The Emerging Role of Gβ Subunits in Human Genetic Diseases

Antimigraine activity of Asarinin by OPRM1 pathway with multifaceted impacts through network analysis

Migraine is a debilitating neurological disorder impacting millions worldwide. Calcitonin Gene-Related Peptide (CGRP) has emerged as a key player in migraine pathophysiology, leading to the development of targeted therapies. This study reviews novel CGRP-targeted treatments, including monoclonal antibodies small molecule inhibitors/nutraceuticals and introduces Asarinin as a potential modulator of the pathway. Asarinin, a natural compound found in various plants, is examined for its pharmacological potential in migraine management. Pharmacokinetic assessments, toxicological modelling, molecular property analysis, and network pharmacology were conducted. Molecular docking and dynamics studies with CGRP reveal potential interactions, providing a foundation for understanding Asarinin's therapeutic effects. Asarinin's favourable pharmacokinetics, safety profile, and bioactivity, supporting its candidacy as a therapeutic agent. In-depth molecular docking studies with the CGRP receptor (PDB: 6ZHO) demonstrate strong binding affinity (- 10.3kcal/mol), while molecular dynamics simulations unveil the dynamic behavior of the Asarinin-CGRP complex, (- 10.53 kcal/mol) for Atogepant-CGRP complex. Network analysis highlights key proteins in migraine pathology, indicating Asarinin's potential efficacy. The groundwork for future investigations, suggests Asarinin as a promising candidate for migraine management by targeting OPRM1 pathway. The integration of diverse assessments provides a comprehensive understanding of Asarinin's potential and paves the way for further preclinical and clinical research.

A detailed multi-omics analysis of GNB2 gene in human cancers

Abstract The Guanine-nucleotide binding protein 2 (GNB2) encodes for β2 subunit (Gβ2) of the G-protein complex. Keeping in view the increased demand of reliable biomarkers in cancer, the current study was planned to extensively explored GNB2 expression variation and its roles in different cancers using online available databases and diverse methodology. In view of our results, the GNB2 was notably up-regulated relative to corresponding controls in twenty three cancer types. As well, the elevated expression of GNB2 was found to be associated with the reduced overall survival (OS) of the Liver Hepatocellular Carcinoma (LIHC) and Rectum Adenocarcinoma (READ) only out of all analyzed cancer types. This implies GNB2 plays vital role in the tumorigenesis of LIHC and READ. Several additional analysis also explored six critical pathways and few important correlations related to GNB2 expression and different other parameters such as promoter methylation, tumor purity, CD8+ T immune cells infiltration, and genetic alteration, and chemotherapeutic drugs. In conclusion, GNB2 gene has been identified in this study as a shared potential biomarker (diagnostic and prognostic) of LIHC and READ.

Epilepsy in a mouse model of GNB1 encephalopathy arises from altered potassium (GIRK) channel signaling and is alleviated by a GIRK inhibitor

De novo mutations in GNB1, encoding the Gβ1 subunit of G proteins, cause a neurodevelopmental disorder with global developmental delay and epilepsy, GNB1 encephalopathy. Here, we show that mice carrying a pathogenic mutation, K78R, recapitulate aspects of the disorder, including developmental delay and generalized seizures. Cultured mutant cortical neurons also display aberrant bursting activity on multi-electrode arrays. Strikingly, the antiepileptic drug ethosuximide (ETX) restores normal neuronal network behavior in vitro and suppresses spike-and-wave discharges (SWD) in vivo. ETX is a known blocker of T-type voltage-gated Ca2+ channels and G protein-coupled potassium (GIRK) channels. Accordingly, we present evidence that K78R results in a gain-of-function (GoF) effect by increasing the activation of GIRK channels in cultured neurons and a heterologous model (Xenopus oocytes)-an effect we show can be potently inhibited by ETX. This work implicates a GoF mechanism for GIRK channels in epilepsy, identifies a new mechanism of action for ETX in preventing seizures, and establishes this mouse model as a pre-clinical tool for translational research with predicative value for GNB1 encephalopathy.

The severity of endothelial dysfunction, oxidative stress, lipid metabolism disorders, decreased elastic properties and tone of peripheral vessels in patients with different POAG course variants, depending on the polymorphism of the genes of the biological clock

The purpose is to find out the relations of the vascular endothelium dysfunction, atherosclerotic damage to the vessels of the upper and lower limbs, the state of the antioxidant and prooxidant systems, and the lipid profile in patients with different POAG course — carriers of biological clock gene polymorphism.Materials and methods. 47 patients with advanced POAG underwent an examination that included visometry, biomicroscopy, ophthalmoscopy, perimetry, tonometry, thermometry, as well as determination of lipid metabolism, indicators of oxidative stress and antioxidant system. All patients were also tested for the degree of endothelial dysfunction by reactive hyperemia method, and the elastic properties and vascular wall tone by the volumetric sphygmomanometry method. POAG progression was determined by static automated perimetry and optical coherence tomography. The hospitalized patients were examined for daily melatonin profile and key biological clock genes typed by real-time polymerase chain reaction. The genetic material was taken by buccal scraping. Polymorphic variants were identified for CLOCK rs1801260 3111T/C and MTNR1B genes. 16 patients (S-POAG — 8, A-POAG — 8) were tested for melatonin taken from saliva samples at different times of the day in laboratory conditions with controlled nutrition and lighting using the DLMO protocol.Results. The predictors of glaucoma progression were found to be pronounced endothelial dysfunction and oxidative stress, which contribute to the acceleration of atherogenesis and a decrease in the elastic properties of the vascular wall of peripheral vessels. Clock 3111t-c circadian gene polymorphism was found to be interrelated with lipid metabolism disorders and increased lipid peroxidation in patients with POAG progression. Carriers of the G allele of the MTNR1B gene tend to have a higher level of triglyceride (TG) which grows in the evening hours if glaucoma is progressing. We showed that the phasal and amplitude characteristics of daily melatonin level, rather than its average level, may affect the state of the vascular wall of peripheral vessels in POAG patients.Conclusion. POAG progression is associated with pronounced oxidative stress, weakened antioxidant protection and dyslipoproteinemia. Differences in the lipid profile (dyslipidemia) and the indicators of oxidative stress and antioxidant protection in patients with stable and progressing glaucoma course are mutually related with Clock 3111t-c gene polymorphism (CG genotype).

Inhibition of G-protein signalling in cardiac dysfunction of intellectual developmental disorder with cardiac arrhythmia (IDDCA) syndrome

BACKGROUND

Pathogenic variants of GNB5 encoding the β5 subunit of the guanine nucleotide-binding protein cause IDDCA syndrome, an autosomal recessive neurodevelopmental disorder associated with cognitive disability and cardiac arrhythmia, particularly severe bradycardia.

METHODS

We used echocardiography and telemetric ECG recordings to investigate consequences of Gnb5 loss in mouse.

RESULTS

We delineated a key role of Gnb5 in heart sinus conduction and showed that Gnb5-inhibitory signalling is essential for parasympathetic control of heart rate (HR) and maintenance of the sympathovagal balance. Gnb5-/- mice were smaller and had a smaller heart than Gnb5+/+ and Gnb5+/- , but exhibited better cardiac function. Lower autonomic nervous system modulation through diminished parasympathetic control and greater sympathetic regulation resulted in a higher baseline HR in Gnb5-/- mice. In contrast, Gnb5-/- mice exhibited profound bradycardia on treatment with carbachol, while sympathetic modulation of the cardiac stimulation was not altered. Concordantly, transcriptome study pinpointed altered expression of genes involved in cardiac muscle contractility in atria and ventricles of knocked-out mice. Homozygous Gnb5 loss resulted in significantly higher frequencies of sinus arrhythmias. Moreover, we described 13 affected individuals, increasing the IDDCA cohort to 44 patients.

CONCLUSIONS

Our data demonstrate that loss of negative regulation of the inhibitory G-protein signalling causes HR perturbations in Gnb5-/- mice, an effect mainly driven by impaired parasympathetic activity. We anticipate that unravelling the mechanism of Gnb5 signalling in the autonomic control of the heart will pave the way for future drug screening.

Extended Phenotyping and Functional Validation Facilitate Diagnosis of a Complex Patient Harboring Genetic Variants in MCCC1 and GNB5 Causing Overlapping Phenotypes

Identifying multiple ultra-rare genetic syndromes with overlapping phenotypes is a diagnostic conundrum in clinical genetics. This study investigated the pathogenicity of a homozygous missense variant in GNB5 (GNB5L; NM_016194.4: c.920T > G (p. Leu307Arg); GNB5S; NM_006578.4: c.794T > G (p. Leu265Arg)) identified through exome sequencing in a female child who also had 3-methylcrotonyl-CoA carboxylase (3-MCC) deficiency (newborn screening positive) and hemoglobin E trait. The proband presented with early-onset intellectual disability, the severity of which was more in keeping with GNB5-related disorder than 3-MCC deficiency. She later developed bradycardia and cardiac arrest, and upon re-phenotyping showed cone photo-transduction recovery deficit, all known only to GNB5-related disorders. Patient-derived fibroblast assays showed preserved GNB5S expression, but bioluminescence resonance energy transfer assay showed abolished function of the variant reconstituted Gβ5S containing RGS complexes for deactivation of D2 dopamine receptor activity, confirming variant pathogenicity. This study highlights the need for precise phenotyping and functional assays to facilitate variant classification and clinical diagnosis in patients with complex medical conditions.

High G protein subunit beta 4 protein level is correlated to poor prognosis of urothelial carcinoma

Data mining on a public domain detected eight potential transcripts which were upregulated in advanced UBUCs, suggesting that they may take part in UC development or/and progression. Retrospectively, immunohistochemistry along with H-score recording was carried out to evaluate the GNB4 protein levels on tissues from UC patients. Correlations between GNB4 H-score and imperative clinicopathological factors, as well as the implication of GNB4 protein level on disease-specific and metastasis-free survivals were assessed. In UTUCs (n = 340) and UBUCs (n = 295), 170 (50.0%) and 148 (50.0%) cases, respectively, were identified to be of high GNB4 expression. The GNB4 protein levels were correlated to numerous clinicopathological features and patients' survivals. Upregulation of the GNB4 protein was significantly associated with primary tumor, nodal metastasis, histological grade, vascular invasion and mitotic rate. High GNB4 protein levels independently and significantly predicted poor disease-specific and metastasis-free in UTUC and UBUC, respectively. Ingenuity pathway analysis furthermore showed that multiple signaling pathways were enriched including 'Communication between Innate and Adaptive Immune Cells' and 'NFκB Signaling'. Our findings demonstrated that the upregulation of the GNB4 protein is an independent unfavorable prognosticator in UC. High GNB4 gene expression plays an important role in UC progression.

Recurrent de novo missense variants in GNB2 can cause syndromic intellectual disability

PURPOSE

Binding proteins (G-proteins) mediate signalling pathways involved in diverse cellular functions and comprise Gα and Gβγ units. Human diseases have been reported for all five Gβ proteins. A de novo missense variant in GNB2 was recently reported in one individual with developmental delay/intellectual disability (DD/ID) and dysmorphism. We aim to confirm GNB2 as a neurodevelopmental disease gene, and elucidate the GNB2-associated neurodevelopmental phenotype in a patient cohort.

METHODS

We discovered a GNB2 variant in the index case via exome sequencing and sought individuals with GNB2 variants via international data-sharing initiatives. In silico modelling of the variants was assessed, along with multiple lines of evidence in keeping with American College of Medical Genetics and Genomics guidelines for interpretation of sequence variants.

RESULTS

We identified 12 unrelated individuals with five de novo missense variants in GNB2, four of which are recurrent: p.(Ala73Thr), p.(Gly77Arg), p.(Lys89Glu) and p.(Lys89Thr). All individuals have DD/ID with variable dysmorphism and extraneurologic features. The variants are located at the universally conserved shared interface with the Gα subunit, which modelling suggests weaken this interaction.

CONCLUSION

Missense variants in GNB2 cause a congenital neurodevelopmental disorder with variable syndromic features, broadening the spectrum of multisystem phenotypes associated with variants in genes encoding G-proteins.

Subtype-dependent regulation of Gβγ signalling

G protein-coupled receptors (GPCRs) transmit information to the cell interior by transducing external signals to heterotrimeric G protein subunits, Gα and Gβγ subunits, localized on the inner leaflet of the plasma membrane. Though the initial focus was mainly on Gα-mediated events, Gβγ subunits were later identified as major contributors to GPCR-G protein signalling. A broad functional array of Gβγ signalling has recently been attributed to Gβ and Gγ subtype diversity, comprising 5 Gβ and 12 Gγ subtypes, respectively. In addition to displaying selectivity towards each other to form the Gβγ dimer, numerous studies have identified preferences of distinct Gβγ combinations for specific GPCRs, Gα subtypes and effector molecules. Importantly, Gβ and Gγ subtype-dependent regulation of downstream effectors, representing a diverse range of signalling pathways and physiological functions have been found. Here, we review the literature on the repercussions of Gβ and Gγ subtype diversity on direct and indirect regulation of GPCR/G protein signalling events and their physiological outcomes. Our discussion additionally provides perspective in understanding the intricacies underlying molecular regulation of subtype-specific roles of Gβγ signalling and associated diseases.

Diversity of the Gβγ complexes defines spatial and temporal bias of GPCR signaling

The signal transduction by G-protein-coupled receptors (GPCRs) is mediated by heterotrimeric G proteins composed from one of the 16 Gα subunits and the inseparable Gβγ complex assembled from a repertoire of 5 Gβ and 12 Gγ subunits. However, the functional role of compositional diversity in Gβγ complexes has been elusive. Using optical biosensors, we examined the function of all Gβγ combinations in living cells and uncovered two major roles of Gβγ diversity. First, we demonstrate that the identity of Gβγ subunits greatly influences the kinetics and efficacy of GPCR responses at the plasma membrane. Second, we show that different Gβγ combinations are selectively dispatched from the plasma membrane to various cellular organelles on a timescale from milliseconds to minutes. We describe the mechanisms regulating these processes and document their implications for GPCR signaling via various Gα subunits, thereby illustrating a role for the compositional diversity of G protein heterotrimers.