International Union of Basic and Clinical Pharmacology. XCIV. Adhesion G protein-coupled receptors

Mechanosensitive adhesion G protein-coupled receptors: Insights from health and disease

Ontogeny cannot be separated from mechanical forces. Cells are continuously subjected to different types of mechanical stimuli that convert into intracellular signals through mechanotransduction. As a member of the G protein-coupled receptor superfamily, adhesion G protein-coupled receptors (aGPCRs) have attracted extensive attention due to their unique extracellular domain and adhesion properties. In the past few decades, increasing evidence has indicated that sensing mechanical stimuli may be one of the main physiological activities of aGPCRs. Here, we review the general structure and activation mechanisms of these receptors and highlight the lesion manifestations relevant to each mechanosensitive aGPCR.

Spatiotemporal profiling of adhesion G protein-coupled receptors in developing mouse and human pancreas reveals a role for GPR56 in islet development

INTRODUCTION

G protein-coupled receptors (GPCRs) are cell-surface proteins that are targeted therapeutically for a range of disorders, including diabetes. Adhesion GPCRs (aGPCRs) are the second largest class of the GPCR superfamily and some members of this family have been implicated in appropriate organ development. However, the role of aGPCRs in endocrine pancreas specification is not yet known.

METHODS

Here, we systematically characterised expression of mRNAs encoding aGPCRs and their ligands in developing mouse and human pancreas using our own and publicly available single-cell RNA sequencing and spatial transcriptomics data, and we conducted qPCR analysis of aGPCR expression in human pancreas at different gestational stages. We then investigated the role of GPR56 (ADGRG1), the most abundant aGPCR in pancreatic endocrine progenitors, in islet development using Gpr56 null mice and their wildtype littermates.

RESULTS

We demonstrated that aGPCRs are dynamically expressed during mouse and human pancreas development, with specific aGPCR mRNAs expressed in distinct endocrine, endothelial, mesenchymal, acinar, ductal, and immune cell clusters. aGPCR ligand mRNAs were mostly expressed by non-endocrine cells, and the most highly expressed receptor-ligand interacting mRNA pairs were those encoding GPR56 and COL3A1. Deletion of Gpr56 in neonatal mice was associated with an altered α-/β-/δ-cell ratio and reduced β-cell proliferation.

CONCLUSION

Our data show that aGPCRs are expressed at key stages of human and mouse pancreas endocrine lineage decisions, and analysis of pancreases from Gpr56 knockout mice implicate this aGPCR in the development of a full complement of β-cells.

Complex G-protein signaling of the adhesion GPCR, ADGRA3

ADGRA3 (GPR125) is an orphan adhesion G protein-coupled receptor (aGPCR) that plays a role in planar cell polarity (PCP), primarily through recruitment of the signaling components Dishevelled (DVL) during vertebrate gastrulation, and Discs large homolog 1 (Dlg1), which is implicated in cancer. Limited knowledge exists of the signaling capacity in the canonical GPCR pathways of ADGRA3. Here, we employed a series of human cell line-based signaling assays to gain insight into the heterotrimeric G protein-mediated signaling of ADGRA3. We based the design of ADGRA3 constructs on analyses of transcript variants in publicly available human liver and brain RNA-seq datasets. As cleavage in the GPCR autoproteolysis site (GPS) is a hallmark for many aGPCRs, we generated a truncated ADGRA3 (C-terminal fragment, CTF) corresponding to a potential cleavage at the GPS. We found low-level activation of Gi and Gs by ADGRA3 and slightly more by its CTF. As the N terminus of the CTF constitutes a class-defined tethered agonist known as the stachel peptide, we removed the initial three amino acids of the CTF. This resulted in abrogated G protein-mediated signaling, as observed for other aGPCRs. Due to the central role of ADGRA3 in PCP signaling through DVL recruitment, we investigated the G-protein signaling in absence of DVL1-3 and found it sustained. No transcriptional activation was observed downstream of β-catenin in an assay reporting T-cell factor/lymphoid enhancer factor (TCF/LEF)-mediated transcriptional activity. Collectively, this establishes a classical G protein-mediated signaling for ADGRA3 in addition to its association with components of non-canonical Wnt-signaling pathways.

Signaling by latrophilin adhesion-GPCRs in synapse assembly

Latrophilins are evolutionarily conserved adhesion-GPCRs with diverse roles, including a prominent function in synapse organization. In mammals, the primary transcripts of three latrophilin genes (ADGRL1-3) are extensively alternatively spliced, producing hundreds of isoforms with diverse cytoplasmic sequences. Extracellularly, latrophilins feature N-terminal lectin- and olfactomedin-like domains that bind to Teneurin and FLRT adhesion molecules, respectively, and are followed by an autoproteolytic GAIN domain typical for adhesion-GPCRs. Since Teneurins and FLRTs in turn interact with other ligands, latrophilins form a large trans-cellular protein interaction network. Intracellularly, latrophilins bind to G proteins, arrestins, and postsynaptic scaffold proteins. Latrophilins stimulate all Gα proteins tested, with the Gα isoform preference regulated by alternative splicing. In brain, latrophilins act as essential postsynaptic organizers that functionally require extracellular binding to teneurins and FLRTs, intracellular activation of GαS, and recruitment of postsynaptic scaffolds. Thus, latrophilins are signaling platforms that connect trans-cellular interactions to cellular responses in a manner regulated by alternative splicing.

The BBS/CCT chaperonin complex ensures the localization of the adhesion G protein-coupled receptor ADGRV1 to the base of primary cilia

Primary cilia are antenna-like sensory organelles present on almost all eukaryotic cells. Their sensory capacity relies on receptors, in particular G-protein-coupled receptors (GPCRs) which localize to the ciliary membrane. Here we show that ADGRV1, a member of the GPCR subfamily of adhesion GPCRs, is part of a large protein network, interacting with numerous proteins of a comprehensive ciliary proteome. ADGRV1 is localized to the base of prototypic primary cilia in cultured cells and the modified primary cilia of retinal photoreceptors, where it interacts with TRiC/CCT chaperonins and the Bardet Biedl syndrome (BBS) chaperonin-like proteins. Knockdown of ADGRV1, CCT2 and 3, and BBS6 result in common ciliogenesis phenotypes, namely reduced ciliated cells combined with shorter primary cilia. In addition, the localization of ADGRV1 to primary cilia depends on the activity of a co-complex of TRiC/CCT chaperonins and the BBS chaperonin-like proteins. In the absence of components of the TRiC/CCT-BBS chaperonin co-complex, ADGRV1 is depleted from the base of the primary cilium and degraded via the proteasome. Defects in the TRiC/CCT-BBS chaperonin may lead to an overload of proteasomal degradation processes and imbalanced proteostasis. Dysfunction or absence of ADGRV1 from primary cilia may underly the pathophysiology of human Usher syndrome type 2 and epilepsy caused by mutations in ADGRV1.

GPCR drug discovery: new agents, targets and indications

G protein-coupled receptors (GPCRs) form one of the largest drug target families, reflecting their involvement in numerous pathophysiological processes. In this Review, we analyse drug discovery trends for the GPCR superfamily, covering compounds, targets and indications that have reached regulatory approval or that are being investigated in clinical trials. We find that there are 516 approved drugs targeting GPCRs, making up 36% of all approved drugs. These drugs act on 121 GPCR targets, one-third of all non-sensory GPCRs. Furthermore, 337 agents targeting 133 GPCRs, including 30 novel targets, are being investigated in clinical trials. Notably, 165 of these agents are approved drugs being tested for additional indications and novel agents are increasingly allosteric modulators and biologics. Remarkably, diabetes and obesity drugs targeting GPCRs had sales of nearly US $30 billion in 2023 and the numbers of clinical trials for GPCR modulators in the metabolic diseases, oncology and immunology areas are increasing strongly. Finally, we highlight the potential of untapped target-disease associations and pathway-biased signalling. Overall, this Review provides an up-to-date reference for the drugged and potentially druggable GPCRome to inform future GPCR drug discovery and development.

The N terminus-only function of adhesion GPCRs: emerging concepts

Adhesion G-protein-coupled receptors (aGPCRs) play key roles in health and disease. They are unique in that they not only activate G-protein pathways but also have distinct functions that rely solely on their N termini, making them complex drug targets. To date there have been only descriptive observations about these enigmatic N terminus-only functions. Emerging evidence from several aGPCRs now indicates that these are a defining characteristic of these receptors that allows them to operate bidirectionally across environments. Recent advances in characterizing aGPCR splice variants and receptor structure have revealed the G protein-independent mechanisms that underlie their N terminus-only functions. This review consolidates current findings, explores how the N termini integrate functions, and identifies common principles across aGPCRs. We consider the therapeutic implications and discuss how specifically targeting N terminus functions provides a novel perspective on the pharmacological potential of aGPCRs.

Mechanisms of Peptide Agonist Dissociation and Deactivation of Adhesion G-Protein-Coupled Receptors

Adhesion G protein-coupled receptors (ADGRs) belong to Class B2 of GPCRs and are involved in a wide array of important physiological processes. ADGRs contain a GPCR autoproteolysis-inducing domain that is proximal to the receptor N-terminus and undergoes autoproteolysis during the biosynthesis to generate two fragments: the N-terminal fragment (NTF) and the C-terminal fragment (CTF). Dissociation of NTF reveals a tethered agonist to activate the CTF of ADGRs for G protein signaling. Synthetic peptides that mimic the tethered agonist can also activate ADGRs. However, mechanisms of peptide agonist dissociation and the deactivation of ADGRs remain poorly understood. In this study, we have performed all-atom enhanced sampling simulations using a novel protein-protein interaction Gaussian-accelerated molecular dynamics (PPI-GaMD) method on the ADGRG2-IP15 and ADGRG1-P7 complexes. The PPI-GaMD simulations captured the dissociation of the IP15 and P7 peptide agonists from their target receptors. We were able to identify important low-energy conformations of ADGRG2 and ADGRG1 in the active, intermediate, and inactive states, as well as different states of the peptide agonists IP15 and P7 during dissociation. Therefore, our PPI-GaMD simulations have revealed dynamic mechanisms of peptide agonist dissociation and deactivation of ADGRG1 and ADGRG2, which will facilitate the rational design of peptide regulators of the two receptors and other ADGRs.

α-Latrotoxin Actions in the Absence of Extracellular Ca2+ Require Release of Stored Ca2

α-Latrotoxin (αLTX) causes exhaustive release of neurotransmitters from nerve terminals in the absence of extracellular Ca2+ (Ca2+e). To investigate the mechanisms underlying this effect, we loaded mouse neuromuscular junctions with BAPTA-AM. This membrane-permeable Ca2+-chelator demonstrates that Ca2+e-independent effects of αLTX require an increase in cytosolic Ca2+ (Ca2+cyt). We also show that thapsigargin, which depletes Ca2+ stores, induces neurotransmitter release, but inhibits the effect of αLTX. We then studied αLTX's effects on Ca2+cyt using neuroblastoma cells expressing signaling-capable or signaling-incapable variants of latrophilin-1, a G protein-coupled receptor of αLTX. Our results demonstrate that αLTX acts as a cation ionophore and a latrophilin agonist. In model cells at 0 Ca2+e, αLTX forms membrane pores and allows the influx of Na+; this reverses the Na+-Ca2+ exchanger, leading to the release of stored Ca2+ and inhibition of its extrusion. Concurrently, αLTX stimulates latrophilin signaling, which depletes a Ca2+ store and induces transient opening of Ca2+ channels in the plasmalemma that are sensitive to inhibitors of store-operated Ca2+ entry. These results indicate that Ca2+ release from intracellular stores and that Ca2+ influx through latrophilin-activated store-operated Ca2+ channels contributes to αLTX actions and may be involved in physiological control of neurotransmitter release at nerve terminals.

C1ql3 knockout affects microglia activation, neuronal integrity, and spontaneous behavior in Wistar rats

BACKGROUND

C1QL3 is widely expressed in the brain and is specifically produced by a subset of excitatory neurons. However, its function is still not clear. We established C1ql3-deficient rats to investigate the role of C1QL3 in the brain.

METHODS

C1ql3 knockout (KO) rats were generated using CRISPR/Cas9. C1ql3 KO was determined by polymerase chain reaction (PCR), DNA sequencing, and western blotting. Microglia morphology and cytokine expression with or without lipopolysaccharide (LPS) stimulus were analyzed using immunohistochemistry and real-time PCR. The brain structure changes in KO rats were examined using magnetic resonance imaging. Neuronal architecture alteration was analyzed by performing Golgi staining. Behavior was evaluated using the open field test, Morris water maze test, and Y maze test.

RESULTS

C1ql3 KO significantly increased the number of ramified microglia and decreased the number of hypertrophic microglia, whereas C1ql3 KO did not influence the expression of pro-inflammatory factors and anti-inflammatory factors except IL-10. C1ql3 KO brains had more amoeboid microglia types and higher Arg-1 expression compared with the WT rats after LPS stimulation. The brain weights and HPC sizes of C1ql3 KO rats did not differ from WT rats. C1ql3 KO damaged neuronal integrity including neuron dendritic arbors and spine density. C1ql3 KO rats demonstrated an increase in spontaneous activity and an impairment in short working memory.

CONCLUSIONS

C1ql3 KO not only interrupts the neuronal integrity but also affects the microglial activation, resulting in hyperactive behavior and impaired short memory in rats, which highlights the role of C1QL3 in the regulation of structure and function of both neuronal and microglial cells.

Intron retention of an adhesion GPCR generates 1TM isoforms required for 7TM-GPCR function

Adhesion G protein-coupled receptors (aGPCRs) are expressed in all organs and are involved in various mechanobiological processes. They are heavily alternatively spliced, forecasting an extraordinary molecular structural diversity. Here, we uncovered the existence of unconventional single-transmembrane (1TM)-containing ADGRL/Cirl proteins devoid of the conventional GPCR layout (i.e., the 7TM signaling unit) in Drosophila. These 1TM proteins are made as a result of intron retention and provide an N-terminal fragment that acts as an interactor to allow Gαo-dependent signaling through conventional 7TM-containing Cirl isoforms encoded by the same gene. This molecular mechanism determines sensory precision of neurons in response to mechanical stimulation in vivo. This action mode of aGPCR provides a promising entry point for experimental and therapeutic approaches to intervene in aGPCR signaling and implicates alternative splicing as a physiological strategy to express a given aGPCR together with its molecular interactor.

Exome sequencing identifies genes for socioeconomic status in 350,770 individuals

Socioeconomic status (SES) is a critical factor in determining health outcomes and is influenced by genetic and environmental factors. However, our understanding of the genetic structure of SES remains incomplete. Here, we conducted a large-scale exome study of SES markers (household income, occupational status, educational attainment, and social deprivation) in 350,770 individuals. For rare coding variants, we identified 56 significant associations by gene-based collapsing tests, unveiling 7 additional SES-associated genes (NRN1, CCDC36, RHOB, EP400, NCAM1, TPTEP2-CSNK1E, and LINC02881). Exome-wide single common variant analysis revealed nine lead single-nucleotide polymorphisms (SNPs) associated with household income and 34 lead SNPs associated with EduYears, replicating previous GWAS findings. The gene-environment correlations had a substantial impact on the genetic associations with SES, as indicated by the significantly increased P values in several associations after controlling for geographic regions. Furthermore, we observed the pleiotropic effects of SES-associated genetic factors on a wide range of health outcomes, such as cognitive function, psychosocial status, and diabetes. This study highlights the contribution of coding variants to SES and their associations with health phenotypes.

An Alternative Mode of GPCR Transactivation: Activation of GPCRs by Adhesion GPCRs

G protein-coupled receptors (GPCRs), critical for cellular communication and signaling, represent the largest cell surface protein family and play important roles in numerous pathophysiological processes. Consequently, GPCRs have become a primary focus in drug discovery efforts. Beyond their traditional G protein-dependent signaling pathways, GPCRs are also capable of activating alternative signaling mechanisms, including G protein-independent signaling, biased signaling, and signaling crosstalk. A particularly novel signaling mode employed by these receptors is GPCR transactivation, which enables cross-communication between GPCRs and other receptor types. Intriguingly, GPCR transactivation by distinct GPCRs has also been identified. In this review, I provide an overview of the known GPCR transactivation mechanisms and explore recently uncovered GPCR transactivation mediated by adhesion-class GPCRs (aGPCRs). These aGPCR-GPCR transactivation processes regulate unique cell type-specific functions, offering an exciting opportunity to develop therapies that precisely modulate specific GPCR-mediated biological effects.

A meta-analysis of genome-wide association studies to identify candidate genes associated with feed efficiency traits in pigs

Pig production is an agricultural sector of great economic and social relevance to Brazil and global markets. Feed efficiency traits directly influence the sustainability of pig production due to the economic impact of feed costs on the production system and the environmental footprint of the industry. Therefore, breeding for improved feed efficiency has been a target of worldwide pig breeding programs. Genome-wide association studies (GWAS) enable the assessment of the genetic background of complex traits, which contributes to a better understanding of the biological mechanisms regulating their phenotypic expression. In this context, the primary objective of this study was to identify and validate genomic regions and candidate genes associated with feed conversion ratio (FCR) and residual feed intake (RFI) in pigs based on a comprehensive systematic review and meta-analysis of GWAS. The METAL software was used to implement the meta-analysis and the Bonferroni multiple testing correction considering a significance threshold 0.05. The significant single nucleotide polymorphisms (SNPs) in the meta-analysis were used to identify candidate genes, followed by a functional genomic enrichment analysis. The systematic review identified 13 studies, of which 7 evaluated FCR, 3 evaluated RFI, and 3 studies investigated both traits, with 160 and 96 SNPs identified for FCR and RFI, respectively. After the meta-analysis, 145 markers were significantly associated with FCR and 90 with RFI. The gene annotation process resulted in 105 and 114 genes for FCR and RFI, respectively. The enrichment analysis for FCR resulted in 16 significant gene ontology (GO) terms, while 6 terms were identified for RFI. The main GO terms were actin cytoskeleton (GO_BP:0030036), membrane (GO_CC:0016020), integral components of the peroxisomal membrane (GO_CC:0005779), and carbohydrate-binding (GO_MF:0030246). The main candidate genes identified were MED18, PHACTR4, ABCC2, TRHDE, FRS2, FAR2 and FIS1 for FCR, and ADGRL2, ASGR1, ASGR2, and MAN2B1 for RFI. These findings contribute to a better understanding of the genetic mechanisms associated with feed efficiency traits in pigs, providing a foundation for future improvements in pig breeding programs.

Novel Isoforms of Adhesion G Protein-Coupled Receptor B1 (ADGRB1/BAI1) Generated from an Alternative Promoter in Intron 17

Brain-specific angiogenesis inhibitor 1 (BAI1) belongs to the adhesion G-protein-coupled receptors, which exhibit large multi-domain extracellular N termini that mediate cell-cell and cell-matrix interactions. To explore the existence of BAI1 isoforms, we queried genomic datasets for markers of active chromatin and new transcript variants in the ADGRB1 (adhesion G-protein-coupled receptor B1) gene. Two major types of mRNAs were identified in human/mouse brain, those with a start codon in exon 2 encoding a full-length protein of a predicted size of 173.5/173.3 kDa and shorter transcripts starting from alternative exons at the intron 17/exon 18 boundary with new or exon 19 start codons, predicting two shorter isoforms of 76.9/76.4 and 70.8/70.5 kDa, respectively. Immunoblots on wild-type and Adgrb1 exon 2-deleted mice, reverse transcription PCR, and promoter-luciferase reporter assay confirmed that the shorter isoforms originate from an alternative promoter in intron 17. The shorter BAI1 isoforms lack most of the N terminus and are very close in structure to the truncated BAI1 isoform generated through GPS processing from the full-length receptor. The cleaved BAI1 isoform has a 19 amino acid extracellular stalk that may serve as a receptor agonist, while the alternative transcripts generate BAI1 isoforms with extracellular N termini of 5 or 60 amino acids. Further studies are warranted to compare the functions of these isoforms and examine the distinct roles they play in different tissues and cell types.

Targeting adhesion G protein-coupled receptors. Current status and future perspectives

G protein-coupled receptors (GPCRs) orchestrate many physiological functions and are a crucial target in drug discovery. Adhesion GPCRs (aGPCRs), the second largest family within this superfamily, are promising yet underexplored targets for treating various diseases, including obesity, psychiatric disorders, and cancer. However, the receptors' unique and complex structure and miscellaneous interactions complicate comprehensive pharmacological studies. Despite recent progress in determining structures and elucidation of the activation mechanism, the function of many receptors remains to be determined. This review consolidates current knowledge on aGPCR ligands, focusing on small molecule orthosteric ligands and allosteric modulators identified for the ADGRGs subfamily (subfamily VIII), (GPR56/ADGRG1, GPR64/ADGRG2, GPR97/ADGRG3, GPR114/ADGRG5, GPR126/ADGRG6, and GPR128/ADGRG7). We discuss challenges in hit identification, target validation, and drug discovery, highlighting molecular compositions and recent structural breakthroughs. ADGRG ligands can offer new insights into aGPCR modulation and have significant potential for novel therapeutic interventions targeting various diseases.

Genetic Variants in the Adhesive G Protein-Coupled Receptor ADGRG6 are Associated with Increased Susceptibility to COPD in the Elderly Han Chinese Population of Southern China

Background

Mutations in ADGRG6 are associated with a variety of cancers and multiple types of diseases. However, the impact of genetic variations in ADGRG6 on chronic obstructive pulmonary disease (COPD) susceptibility has not yet been evaluated.

Methods

Considering the high prevalence of COPD among the elderly population in China, this study specifically targets the elderly Han population in Southern China as the study subject. Following the acquisition of participants' whole-genome DNA, genotyping was conducted using the Agena MassARRAY platform. The online tool 'SNPStats', which utilizes logistic regression, was employed to analyze and assess the correlation. Multi-factor dimensionality reduction was utilized to clarify the impact of "SNP-SNP" interactions on COPD risk. The False-Positive Report Probability (FPRP) was applied to determine whether significant results are noteworthy findings.

Results

The mutant allele "C" of rs11155242 was a protective genetic factor against COPD susceptibility (OR = 0.57, 95% CI = 0.36 to 0.91, p = 0.017). The heterozygous mutant genotype "CA" of rs11155242 was found to be significantly associated with reduced COPD risk (CA Vs AA: OR = 0.53, 95% CI = 0.32 to 0.90, p = 0.018). ADGRG6-rs11155242 was found to be strongly associated with a reduced risk of COPD in males, non-smokers, and subjects with a BMI below 24 kg/m2 (OR < 1, p < 0.05). The FPRP analysis indicated that the positive results identified in this study are noteworthy new findings.

Conclusion

The mutant allele "C" and mutant genotype "CA" of rs11155242 act as protective genetic factors against COPD susceptibility. This study will provide a new research direction for the personalized prevention and treatment of COPD in the elderly Han population in southern China, and lay a potential scientific basis.

RNA sequencing reveals dynamic expression of genes related to innate immune responses in canine small intestinal epithelial cells induced by Echinococcus granulosus protoscoleces

Background

Dogs are definitive hosts of Echinococcus granulosus, with the small intestine being the only site of parasitic infections. However, the immunomodulatory processes that occur during interactions between E. granulosus and its definitive host remain unclear. Therefore, this study aimed to evaluate gene transcription patterns in canine small intestinal epithelial cells (CIECs) following stimulation by E. granulosus protoscoleces (PSCs). Particularly, this study investigated the roles of pattern recognition receptors (PRRs), involved in recognizing pathogen-associated molecular patterns (PAMPs) and mediating the host innate immune response to the tapeworm E. granulosus.

Methods

RNA sequencing (RNA-seq) was used to examine gene transcription patterns in CIECs following stimulation with PSCs for 12 and 24 h. The potential roles of differentially expressed (DE) genes were inferred through Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses.

Results

RNA-seq analysis identified 78,206,492-90,548,214 clean reads in 12 RNA samples. This included six samples stimulated with PSCs for 12 h (PSC1_12h-PSC3_12h) and 24 h (PSC1_24h-PSC3_24h) and six corresponding control samples (PBS1_12h-PBS3_12h and PBS1_24h-PBS3_24h). In the PSC_12h vs. PBS_12h and PSC_24h vs. PBS_24h groups, 3,520 (2,359 upregulated and 1,161 downregulated) and 3,287 (1765 upregulated and 1,522 downregulated) DEgenes were identified, respectively. The expression of 45 PRRs genes was upregulated in the PSC_12h and PSC_24h groups compared to those in the control groups, including 4 Toll-like receptors (TLRs), 4C-type lectin receptors (CLRs), 3 NOD-like receptors (NLRs), 17 G protein-coupled receptors (GPCRs), 4 scavenger receptors (SRs), and 13 leucine-rich repeat-containing proteins (LRRCs). GO enrichment and KEGG analyses revealed that these DEgenes were mainly involved in the regulation of host immune response processes and molecules. These included antigen processing and presentation, Th17, PI3K-Akt, Th1, and Th2 cell differentiation, neutrophil extracellular trap formation, NOD- and Toll-like receptors, TNF, intestinal immune network for IgA production and IL-17 signaling pathway. Furthermore, the identified DEgenes were involved in the regulation of signaling molecules and interaction (e.g., cell adhesion molecules and ECM-receptor interaction).

Conclusion

These preliminary findings provide novel perspectives on the host innate immune response to E. granulosus PSC stimulation, with a focus on the involvement of E. granulosus-specific PRRs in host defense mechanisms against infection.

Latrophilin-2 Deletion in Cardiomyocyte Disrupts Cell Junction, Leading to D-CMP

BACKGROUND

Latrophilin-2 (Lphn2), an adhesive GPCR (G protein-coupled receptor), was found to be a specific marker of cardiac progenitors during the differentiation of pluripotent stem cells into cardiomyocytes or during embryonic heart development in our previous studies. Its role in adult heart physiology, however, remains unclear.

METHODS

The embryonic lethality resulting from Lphn2 deletion necessitates the establishment of cardiomyocyte-specific, tamoxifen-inducible Lphn2 knockout mice, which was achieved by crossing Lphn2 flox/flox mice with mice having MerCreMer (tamoxifen-inducible Cre [Cyclization recombinase] recombinase) under the α-myosin heavy chain promoter.

RESULTS

Tamoxifen treatment for several days completely suppressed Lphn2 expression, specifically in the myocardium, and induced the dilated cardiomyopathy (D-CMP) phenotype with serious arrhythmia and sudden death in a short period of time. Transmission electron microscopy showed mitochondrial abnormalities, blurred Z-discs, and dehiscent myofibrils. The D-CMP phenotype, or heart failure, worsened during myocardial infarction. In a mechanistic study of D-CMP, Lphn2 knockout suppressed PGC-1α (Peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and mitochondrial dysfunction, leading to the accumulation of reactive oxygen species and the global suppression of junctional molecules, such as N-cadherin (adherens junction), DSC-2 (desmocollin-2; desmosome), and connexin-43 (gap junction), leading to the dehiscence of cardiac myofibers and serious arrhythmia. In an experimental therapeutic trial, activators of p38-MAPK (p38 mitogen-activated protein kinases), which is a downstream signaling molecule of Lphn2, remarkably rescued the D-CMP phenotype of Lphn2 knockout in the heart by restoring PGC-1α and mitochondrial function and recovering global junctional proteins.

CONCLUSIONS

Lphn2 is a critical regulator of heart integrity by controlling mitochondrial functions and cell-to-cell junctions in cardiomyocytes. Its deficiency leads to D-CMP, which can be rescued by activators of the p38-MAPK pathway.

The N terminus-only (trans) function of the adhesion G protein-coupled receptor latrophilin-1 controls multiple processes in reproduction of Caenorhabditis elegans

Adhesion G protein-coupled receptors are unique molecules. They are able to transmit classical signals via G protein activation as well as mediate functions solely through their extracellular N termini, completely independently of the seven transmembrane helices domain and the C terminus. This dual mode of action is highly unusual for G protein-coupled receptors and allows for a plethora of possible cellular consequences. However, the physiological implications and molecular details of this N terminus-mediated signaling are poorly understood. Here, we show that several distinct seven transmembrane helices domain-independent/trans functions of the adhesion G protein-coupled receptor latrophilin homolog latrophilin-1 in the nematode Caenorhabditis elegans together regulate reproduction: sperm guidance, ovulation, and germ cell apoptosis. In these contexts, the receptor elicits its functions in a noncell autonomous manner. The functions might be realized through alternative splicing of the receptor specifically generating N terminus-only variants. Thus, our findings shed light on the versatility of seven transmembrane helices domain-independent/N terminus-only/trans functions of adhesion G protein-coupled receptor and discuss possible molecular details.

The Adhesion GPCR ADGRL2/LPHN2 Can Protect Against Cellular and Organismal Dysfunction

The most common trigger of sepsis and septic shock is bacterial lipopolysaccharide (LPS). Endothelial cells are among the first to encounter LPS directly. Generally, their function is closely linked to active endothelial NO Synthase (eNOS), which is significantly reduced under septic conditions. LPS treatment of endothelial cells leads to their activation and apoptosis, resulting in loss of integrity and vascular leakage, a hallmark of septic shock. Hence, therapies that prevent endothelial leakage or restore the endothelial barrier would be invaluable for patients. Adhesion GPCRs (aGPCRs) have been largely overlooked in this context, although particularly one of them, ADGRL2/LPHN2, has been implicated in endothelial barrier function. Our study shows that overexpression of ADGRL2 protects endothelial cells from LPS-induced activation, apoptosis, and impaired migration. Mechanistically, ADGRL2 preserves eNOS activity by shifting its binding from Caveolin-1 to Heat Shock Protein 90. Furthermore, ADGRL2 enhances antioxidative responses by increasing NRF2 activity. Notably, we found that this function may be evolutionarily conserved. In the absence of lat-2, a homolog of ADGRL2 in Caenorhabditis elegans, worms show higher ROS levels and altered stress response gene expression. Additionally, lat-2 mutants have a significantly reduced lifespan, altogether indicating a protective role of ADGRL2 against oxidative stress across species.

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.

In Search of the Role of Three-Finger Starfish Proteins

Three-finger proteins (TFPs), or Ly6/uPAR proteins, are characterized by the beta-structural LU domain containing three protruding "fingers" and stabilized by four conserved disulfide bonds. TFPs were initially characterized as snake alpha-neurotoxins, but later many studies showed their regulatory roles in different organisms. Despite a known expression of TFPs in vertebrates, they are poorly studied in other taxa. The presence of TFPs in starfish was previously shown, but their targets and functional role still remain unknown. Here, we analyzed expression, target, and possible function of the Lystar5 protein from the Asterias rubens starfish using bioinformatics, qPCR, and immunoassay. First, the presence of Lystar5 homologues in all classes of echinoderms was demonstrated. qPCR revealed that mRNA of Lystar5 and LyAr2 are expressed mainly in coelomocytes and coelomic epithelium of Asterias, while mRNA of other TFPs, LyAr3, LyAr4, and LyAr5, were also found in a starfish body wall. Using anti-Lystar5 serum from mice immunized by a recombinant Lystar5, we confirmed that this protein is expressed on the surface of coelomocytes and coelomic epithelium cells. According to ELISA, a recombinant analogue of Lystar5 bound to the membrane fraction of coelomocytes and coelomic epithelium but not to the body wall or starfish arm tip. Analysis by LC-MALDI MS/MS suggested integrin α-8-like protein expressed in the coelomocytes and coelomic epithelium as a target of Lystar5. Thus, our insights propose the important role of TFPs in regulation of starfish physiology and show prospects for their further research.

GPR97 depletion aggravates imiquimod-induced psoriasis pathogenesis via amplifying IL-23/IL-17 axis signal pathway

Skin psoriasis is defined as receiving external stimulation to activate skin dendritic cells (DCs) which can release interleukin 23 (IL-23) to interlink the innate and adaptive immunity as well as induce T helper 17 (Th17) cell differentiation leading to elevated production of interleukin 17 (IL-17) for keratinocytes over production. This autoimmune loop in psoriasis pathogenesis is influenced by G protein-coupled receptor (GPCR) signalling transduction, and in particular, function of adhesion molecule GPR97 in psoriasis endures to be utterly addressed. In this research, our team allocated GPR97 depletion (GPR97-/-), GPR97 conditional depletion on dendritic cell (DC-cKO), and keratin 14-conditional knockout (K14-cKO) mice models to explore the function of GPR97 which influences keratinocytes and skin immunity. It was found that significantly aggravated psoriasis-like lesion in GPR97-/- mice. In addition, hyperproliferative keratinocytes as well as accumulation of DCs and Th17 cells were detected in imiquimod (IMQ)-induced GPR97-/- mice, which was consistent with the results in DC-cKO and K14-cKO psoriasis model. Additional investigations indicated that beclomethasone dipropionate (BDP), an agonist of GPR97, attenuated the psoriasis-like skin disease and restricted HaCaT cells abnormal proliferation as well as Th17 cells differentiation. Particularly, we found that level of NF-κB p65 was increased in GPR97-/- DCs and BDP could inhibit p65 activation in DCs. Role of GPR97 is indispensable and this adhesion receptor may affect immune cell enrichment and function in skin and alter keratinocytes proliferation as well as differentiation in psoriasis.

Research Progress of EMR2 Receptor Function in Glioma and its Potential Application as Therapeutic Target

The most frequent primary brain malignancy is glioma. Alterations in several adhesion G-protein-coupled receptors (aGPCRs) are present in cancer as they regulate adhesion, migration, and guidance. Epidermal growth factor (EGF) module-containing mucin-like receptor 2 (EMR2) is included in group II GPCRs and functionally in a family of brain angiogenesis inhibitor molecules (BAIs). Recent studies have shown that BAIs regulate phagocytosis and synaptogenesis, and their extracellular domain inhibits angiogenesis and tumor growth. In neoplastic processes, EMR2 appears to play a role in disease aggressiveness, patient survival rates, and tumor grade. This review summarizes the EMR2 involvement in cellular mechanisms and pathologies, particularly in cancer. We searched the Pubmed Central, Google Scholar and Scopus databases for terms "EMR2" and "glioma". The initial search yielded a total of 92 results. After excluding studies not written in English, based on design, and excluding duplicates and non-relevant studies, we included 38 studies in the review. EMR2 was shown to be expressed in various histologic grades of gliomas and to be linked to the PI3K pathway, as both are upregulated in glioblastoma after bevacizumab therapy. The PI3K-Akt pathway is involved in tumorigenesis, and upregulation of EMR2 may in turn upregulate PI3K, leading to increased tumor invasiveness. Indeed, overexpression of EMR2 was associated with the mesenchymal glioblastoma subtype, tumor invasiveness, and poor survival. EMR2 also regulates neutrophil function by producing reactive oxygen species (ROS) and degranulation. Possible therapeutic approaches have been studied, such as the stimulation of microglia and monocytes to inhibit tumor-initiating cells by down-regulating the EMR2 gene or through an antibody against EMR2. The current review summarizes the knowledge about the EMR2 receptor that can serve as motivation for future studies on its role in the clinical evolution and tumor biology of gliomas in order to find new modulator therapeutic approaches.

Loss of cardiomyocyte-specific adhesion G-protein-coupled receptor G1 (ADGRG1/GPR56) promotes pressure overload-induced heart failure

Adhesion G-protein-coupled receptors (AGPCRs), containing large N-terminal ligand-binding domains for environmental mechano-sensing, have been increasingly recognized to play important roles in numerous physiologic and pathologic processes. However, their impact on the heart, which undergoes dynamic mechanical alterations in healthy and failing states, remains understudied. ADGRG1 (formerly known as GPR56) is widely expressed, including in skeletal muscle where it was previously shown to mediate mechanical overload-induced muscle hypertrophy; thus, we hypothesized that it could impact the development of cardiac dysfunction and remodeling in response to pressure overload. In this study, we generated a cardiomyocyte (CM)-specific ADGRG1 knockout mouse model, which, although not initially displaying features of cardiac dysfunction, does develop increased systolic and diastolic LV volumes and internal diameters over time. Notably, when challenged with chronic pressure overload, CM-specific ADGRG1 deletion accelerates cardiac dysfunction, concurrent with blunted CM hypertrophy, enhanced cardiac inflammation and increased mortality, suggesting that ADGRG1 plays an important role in the early adaptation to chronic cardiac stress. Altogether, the present study provides an important proof-of-concept that targeting CM-expressed AGPCRs may offer a new avenue for regulating the development of heart failure.

Mechanisms of peptide agonist dissociation and deactivation of adhesion G-protein-coupled receptors

Adhesion G protein-coupled receptors (ADGRs) belong to Class B2 of GPCRs and are involved in a wide array of important physiological processes. ADGRs contain a GPCR autoproteolysis-inducing (GAIN) domain that is proximal to the receptor N-terminus and undergoes autoproteolysis during biosynthesis to generate two fragments: the N-terminal fragment (NTF) and C-terminal fragment (CTF). Dissociation of NTF reveals a tethered agonist to activate CTF of ADGRs for G protein signaling. Synthetic peptides that mimic the tethered agonist can also activate the ADGRs. However, mechanisms of peptide agonist dissociation and deactivation of ADGRs remain poorly understood. In this study, we have performed all-atom enhanced sampling simulations using a novel Protein-Protein Interaction-Gaussian accelerated Molecular Dynamics (PPI-GaMD) method on the ADGRG2-IP15 and ADGRG1-P7 complexes. The PPI-GaMD simulations captured dissociation of the IP15 and P7 peptide agonists from their target receptors. We were able to identify important low-energy conformations of ADGRG2 and ADGRG1 in the active, intermediate, and inactive states, as well as exploring different states of the peptide agonists IP15 and P7 during dissociation. Therefore, our PPI-GaMD simulations have revealed dynamic mechanisms of peptide agonist dissociation and deactivation of ADGRG1 and ADGRG2, which will facilitate rational design of peptide regulators of the two receptors and other ADGRs.

Mammalian Inner Ear-Resident Immune Cells-A Scoping Review

BACKGROUND

Several studies have demonstrated the presence of resident immune cells in the healthy inner ear.

AIM

This scoping review aimed to systematize this knowledge by collecting the data on resident immune cells in the inner ear of different species under steady-state conditions.

METHODS

The databases PubMed, MEDLINE (Ovid), CINAHL (EBSCO), and LIVIVO were used to identify articles. Systematic reviews, experimental studies, and clinical data in English and German were included without time limitations.

RESULTS

The search yielded 49 eligible articles published between 1979 and 2022. Resident immune cells, including macrophages, lymphocytes, leukocytes, and mast cells, have been observed in various mammalian inner ear structures under steady-state conditions. However, the physiological function of these cells in the healthy cochlea remains unclear, providing an opportunity for basic research in inner ear biology.

CONCLUSIONS

This review highlights the need for further investigation into the role of these cells, which is crucial for advancing the development of therapeutic methods for treating inner ear disorders, potentially transforming the field of otolaryngology and immunology.

A correlation study of adhesion G protein-coupled receptors as potential therapeutic targets for breast cancer

BACKGROUND

Adhesion G protein-coupled receptors (aGPCRs), a distinctive subset of the G protein-coupled receptor (GPCR) superfamily, play crucial roles in various physiological and pathological processes, with implications in tumor development. Despite the global prevalence of breast cancer (BRCA), specific aGPCRs as potential drug targets or biomarkers remain underexplored.

METHODS

UALCAN, GEPIA, Kaplan-Meier Plotter, MethSurv, cBiopportal, String, GeneMANIA, DAVID, Timer, Metascape, and qPCR were applied in this work.

RESULTS

Our analysis revealed significantly increased transcriptional levels of ADGRB2, ADGRC1, ADGRC2, ADGRC3, ADGRE1, ADGRF2, ADGRF4, and ADGRL1 in BRCA primary tumors. Further analysis indicated a significant correlation between the expressions of certain aGPCRs and the pathological stage of BRCA. High expression of ADGRA1, ADGRF2, ADGRF4, ADGRG1, ADGRG2, ADGRG4, ADGRG6, and ADGRG7 was significantly correlated with poor overall survival (OS) in BRCA patients. Additionally, high expression of ADGRF2 and ADGRF4 indicated inferior recurrence-free survival (RFS) in BRCA patients. The RT-qPCR experiments also confirmed that the mRNA levels of ADGRF2 and ADGRF4 were higher in BRCA cells and tissues. Functional analysis highlighted the diverse roles of aGPCRs, encompassing GPCR signaling and metabolic energy reserves. Moreover, aGPCRs may exert influence or actively participate in the development of BRCA through their impact on immune status.

CONCLUSION

aGPCRs, particularly ADGRF2 and ADGRF4, hold promise as immunotherapeutic targets and prognostic biomarkers in BRCA.

Expression of GPR56 reflects a hypoactivated state of circulating B cells and is downregulated in B cell subsets in patients with early-stage lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most prevalent subtype of lung cancer, and the early detection and diagnosis of this disease are crucial in reducing mortality rates. The timely diagnosis of LUAD is essential for controlling tumour development and enabling early surgical treatment. GPR56 is a vital G protein-coupled receptor and its role in T lymphocytes has received considerable attention. However, its function in B cells remains unclear. This study aimed to investigate the significance of GPR56 in LUAD. We found that GPR56 exhibited a significant increase in circulating plasmablasts and a decrease in new memory B cells. GPR56 expression in B cells was significantly reduced after LPS stimulation and the proportion of HLA-DR+ and CD40+ proportions were also decreased in GPR56+ B cells after stimulation. Additionally, GPR56 exhibited significant down-regulation in circulating B cell subsets of early-stage LUAD patients, and there were significant correlations between GPR56+ B cell subsets and tumour markers. In conclusion, GPR56 could reflect the hypoactivation state of B cells and the decreased proportion of GPR56+ B cell subset in LUAD patients can signify the active humoral immunity in vivo. The expression of GPR56 in B cells could potentially hold value in the early diagnosis of LUAD.

GPR56: A potential therapeutic target for neurological and psychiatric disorders

GPR56, also known as GPR56/ADGRG1, is a member of the ADGRG subgroup belonging to adhesion G protein-coupled receptors (aGPCRs). aGPCRs are the second largest subfamily of the GPCR superfamily, which is the largest family of membrane protein receptors in the human genome. Studies in recent years have demonstrated that GPR56 is integral to the normal development of the brain and functions as an important player in cortical development, suggesting that GPR56 is involved in many physiological processes. Indeed, aberrant expression of GPR56 has been implicated in multiple neurological and psychiatric disorders, including bilateral frontoparietal polymicrogyria (BFPP), depression and epilepsy. In a recent study, it was found that upregulated expression of GPR56 reduced depressive-like behaviours in an animal model of depression, indicating that GPR56 plays an important role in the antidepressant response. Given the link of GPR56 with the antidepressant response, the function of GPR56 has become a focus of research. Although GPR56 may be a potential target for the development of antidepressants, the underlying molecular mechanisms remain largely unknown. Therefore, in this review, we will summarize the latest findings of GPR56 function in neurological and psychiatric disorders (depression, epilepsy, autism, and BFPP) and emphasize the mechanisms of GPR56 in activation and signalling in those conditions. After reviewing several studies, attributing to its significant biological functions and exceptionally long extracellular N-terminus that interacts with multiple ligands, we draw a conclusion that GPR56 may serve as an important drug target for neuropsychological diseases.

Iron Chelator Deferiprone Restores Iron Homeostasis and Inhibits Retinal Neovascularization in Experimental Neovascular Age-Related Macular Degeneration

Purpose

Retinal neovascularization is a significant feature of advanced age-related macular degeneration (AMD) and a major cause of blindness in patients with AMD. However, the underlying mechanism of this pathological neovascularization remains unknown. Iron metabolism has been implicated in various biological processes. This study was conducted to investigate the effects of iron metabolism on retinal neovascularization in neovascular AMD (nAMD).

Methods

C57BL/6J and very low-density lipoprotein receptor (VLDLR) knockout (Vldlr-/-) mice, a murine model of nAMD, were used in this study. Bulk-RNA sequencing was used to identify differentially expressed genes. Western blot analysis was performed to test the expression of proteins. Iron chelator deferiprone (DFP) was administrated to the mice by oral gavage. Fundus fluorescein angiography was used to evaluate retinal vascular leakage. Immunofluorescence staining was used to detect macrophages and iron-related proteins.

Results

RNA sequencing (RNA-seq) results showed altered transferrin expression in the retina and RPE of Vldlr-/- mice. Disrupted iron homeostasis was observed in the retina and RPE of Vldlr-/- mice. DFP mitigated iron overload and significantly reduced retinal neovascularization and vascular leakage. In addition, DFP suppressed the inflammation in Vldlr-/- retinas. The reduced signals of macrophages were observed at sites of neovascularization in the retina and RPE of Vldlr-/- mice after DFP treatment. Further, the IL-6/JAK2/STAT3 signaling pathway was activated in the retina and RPE of Vldlr-/- mice and reversed by DFP treatment.

Conclusions

Disrupted iron metabolism may contribute to retinal neovascularization in nAMD. Restoring iron homeostasis by DFP could be a potential therapeutic approach for nAMD.

PCLAF induces bone marrow adipocyte senescence and contributes to skeletal aging

Bone marrow adipocytes (BMAds) affect bone homeostasis, but the mechanism remains unclear. Here, we showed that exercise inhibited PCNA clamp-associated factor (PCLAF) secretion from the bone marrow macrophages to inhibit BMAds senescence and thus alleviated skeletal aging. The genetic deletion of PCLAF in macrophages inhibited BMAds senescence and delayed skeletal aging. In contrast, the transplantation of PCLAF-mediated senescent BMAds into the bone marrow of healthy mice suppressed bone turnover. Mechanistically, PCLAF bound to the ADGRL2 receptor to inhibit AKT/mTOR signaling that triggered BMAds senescence and subsequently spread senescence among osteogenic and osteoclastic cells. Of note, we developed a PCLAF-neutralizing antibody and showed its therapeutic effects on skeletal health in old mice. Together, these findings identify PCLAF as an inducer of BMAds senescence and provide a promising way to treat age-related osteoporosis.

Magnetogenetics as a promising tool for controlling cellular signaling pathways

Magnetogenetics emerges as a transformative approach for modulating cellular signaling pathways through the strategic application of magnetic fields and nanoparticles. This technique leverages the unique properties of magnetic nanoparticles (MNPs) to induce mechanical or thermal stimuli within cells, facilitating the activation of mechano- and thermosensitive proteins without the need for traditional ligand-receptor interactions. Unlike traditional modalities that often require invasive interventions and lack precision in targeting specific cellular functions, magnetogenetics offers a non-invasive alternative with the capacity for deep tissue penetration and the potential for targeting a broad spectrum of cellular processes. This review underscores magnetogenetics' broad applicability, from steering stem cell differentiation to manipulating neuronal activity and immune responses, highlighting its potential in regenerative medicine, neuroscience, and cancer therapy. Furthermore, the review explores the challenges and future directions of magnetogenetics, including the development of genetically programmed magnetic nanoparticles and the integration of magnetic field-sensitive cells for in vivo applications. Magnetogenetics stands at the forefront of cellular manipulation technologies, offering novel insights into cellular signaling and opening new avenues for therapeutic interventions.

Essential Role of Latrophilin-1 Adhesion GPCR Nanoclusters in Inhibitory Synapses

Latrophilin-1 (Lphn1, aka CIRL1 and CL1; gene symbol Adgrl1) is an adhesion GPCR that has been implicated in excitatory synaptic transmission as a candidate receptor for α-latrotoxin. Here we analyzed conditional knock-in/knock-out mice for Lphn1 that contain an extracellular myc epitope tag. Mice of both sexes were used in all experiments. Surprisingly, we found that Lphn1 is localized in cultured neurons to synaptic nanoclusters that are present in both excitatory and inhibitory synapses. Conditional deletion of Lphn1 in cultured neurons failed to elicit a detectable impairment in excitatory synapses but produced a decrease in inhibitory synapse numbers and synaptic transmission that was most pronounced for synapses close to the neuronal soma. No changes in axonal or dendritic outgrowth or branching were observed. Our data indicate that Lphn1 is among the few postsynaptic adhesion molecules that are present in both excitatory and inhibitory synapses and that Lphn1 by itself is not essential for excitatory synaptic transmission but is required for some inhibitory synaptic connections.

ERNEST COST action overview on the (patho)physiology of GPCRs and orphan GPCRs in the nervous system

G protein-coupled receptors (GPCRs) are a large family of cell surface receptors that play a critical role in nervous system function by transmitting signals between cells and their environment. They are involved in many, if not all, nervous system processes, and their dysfunction has been linked to various neurological disorders representing important drug targets. This overview emphasises the GPCRs of the nervous system, which are the research focus of the members of ERNEST COST action (CA18133) working group 'Biological roles of signal transduction'. First, the (patho)physiological role of the nervous system GPCRs in the modulation of synapse function is discussed. We then debate the (patho)physiology and pharmacology of opioid, acetylcholine, chemokine, melatonin and adhesion GPCRs in the nervous system. Finally, we address the orphan GPCRs, their implication in the nervous system function and disease, and the challenges that need to be addressed to deorphanize them.

Genome-wide association studies of egg production traits by whole genome sequencing of Laiwu Black chicken

Compared to high-yield commercial laying hens, Chinese indigenous chicken breeds have poor egg laying capacity due to the lack of intensive selection. However, as these breeds have not undergone systematic selection, it is possible that there is a greater abundance of genetic variations related to egg laying traits. In this study, we assessed 5 egg number (EN) traits at different stages of the egg-laying period: EN1 (from the first egg to 23 wk), EN2 (from 23 to 35 wk), EN3 (from 35 to 48 wk), EN4 (from the first egg to 35 wk), and EN5 (from the first egg to 48 wk). To investigate the molecular mechanisms underlying egg number traits in a Chinese local chicken breed, we conducted a genome-wide association study (GWAS) using data from whole-genome sequencing (WGS) of 399 Laiwu Black chickens. We obtained a total of 3.01 Tb of raw data with an average depth of 7.07 × per individual. A total of 86 genome-wide suggestive or significant single-nucleotide polymorphisms (SNP) contained within a set of 45 corresponding candidate genes were identified and found to be associated with stages EN1-EN5. The genes vitellogenin 2 (VTG2), lipase maturation factor 1 (LMF1), calcium voltage-gated channel auxiliary subunit alpha2delta 3 (CACNA2D3), poly(A) binding protein cytoplasmic 1 (PABPC1), programmed cell death 11 (PDCD11) and family with sequence similarity 213 member A (FAM213A) can be considered as the candidate genes associated with egg number traits, due to their reported association with animal reproduction traits. Noteworthy, results suggests that VTG2 and PDCD11 are not only involved in the regulation of EN3, but also in the regulation of EN5, implies that VTG2 and PDCD11 have a significant influence on egg production traits. Our study offers valuable genomic insights into the molecular genetic mechanisms that govern egg number traits in a Chinese indigenous egg-laying chicken breed. These findings have the potential to enhance the egg-laying performance of chickens.

Modulation of GPR133 (ADGRD1) signaling by its intracellular interaction partner extended synaptotagmin 1

GPR133 (ADGRD1) is an adhesion G-protein-coupled receptor that signals through Gαs/cyclic AMP (cAMP) and is required for the growth of glioblastoma (GBM), an aggressive brain malignancy. The regulation of GPR133 signaling is incompletely understood. Here, we use proximity biotinylation proteomics to identify ESYT1, a Ca2+-dependent mediator of endoplasmic reticulum-plasma membrane bridge formation, as an intracellular interactor of GPR133. ESYT1 knockdown or knockout increases GPR133 signaling, while its overexpression has the opposite effect, without altering GPR133 levels in the plasma membrane. The GPR133-ESYT1 interaction requires the Ca2+-sensing C2C domain of ESYT1. Thapsigargin-mediated increases in cytosolic Ca2+ relieve signaling-suppressive effects of ESYT1 by promoting ESYT1-GPR133 dissociation. ESYT1 knockdown or knockout in GBM slows tumor growth, suggesting tumorigenic functions of ESYT1. Our findings demonstrate a mechanism for the modulation of GPR133 signaling by increased cytosolic Ca2+, which reduces the signaling-suppressive interaction between GPR133 and ESYT1 to raise cAMP levels.

Adhesion G Protein-Coupled Receptor Gpr126 (Adgrg6) Expression Profiling in Diseased Mouse, Rat, and Human Kidneys

Uncovering the function of understudied G protein-coupled receptors (GPCRs) provides a wealth of untapped therapeutic potential. The poorly understood adhesion GPCR Gpr126 (Adgrg6) is widely expressed in developing kidneys. In adulthood, Gpr126 expression is enriched in parietal epithelial cells (PECs) and epithelial cells of the collecting duct and urothelium. Whether Gpr126 plays a role in kidney disease remains unclear. Here, we characterized Gpr126 expression in diseased kidneys in mice, rats, and humans. RT-PCR data show that Gpr126 expression is altered in kidney disease. A quantitative RNAscope® analysis utilizing cell type-specific markers revealed that Gpr126 expression upon tubular damage is mainly increased in cell types expressing Gpr126 under healthy conditions as well as in cells of the distal and proximal tubules. Upon glomerular damage, an increase was mainly detected in PECs. Notably, Gpr126 expression was upregulated in an ischemia/reperfusion model within hours, while upregulation in a glomerular damage model was only detected after weeks. An analysis of kidney microarray data from patients with lupus nephritis, IgA nephropathy, focal segmental glomerulosclerosis (FSGS), hypertension, and diabetes as well as single-cell RNA-seq data from kidneys of patients with acute kidney injury and chronic kidney disease indicates that GPR126 expression is also altered in human kidney disease. In patients with FSGS, an RNAscope® analysis showed that GPR126 mRNA is upregulated in PECs belonging to FSGS lesions and proximal tubules. Collectively, we provide detailed insights into Gpr126 expression in kidney disease, indicating that GPR126 is a potential therapeutic target.

The far extracellular CUB domain of the adhesion GPCR ADGRG6/GPR126 is a key regulator of receptor signaling

Adhesion G Protein-coupled receptors (aGPCRs) transduce extracellular adhesion signals into cytoplasmic signaling pathways. ADGRG6/GPR126 is an aGPCR critical for axon myelination, heart development and ear development; and is associated with developmental diseases and cancers. ADGRG6 has a large, alternatively-spliced, five-domain extracellular region (ECR) that samples different conformations and regulates receptor signaling. However, the molecular details of how the ECR regulates signaling are unclear. Herein, we studied the conformational dynamics of the conserved CUB domain which is located at the distal N-terminus of the ECR and is deleted in an alternatively-spliced isoform ( Δ CUB). We showed that the Δ CUB isoform has decreased signaling. Molecular dynamics simulations suggest that the CUB domain is involved in interdomain contacts to maintain a compact ECR conformation. A cancer-associated CUB domain mutant, C94Y, drastically perturbs the ECR conformation and results in elevated signaling, whereas another CUB mutant, Y96A, located near a conserved Ca 2+ -binding site, decreases signaling. Our results suggest an ECR-mediated mechanism for ADGRG6 regulation in which the CUB domain instructs conformational changes within the ECR to regulate receptor signaling.

Dysfunction of the adhesion G protein-coupled receptor latrophilin 1 (ADGRL1/LPHN1) increases the risk of obesity

Obesity is one of the diseases with severe health consequences and rapidly increasing worldwide prevalence. Understanding the complex network of food intake and energy balance regulation is an essential prerequisite for pharmacological intervention with obesity. G protein-coupled receptors (GPCRs) are among the main modulators of metabolism and energy balance. They, for instance, regulate appetite and satiety in certain hypothalamic neurons, as well as glucose and lipid metabolism and hormone secretion from adipocytes. Mutations in some GPCRs, such as the melanocortin receptor type 4 (MC4R), have been associated with early-onset obesity. Here, we identified the adhesion GPCR latrophilin 1 (ADGRL1/LPHN1) as a member of the regulating network governing food intake and the maintenance of energy balance. Deficiency of the highly conserved receptor in mice results in increased food consumption and severe obesity, accompanied by dysregulation of glucose homeostasis. Consistently, we identified a partially inactivating mutation in human ADGRL1/LPHN1 in a patient suffering from obesity. Therefore, we propose that LPHN1 dysfunction is a risk factor for obesity development.

The repertoire and structure of adhesion GPCR transcript variants assembled from publicly available deep-sequenced human samples

Alternative splicing and multiple transcription start and termination sites can produce a diverse repertoire of mRNA transcript variants from a given gene. While the full picture of the human transcriptome is still incomplete, publicly available RNA datasets have enabled the assembly of transcripts. Using publicly available deep sequencing data from 927 human samples across 48 tissues, we quantified known and new transcript variants, provide an interactive, browser-based application Splice-O-Mat and demonstrate its relevance using adhesion G protein-coupled receptors (aGPCRs) as an example. On average, 24 different transcript variants were detected for each of the 33 human aGPCR genes, and several dominant transcript variants were not yet annotated. Variable transcription starts and complex exon-intron structures encode a flexible protein domain architecture of the N- and C termini and the seven-transmembrane helix domain (7TMD). Notably, we discovered the first GPCR (ADGRG7/GPR128) with eight transmembrane helices. Both the N- and C terminus of this aGPCR were intracellularly oriented, anchoring the N terminus in the plasma membrane. Moreover, the assessment of tissue-specific transcript variants, also for other gene classes, in our application may change the evaluation of disease-causing mutations, as their position in different transcript variants may explain tissue-specific phenotypes.

Advances in prognostic models for osteosarcoma risk

The risk prognosis model is a statistical model that uses a set of features to predict whether an individual will develop a specific disease or clinical outcome. It can be used in clinical practice to stratify disease severity and assess risk or prognosis. With the advancement of large-scale second-generation sequencing technology, along Prognosis models for osteosarcoma are increasingly being developed as large-scale second-generation sequencing technology advances and clinical and biological data becomes more abundant. This expansion greatly increases the number of prognostic models and candidate genes suitable for clinical use. This article will present the predictive effects and reliability of various prognosis models, serving as a reference for their evaluation and application.

Exploring research hotspots and future directions in neural tube defects field by bibliometric and bioinformatics analysis

Background

Neural tube defects (NTDs) is the most common birth defect of the central nervous system (CNS) which causes the death of almost 88,000 people every year around the world. Much efforts have been made to investigate the reasons that contribute to NTD and explore new ways to for prevention. We trawl the past decade (2013-2022) published records in order to get a worldwide view about NTDs research field.

Methods

7,437 records about NTDs were retrieved from the Web of Science (WOS) database. Tools such as shell scripts, VOSviewer, SCImago Graphica, CiteSpace and PubTator were used for data analysis and visualization.

Results

Over the past decade, the number of publications has maintained an upward trend, except for 2022. The United States is the country with the highest number of publications and also with the closest collaboration with other countries. Baylor College of Medicine has the closest collaboration with other institutions worldwide and also was the most prolific institution. In the field of NTDs, research focuses on molecular mechanisms such as genes and signaling pathways related to folate metabolism, neurogenic diseases caused by neural tube closure disorders such as myelomeningocele and spina bifida, and prevention and treatment such as folate supplementation and surgical procedures. Most NTDs related genes are related to development, cell projection parts, and molecular binding. These genes are mainly concentrated in cancer, Wnt, MAPK, PI3K-Akt and other signaling pathways. The distribution of NTDs related SNPs on chromosomes 1, 3, 5, 11, 14, and 17 are relatively concentrated, which may be associated with high-risk of NTDs.

Conclusion

Bibliometric analysis of the literature on NTDs field provided the current status, hotspots and future directions to some extant. Further bioinformatics analysis expanded our understanding of NTDs-related genes function and revealed some important SNP clusters and loci. This study provided some guidance for further studies. More extensive cooperation and further research are needed to overcome the ongoing challenge in pathogenesis, prevention and treatment of NTDs.

The adhesion GPCR and PCP component flamingo (FMI-1) alters body size and regulates the composition of the extracellular matrix

The extracellular matrix (ECM) is a network of macromolecules that presents a vital scaffold for cells and enables multiple ways of cellular communication. Thus, it is essential for many physiological processes such as development, tissue morphogenesis, homeostasis, the shape and partially the size of the body and its organs. To ensure these, the composition of the ECM is tissue-specific and highly dynamic. ECM homeostasis is therefore tightly controlled by several mechanisms. Here, we show that FMI-1, the homolog of the Adhesion GPCR Flamingo/CELSR/ADGRC in the nematode Caenorhabditis elegans, modulates the composition of the ECM by controlling the production both of ECM molecules such as collagens and also of ECM modifying enzymes. Thereby, FMI-1 affects the morphology and functionality of the nematode´s cuticle, which is mainly composed of ECM, and also modulates the body size. Mechanistic analyses highlight the fact that FMI-1 exerts its function from neurons non-cell autonomously (trans) solely via its extracellular N terminus. Our data support a model, by which the activity of the receptor, which has a well-described role in the planar cell polarity (PCP) pathway, involves the PCP molecule VANG-1, but seems to be independent of the DBL-1/BMP pathway.

Single-cell RNA-seq data analysis reveals functionally relevant biomarkers of early brain development and their regulatory footprints in human embryonic stem cells (hESCs)

The complicated process of neuronal development is initiated early in life, with the genetic mechanisms governing this process yet to be fully elucidated. Single-cell RNA sequencing (scRNA-seq) is a potent instrument for pinpointing biomarkers that exhibit differential expression across various cell types and developmental stages. By employing scRNA-seq on human embryonic stem cells, we aim to identify differentially expressed genes (DEGs) crucial for early-stage neuronal development. Our focus extends beyond simply identifying DEGs. We strive to investigate the functional roles of these genes through enrichment analysis and construct gene regulatory networks to understand their interactions. Ultimately, this comprehensive approach aspires to illuminate the molecular mechanisms and transcriptional dynamics governing early human brain development. By uncovering potential links between these DEGs and intelligence, mental disorders, and neurodevelopmental disorders, we hope to shed light on human neurological health and disease. In this study, we have used scRNA-seq to identify DEGs involved in early-stage neuronal development in hESCs. The scRNA-seq data, collected on days 26 (D26) and 54 (D54), of the in vitro differentiation of hESCs to neurons were analyzed. Our analysis identified 539 DEGs between D26 and D54. Functional enrichment of those DEG biomarkers indicated that the up-regulated DEGs participated in neurogenesis, while the down-regulated DEGs were linked to synapse regulation. The Reactome pathway analysis revealed that down-regulated DEGs were involved in the interactions between proteins located in synapse pathways. We also discovered interactions between DEGs and miRNA, transcriptional factors (TFs) and DEGs, and between TF and miRNA. Our study identified 20 significant transcription factors, shedding light on early brain development genetics. The identified DEGs and gene regulatory networks are valuable resources for future research into human brain development and neurodevelopmental disorders.

The dark sides of the GPCR tree - research progress on understudied GPCRs

A large portion of the human GPCRome is still in the dark and understudied, consisting even of entire subfamilies of GPCRs such as odorant receptors, class A and C orphans, adhesion GPCRs, Frizzleds and taste receptors. However, it is undeniable that these GPCRs bring an untapped therapeutic potential that should be explored further. Open questions on these GPCRs span diverse topics such as deorphanisation, the development of tool compounds and tools for studying these GPCRs, as well as understanding basic signalling mechanisms. This review gives an overview of the current state of knowledge for each of the diverse subfamilies of understudied receptors regarding their physiological relevance, molecular mechanisms, endogenous ligands and pharmacological tools. Furthermore, it identifies some of the largest knowledge gaps that should be addressed in the foreseeable future and lists some general strategies that might be helpful in this process.

Conformational transitions and activation of the adhesion receptor CD97

Adhesion G protein-coupled receptors (aGPCRs) are evolutionarily ancient receptors involved in a variety of physiological and pathophysiological processes. Modulators of aGPCR, particularly antagonists, hold therapeutic promise for diseases like cancer and immune and neurological disorders. Hindered by the inactive state structural information, our understanding of antagonist development and aGPCR activation faces challenges. Here, we report the cryo-electron microscopy structures of human CD97, a prototypical aGPCR that plays crucial roles in immune system, in its inactive apo and G13-bound fully active states. Compared with other family GPCRs, CD97 adopts a compact inactive conformation with a constrained ligand pocket. Activation induces significant conformational changes for both extracellular and intracellular sides, creating larger cavities for Stachel sequence binding and G13 engagement. Integrated with functional and metadynamics analyses, our study provides significant mechanistic insights into the activation and signaling of aGPCRs, paving the way for future drug discovery efforts.

Single-cell RNA sequencing reveals the epithelial cell, fibroblast, and key gene alterations in chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a chronic inflammatory disease of the nasal mucosa, and epithelial-mesenchymal transition (EMT) is thought to be an essential process in the pathogenesis of CRSwNP. However, the mechanisms of epithelial and fibroblastic changes at the single-cell level are unclear. In this study, we investigated the epithelial cell, fibroblast, and key gene alterations in the development of CRSwNP. We revealed major cell types involved in CRSwNP and nasal mucosal inflammation formation, then mapped epithelial and fibroblast subpopulations. We showed that the apical and glandular epithelial cells and the ADGRB3+ and POSTN+ fibroblasts were the key cell subtypes in the progression of CRSwNP. Pseudotime and cell cycle analysis identified dynamic changes between epithelial cells and fibroblasts during its development. WFDC2 and CCL26 were identified as the key marker genes involved in the development of CRSwNP and were validated by IHC staining, which may provide a potential novel target for future CRSwNP therapy. ScRNA-seq data provided insights into the cellular landscape and the relationship between epithelial cells and fibroblasts in the progression of CRSwNP. WFDC2 and CCL26 were identified as the key genes involved in the development of CRSwNP and may be the potential markers for gene therapy.

Structure of the extracellular region of the adhesion GPCR CELSR1 reveals a compact module which regulates G protein-coupling

Cadherin EGF Laminin G seven-pass G-type receptors (CELSRs or ADGRCs) are conserved adhesion G protein-coupled receptors which are essential for animal development. CELSRs have extracellular regions (ECRs) containing 23 adhesion domains which couple adhesion to intracellular signaling. However, molecular-level insight into CELSR function is sparsely available. We report the 4.3 Å cryo-EM reconstruction of the mCELSR1 ECR with 13 domains resolved in the structure. These domains form a compact module mediated by interdomain interactions with contact between the N- and C-terminal domains. We show the mCELSR1 ECR forms an extended species in the presence of Ca 2+ , which we propose represents the antiparallel cadherin repeat dimer. Using assays for adhesion and G protein-coupling, we assign the N-terminal CADH1-8 module as necessary for cell adhesion and we show the C-terminal CAHD9-GAIN module regulates signaling. Our work provides important molecular context to the literature on CELSR function and opens the door towards further mechanistic studies.