this problematic and, thus, comprehending its details is a most important task. Here we use the Cannabinoid type-1 receptor (CB1R) in trying to shed light on this issue, focusing on positive allosteric modulation. This is done by using the protein-dipole Langevin-dipole (PDLD) within the linear response approximation (LRA) framework (PDLD/S-2000) along with our coarse-grained (CG) model of membrane proteins to evaluate the dissociation constants (K Bs) and cooperativity factors (αs) for a diverse series of CB1R positive allosteric modulators belonging to the 2-phenylindole structural class, considering CP55940 as an agonist. The agreement with the experimental data evinces that significantly populated allosteric modulator:CB1R and allosteric modulator:CP55940:CB1R complexes have been identified and characterized successfully. Analyzing them, it has been determined that CB1R positive allosteric modulation lies in an outwards displacement of transmembrane α helix (TM) 4 extracellular end and in the regulation of the range of motion of a compound TM7 movement for binary and ternary complexes, respectively. In this respect, we achieved a better comprehension of the molecular architecture of CB1R positive allosteric site, identifying Lys1923.28 and Gly1943.30 as key residues regarding electrostatic interactions inside this cavity, and to rationalize (at both structural and molecular level) the exhibited stereoselectivity in relation to positive allosteric modulation activity by considered CB1R allosteric modulators. Additionally, putative/postulated allosteric binding sites have been screened successfully, identifying the real CB1R positive allosteric site, and most structure-activity relationship (SAR) studies of CB1R 2-phenylindole allosteric modulators have been rationalized. All these findings point out towards the predictive value of the methodology used in the current work, which can be applied to other biophysical systems of interest. The results presented in this study contribute significantly to understand GPCRs allosteric modulation and, hopefully, will encourage a more thorough exploration of the topic.

Novel CXCR2 antibodies exhibit enhanced anti-tumor activity in pancreatic cancer

G protein-coupled receptors (GPCRs) are crucial in several physiological and pathological processes and are associated with numerous diseases across all therapeutic areas. Antibodies are well-established therapeutics with better selectivity, stability, and half-life than small molecules and peptides. CXC motif chemokine receptor 2 (CXCR2) and its ligands play functional roles in the progression and metastasis of tumors and activation and trafficking of inflammatory mediators. Several chemical-based antagonists that inhibit the CXCLs/CXCR2 signaling axis are under clinical study in cancer or inflammatory disease research; however, therapeutic antibodies have not yet been successfully established. In this study, we used phage display technology to identify single-chain variable fragment proteins that target the N-terminal domain of human CXCR2. Subsequently, we performed an enzyme-linked immunosorbent assay to validate the interaction of these IgG1 candidates and bio-layer interferometry to determine their affinity. The association of these antibodies, IgG18 and IgG56, with stable HEK293 cell lines expressing hCXCR2 and various cancer cell lines, including pancreatic cancer cells, was further analyzed. We found that IgG18 and IgG56 antibodies antagonized CXCL8-induced CXCR2 signaling, suppressed CXCL8-mediated cell proliferation and migration, and induced apoptosis in pancreatic cancer cells. In a xenograft model of pancreatic cancer, CXCR2 antibodies, IgG18 and IgG56, decreased tumor growth and induced apoptosis in vivo. Our results indicate that CXCR2 inhibitory antibodies attenuate tumor progression and may be potential candidates for anti-tumor therapeutics.

Smoothened inhibition of PKA at cilia transduces Hedgehog signals

Hedgehog (HH) signaling in vertebrates is dependent on the primary cilium, an organelle that scaffolds signal transduction. HH signals induce Smoothened (SMO) enrichment in the cilium and indirectly triggers the conversion of GLI proteins into transcriptional activators of HH target genes. Recently, SMO has been shown to inhibit protein kinase A (PKA). To test the hypothesis that SMO specifically inhibits PKA at cilia to activate the HH signal transduction pathway, we developed a ciliary PKA biosensor. Activation of the HH signal transduction pathway by either Sonic hedgehog (SHH) or SMO agonist (SAG) inhibited ciliary PKA activity. Blocking SMO phosphorylation by GRK2/3 prevented ciliary SMO from inhibiting ciliary PKA activity. Gα i was dispensable for SMO inhibition of ciliary PKA. In contrast, mutating the SMO C-terminal tail protein kinase inhibitor (PKI) pseudosubstrate site interfered with the ability of SMO to inhibit ciliary PKA. Therefore, HH signaling is transduced via SMO direct inhibition of PKA at cilia, in a manner dependent on GRK2/3.

Projection-targeted photopharmacology reveals distinct anxiolytic roles for presynaptic mGluR2 in prefrontal- and insula-amygdala synapses

Dissecting how membrane receptors regulate neural circuits is critical for deciphering principles of neuromodulation and mechanisms of drug action. Here, we use a battery of optical approaches to determine how presynaptic metabotropic glutamate receptor 2 (mGluR2) in the basolateral amygdala (BLA) controls anxiety-related behavior in mice. Using projection-specific photopharmacological activation, we find that mGluR2-mediated presynaptic inhibition of ventromedial prefrontal cortex (vmPFC)-BLA, but not posterior insular cortex (pIC)-BLA, connections produces a long-lasting decrease in spatial avoidance. In contrast, presynaptic inhibition of pIC-BLA connections decreases social avoidance and novelty-induced hypophagia without impairing working memory, establishing this projection as a novel target for the treatment of anxiety disorders. Fiber photometry and viral mapping reveal distinct activity patterns and anatomical organization of vmPFC-BLA and pIC-BLA circuits. Together, this work reveals new aspects of BLA neuromodulation with therapeutic implications while establishing a powerful approach for optical mapping of drug action.

Artificial Intelligence: A New Tool for Structure-Based G Protein-Coupled Receptor Drug Discovery

Understanding protein structures can facilitate the development of therapeutic drugs. Traditionally, protein structures have been determined through experimental approaches such as X-ray crystallography, NMR spectroscopy, and cryo-electron microscopy. While these methods are effective and are considered the gold standard, they are very resource-intensive and time-consuming, ultimately limiting their scalability. However, with recent developments in computational biology and artificial intelligence (AI), the field of protein prediction has been revolutionized. Innovations like AlphaFold and RoseTTAFold enable protein structure predictions to be made directly from amino acid sequences with remarkable speed and accuracy. Despite the enormous enthusiasm associated with these newly developed AI-approaches, their true potential in structure-based drug discovery remains uncertain. In fact, although these algorithms generally predict overall protein structures well, essential details for computational ligand docking, such as the exact location of amino acid side chains within the binding pocket, are not predicted with the necessary accuracy. Additionally, docking methodologies are considered more as a hypothesis generator rather than a precise predictor of ligand-target interactions, and thus, usually identify many false-positive hits among only a few correctly predicted interactions. In this paper, we are reviewing the latest development in this cutting-edge field with emphasis on the GPCR target class to assess the potential role of AI approaches in structure-based drug discovery.

Interleukin-27-polarized HIV-resistant M2 macrophages are a novel subtype of macrophages that express distinct antiviral gene profiles in individual cells: implication for the antiviral effect via different mechanisms in the individual cell-dependent manner

Introduction

Interleukin (IL)-27 is an anti-viral cytokine. IL-27-treated monocyte-derived macrophages (27-Mac) suppressed HIV replication. Macrophages are generally divided into two subtypes, M1 and M2 macrophages. M2 macrophages can be polarized into M2a, M2b, M2c, and M2d by various stimuli. IL-6 and adenosine induce M2d macrophages. Since IL-27 is a member of the IL-6 family of cytokines, 27-Mac was considered M2d macrophages. In the current study, we compared biological function and gene expression profiles between 27-Mac and M2d subtypes.

Methods

Monocytes derived from health donors were differentiated to M2 using macrophage colony-stimulating factor. Then, the resulting M2 was polarized into different subtypes using IL-27, IL-6, or BAY60-658 (an adenosine analog). HIV replication was monitored using a p24 antigen capture assay, and the production of reactive oxygen species (ROS) was determined using a Hydrogen Peroxide Assay. Phagocytosis assay was run using GFP-labeled opsonized E. coli. Cytokine production was detected by the IsoPlexis system, and the gene expression profiles were analyzed using single-cell RNA sequencing (scRNA-seq).

Results and Discussion

27-Mac and BAY60-658-polarized M2d (BAY-M2d) resisted HIV infection, but IL-6-polarized M2d (6-M2d) lacked the anti-viral effect. Although phagocytosis activity was comparable among the three macrophages, only 27-Mac, but neither 6-M2d nor BAY-M2d, enhanced the generation of ROS. The cytokine-producing profile of 27-Mac did not resemble that of the two subtypes. The scRNA-seq revealed that 27-Mac exhibited a different clustering pattern compared to other M2ds, and each 27-Mac expressed a distinct combination of anti-viral genes. Furthermore, 27-Mac did not express the biomarkers of M2a, M2b, and M2c. However, it significantly expressed CD38 (p<0.01) and secreted CXCL9 (p<0.001), which are biomarkers of M1.

Conclusions

These data suggest that 27-Mac may be classified as either an M1-like subtype or a novel subset of M2, which resists HIV infection mediated by a different mechanism in individual cells using different anti-viral gene products. Our results provide a new insight into the function of IL-27 and macrophages.

Genetic variants of accessory proteins and G proteins in human genetic disease

We present a series of three articles on the genetics and pharmacogenetics of G protein- coupled receptors (GPCR). In the first article, we discuss genetic variants of the G protein subunits and accessory proteins that are associated with human phenotypes; in the second article, we build upon this to discuss "G protein-coupled receptor (GPCR) gene variants and human genetic disease" and in the third article, we survey "G protein-coupled receptor pharmacogenomics". In the present article, we review the processes of ligand binding, GPCR activation, inactivation, and receptor trafficking to the membrane in the context of human genetic disease resulting from pathogenic variants of accessory proteins and G proteins. Pathogenic variants of the genes encoding G protein α and β subunits are examined in diverse phenotypes. Variants in the genes encoding accessory proteins that modify or organize G protein coupling have been associated with disease; these include the contribution of variants of the regulator of G protein signaling (RGS) to hypertension; the role of variants of activator of G protein signaling type III in phenotypes such as hypoxia; the contribution of variation at the RGS10 gene to short stature and immunological compromise; and the involvement of variants of G protein-coupled receptor kinases (GRKs), such as GRK4, in hypertension. Variation in genes that encode proteins involved in GPCR signaling are outlined in the context of the changes in structure and function that may be associated with human phenotypes.

Sustained Gαs signaling mediated by vasopressin type 2 receptors is ligand dependent but endocytosis and β-arrestin independent

The canonical model of G protein-coupled receptor (GPCR) signaling comprises G protein activation at the plasma membrane, followed by receptor phosphorylation and β-arrestin recruitment, which leads to receptor desensitization and endocytosis. However, the activation of some GPCRs results in sustained G protein signaling from intracellular compartments in a manner reportedly dependent on β-arrestin and receptor endocytosis. The vasopressin type 2 receptor (V2R) can be activated by two structurally similar hormones, arginine vasopressin and oxytocin, both of which stimulate the production of the second messenger cyclic adenosine monophosphate (cAMP). In this study, we showed that sustained V2R signaling and endosomal Gαs (stimulatory G protein alpha subunit) translocation could occur without β-arrestin-mediated receptor endocytosis and was primarily controlled by the residence time of the ligand on the receptor. β-Arrestin had opposing effects on sustained signaling: It facilitated receptor internalization into endosomes, where it activated Gαs, and promoted cAMP production from this compartment. However, β-arrestin-mediated receptor endocytosis also induced ligand dissociation due to the acidic endosomal environment, thereby limiting the signal. Overall, our data suggest that signals originating at the plasma membrane play a dominant role in sustained V2R signaling stimulated by arginine vasopressin.

Reviewing the Mechanisms of the Interaction of Characteristic Aroma Compounds of Longjing Tea with S-curve, Molecular Docking, and Molecular Dynamics Simulation: With a Focus on (+)-(1R,2S)-Methyl Epijasmonate and β-Ionone as Examples

The S-curve method, molecular docking, and molecular dynamics simulation (MDS) were used to explore the interaction between the aroma compounds of Longjing tea and receptors. The ratio of experimental and theoretical threshold (D) values for (+)-(1R,2S)-methyl epijasmonate and β-ionone was 0.46, indicating a synergistic effect between them. Similarly, synergistic interactions occurred between (R)-(+)-γ-nonanolactone and (R)-(+)-γ-decalactone (D = 0.42), 3-methylbutanal and 2-ethyl-3,5-dimethylpyrazine (D = 0.43). Molecular docking indicates significant changes in the affinity and stability between the binary system and individual compounds with receptors (OR52D1 and OR1A1). Through MDS analysis, it was found that the hydrophobic residues in OR52D1-β-ionone changed from Leu203, Val205, Ala206, Ala258, and Met210 to Tyr111, Ala112, Met210, Ala209, and Ala206 after addition of (+)-(1R,2S)-methyl epijasmonate. Hydrophobic interactions play an integral and important role in the formation of a stable ternary architecture between (+)-(1R,2S)-methyl epijasmonate-β-ionone and OR52D1. By calculating the binding energy of MMGBSA, it was found that the addition of (+)-(1R,2S)-methyl epijasmonate reduced the energy of the binary system from -53.58 to -58.48 kcal/mol, indicating better stability of the new system. The molecular mechanisms of interactions between the characteristic compounds of Longjing tea were revealed, thus providing theoretical support for improving the flavor of Longjing tea.

Chemistries on the inner leaflet of the cell membrane

The cell membrane, characterized by its inherent asymmetry, functions as a dynamic barrier that regulates numerous cellular activities. This Highlight aims to provide the chemistry community with a comprehensive overview of the intriguing and underexplored inner leaflet, encompassing both fundamental biology and emerging synthetic modification strategies. We begin by describing the asymmetric nature of the plasma membrane, with a focus on the distinct roles of lipids, proteins, and glycan chains, highlighting the composition and biofunctions of the inner leaflet and the biological mechanisms that sustain membrane asymmetry. Next, we explore chemical biological strategies for engineering the inner leaflet, including genetic engineering, transmembrane peptides, and liposome fusion-based transport. In the perspective section, we discuss the challenges in developing chemistries for the inner leaflet of the cell membrane, aiming to inspire researchers and collaborators to explore this field and address its unanswered biological questions.

DRD4 Interacts with TGF-β Receptors to Drive Colorectal Cancer Metastasis Independently of Dopamine Signaling Pathway

The functional and pharmacological significance of dopamine receptor D4 (DRD4) in psychiatric and neurological disorders is well elucidated. However, the roles of DRD4 in colorectal cancer (CRC) remain unclear. This study observes a significant upregulation of DRD4 expression in clinical samples, which is negatively correlated with patient prognosis. In vitro, overexpression of DRD4 causes a constitutive activation of β-Arrestin2/PP2A/AKT independent of dopamine. Interestingly, this classical signaling pathway is not associated with the phenotype of DRD4-promoted migration and invasion in CRC cells. Instead, DRD4 interacts with transforming growth factor beta receptors (TGFBR1 and TGFBR2) to activate Smad2 phosphorylation and promote Smad2/Smad4 complex nucleus translocation. Then, SNAI1 and JAG1 are transcriptionally activated to induce epithelial-mesenchymal transition and enhance the metastatic potential of CRC. Notably, the COOH-terminal domain is identified as the key intracellular region for the pro-metastatic roles of DRD4. Furthermore, treatment with a TGFBR1 inhibitor combined with a BMP inhibitor effectively counteracts the pro-metastatic effects induced by DRD4 both in vitro and in vivo. In conclusion, these findings uncover an unconventional role for DRD4 beyond its classic function as a neurotransmitter receptor. The intracellular signaling of DRD4 interacting with TGFBR1 can be targeted pharmacologically for CRC therapy.

Gαo1 and Gαo1/Gαo2 deletion differentially affect hippocampal mossy fiber tract anatomy and neuronal morphogenesis

The heterotrimeric G-protein αo subunit is ubiquitously expressed in the CNS as two splice variants Gαo1 and Gαo2, regulating various brain functions. Here, we investigated the effect of single Gαo1, Gαo2, and double Gαo1/2 knockout on the postnatal development of the murine mossy fiber tract, a central pathway of the hippocampal connectivity circuit. The size of the hippocampal synaptic termination fields covered by mossy fiber boutons together with various fiber length parameters of the tract was analyzed by immunohistochemical staining of the vesicular Zinc transporter 3 (ZnT3) or Synaptoporin at postnatal days 2, 4, 8, 12, 16, and in the adult. Ultimately, Gαo1 knockout resulted in a reduced developmental growth of synaptic mossy fiber terminal fields by 37% in the adult Stratum lucidum and by 30% in the total mossy fiber tract size. Other morphological parameters such as projection length of the infrapyramidal bundle of the tract were increased (+52% in Gαo1 -/- mice). In contrast, Gαo2 knockout had no effects on the mossy fiber tract. Moreover, by using primary heterozygous and homozygous Gαo1 knockout hippocampal cultures, we detected a strongly pronounced reduction in axon and dendrite length (-50% and -38%, respectively) as well as axon and dendrite arborization complexity (-75% and -72% branch nodes, respectively) in the homozygous knockout. Deletion of both splice variants Gαo1 and Gαo2 partially rescued the in vivo and completely reconstituted the in vitro effects, indicating an opposing functional relevance of the two Gαo splice variants for neuronal development and synaptic connectivity.

KCNJ15 inhibits chemical-induced lung carcinogenesis and progression through GNB1 mediated Hippo pathway

Polycyclic aromatic hydrocarbons (PAHs) are important environmental carcinogens that can cause lung cancer. However, the underlying epigenetic mechanism during PAHs-induced lung carcinogenesis has remained largely unknown. Previously, we screened some novel epigenetic regulatory genes during 3-methylcholanthrene (3-MCA)-induced lung carcinogenesis, including the potassium inwardly rectifying channel subfamily J member 15 (KCNJ15) gene. This study aimed to investigate the expression regulation, function, and mechanism of KCNJ15 through database analysis, malignant transformed cell model, and xenograft tumor models. We found that KCNJ15 was remarkably under-expressed during lung carcinogenesis and progression. High levels of DNA methylation led to low KCNJ15 expression in 3-MCA-induced malignantly transformed HBE cells. High expression of KCNJ15 was positively correlated with good survival prognosis in lung cancer patients. KCNJ15 overexpression significantly inhibited the growth, invasion, and migration of lung cancer cells both in vitro and in vivo. Knockdown of KCNJ15 resulted in an opposite phenotype. KCNJ15 regulated the Hippo pathway by activating YAP phosphorylation and inhibiting YAP expression. There was a significant protein-protein interaction between KCNJ15 and the G protein subunit beta 1 (GNB1). GNB1 overexpression effectively reduced the effect of KCNJ15 on Hippo pathway. Our data demonstrated that KCNJ15, as a novel epigenetic silencing tumor suppressor, regulates cell growth, invasion, and migration by interaction with GNB1 protein mediating the Hippo-YAP signaling pathway during chemical-induced lung carcinogenesis and progression. It provides novel insights into epigenetic regulation mechanism during carcinogenesis induced by environmental pollutants.

Targeting G Protein-Coupled Receptors in Immuno-Oncological Therapies

The advent of cancer immunotherapy based on PD-1 and CTLA-4 immune checkpoint blockade (ICB) has revolutionized cancer treatment. However, many cancers do not respond to ICB, highlighting the urgent need for additional approaches to achieve durable cancer remission. The large family of G protein-coupled receptors (GPCRs) is the target of more than 30% of all approved drugs, but GPCRs have been underexploited in cancer immunotherapy. In this review, we discuss the central role of GPCRs in immune cell migration and function and describe how single-cell transcriptomic studies are illuminating the complexity of the human tumor immune GPCRome. These receptors include multiple GPCRs expressed in CD8 T cells that are activated by inflammatory mediators, protons, neurotransmitters, and metabolites that accumulate in the tumor microenvironment, thereby promoting T cell dysfunction. We also discuss new opportunities to target GPCRs as a multimodal approach to enhance the response to ICB for a myriad of human malignancies.

Indirect influence on the BDNF/TrkB receptor signaling pathway via GPCRs, an emerging strategy in the treatment of neurodegenerative disorders

Neuronal survival depends on neurotrophins and their receptors. There are two types of neurotrophin receptors: a nonenzymatic, trans-membrane protein of the tumor necrosis factor receptor (TNFR) family-p75 receptor and the tyrosine kinase receptors (TrkR) A, B, and C. Activation of the TrkBR by brain-derived neurotrophic factor (BDNF) or neurotrophin 4/5 (NT-4/5) promotes neuronal survival, differentiation, and synaptic function. It is shown that in the pathogenesis of several neurodegenerative conditions (Alzheimer's disease, Parkinson's disease, Huntington's disease) the BDNF/TrkBR signaling pathway is impaired. Since it is known that GPCRs and TrkR are regulating several cell functions by interacting with each other and generating a cross-communication in this review we have focused on the interaction between different GPCRs and their ligands on BDNF/TrkBR signaling pathway.

Endomembrane GPCR signaling: 15 years on, the quest continues

G-protein-coupled receptors (GPCRs) are the largest family of cell receptors. They mediate the effects of a multitude of endogenous and exogenous cues, are deeply involved in human physiology and disease, and are major pharmacological targets. Whereas GPCRs were long thought to signal exclusively at the plasma membrane, research over the past 15 years has revealed that they also signal via classical G-protein-mediated pathways on membranes of intracellular organelles such as endosomes and the Golgi complex. This review provides an overview of recent advances and emerging concepts related to endomembrane GPCR signaling, as well as ongoing research aimed at a better understanding of its mechanisms, physiological relevance, and potential therapeutic applications.

The β2 adrenergic receptor cross-linked interactome identifies 14-3-3 proteins as regulating the availability of signaling-competent receptors

The emerging picture of G protein-coupled receptor function suggests that the global signaling response is an integrated sum of a multitude of individual receptor responses, each regulated by their local protein environment. The β2 adrenergic receptor (B2AR) has long served as an example receptor in the development of this model. However, the mechanism and the identity of the protein-protein interactions that govern the availability of receptors competent for signaling remain incompletely characterized. To address this question, we characterized the interactome of agonist-stimulated B2AR in human embryonic kidney 293 cells using FLAG coimmunoprecipitation coupled to stable isotope labeling by amino acids in cell culture and mass spectrometry. Our B2AR cross-linked interactome identified 190 high-confidence proteins, including almost all known interacting proteins and 6 out of 7 isoforms of the 14-3-3 family of scaffolding proteins. Inhibiting 14-3-3 proteins with the peptide difopein enhanced isoproterenol-stimulated adrenergic signaling via cAMP approximately 3-fold and increased both miniGs and arrestin recruitment to B2AR more than 2-fold each, without noticeably changing EC50 with respect to cAMP signaling or effector recruitment upon stimulation. Our results show that 14-3-3 proteins negatively regulate downstream signaling by inhibiting access of B2AR to effector proteins. We propose that 14-3-3 proteins maintain a dynamic pool of B2AR that has reduced signaling efficacy in response to acute agonist stimulation, limiting the number of signaling-competent receptors at the plasma membrane. SIGNIFICANCE STATEMENT: This study presents a new interactome of the agonist-stimulated β2 adrenergic receptor, a paradigmatic G protein-coupled receptor that is both a model system for members of this class and an important signaling protein in respiratory, cardiovascular, and metabolic regulation. We identify 14-3-3 proteins as responsible for restricting β2 adrenergic receptor access to signaling effectors and maintaining a receptor population that is insensitive to acute stimulation by agonists.

FMRFamide G protein-coupled receptors (GPCR) in the cuttlefish Sepiella japonica: Identification, characterization and expression profile

FMRFamide is a ubiquitous neuromodulator in the animal kingdom. Once FMRFamide or similar neuropeptides bind to their G protein-coupled receptors (GPCR), a series of signal transduction events are triggered, thereby mediating various physiological effects. FMRFamide had been reported to be involved in the regulation of sexual maturation in Sepiella japonica. In this research, the full-length cDNA of FMRFamide G protein-coupled receptor of S. japonica (SjFaGPCR) was cloned. The sequence is 1396 bp long and encodes a protein consisting of 418 amino acid residues, lacking a signal peptide at the N-terminal region. The 3D structure of SjFaGPCR was predicted using Todarodes pacificus rhodopsin as a template, and the result indicated the presence of seven transmembrane regions. Multiple sequence alignments and phylogenetic trees indicated that SjFaGPCR is conserved among invertebrates, and shares highly similar sequence characteristics with other cephalopods. In situ hybridization (ISH) results revealed that significant signals of SjFaGPCR were detected in the central medulla and the granular layer cells of the optic lobe, and were also observed in the supraesophageal and subesophageal masses of the brain. Meanwhile, quantitative real-time PCR (qRT-PCR) results showed that a higher expression level of SjFaGPCR mRNA was detected in the brain and optic lobe of female cuttlefish at stage III and stage VI, and also in the brain (stage V) and optic lobe (stages IV and V) of male cuttlefish than that in other tissues. The co-localization results demonstrated that fluorescence signals of SjFMRFamide and SjFaGPCR were overlapped in HEK293 cells, suggesting a possible interaction between the SjFMRFamide and SjFaGPCR. These findings provide molecular support for further exploring the roles of FMRFamide and FaGPCR in the reproductive regulation of S. japonica.

Optogenetic Control of Dopamine Receptor 2 Reveals a Novel Aspect of Dopaminergic Neurotransmission in Motor Function

Dopaminergic neurotransmission plays a crucial role in motor function through the coordination of dopamine receptor (DRD) subtypes, such as DRD1 and DRD2, thus the functional imbalance of these receptors can lead to Parkinson's disease. However, due to the complexity of dopaminergic circuits in the brain, it is limited to investigating the individual functions of each DRD subtype in specific brain regions. Here, we developed a light-responsive chimeric DRD2, OptoDRD2, which can selectively activate DRD2-like signaling pathways with spatiotemporal resolution. OptoDRD2 was designed to include the light-sensitive component of rhodopsin and the intracellular signaling domain of DRD2. Upon illumination with blue light, OptoDRD2 triggered DRD2-like signaling pathways, such as Gαi/o subtype recruitment, a decrease in cAMP levels, and ERK phosphorylation. To explore unknown roles of DRD2 in glutamatergic cell populations of basal ganglia circuitry, OptoDRD2 was genetically expressed in excitatory neurons in lateral globus pallidus (LGP) of the male mouse brain. The optogenetic stimulation of OptoDRD2 in the LGP region affected a wide range of locomotion-related parameters, such as increased frequency of movement and decreased immobility time, resulting in the facilitation of motor function of living male mice. Therefore, our findings indicate a potentially novel role for DRD2 in the excitatory neurons of the LGP region, suggesting that OptoDRD2 can be a valuable tool enabling the investigation of unknown roles of DRD2 at specific cell types or brain regions.

A Dual-Color Fluorescence-Based Ratiometric Assay to Measure Endocytic Trafficking of Surface Proteins

Many membrane proteins on the cell surface are constantly internalized from, and re-delivered to, the plasma membrane. This endocytic cycling, which relies on accurate SNARE-mediated fusion of vesicles containing cargo proteins, is highly important for the function of many proteins such as signaling receptors. While the SNARE proteins that mediate fusion during specific events, such as neurotransmitter and hormone release, in mammalian cells has been heavily studied, the SNARE proteins that mediate surface delivery of specific cargo such as the receptors for these released factors are still not known. A primary barrier to defining core fusion components has been the lack of a quantitative and accessible assay to measure endocytic cycling of cargo proteins as well as SNAREs themselves. Here, we describe an internally controlled dual-color ratiometric fluorescence-based assay to monitor and measure the internalization and recycling of a pool of pre-existing surface cargo proteins, avoiding the confounding effects of other pathways and accounting for cell-to-cell variation in protein expression. This quantitative method will be useful for mechanistically investigating the SNARE and related fusion proteins that mediate surface delivery of specific cargo.

G Protein-Coupled Receptor Heteromers in Brain: Functional and Therapeutic Importance in Neuropsychiatric Disorders

G protein-coupled receptors (GPCRs) represent the largest family of plasma membrane proteins targeted for therapeutic development. For decades, GPCRs were investigated as monomeric entities during analysis of their pharmacology or signaling and during drug development. However, a considerable body of evidence now indicates that GPCRs function as dimers or higher-order oligomers. Greater acceptance of oligomerization occurred with the recognition that GPCR interactions form heteromeric receptor complexes, which was validated in vivo, often with pharmacologic, signaling, and functional properties distinct from the constituent protomers. GPCR heteromerization is reviewed in the context of brain disorders, with examples illustrating their functional implication in diverse neuropsychiatric and neurodegenerative disorders, making them an enormous unexploited resource for selective pharmacotherapy target identification. The strategies for development of heteromer-selective ligands are discussed as a new opportunity to precisely target the function of a receptor complex with greater specificity, in contrast to the classical ligands targeting individual receptors.

Proteome-wide analysis reveals G protein-coupled receptor-like proteins in rice (Oryza sativa)

G protein-coupled receptors (GPCRs) constitute the largest family of transmembrane proteins in metazoans that mediate the regulation of various physiological responses to discrete ligands through heterotrimeric G protein subunits. The existence of GPCRs in plant is contentious, but their comparable crucial role in various signaling pathways necessitates the identification of novel remote GPCR-like proteins that essentially interact with the plant G protein α subunit and facilitate the transduction of various stimuli. In this study, we identified three putative GPCR-like proteins (OsGPCRLPs) (LOC_Os06g09930.1, LOC_Os04g36630.1, and LOC_Os01g54784.1) in the rice proteome using a stringent bioinformatics workflow. The identified OsGPCRLPs exhibited a canonical GPCR 'type I' 7TM topology, patterns, and biologically significant sites for membrane anchorage and desensitization. Cluster-based interactome mapping revealed that the identified proteins interact with the G protein α subunit which is a characteristic feature of GPCRs. Computational results showing the interaction of identified GPCR-like proteins with G protein α subunit and its further validation by the membrane yeast-two-hybrid assay strongly suggest the presence of GPCR-like 7TM proteins in the rice proteome. The absence of a regulator of G protein signaling (RGS) box in the C- terminal domain, and the presence of signature motifs of canonical GPCR in the identified OsGPCRLPs strongly suggest that the rice proteome contains GPCR-like proteins that might be involved in signal transduction.

A small molecule enhances arrestin-3 binding to the β2-adrenergic receptor

G protein-coupled receptor (GPCR) signaling is terminated by arrestin binding to a phosphorylated receptor. Binding propensity has been shown to be modulated by stabilizing the pre-activated state of arrestin through point mutations or C-tail truncation. Here, we hypothesize that pre-activated rotated states can be stabilized by small molecules, and this can promote binding to phosphorylation-deficient receptors, which underly a variety of human disorders. We performed virtual screening on druggable pockets identified on pre-activated conformations in Molecular Dynamics trajectories of arrestin-3, and found a compound targeting an activation switch, the back loop at the inter-domain interface. According to our model, consistent with available biochemical and structural data, the compound destabilized the ionic lock between the finger and the back loop, and enabled transition of the `gate loop` towards the pre-activated state, which stabilizes pre-activated inter-domain rotation. The predicted binding pocket is consistent with saturation-transfer difference NMR data indicating close contact between the piperazine moiety of the compound and C/finger loops. The compound increases in-cell arrestin-3 binding to phosphorylation-deficient and wild-type β2-adrenergic receptor, but not to muscarinic M2 receptor, as verified by FRET and NanoBiT. This study demonstrates that the back loop can be targeted to modulate interaction of arrestin with phosphorylation-deficient GPCRs in a receptor-specific manner.

Essential strategies for the detection of constitutive and ligand-dependent Gi-directed activity of 7TM receptors using bioluminescence resonance energy transfer

The constitutive (ligand-independent) signaling of G protein-coupled receptors (GPCRs) is being increasingly appreciated as an integral aspect of their function; however, it can be technically hard to detect for poorly characterized, e.g. orphan, receptors of the cAMP-inhibitory Gi-coupled (GiPCR) family. In this study, we delineate the optimal strategies for the detection of such activity across several GiPCRs in two cell lines. As our study examples, we chose two canonical GiPCRs - the constitutively active Smoothened and the ligand-activated CXCR4, - and one atypical GPCRs, the chemokine receptor ACKR3. We verified the applicability of three Bioluminescence Resonance Energy Transfer (BRET)-based assays - one measuring changes in intracellular cAMP, another in Gβγ/GRK3ct association and third in Gαi-Gβγ dissociation, - for assessing both constitutive and ligand-modulated activity of these receptors. We also revealed the possible caveats and sources of false positives, and proposed optimization strategies. All three types of assays confirmed the ligand-dependent activity of CXCR4, the controversial G protein incompetence of ACKR3, the constitutive Gi-directed activity of SMO, and its modulation by PTCH1. We also demonstrated that PTCH1 promotes SMO localization to the cell surface, thus enhancing its responsiveness not only to agonists but also to antagonists, which is a novel mechanism of regulation of a Class F GiPCR Smoothened.

Structural plasticity of arrestin-G protein coupled receptor complexes as a molecular determinant of signaling

G protein coupled receptors (GPCRs) are critically regulated by arrestins. In this study, high-resolution data was combined with molecular dynamics simulations to infer the determinants of β-arrestin 1 (βarr1)-GPCR coupling, using the V2 vasopressin receptor (V2R) as a model system. The study highlighted the extremely high plasticity of βarr1-GPCR complexes, dependent on receptor type, state, and membrane environment. The multiple functions of receptor-bound βarr1 are likely determined by the interplay of intrinsic flexibility and collective motions both as a bi-domain protein and as a whole. The two major collective motions of the whole βarr1, consisting in rotation parallel to the membrane plane and inclination with respect to the receptor main axis, are distinctly linked to the two intermolecular interfaces involved in tail and core interactions. The intermolecular dynamic coupling between βarr1 and V2R depends on the allosteric effect of the agonist arginine-vasopressin (AVP). In the absence of AVP the dynamic coupling concerns only tail interactions, while in the presence of AVP it involves both tail and core interactions. This suggests that constitutive and agonist-induced arrestin-receptor dynamic coupling is linked to distinct arrestin functions.

The mechanism of PDE7B inhibiting the development of hepatocellular carcinoma through oxidative stress

Background

Liver cancer presents a significant challenge to global health and is currently ranked as the sixth most common form of cancer worldwide. Recent research indicates that phosphodiesterases play a role in various physiological and pathological processes, with a specific focus on their impact on cancer advancement. There is a scarcity of studies investigating the function and mechanisms of phosphodiesterases in the development and progression of hepatocellular carcinoma (HCC).

Methods

Real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) and Western blotting were employed to analyze the expression of PDE7B in hepatocellular carcinoma tissues and cells. The biological role of PDE7B in HCC was investigated by both overexpressing and knocking down PDE7B in liver cancer cell lines. Furthermore, potential target proteins of PDE7B were identified through transcriptome sequencing.

Results

PDE7B is conspicuously reduced in tissues and cells of hepatocellular carcinoma, showing a connection with an unfavorable prognosis. Inhibiting PDE7B boosts the growth, movement, and infiltration of liver cancer cells, while its increased expression has the reverse impact. According to our trials relating to oxidative stress, PDE7B appears to control cell death in liver cancer cells by impacting the production of reactive oxygen species. Therefore, we propose that PDE7B could hinder the initiation and advancement of HCC through an oxidative stress pathway.

Conclusion

The research we conducted reveals that PDE7B, a gene with minimal levels of activity in hepatocellular carcinoma, possesses the capacity to inhibit the proliferation, invasion, and migration of HCC cells. PDE7B can impact the development of hepatocellular carcinoma by adjusting mechanisms related to oxidative stress.

Gq/G11 oncogenic mutations promote PD-L1 expression and suppress tumor immunity

Uveal melanoma (UM) is the predominant form of eye cancer. The genes GNAQ and GNA11, encoding Gq and G11 respectively, are most frequently mutated in UM and are considered the major drivers of UM carcinogenesis by activating YAP. However, the mechanisms by which metastatic UM evades the immune system remain poorly understood. In this study, we found that oncogenic mutations of Gq/G11 promoted YAP and PD-L1 expression, modifying the tumor microenvironment and promoting immune evasion of UM. Consistently, the levels of GNAQ/GNA11 and YAP positively correlated to PD-L1 expression in UM patients. Furthermore, silencing YAP or treating with its inhibitor, Verteporfin, attenuated PD-L1 expression induced by Gq/G11 mutations, thereby enhancing T cell activation and T cell-mediated cytotoxicity. Collectively, this study reveals a potential role of Gq/G11 mutations on immune evasion of UM, a new mechanism of Gq/11 mutations-induced tumorigenesis, highlighting Gq/G11 and YAP as potential immunotherapeutic targets and suggesting Verteporfin as an adjuvant for immunotherapy of UM patients with GNAQ or GNA11 mutations.

Integrin-Specific Stimuli-Responsive Nanomaterials for Cancer Theranostics

Background: Cancer is one of the leading causes of death worldwide. The tumor microenvironment makes the tumor difficult to treat, favoring drug resistance and the formation of metastases, resulting in death. Methods: Stimuli-responsive nanoparticles have shown great capacity to be used as a powerful strategy for cancer treatment, diagnostic, as well as theranostic. Nanocarriers are not only able to respond to internal stimuli such as oxidative stress, weakly acidic pH, high temperature, and the high expression of particular enzymes, but also to external stimuli such as light and paramagnetic characteristics to be exploited. Results: In this work, stimulus-responsive nanocarriers functionalized with arginine-glycine-aspartic acid (Arg-Gly-Asp) sequence as well as mimetic sequences with the capability to recognize integrin receptors are analyzed. Conclusions: This review highlights the progress that has been made in the development of new nanocarriers, capable of responding to endogenous and exogenous stimuli essential to combat cancer.

Visualization of endogenous G proteins on endosomes and other organelles

Classical G-protein-coupled receptor (GPCR) signaling takes place in response to extracellular stimuli and involves receptors and heterotrimeric G proteins located at the plasma membrane. It has recently been established that GPCR signaling can also take place from intracellular membrane compartments, including endosomes that contain internalized receptors and ligands. While the mechanisms of GPCR endocytosis are well understood, it is not clear how well internalized receptors are supplied with G proteins. To address this gap, we use gene editing, confocal microscopy, and bioluminescence resonance energy transfer to study the distribution and trafficking of endogenous G proteins. We show here that constitutive endocytosis is sufficient to supply newly internalized endocytic vesicles with 20-30% of the G protein density found at the plasma membrane. We find that G proteins are present on early, late, and recycling endosomes, are abundant on lysosomes, but are virtually undetectable on the endoplasmic reticulum, mitochondria, and the medial-trans Golgi apparatus. Receptor activation does not change heterotrimer abundance on endosomes. Our findings provide a subcellular map of endogenous G protein distribution, suggest that G proteins may be partially excluded from nascent endocytic vesicles, and are likely to have implications for GPCR signaling from endosomes and other intracellular compartments.

Protein-small molecule binding site prediction based on a pre-trained protein language model with contrastive learning

Predicting protein-small molecule binding sites, the initial step in structure-guided drug design, remains challenging for proteins lacking experimentally derived ligand-bound structures. Here, we propose CLAPE-SMB, which integrates a pre-trained protein language model with contrastive learning to provide high accuracy predictions of small molecule binding sites that can accommodate proteins without a published crystal structure. We trained and tested CLAPE-SMB on the SJC dataset, a non-redundant dataset based on sc-PDB, JOINED, and COACH420, and achieved an MCC of 0.529. We also compiled the UniProtSMB dataset, which merges sites from similar proteins based on raw data from UniProtKB database, and achieved an MCC of 0.699 on the test set. In addition, CLAPE-SMB achieved an MCC of 0.815 on our intrinsically disordered protein (IDP) dataset that contains 336 non-redundant sequences. Case studies of DAPK1, RebH, and Nep1 support the potential of this binding site prediction tool to aid in drug design. The code and datasets are freely available at https://github.com/JueWangTHU/CLAPE-SMB . SCIENTIFIC CONTRIBUTION: CLAPE-SMB combines a pre-trained protein language model with contrastive learning to accurately predict protein-small molecule binding sites, especially for proteins without experimental structures, such as IDPs. Trained across various datasets, this model shows strong adaptability, making it a valuable tool for advancing drug design and understanding protein-small molecule interactions.

A Structural Mechanism for Noncanonical GPCR Signal Transduction in the Hedgehog Pathway

The Hedgehog (Hh) signaling pathway is fundamental to embryogenesis, tissue homeostasis, and cancer. Hh signals are transduced via an unusual mechanism: upon agonist-induced phosphorylation, the noncanonical G protein-coupled receptor SMOOTHENED (SMO) binds the catalytic subunit of protein kinase A (PKA-C) and physically blocks its enzymatic activity. By combining computational structural approaches with biochemical and functional studies, we show that SMO mimics strategies prevalent in canonical GPCR and PKA signaling complexes, despite little sequence or secondary structural homology. An intrinsically disordered region of SMO binds the PKA-C active site, resembling the PKA regulatory subunit (PKA-R) / PKA-C holoenzyme, while the SMO transmembrane domain binds a conserved PKA-C interaction hub, similar to other GPCR-effector complexes. In contrast with prevailing GPCR signal transduction models, phosphorylation of SMO promotes intramolecular electrostatic interactions that stabilize key structural elements within the SMO cytoplasmic domain, thereby remodeling it into a PKA-inhibiting conformation. Our work provides a structural mechanism for a central step in the Hh cascade and defines a paradigm for disordered GPCR domains to transmit signals intracellularly.

Meloidogyne incognita genes involved in the repellent behavior in response to ascr#9

Meloidogyne incognita is one of the globally serious plant parasitic nematodes. New control measure is urgently needed to replace the common chemical control method. Ascarosides are pheromones regulating the nematodes' aggregation, avoidance, mating, dispersal and dauer recovery and formation. Ascr#9, one of the ascarosides, exhibits the potential to repel M. incognita. However, the nematode genes involved in the perception of ascr# 9 signal are totally unknown. In this study, the transcriptome of ascr#9-treated second stage M. incognita juveniles (J2s) was analyzed, 44 pathways were significantly affected, multiple ligand-receptor and mucin type O-glycan were induced, and olfactory transduction was disturbed. A total of 11 highly differentially expressed genes involved in neuroactive ligand-receptor interaction and FMRFamide-like peptide related process were identified and knocked down by RNAi. The dispersal rates of M. incognita with three knocked-down genes (flp-14, mgl-1 and ADOR-1) significantly decreased, respectively, when ascr#9 was present. The results demonstrate that flp-14, mgl-1, and ADOR-1 are involved in the dispersal behavior of M. incognita nematodes responding to ascr#9, which promotes the interaction study between ascarosides and M. incognita, and provides new ideas for the prevention and control of M. incognita by using pheromone ascarosides.

Functional bias of contractile control in mouse resistance arteries

Constrictor agonists set arterial tone through two coupling processes, one tied to (electromechanical), the other independent (pharmacomechanical) of, membrane potential (VM). This dual arrangement raises an intriguing question: is the contribution of each mechanism (1) fixed and proportionate, or (2) variable and functionally biased. Examination began in mouse mesenteric arteries with a vasomotor assessment to a classic Gq/11 (phenylephrine) or Gq/11/G12/13 (U46619) agonist, in the absence and presence of nifedipine, to separate among the two coupling mechanisms. Each constrictor elicited a concentration response curve that was attenuated and rightward shifted by nifedipine, findings consistent with functional bias. Electromechanical coupling preceded pharmacomechanical, the latter's importance rising with agonist concentration. In this regard, ensuing contractile and phosphorylation (CPI-17 & MYPT1 (T-855 & T-697)) measures revealed phenylephrine-induced pharmacomechanical coupling was tied to protein kinase C (PKC) activity, while that enabled by U46619 to PKC and Rho-kinase. A complete switch to pharmacomechanical coupling arose when agonist superfusion was replaced by pipet application to a small portion of artery. This switch was predicted, a priori, by a computer model of electromechanical control and supported by additional measures of VM and cytosolic Ca2+. We conclude that the coupling mechanisms driving agonist-induced constriction are variable and functionally biased, their relative importance set in accordance with agonist concentration and manner of application. These findings have important implications to hemodynamic control in health and disease, including hypertension and arterial vasospasm.

Steviol rebaudiosides bind to four different sites of the human sweet taste receptor (T1R2/T1R3) complex explaining confusing experiments

Sucrose provides both sweetness and energy by binding to both Venus flytrap domains (VFD) of the heterodimeric sweet taste receptor (T1R2/T1R3). In contrast, non-caloric sweeteners such as sucralose and aspartame only bind to one specific domain (VFD2) of T1R2, resulting in high-intensity sweetness. In this study, we investigate the binding mechanism of various steviol glycosides, artificial sweeteners, and a negative allosteric modulator (lactisole) at four distinct binding sites: VFD2, VFD3, transmembrane domain 2 (TMD2), and TMD3 through binding experiments and computational docking studies. Our docking results reveal multiple binding sites for the tested ligands, including the radiolabeled ligands. Our experimental evidence demonstrates that the C20 carboxy terminus of the Gα protein can bind to the intracellular region of either TMD2 or TMD3, altering GPCR affinity to the high-affinity state for steviol glycosides. These findings provide a mechanistic understanding of the structure and function of this heterodimeric sweet taste receptor.

Genome-wide identification of 769 G protein-coupled receptor (GPCR) genes from the marine medaka Oryzias melastigma

The marine medaka Oryzias melastigma is a useful fish model for marine and estuarine ecotoxicology studies and can be applied to field-based population genomics because of its distribution in Asian estuaries and other coastal areas. We identified 769 full-length G protein-coupled receptor genes in the O. melastigma genome and classified them into five distinct classes. A phylogenetic comparison of GPCR genes in O. melastigma to humans and two other small fish species revealed a high-level orthological relationship. Purinergic and chemokine receptors were highly differentiated in humans whereas significant differentiation of chemosensory receptors was evident in fish species. Our results suggest that the GPCR gene families among the species used in this study exhibit evidence of sporadic evolutionary processes. These results may help improve our understanding of the advanced repertoires of GPCR and expand our knowledge of physiological mechanisms of fish in response to various environmental stimuli.

Designed dualsteric modulators: A novel route for drug discovery

Orthosteric and allosteric modulators, which constitute the majority of current drugs, bind to the orthosteric and allosteric sites of target proteins, respectively. However, the clinical efficacy of these agents is frequently compromised by poor selectivity or reduced potency. Dualsteric modulators feature two linked pharmacophores that bind to orthosteric and allosteric sites of the target proteins simultaneously, thereby offering a promising avenue to achieve both potency and specificity. In this review, we summarize recent structures available for dualsteric modulators in complex with their target proteins, elucidating detailed drug-target interactions and dualsteric action patterns. Moreover, we provide a design and optimization strategy for dualsteric modulators based on structure-based drug design approaches.

Subcellular activation of β-adrenergic receptors using a spatially restricted antagonist

Gprotein-coupled receptors (GPCRs) regulate several physiological and pathological processes and represent the target of approximately 30% of Food and Drug Administration-approved drugs. GPCR-mediated signaling was thought to occur exclusively at the plasma membrane. However, recent studies have unveiled their presence and function at subcellular membrane compartments. There is a growing interest in studying compartmentalized signaling of GPCRs. This requires development of tools to separate GPCR signaling at the plasma membrane from the ones initiated at intracellular compartments. We leveraged the structural and pharmacological information available for β-adrenergic receptors (βARs) and focused on β1AR as exemplary GPCR that functions at subcellular compartments, and rationally designed spatially restricted antagonists. We generated a cell-impermeable βAR antagonist by conjugating a suitable pharmacophore to a sulfonate-containing fluorophore. This cell-impermeable antagonist only inhibited β1AR on the plasma membrane. In contrast, a cell-permeable βAR antagonist containing a nonsulfonated fluorophore efficiently inhibited both the plasma membrane and Golgi pools of β1ARs. Furthermore, the cell-impermeable antagonist selectively inhibited the phosphorylation of PKA downstream effectors near the plasma membrane, which regulate sarcoplasmic reticulum (SR) Ca2+ release in adult cardiomyocytes, while the β1AR Golgi pool remained active. Our tools offer promising avenues for investigating compartmentalized βAR signaling in various contexts, potentially advancing our understanding of βAR-mediated cellular responses in health and disease. They also offer a general strategy to study compartmentalized signaling for other GPCRs in various biological systems.

G protein selectivity profile of GPR56/ADGRG1 and its effect on downstream effectors

GPR56, an adhesion G-protein coupled receptor (aGPCRs) with constitutive and ligand-promoted activity, is involved in many physiological and pathological processes. Whether the receptor's constitutive or ligand-promoted activation occur through the same molecular mechanism, and whether different activation modes lead to functional selectivity between G proteins is unknown. Here we show that GPR56 constitutively activates both G12 and G13. Unlike constitutive activation and activation with 3-a-acetoxydihydrodeoxygedunin (3αDOG), stimulation with an antibody, 10C7, directed against GPR56's extracellular domain (ECD) led to an activation that favors G13 over G12. An autoproteolytically deficient mutant, GPR56-T383A, was also activated by 10C7 indicating that the tethered agonist (TA) exposed through autocatalytic cleavage, is not required for this activation modality. In contrast, this proteolysis-resistant mutant could not be activated by 3αDOG indicating different modes of activation by the two ligands. We show that an N-terminal truncated GPR56 construct (GPR56-Δ1-385) is devoid of constitutive activity but was activated by 3αDOG. Similarly to 3αDOG, 10C7 promoted the recruitment of b-arrestin-2 but GPR56 internalization was β-arrestin independent. Despite the slow activation mode of 10C7 that favors G13 over G12, it efficiently activated the downstream Rho pathway in BT-20 breast cancer cells. These data show that different GPR56 ligands have different modes of activation yielding differential G protein selectivity but converging on the activation of the Rho pathway both in heterologous expressions system and in cancer cells endogenously expressing the receptor. 10C7 is therefore an interesting tool to study both the processes underlying GPR56 activity and its role in cancer cells.

G protein selectivity profile of GPR56/ADGRG1 and its effect on downstream effectors

GPR56, an adhesion G-protein coupled receptor (aGPCRs) with constitutive and ligand-promoted activity, is involved in many physiological and pathological processes. Whether the receptor's constitutive or ligand-promoted activation occur through the same molecular mechanism, and whether different activation modes lead to functional selectivity between G proteins is unknown. Here we show that GPR56 constitutively activates both G12 and G13. Unlike constitutive activation and activation with 3-α-acetoxydihydrodeoxygedunin (3αDOG), stimulation with an antibody, 10C7, directed against GPR56's extracellular domain (ECD) led to an activation that favors G13 over G12. An autoproteolytically deficient mutant, GPR56-T383A, was also activated by 10C7 indicating that the tethered agonist (TA) exposed through autocatalytic cleavage, is not required for this activation modality. In contrast, this proteolysis-resistant mutant could not be activated by 3αDOG indicating different modes of activation by the two ligands. We show that an N-terminal truncated GPR56 construct (GPR56-Δ1-385) is devoid of constitutive activity but was activated by 3αDOG. Similarly to 3αDOG, 10C7 promoted the recruitment of β-arrestin-2 but GPR56 internalization was β-arrestin independent. Despite the slow activation mode of 10C7 that favors G13 over G12, it efficiently activated the downstream Rho pathway in BT-20 breast cancer cells. These data show that different GPR56 ligands have different modes of activation yielding differential G protein selectivity but converging on the activation of the Rho pathway both in heterologous expressions system and in cancer cells endogenously expressing the receptor. 10C7 is therefore an interesting tool to study both the processes underlying GPR56 activity and its role in cancer cells.

Delineating the stepwise millisecond allosteric activation mechanism of the class C GPCR dimer mGlu5

Two-thirds of signaling hormones and one-third of approved drugs exert their effects by binding and modulating the G protein-coupled receptors (GPCRs) activation. While the activation mechanism for monomeric GPCRs has been well-established, little is known about GPCRs in dimeric form. Here, by combining transition pathway generation, extensive atomistic simulation-based Markov state models, and experimental signaling assays, we reveal an asymmetric, stepwise millisecond allosteric activation mechanism for the metabotropic glutamate receptor subtype 5 receptor (mGlu5), an obligate dimeric class C GPCR. The dynamic picture is presented that agonist binding induces dimeric ectodomains compaction, amplified by the precise association of the cysteine-rich domains, ultimately loosely bringing the intracellular 7-transmembrane (7TM) domains into proximity and establishing an asymmetric TM6-TM6 interface. The active inter-domain interface enhances their intra-domain flexibility, triggering the activation of micro-switches crucial for downstream signal transduction. Furthermore, we show that the positive allosteric modulator stabilizes both the active inter-domain 7TM interface and an open, extended intra-domain ICL2 conformation. This stabilization leads to the formation of a pseudo-cavity composed of the ICL2, ICL3, TM3, and C-terminus, which facilitates G protein coordination. Our strategy may be generalizable for characterizing millisecond events in other allosteric systems.

G12/13 signaling in asthma

Shortening of airway smooth muscle and bronchoconstriction are pathognomonic for asthma. Airway shortening occurs through calcium-dependent activation of myosin light chain kinase, and RhoA-dependent calcium sensitization, which inhibits myosin light chain phosphatase. The mechanism through which pro-contractile stimuli activate calcium sensitization is poorly understood. Our review of the literature suggests that pro-contractile G protein coupled receptors likely signal through G12/13 to activate RhoA and mediate calcium sensitization. This hypothesis is consistent with the effects of pro-contractile agonists on RhoA and Rho kinase activation, actin polymerization and myosin light chain phosphorylation. Recognizing the likely role of G12/13 signaling in the pathophysiology of asthma rationalizes the effects of pro-contractile stimuli on airway hyperresponsiveness, immune activation and airway remodeling, and suggests new approaches for asthma treatment.