G-protein Coupled Receptor Family Research Articles

Photo-BQCA: Positive Allosteric Modulators Enabling Optical Control of the M1 Receptor.

The field of G protein-coupled receptor (GPCR) research has greatly benefited from the spatiotemporal resolution provided by light controllable, i.e., photoswitchable ligands. Most of the developed tools have targeted the Rhodopsin-like family (Class A), the largest family of GPCRs. However, to date, all such Class A photoswitchable ligands were designed to act at the orthosteric binding site of these receptors. Herein, we report the development of the first photoswitchable allosteric modulators of Class A GPCRs, designed to target the M1 muscarinic acetylcholine receptor. The presented benzyl quinolone carboxylic acid (BQCA) derivatives, Photo-BQCisA and Photo-BQCtrAns, exhibit complementary photopharmacological behavior and allow reversible control of the receptor using light as an external stimulus. This makes them valuable tools to further investigate M1 receptor signaling and a proof of concept for photoswitchable allosteric modulators at Class A receptors.

Coordinated cellular behavior regulated by epinephrine neurotransmitters in the nerveless placozoa

Understanding how cells communicated before the evolution of nervous systems in early metazoans is key to unraveling the origins of multicellular life. We focused on Trichoplax adhaerens, one of the earliest multicellular animals, to explore this question. Through screening a small compound library targeting G protein-coupled receptors (GPCRs), we found that Trichoplax exhibits distinctive rotational movements when exposed to epinephrine. Further studies suggested that, akin to those in humans, this basal organism also utilizes adrenergic signals to regulate its negative taxis behavior, with the downstream signaling pathway being more straightforward and efficient. Mechanistically, the binding of ligands activates downstream calcium signaling, subsequently modulating ciliary redox signals. This process ultimately regulates the beating direction of cilia, governing the coordinated movement of the organism. Our findings not only highlight the enduring presence of adrenergic signaling in stress responses during evolution but also underscore the importance of early metazoan expansion of GPCR families. This amplification empowers us with the ability to sense external cues and modulate cellular communication effectively.

Progress on the development of Class A GPCR-biased ligands.

Class A G protein-coupled receptors (GPCRs) continue to garner interest for their essential roles in cell signalling and their importance as drug targets. Although numerous drugs in the clinic target these receptors, over 60% GPCRs remain unexploited. Moreover, the adverse effects triggered by the available unbiased GPCR modulators, limit their use and therapeutic value. In this context, the elucidation of biased signalling has opened up new pharmacological avenues holding promise for safer therapeutics. Functionally selective ligands favour receptor conformations facilitating the recruitment of specific effectors and the modulation of the associated pathways. This review surveys the current drug discovery landscape of GPCR-biased modulators with a focus on recent advances. Understanding the biological effects of this preferential coupling is at different stages depending on the Class A GPCR family. Therefore, with a focus on individual GPCR families, we present a compilation of the functionally selective modulators reported over the past few years. In doing so, we dissect their therapeutic relevance, molecular determinants and potential clinical applications.

Abstract P166: Genetic Ablation of the Bile Acid Receptor- Takeda G-protein Coupled Receptor 5 (TGR5) Promotes Weight Gain but Lowers Hypertension

Introduction: TGR5 belongs to G-protein coupled receptor family, that mediates bile acid signaling. Activation of TGR5 by bile acids triggers intestinal glucagon-like peptide-1 secretion, whereby pharmacological activation of TGR5 constitutes a promising incretin-based strategy for the treatment of metabolic disorders. Hypertension is one of the hallmark features of metabolic disorders. We previously reported that hypertension is associated with lower conjugated bile acids, which are ligands for TGR5. Therefore, we hypothesized that lack of activation of TGR5-mediated bile acid signaling promotes not only body weight gain, but also hypertension. Methods: CRISPR/Cas9 technology was used to generate Tgr5 -/- rats from hypertensive Dahl Salt-sensitive (S) rats. Twenty-four-hour blood pressure (BP) readings of 8-weeks-old control female Tgr5 +/+ S rats and age-matched female Tgr5 -/- S rats (n=7/group) were monitored by radiotelemetry for 4 weeks. Body weight, food intake, and water intake were recorded every week. At the end of the study, vascular function was examined using wire myography of dorsal and mesenteric resistance arteries, cardiac function was assessed by echocardiography, and microbiota profiling was conducted via fecal 16S rRNA gene sequencing using Miseq. Results: In support of our hypothesis, despite no difference in food and water intake, at 4 weeks, the body weights of Tgr5 -/- S rats were significantly higher compared to Tgr5 +/+ S rats (236.3gm vs. 225.4gm; p<0.01). Surprisingly, in contrast to our hypothesis, at 4 weeks, Tgr5 -/- S rats had significantly lower systolic BP (151.8mmHg vs. 156.9mmHg, p<0.0001), diastolic BP (107.9mmHg vs. 115.5mmHg, p<0.0001), and mean arterial BP (128.8mmHg vs. 134.9mmHg, p<0.0001) compared to Tgr5 +/+ S rats. However, no significant differences were observed either in vascular reactivity or cardiac function between the groups. Interestingly, fecal microbiota analysis revealed that Tgr5 -/- S rats presented with significant remodeling of gut microbiota with lower α-diversity (observed features; p=0.05), b-diversity (Bray-Curtis; p<0.05, Jaccard; p<0.01), and higher relative abundance of the BP-lowering genera Akkermansia . Conclusion: Our study revealed that deletion of TGR5 resulted in weight gain but lowered BP. It implies that activation of TGR5 may be a risk factor for raising BP. The mechanism by which TGR5 regulates BP seem independent of changes in vascular or cardiac function but is likely mediated by gut microbiota.

Larvicidal activity of β-Citral: An In-vitro and In-silico study to understand its potential against mosquito

Tropical and subtropical regions face millions of deaths from mosquito-borne illnesses yearly. Insecticides prevent transmission but pose health risks like dermatitis and allergies. The primary objective was to mitigate the recurring dependence on synthetic insecticides, thereby curbing the development of mosquito resistance. Leaves of Cymbopogon flexuosus (lemongrass) was collected from Mayurbhanj, India, processed, then extracted by steam distillation for essential oils & analyzed spectroscopically. Larvicidal assays were performed across varying concentrations, revealing the significant mortality induced by the Cymbopogon flexuosus extract against Anopheles stephensi larvae. 3D structure was modelled by using G protein-coupled receptors (GPCR) sequence and structural stability was also validated. After docking the binding free energy was determined from GPCR protein with β-citral complex. Molecular dynamics (MD) study was conducted on the docked pose that displayed an optimal interactome profile. The larvicidal assay at the 12th and 24th hour revealed the highest LC50 (lethal concentration) of 23.493 ppm and 19.664 ppm . β-Citral has a high binding affinity and an identifiable binding site, which suggests that it may play a larvicidal role in regulating the receptor's function by creating stable complexes with it. β-Citral from lemongrass oils has potential larvicidal activity and effective against GPCR family 1 of mosquito and highly effective repellents against mosquito-borne diseases.

Isoquinoline small molecule ligands are agonists and probe-dependent allosteric modulators of the glucagon subfamily of GPCRs

Class B1 G protein-coupled receptors (GPCRs) are peptide hormone receptors and well validated therapeutic targets, however development of non-peptide drugs targeting this class of receptors is challenging. Recently, a series of isoquinoline-based derivates were reported in the patent literature as allosteric ligands for the glucagon receptor subfamily, and two compounds, LSN3451217 and LSN3556672, were used to facilitate structural studies with the glucagon-like peptide-1 receptor (GLP-1R) and glucose dependent insulinotropic peptide receptor (GIPR) bound to orthosteric agonists. Here we pharmacologically characterized stereoisomers of LSN3451217 and LSN3556672, across the class B1 GPCR family. This revealed LSN3556672 isomers are agonists for the glucagon receptor (GCGR), GLP-1R, GIPR and the calcitonin receptor (CTR), albeit the degree of agonism varied at each receptor. In contrast, LSN3451217 isomers were more selective agonists at the GLP-1R, with lower potency at the GCGR and CTR and no activity at the GIPR. All compounds also modulated peptide-mediated cyclic adenosine monophosphate (cAMP) signaling at the GIPR, and to a lesser extent the GLP-1R, in a probe-dependent manner, with modest positive allosteric modulation observed for some peptides, and negligible effects observed with other peptides. In contrast neutral or weak negative/positive allosteric modulation was observed with peptides assessed at the GCGR and CTR. This study expands our knowledge on class B1 GPCR allosteric modulation and may have implications for future structural and drug discovery efforts targeting the class B1 GPCR subfamily.

Class B1 GPCRs: insights into multireceptor pharmacology for the treatment of metabolic disease.

The secretin-like, class B1 subfamily of seven transmembrane-spanning G protein-coupled receptors (GPCRs) consists of 15 members that coordinate important physiological processes. These receptors bind peptide ligands and use a distinct mechanism of activation that is driven by evolutionarily conserved structural features. For the class B1 receptors, the C-terminus of the cognate ligand is initially recognized by the receptor via an N-terminal extracellular domain that forms a hydrophobic ligand-binding groove. This binding enables the N-terminus of the ligand to engage deep into a large volume, open transmembrane pocket of the receptor. Importantly, the phylogenetic basis of this ligand-receptor activation mechanism has provided opportunities to engineer analogs of several class B1 ligands for therapeutic use. Among the most accepted of these are drugs targeting the glucagon-like peptide-1 (GLP-1) receptor for the treatment of type 2 diabetes and obesity. Recently, multifunctional agonists possessing activity at the GLP-1 receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor, such as tirzepatide, and others that also contain glucagon receptor activity, have been developed. In this article, we review members of the class B1 GPCR family with focus on receptors for GLP-1, GIP, and glucagon, including their signal transduction and receptor trafficking characteristics. The metabolic importance of these receptors is also highlighted, along with the benefit of polypharmacologic ligands. Furthermore, key structural features and comparative analyses of high-resolution cryogenic electron microscopy structures for these receptors in active-state complexes with either native ligands or multifunctional agonists are provided, supporting the pharmacological basis of such therapeutic agents.

Activation of Polycystin-1 Signaling by Binding of Stalk-derived Peptide Agonists.

Polycystin-1 (PC1) is the membrane protein product of the PKD1 gene whose mutation is responsible for 85% of the cases of autosomal dominant polycystic kidney disease (ADPKD). ADPKD is primarily characterized by the formation of renal cysts and potential kidney failure. PC1 is an atypical G protein-coupled receptor (GPCR) consisting of 11 transmembrane helices and an autocatalytic GAIN domain that cleaves PC1 into extracellular N-terminal (NTF) and membrane-embedded C-terminal (CTF) fragments. Recently, signaling activation of the PC1 CTF was shown to be regulated by a stalk tethered agonist (TA), a distinct mechanism observed in the adhesion GPCR family. A novel allosteric activation pathway was elucidated for the PC1 CTF through a combination of Gaussian accelerated molecular dynamics (GaMD), mutagenesis and cellular signaling experiments. Here, we show that synthetic, soluble peptides with 7 to 21 residues derived from the stalk TA, in particular, peptides including the first 9 residues (p9), 17 residues (p17) and 21 residues (p21) exhibited the ability to re-activate signaling by a stalkless PC1 CTF mutant in cellular assays. To reveal molecular mechanisms of stalk peptide-mediated signaling activation, we have applied a novel Peptide GaMD (Pep-GaMD) algorithm to elucidate binding conformations of selected stalk peptide agonists p9, p17 and p21 to the stalkless PC1 CTF. The simulations revealed multiple specific binding regions of the stalk peptide agonists to the PC1 protein including an "intermediate" bound yet inactive state. Our Pep-GaMD simulation findings were consistent with the cellular assay experimental data. Binding of peptide agonists to the TOP domain of PC1 induced close TOP-putative pore loop interactions, a characteristic feature of the PC1 CTF signaling activation mechanism. Using sequence covariation analysis of PC1 homologs, we further showed that the peptide binding regions were consistent with covarying residue pairs identified between the TOP domain and the stalk TA. Therefore, structural dynamic insights into the mechanisms of PC1 activation by stalk-derived peptide agonists have enabled an in-depth understanding of PC1 signaling. They will form a foundation for development of PC1 as a therapeutic target for the treatment of ADPKD.

Therapeutic Approaches for Treatment and Management of Depressive Disorder: A Comprehensive Review

Depression, which is associated with high levels of cognitive and functional activity, melancholy, reduced activity, difficulty understanding, failure to focus, dietary abnormalities, sleep disturbances, and emotions of feelings of sadness, suicidal thoughts, and lack of hope are symptoms of a psychoneurotic disorder. It is a common and recurring disorder with a high morbidity and death rate throughout the world. Despite advances in depression treatment, such as selective serotonin reuptake inhibitors (SSRIs) and selective norepinephrine reuptake inhibitors (SNRIs), there remain several unmet clinical requirements in terms of effectiveness and adverse effects. These requirements range from enhanced to decreased side effects like emesis and erectile problems in treatment-resistant patients. There are a variety of combination therapies available to meet these needs. Several combination medicines and novel strategies have been found, all of which have the potential to improve one or so more areas. The kinds of targets and methods being used are extremely diverse. Therapeutic approaches, on the one hand, provide the benefits of SSRIs while including alternative routes in an attempt to improve efficacy or reduce undesirable effects. Neurotrophins (BDNF, IGF) are more novel targets on the other end of the spectrum, based on the most recent research suggesting antidepressants enhance neurogenesis. Antidepressants act by blocking many proteins, such as neurotransmitter transporters and G-protein coupled receptor families, in the brain. Some of the computational approaches that are useful for uncovering drug action mechanisms and are important for drug development are molecular docking, molecular dynamics, and drug candidates.

Restoring function to inactivating G protein-coupled receptor variants in the hypothalamic-pituitary-gonadal axis1.

G protein-coupled receptors (GPCRs) are central to the functioning of the hypothalamic-pituitary-gonadal axis (HPG axis) and include the rhodopsin-like GPCR family members, neurokinin 3 receptor, kappa-opioid receptor, kisspeptin 1 receptor, gonadotropin-releasing hormone receptor, and the gonadotropin receptors, luteinizing hormone/choriogonadotropin receptor and follicle-stimulating hormone receptor. Unsurprisingly, inactivating variants of these receptors have been implicated in a spectrum of reproductive phenotypes, including failure to undergo puberty, and infertility. Clinical induction of puberty in patients harbouring such variants is possible, but restoration of fertility is not always a realisable outcome, particularly for those patients suffering from primary hypogonadism. Thus, novel pharmaceuticals and/or a fundamental change in approach to treating these patients are required. The increasing wealth of data describing the effects of coding-region genetic variants on GPCR function has highlighted that the majority appear to be dysfunctional as a result of misfolding of the encoded receptor protein, which, in turn, results in impaired receptor trafficking through the secretory pathway to the cell surface. As such, these intracellularly retained receptors may be amenable to 'rescue' using a pharmacological chaperone (PC)-based approach. PCs are small, cell permeant molecules hypothesised to interact with misfolded intracellularly retained proteins, stabilising their folding and promoting their trafficking through the secretory pathway. In support of the use of this approach as a viable therapeutic option, it has been observed that many rescued variant GPCRs retain at least a degree of functionality when 'rescued' to the cell surface. In this review, we examine the GPCR PC research landscape, focussing on the rescue of inactivating variant GPCRs with important roles in the HPG axis, and describe what is known regarding the mechanisms by which PCs restore trafficking and function. We also discuss some of the merits and obstacles associated with taking this approach forward into a clinical setting.

Unlocking hope: talquetamab in multiple myeloma treatment: a bispecific breakthrough targeting CD3 and GPRC5D

Multiple myeloma (MM) presents a significant global health burden, with disparities in incidence and outcomes reflecting challenges in recognition and treatment. Talquetamab, a bispecific CD3 T-cell engager targeting G-protein coupled receptor family C group 5 member D (GPRC5D), has emerged as a promising immunotherapy for relapsed/refractory MM (RRMM). In August 2023, talquetamab received accelerated approval from the US FDA for RRMM treatment, followed by conditional marketing authorization from the EMA. Clinical trials demonstrated talquetamab's efficacy, with overall response rates (ORR) of 69% and 76% in heavily pretreated RRMM patients. The phase I monumenTAL-1 trial showcased talquetamab's effectiveness, particularly in high-risk MM and extramedullary disease, with ORRs around 71-74%. Subsequent phase 2 results reaffirmed its efficacy, even in patients with prior T-cell redirection therapies. Combination therapy with daratumumab further enhanced talquetamab's efficacy, addressing concerns of T cell exhaustion. Pharmacokinetic studies revealed sustained responses and manageable adverse events with subcutaneous administration, facilitating convenient dosing regimens. However, talquetamab carries risks of cytokine release syndrome (CRS) and neurologic toxicity, necessitating close monitoring and prompt management. Common adverse events included fever, CRS, musculoskeletal pain, and infections, although severe events were infrequent. Vigilant management strategies, including prophylactic measures and supportive care, mitigate these risks. In conclusion, talquetamab represents a significant advancement in RRMM treatment, offering a promising avenue for T-cell redirection therapy. Ongoing research aims to optimize treatment sequencing and combination strategies, fostering improved outcomes for MM patients. Continued investigation will refine the strategic integration of talquetamab and other immunotherapies, paving the way for enhanced treatment efficacy and patient care in RRMM.

Cardiomyocyte-specific deletion of adhesion G protein-coupled receptor F5 (ADGRF5) increases susceptibility to stress and arrhythmia

G-Protein Coupled Receptors (GPCR) represent the largest family of cell surface receptors in the human body and serve as targets for more than 30% of all approved drugs. Adhesion GPCRs (AGPCR) are an understudied GPCR family containing numerous extracellular domains that interact with extracellular proteins, including many known mediators of cardiac remodeling responses to pathologic stress. However, their relative expression in the heart and impact on cardiac function normally or during disease has been largely unstudied. To address this, we evaluated RNASeq-attained AGPCR expression from left ventricular (LV) samples of adult mice, of which Adgrf5 was one of the most highly expressed. Notably, decreased ADGRF5 expression is observed across numerous failing human LV tissue GEO datasets, and C57BL6/J mice subjected to transaortic constriction (TAC) surgery to induce pressure overload-induced HF also displayed reduced LV Adgrf5 expression by 12 weeks post-TAC. Analysis of published single cell (sc)-RNASeq datasets confirmed Adgrf5 expression in cardiomyocytes (CM), which also decreased following TAC in mice and in CM from failing human hearts. To investigate the impact of CM-specific ADGRF5 on cardiac function and remodeling normally or during disease progression, we crossed floxed ADGRF5 (ADGRF5f/f) and αMHC-Cre mice to generate constitutive, CM-specific ADGRF5 knockout mice (F5cmKO). These mice display normal cardiac structure and function at 12 weeks of age versus αMHC-Cre mice, as assessed via echocardiography, gravimetrics and immunohistochemistry. However, F5cmKO mice develop cardiac dysfunction, maladaptive remodeling, and increased mortality over time, even in the absence of pathologic insult, suggesting a homeostatic function of CM-specific ADGRF5. Following TAC surgery, F5cmKO mice display similar outcomes including enhanced cardiac dysfunction with accelerated remodeling and increased mortality. To attain mechanistic insight into these outcomes, we performed RNA-sequencing on LV tissue of 12-week-old F5cmKO mice, identifying and subsequently validating Scn1b as significantly upregulated in F5cmKO CM. Scn1b encodes for the β subunits of voltage-gated sodium channels (Scnβ1/β1B), which regulate gating and kinetics of Nav1.5 as well as adhesive CM-CM interactions, disruption of which could lead to arrhythmias. Indeed, conscious electrocardiogram (ECG) readings via telemetry indicated F5cmKO mice had a high burden of premature ventricular contractions (PVC), including ventricular tachycardia associated with cardiac enlargement. Using a combination of luciferase and fluorescence resonance energy transfer (FRET) reporters and gene expression analyses in neonatal rat ventricular myocytes (NRVM), we confirmed that ADGRF5 controls Scn1b expression in a Gαq/11 protein-dependent manner. In all, we have discovered that loss of CM-specific ADGRF5 leads to increased Scn1b expression with enhanced susceptibility to stress, arrythmias and sudden death, thus may provide a novel GPCR target to promote the maintenance of cardiac rhythm. AHA Predoctoral Fellowship 834906 to J.M.E. P01 HL147841 to D.T. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Stepwise activation of a metabotropic glutamate receptor.

Metabotropic glutamate receptors belong to a family of Gprotein-coupled receptors that are obligate dimers and possess a large extracellular ligand-binding domain that is linked via a cysteine-rich domain to their 7-transmembrane domain1. Upon activation, these receptors undergo a large conformational change to transmit the ligand binding signal from the extracellular ligand-binding domain to the Gprotein-coupling 7-transmembrane domain2. In this manuscript, we propose a model for a sequential, multistep activation mechanism of metabotropic glutamate receptor subtype 5. We present a series of structures in lipid nanodiscs, from inactive to fully active, including agonist-bound intermediate states. Further, using bulk and single-molecule fluorescence imaging, we reveal distinct receptor conformations upon allosteric modulator and Gprotein binding.

Local anesthetics inhibit muscarinic acetylcholine receptor-mediated calcium responses and the recruitment of β-arrestin in HSY human parotid cells

ObjectivesLocal anesthetics act on G protein-coupled receptors (GPCRs); thus, their potential as allosteric modulators of GPCRs has attracted attention. Intracellular signaling via GPCRs involves both G-protein- and β-arrestin-mediated pathways. To determine the effects of local anesthetics on muscarinic acetylcholine receptors (mAChR), a family of GPCRs, we analyzed the effects of local anesthetics on mAChR-mediated Ca2+ responses and formation of receptor–β-arrestin complexes in the HSY human parotid cell line. MethodsCa2+ responses were monitored by fura-2 spectrofluorimetry. Ligand-induced interactions between mAChR and β-arrestin were examined using a β-arrestin GPCR assay kit. ResultsLidocaine reduced mAChR-mediated Ca2+ responses but did not change the intracellular Ca2+ concentration in non-stimulated cells. The membrane-impermeant lidocaine analog QX314 and procaine inhibited mAChR-mediated Ca2+ responses, with EC50 values of 48.0 and 20.4 μM, respectively, for 50 μM carbachol-stimulated Ca2+ responses. In the absence of extracellular Ca2+, the pretreatment of cells with QX314 reduced carbachol-induced Ca2+ release, indicating that QX314 reduced Ca2+ release from intracellular stores. Lidocaine and QX314 did not affect store-operated Ca2+ entry as they did not alter the thapsigargin-induced Ca2+ response. QX314 and procaine reduced the carbachol-mediated recruitment of β-arrestin, and administration of procaine suppressed pilocarpine-induced salivary secretion in mice. ConclusionLocal anesthetics, including QX314, act on mAChR to reduce carbachol-induced Ca2+ release from intracellular stores and the recruitment of β-arrestin. These findings support the notion that local anesthetics and their derivatives are starting points for the development of functional allosteric modulators of mAChR.

Bispecific antibodies for the treatment of relapsed/refractory multiple myeloma: updates and future perspectives.

Patients with relapsed/refractory multiple myeloma (RRMM) that are refractory to the five most active anti-MM drugs, so-called penta-refractory MM, have historically had dismal outcomes with subsequent therapies. Progressive immune dysfunction, particularly of the T-cell repertoire, is implicated in the development of disease progression and refractory disease. However, the advent of novel immunotherapies such as bispecific antibodies are rapidly changing the treatment landscape and improving the survival outcomes of patients with RRMM. Bispecific antibodies are antibodies that are engineered to simultaneously engage cytotoxic immune effector cells (T cells or NK cells) and malignant plasma cells via binding to immune effector cell antigens and extracellular plasma cell antigens leading to immune effector cell activation and malignant plasma cell destruction. Currently, bispecific antibodies that bind CD3 on T cells and plasma cell epitopes such as B-cell maturation antigen (BCMA), G-protein coupled receptor family C group 5 member D (GPRC5d), and Fc receptor homologue 5 (FcRH5) are the most advanced in clinical development and are showing unprecedented response rates in patients with RRMM, including patients with penta-refractory disease. In this review article, we explore the available clinical data of bispecific antibodies in RRMM and summarize the efficacy, safety, toxicity, clinical outcomes, mechanisms of resistance, and future directions of these therapies in patients with RRMM.

Unveiling the therapeutic prospects of EGFR inhibition in rotenone-mediated parkinsonism in rats: Modulation of dopamine D3 receptor

Parkinson’s disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra. The dopamine D3 receptor (D3R) plays a significant role in the pathogenesis and treatment of PD. Activation of receptor tyrosine kinases (RTKs) inhibits signaling mediated by G protein-coupled receptor (GPCR). Epidermal growth factor receptors (EGFRs) and dopamine D3 receptors in the brain are directly associated with PD, both in terms of its development and potential treatment. Therefore, we investigated the impact of modulating the EGFR, a member of the RTKs family, and the dopamine D3R, a member of the GPCR family. In the present study, 100 mg/kg of lapatinib (LAP) was administered to rotenone-intoxicated rats for three weeks. Our findings indicate that LAP effectively alleviated motor impairment, improved histopathological abnormalities, and restored dopaminergic neurons in the substantia nigra. This restoration was achieved through the upregulation of dopamine D3R and increase of tyrosine hydroxylase (TH) expression, as well as boosting dopamine levels. Furthermore, LAP inhibited the activity of p-EGFR, GRK2, and SCR. Additionally, LAP exhibited antioxidant properties by inhibiting the 4-hydroxynonenal (4-HNE) and PLCγ/PKCβII pathway, while enhancing the antioxidant defense mechanism by increasing GSH-GPX4 pathway. The current study offers insights into the potential repositioning of LAP as a disease-modifying drug for PD. This could be achieved by modulating the dopaminergic system and curbing oxidative stress.

Knockout of formyl peptide receptor 1 reduces osteogenesis and bone healing

AimsFormyl peptide receptor 1 (FPR1), from a G-protein coupled receptor family, was previously well-characterized in immune cells. But the function of FPR1 in osteogenesis and fracture healing was rarely reported. This study, using the FPR1 knockout (KO) mouse, is one of the first studies that try to investigate FPR1 function to osteogenic differentiation of bone marrow-derived stem cells (BMSCs) in vitro and bone fracture healing in vivo. Materials and methodsPrimary BMSCs were isolated from both FPR1 KO and wild type (WT) mice. Cloned mouse BMSCs (D1 cells) were used to examine role of FoxO1 in FPR1 regulation of osteogenesis. A closed, transverse fracture at the femoral midshaft was created to compare bone healing between KO and WT mice. Biomechanical and structural properties of femur were compared between healthy WT and KO mice. Key findingsFPR1 expression increased significantly during osteogenesis of both primary and cloned BMSCs. Compared to BMSCs from FPR1 KO mice, WT BMSCs displayed considerably higher levels of osteogenic markers as well as mineralization. Osteogenesis by D1 cells was inhibited by either an FPR1 antagonist cFLFLF or a specific inhibitor of FoxO1, AS1842856. In addition, the femur from WT mice had better biomechanical properties than FPR1 KO mice. Furthermore, bone healing in WT mice was remarkably improved compared to FPR1 KO mice analyzed by X-ray and micro-CT. SignificanceThese findings indicated that FPR1 played a vital role in osteogenic differentiation and regenerative capacity of fractured bone, probably through the activation of FoxO1 related signaling pathways.

ADGRG1, an adhesion G protein-coupled receptor, forms oligomers.

G protein-coupled receptor (GPCR) oligomerization is a highly debated topic in the field. While initially believed to function as monomers, current literature increasingly suggests that these cell surface receptors, spanning almost all GPCR families, function as homo- or hetero-oligomers. Yet, the functional consequences of these oligomeric complexes remain largely unknown. Adhesion GPCRs (aGPCRs) present an intriguing family of receptors characterized by their large and multi-domain N-terminal fragments (NTFs), intricate activation mechanisms, and the prevalence of numerous splice variants in almost all family members. In the present study, bioluminescence energy transfer (BRET) and Förster resonance energy transfer (FRET) were used to study the homo-oligomerization of adhesion G protein-coupled receptor G1 (ADGRG1; also known as GPR56) and to assess the involvement of NTFs in these receptor complexes. Based on the results presented herein, we propose that ADGRG1 forms 7-transmembrane-driven homo-oligomers on the plasma membrane. Additionally, Stachel motif interactions appear to influence the conformation of these receptor complexes.

Evaluating conserved domains and motifs of decapod gonadotropin-releasing hormone G protein-coupled receptor superfamily.

G protein-coupled receptors (GPCRs) are an ancient family of signal transducers that are both abundant and consequential in metazoan endocrinology. The evolutionary history and function of the GPCRs of the decapod superfamilies of gonadotropin-releasing hormone (GnRH) are yet to be fully elucidated. As part of which, the use of traditional phylogenetics and the recycling of a diminutive set of mis-annotated databases has proven insufficient. To address this, we have collated and revised eight existing and three novel GPCR repertoires for GnRH of decapod species. We developed a novel bioinformatic workflow that included clustering analysis to capture likely GnRH receptor-like proteins, followed by phylogenetic analysis of the seven transmembrane-spanning domains. A high degree of conservation of the sequences and topology of the domains and motifs allowed the identification of species-specific variation (up to ~70%, especially in the extracellular loops) that is thought to be influential to ligand-binding and function. Given the key functional role of the DRY motif across GPCRs, the classification of receptors based on the variation of this motif can be universally applied to resolve cryptic GPCR families, as was achieved in this work. Our results contribute to the resolution of the evolutionary history of invertebrate GnRH receptors and inform the design of bioassays in their deorphanization and functional annotation.

Decrypting orphan GPCR drug discovery via multitask learning

The drug discovery of G protein-coupled receptors (GPCRs) superfamily using computational models is often limited by the availability of protein three-dimensional (3D) structures and chemicals with experimentally measured bioactivities. Orphan GPCRs without known ligands further complicate the process. To enable drug discovery for human orphan GPCRs, multitask models were proposed for predicting half maximal effective concentrations (EC50) of the pairs of chemicals and GPCRs. Protein multiple sequence alignment features, and physicochemical properties and fingerprints of chemicals were utilized to encode the protein and chemical information, respectively. The protein features enabled the transfer of data-rich GPCRs to orphan receptors and the transferability based on the similarity of protein features. The final model was trained using both agonist and antagonist data from 200 GPCRs and showed an excellent mean squared error (MSE) of 0.24 in the validation dataset. An independent test using the orphan dataset consisting of 16 receptors associated with less than 8 bioactivities showed a reasonably good MSE of 1.51 that can be further improved to 0.53 by considering the transferability based on protein features. The informative features were identified and mapped to corresponding 3D structures to gain insights into the mechanism of GPCR-ligand interactions across the GPCR family. The proposed method provides a novel perspective on learning ligand bioactivity within the diverse human GPCR superfamily and can potentially accelerate the discovery of therapeutic agents for orphan GPCRs.