Gpr97 is essential for the follicular versus marginal zone B-lymphocyte fate decision

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.

Exploring Protein S-Palmitoylation: Mechanisms, Detection, and Strategies for Inhibitor Discovery

S-palmitoylation is a reversible and dynamic process that involves the addition of long-chain fatty acids to proteins. This protein modification regulates various aspects of protein function, including subcellular localization, stability, conformation, and biomolecular interactions. The zinc finger DHHC (ZDHHC) domain-containing protein family is the main group of enzymes responsible for catalyzing protein S-palmitoylation, and 23 members have been identified in mammalian cells. Many proteins that undergo S-palmitoylation have been linked to disease pathogenesis and progression, suggesting that the development of effective inhibitors is a promising therapeutic strategy. Reducing the protein S-palmitoylation level can target either the PATs directly or their substrates. However, there are rare clinically effective S-palmitoylation inhibitors. This review aims to provide an overview of the S-palmitoylation field, including the catalytic mechanism of ZDHHC, S-palmitoylation detection methods, and the functional impact of protein S-palmitoylation. Additionally, this review focuses on current strategies for expanding the chemical toolbox to develop novel and effective inhibitors that can reduce the level of S-palmitoylation of the target protein.

Whole-genome resequencing reveals genomic variation and dynamics in Ethiopian indigenous goats

Ethiopia has about 52 million indigenous goats with marked phenotypic variability, which is the outcome of natural and artificial selection. Here, we obtained whole-genome sequence data of three Ethiopian indigenous goat populations (Arab, Fellata, and Oromo) from northwestern Ethiopia and analyzed their genome-wide genetic diversity, population structure, and signatures of selection. We included genotype data from four other Ethiopian goat populations (Abergelle, Keffa, Gumuz, and Woyto-Guji) and goats from Asia; Europe; and eastern, southern, western, and northern Africa to investigate the genetic predisposition of the three Ethiopian populations and performed comparative genomic analysis. Genetic diversity analysis showed that Fellata goats exhibited the lowest heterozygosity values (Ho = 0.288 ± 0.005 and He = 0.334 ± 0.0001). The highest values were observed in Arab goats (Ho = 0.310 ± 0.010 and He = 0.347 ± 4.35e-05). A higher inbreeding coefficient (FROH = 0.137 ± 0.016) was recorded for Fellata goats than the 0.105 ± 0.030 recorded for Arab and the 0.112 ± 0.034 recorded for Oromo goats. This indicates that the Fellata goat population should be prioritized in future conservation activities. The three goat populations showed the majority (∼63%) of runs of homozygosity in the shorter (100-150 Kb) length category, illustrating ancient inbreeding and/or small founder effects. Population relationship and structure analysis separated the Ethiopian indigenous goats into two distinct genetic clusters lacking phylogeographic structure. Arab, Fellata, Oromo, Abergelle, and Keffa represented one genetic cluster. Gumuz and Woyto-Guji formed a separate cluster and shared a common genetic background with the Kenyan Boran goat. Genome-wide selection signature analysis identified nine strongest regions spanning 163 genes influencing adaptation to arid and semi-arid environments (HOXC12, HOXC13, HOXC4, HOXC6, and HOXC9, MAPK8IP2), immune response (IL18, TYK2, ICAM3, ADGRG1, and ADGRG3), and production and reproduction (RARG and DNMT1). Our results provide insights into a thorough understanding of genetic architecture underlying selection signatures in Ethiopian indigenous goats in a semi-arid tropical environment and deliver valuable information for goat genetic improvement, conservation strategy, genome-wide association study, and marker-assisted breeding.

The cancer-immune dialogue in the context of stress

Although there is little direct evidence supporting that stress affects cancer incidence, it does influence the evolution, dissemination and therapeutic outcomes of neoplasia, as shown in human epidemiological analyses and mouse models. The experience of and response to physiological and psychological stressors can trigger neurological and endocrine alterations, which subsequently influence malignant (stem) cells, stromal cells and immune cells in the tumour microenvironment, as well as systemic factors in the tumour macroenvironment. Importantly, stress-induced neuroendocrine changes that can regulate immune responses have been gradually uncovered. Numerous stress-associated immunomodulatory molecules (SAIMs) can reshape natural or therapy-induced antitumour responses by engaging their corresponding receptors on immune cells. Moreover, stress can cause systemic or local metabolic reprogramming and change the composition of the gastrointestinal microbiota which can indirectly modulate antitumour immunity. Here, we explore the complex circuitries that link stress to perturbations in the cancer-immune dialogue and their implications for therapeutic approaches to cancer.

Functional partnerships between GPI-anchored proteins and adhesion GPCRs

Specific extracellular interaction between glycophosphatidylinositol (GPI)-anchored proteins and adhesion G protein-coupled receptors (aGPCRs) plays an important role in unique biological functions. GPI-anchored proteins are derived from a novel post-translational modification of single-span membrane molecules, while aGPCRs are bona fide seven-span transmembrane proteins with a long extracellular domain. Although various members of the two structurally-distinct protein families are known to be involved in a wide range of biological processes, many remain as orphans. Interestingly, accumulating evidence has pointed to a complex interaction and functional synergy between these two protein families. I discuss herein current understanding of specific functional partnerships between GPI-anchored proteins and aGPCRs.

Novel transcriptomic signatures associated with premature kidney allograft failure

BACKGROUND

The power to predict kidney allograft outcomes based on non-invasive assays is limited. Assessment of operational tolerance (OT) patients allows us to identify transcriptomic signatures of true non-responders for construction of predictive models.

METHODS

In this observational retrospective study, RNA sequencing of peripheral blood was used in a derivation cohort to identify a protective set of transcripts by comparing 15 OT patients (40% females), from the TOMOGRAM Study (NCT05124444), 14 chronic active antibody-mediated rejection (CABMR) and 23 stable graft function patients ≥15 years (STA). The selected differentially expressed transcripts between OT and CABMR were used in a validation cohort (n = 396) to predict 3-year kidney allograft loss at 3 time-points using RT-qPCR.

FINDINGS

Archetypal analysis and classifier performance of RNA sequencing data showed that OT is clearly distinguishable from CABMR, but similar to STA. Based on significant transcripts from the validation cohort in univariable analysis, 2 multivariable Cox models were created. A 3-transcript (ADGRG3, ATG2A, and GNLY) model from POD 7 predicted graft loss with C-statistics (C) 0.727 (95% CI, 0.638-0.820). Another 3-transcript (IGHM, CD5, GNLY) model from M3 predicted graft loss with C 0.786 (95% CI, 0.785-0.865). Combining 3-transcripts models with eGFR at POD 7 and M3 improved C-statistics to 0.860 (95% CI, 0.778-0.944) and 0.868 (95% CI, 0.790-0.944), respectively.

INTERPRETATION

Identification of transcripts distinguishing OT from CABMR allowed us to construct models predicting premature graft loss. Identified transcripts reflect mechanisms of injury/repair and alloimmune response when assessed at day 7 or with a loss of protective phenotype when assessed at month 3.

FUNDING

Supported by the Ministry of Health of the Czech Republic under grant NV19-06-00031.

GPR97 deficiency ameliorates renal interstitial fibrosis in mouse hypertensive nephropathy

Hypertensive nephropathy (HTN) ranks as the second-leading cause of end-stage renal disease (ESRD). Accumulating evidence suggests that persistent hypertension injures tubular cells, leading to tubulointerstitial fibrosis (TIF), which is involved in the pathogenesis of HTN. G protein-coupled receptors (GPCRs) are implicated in many important pathological and physiological processes and act as important drug targets. In this study, we explored the intrarenal mechanisms underlying hypertension-associated TIF, and particularly, the potential role of GPR97, a member of the adhesion GPCR subfamily, in TIF. A deoxycorticosterone acetate (DOCA)/salt-induced hypertensive mouse model was used. We revealed a significantly upregulated expression of GPR97 in the kidneys, especially in renal tubules, of the hypertensive mice and 10 patients with biopsy-proven hypertensive kidney injury. GPR97-/- mice showed markedly elevated blood pressure, which was comparable to that of wild-type mice following DOCA/salt treatment, but dramatically ameliorated renal injury and TIF. In NRK-52E cells, we demonstrated that knockdown of GPR97 suppressed the activation of TGF-β signaling by disturbing small GTPase RhoA-mediated cytoskeletal reorganization, thus inhibiting clathrin-mediated endocytosis of TGF-β receptors and subsequent Smad activation. Collectively, this study demonstrates that GPR97 contributes to hypertension-associated TIF at least in part by facilitating TGF-β signaling, suggesting that GPR97 is a pivotal intrarenal factor for TIF progression under hypertensive conditions, and therapeutic strategies targeting GPR97 may improve the outcomes of patients with HTN.

Role of Adhesion G Protein-Coupled Receptors in Immune Dysfunction and Disorder

Disorders of the immune system, including immunodeficiency, immuno-malignancy, and (auto)inflammatory, autoimmune, and allergic diseases, have a great impact on a host’s health. Cellular communication mediated through cell surface receptors, among different cell types and between cell and microenvironment, plays a critical role in immune responses. Selective members of the adhesion G protein-coupled receptor (aGPCR) family are expressed differentially in diverse immune cell types and have been implicated recently in unique immune dysfunctions and disorders in part due to their dual cell adhesion and signaling roles. Here, we discuss the molecular and functional characteristics of distinctive immune aGPCRs and their physiopathological roles in the immune system.

GPR97 triggers inflammatory processes in human neutrophils via a macromolecular complex upstream of PAR2 activation

Neutrophils play essential anti-microbial and inflammatory roles in host defense, however, their activities require tight regulation as dysfunction often leads to detrimental inflammatory and autoimmune diseases. Here we show that the adhesion molecule GPR97 allosterically activates CD177-associated membrane proteinase 3 (mPR3), and in conjugation with several protein interaction partners leads to neutrophil activation in humans. Crystallographic and deletion analysis of the GPR97 extracellular region identified two independent mPR3-binding domains. Mechanistically, the efficient binding and activation of mPR3 by GPR97 requires the macromolecular CD177/GPR97/PAR2/CD16b complex and induces the activation of PAR2, a G protein-coupled receptor known for its function in inflammation. Triggering PAR2 by the upstream complex leads to strong inflammatory activation, prompting anti-microbial activities and endothelial dysfunction. The role of the complex in pathologic inflammation is underscored by the finding that both GPR97 and mPR3 are upregulated on the surface of disease-associated neutrophils. In summary, we identify a PAR2 activation mechanism that directs neutrophil activation, and thus inflammation. The PR3/CD177/GPR97/PAR2/CD16b protein complex, therefore, represents a potential therapeutic target for neutrophil-mediated inflammatory diseases.

Adhesion G protein-coupled receptors: structure, signaling, physiology, and pathophysiology

Adhesion G protein-coupled receptors (AGPCRs) are a family of 33 receptors in humans exhibiting a conserved general structure but diverse expression patterns and physiological functions. The large NH2 termini characteristic of AGPCRs confer unique properties to each receptor and possess a variety of distinct domains that can bind to a diverse array of extracellular proteins and components of the extracellular matrix. The traditional view of AGPCRs, as implied by their name, is that their core function is the mediation of adhesion. In recent years, though, many surprising advances have been made regarding AGPCR signaling mechanisms, activation by mechanosensory forces, and stimulation by small-molecule ligands such as steroid hormones and bioactive lipids. Thus, a new view of AGPCRs has begun to emerge in which these receptors are seen as massive signaling platforms that are crucial for the integration of adhesive, mechanosensory, and chemical stimuli. This review article describes the recent advances that have led to this new understanding of AGPCR function and also discusses new insights into the physiological actions of these receptors as well as their roles in human disease.

Mechanistic Understanding of the Palmitoylation of Go Protein in the Allosteric Regulation of Adhesion Receptor GPR97

Adhesion G-protein-coupled receptors (aGPCRs)—a major family of GPCRs—play critical roles in the regulation of tissue development and cancer progression. The orphan receptor GPR97, activated by glucocorticoid stress hormones, is a prototypical aGPCR. Although it has been established that the palmitoylation of the C-terminal G_o protein is essential for G_o’s efficient engagement with the active GPR97, the detailed allosteric mechanism remains to be clarified. Hence, we performed extensive large-scale molecular dynamics (MD) simulations of the GPR97−G_o complex in the presence or absence of G_o palmitoylation. The conformational landscapes analyzed by Markov state models revealed that the overall conformation of GPR97 is preferred to be fully active when interacting with palmitoylated G_o protein. Structural and energetic analyses indicated that the palmitoylation of G_o can allosterically stabilize the critical residues in the ligand-binding pocket of GPR97 and increase the affinity of the ligand for GPR97. Furthermore, the community network analysis suggests that the palmitoylation of G_o not only allosterically strengthens the internal interactions between G_αo and G_βγ, but also enhances the coupling between G_o and GPR97. Our study provides mechanistic insights into the regulation of aGPCRs via post-translational modifications of the G_o protein, and offers guidance for future drug design of aGPCRs.

The single nucleotide polymorphism rs1814521 in long non-coding RNA ADGRG3 associates with the susceptibility to silicosis: a multi-stage study

Background

This study aimed to evaluate the correlation between long non-coding RNA (lncRNA)-related single nucleotide polymorphisms (SNPs) and susceptibility to silicosis.

Methods

First, RNA-sequencing (RNA-seq) data were comprehensively analyzed in the peripheral blood lymphocytes of eight participants (four silicosis cases and four healthy controls) exposed to silica dust to identify differentially expressed lncRNAs (DE-lncRNAs). The functional SNPs in the identified DE-lncRNAs were then identified using several databases. Finally, the association between functional SNPs and susceptibility to silicosis was evaluated by a two-stage case-control study. The SNPs of 155 silicosis cases and 141 healthy silica-exposed controls were screened by genome-wide association study (GWAS), and the candidate SNPs of 194 silicosis cases and 235 healthy silica-exposed controls were validated by genotyping using the improved Mutiligase Detection Reaction (iMLDR) system.

Results

A total of 76 DE-lncRNAs were identified by RNA-seq data analysis (cut-offs: fold change > 2 or fold change < 0.5, P < 0.05), while 127 functional SNPs among those 76 DE-lncRNAs were identified through multiple public databases. Furthermore, five SNPs were found to be significantly correlated with the risk of silicosis by GWAS screening (P < 0.05), while the results of GWAS and iMLDR validation indicated that the variant A allele of rs1814521 was associated with a reduced risk of silicosis (OR = 0.76, 95% CI = 0.62–0.94, P = 0.011).

Conclusion

The presence of the SNP rs1814521 in the lncRNA ADGRG3 is associated with susceptibility to silicosis. Moreover, ADGRG3 was found to be lowly expressed in silicosis cases. The underlying biological mechanisms by which lncRNA ADGRG3 and rs1814521 regulate the development of silicosis need further study.

Supplementary information

The online version contains supplementary material available at https://doi.org/10.1265/ehpm.21-00338.

Bioinformatic analysis identifies potential key genes of epilepsy

Background

Epilepsy is one of the most common brain disorders worldwide. It is usually hard to be identified properly, and a third of patients are drug-resistant. Genes related to the progression and prognosis of epilepsy are particularly needed to be identified.

Methods

In our study, we downloaded the Gene Expression Omnibus (GEO) microarray expression profiling dataset GSE143272. Differentially expressed genes (DEGs) with a fold change (FC) >1.2 and a P-value <0.05 were identified by GEO2R and grouped in male, female and overlapping DEGs. Functional enrichment analysis and Protein-Protein Interaction (PPI) network analysis were performed.

Results

In total, 183 DEGs overlapped (77 ups and 106 downs), 302 DEGs (185 ups and 117 downs) in the male dataset, and 750 DEGs (464 ups and 286 downs) in the female dataset were obtained from the GSE143272 dataset. These DEGs were markedly enriched under various Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) terms. 16 following hub genes were identified based on PPI network analysis: ADCY7, C3AR1, DEGS1, CXCL1 in male-specific DEGs, TOLLIP, ORM1, ELANE, QPCT in female-specific DEGs and FCAR, CD3G, CLEC12A, MOSPD2, CD3D, ALDH3B1, GPR97, PLAUR in overlapping DEGs.

Conclusion

This discovery-driven study may be useful to provide a novel insight into the diagnosis and treatment of epilepsy. However, more experiments are needed in the future to study the functional roles of these genes in epilepsy.

Structures of the glucocorticoid-bound adhesion receptor GPR97-Go complex

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

Structures of the glucocorticoid-bound adhesion receptor GPR97-Go complex

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

Genetic basis of functional variability in adhesion G protein-coupled receptors

The enormous sizes of adhesion G protein-coupled receptors (aGPCRs) go along with complex genomic exon-intron architectures giving rise to multiple mRNA variants. There is a need for a comprehensive catalog of aGPCR variants for proper evaluation of the complex functions of aGPCRs found in structural, in vitro and animal model studies. We used an established bioinformatics pipeline to extract, quantify and visualize mRNA variants of aGPCRs from deeply sequenced transcriptomes. Data analysis showed that aGPCRs have multiple transcription start sites even within introns and that tissue-specific splicing is frequent. On average, 19 significantly expressed transcript variants are derived from a given aGPCR gene. The domain architecture of the N terminus encoded by transcript variants often differs and N termini without or with an incomplete seven-helix transmembrane anchor as well as separate seven-helix transmembrane domains are frequently derived from aGPCR genes. Experimental analyses of selected aGPCR transcript variants revealed marked functional differences. Our analysis has an impact on a rational design of aGPCR constructs for structural analyses and gene-deficient mouse lines and provides new support for independent functions of both, the large N terminus and the transmembrane domain of aGPCRs.

The Adhesion G Protein-Coupled Receptor GPR97/ADGRG3 Is Expressed in Human Granulocytes and Triggers Antimicrobial Effector Functions

The adhesion family of G protein-coupled receptors (aGPCRs) comprises 33 members in human, several of which are distinctly expressed and functionally involved in polymorphonuclear cells (PMNs). As former work indicated the possible presence of the aGPCR GPR97 in granulocytes, we studied its cellular distribution, molecular structure, signal transduction, and biological function in PMNs. RNA sequencing and mass-spectrometry revealed abundant RNA and protein expression of ADGRG3/GPR97 in granulocyte precursors and terminally differentiated neutrophilic, eosinophilic, and basophilic granulocytes. Using a newly generated GPR97-specific monoclonal antibody, we confirmed that endogenous GPR97 is a proteolytically processed, dichotomous, N-glycosylated receptor. GPR97 was detected in tissue-infiltrating PMNs and upregulated during systemic inflammation. Antibody ligation of GPR97 increased neutrophil reactive oxygen species production and proteolytic enzyme activity, which is accompanied by an increase in mitogen-activated protein kinases and IκBα phosphorylation. In-depth analysis of the GPR97 signaling cascade revealed a possible switch from basal Gαs/cAMP-mediated signal transduction to a Gαi-induced reduction in cAMP levels upon mutation-induced activation of the receptor, in combination with an increase in downstream effectors of Gβγ, such as SRE and NF-κB. Finally, ligation of GPR97 increased the bacteria uptake and killing activity of neutrophils. We conclude that the specific presence of GPR97 regulates antimicrobial activity in human granulocytes.

Interleukin-7 improves in vitro maturation of ovine cumulus-oocyte complexes in a dose dependent manner

Interleukin-7 (IL-7) mediated signals are linked to development, proliferation, survival and differentiation of cells. Recent evidences indicate its role in oocyte maturation process as well. Nevertheless, the underlying mechanisms of IL-7 involvement in oocyte maturation are not well characterized. In addition, currently no information is available on the effect of exogenous IL-7 on oocyte maturation in ovine or any other species. In this study, the effect of IL-7 supplementation during in vitro maturation (IVM) on the maturation rate, production of reactive oxygen species (ROS) and gene expression of ovine cumulus-oocyte complexes (COC) was assessed. IL-7 (0.5, 1, 2, 5 and 10 ng/ml) was supplemented in IVM medium at the beginning (0 h) and maturation rate of COC was assessed at the completion of IVM (24 h). The maturation rate (%) was found significantly (P = 0.000) greater with the 1 ng/ml of IL-7 supplementation (69.5) than control (60.0). In contrast, the maturation rate was reduced significantly (P = 0.000) with the 2 (47.1), 5 (39.2) and 10 ng/ml (39.1) of IL-7 as compared to the control. The level of intracellular ROS in the matured COC was found considerably higher with the 5 ng/ml of IL-7 followed by 1 ng/ml of IL-7 and control. It was evident that in the presence of superoxide dismutase-inhibitor, 1 ng/ml of IL-7 did not stimulate oocyte maturation. In contrast, oocyte maturation was improved with 5 ng/ml of IL-7 supplementation in the presence of NADPH-oxidase-inhibitor. IL-7 supplementation influenced gene expression in COC in a dose and time dependant manner. The expression of genes related to ROS production and apoptosis were upregulated and the genes associated with antioxidant mechanisms were downregulated noticeably with the supplementation of 5 ng/ml of IL-7. In conclusion, IL-7 at low concentration was beneficial for oocyte maturation, which was likely mediated through the favourable level of intracellular ROS and antioxidant mechanisms. In contrast, the detrimental effects of greater IL-7 concentrations on oocyte maturation were possibly arbitrated through the ROS-mediated oxidative stress, compromised antioxidant mechanism and stimulated apoptotic signalling.

Gpr97/Adgrg3 ameliorates experimental autoimmune encephalomyelitis by regulating cytokine expression

Multiple sclerosis and its primary animal model, experimental autoimmune encephalomyelitis (EAE), are inflammatory diseases of the central nervous system (CNS) characterized by immune-mediated demyelination and neurodegeneration that may be mediated by inhibition of the nuclear factor-κB (NF-κB) signaling pathway. Gpr97, encoded by Adgrg3, has been reported to regulate the activity of NF-κB. In this study, using a previously established Adgrg3-knockout mouse model, we investigated the roles of Gpr97 in the development of autoimmune CNS disease in mice. We found a marked increase in the expression of Adgrg3 in spinal cords of mice with EAE. Adgrg3-deficient (Adgrg3-/-) mice with EAE exhibited increases in peak severity and the cumulative disease score compared with littermate controls, followed by a notable increase of leukocyte infiltration and more extensive demyelination. The percentages of Th1/Th17 cells in the CNS were significantly increased in Adgrg3-/- mice and accompanied by high levels of interleukin (IL)-6, interferon-γ, tumor necrosis factor-α, and IL-17. An in vitro culture assay verified that Gpr97 regulated proinflammatory cytokine production. Taken together, our results show that Gpr97 plays an important role in the development of EAE and may have a therapeutic potential for the treatment of CNS autoimmunity.

Immunoregulatory Effects of Myeloid-Derived Suppressor Cell Exosomes in Mouse Model of Autoimmune Alopecia Areata

The treatment of autoimmune diseases still poses a major challenge, frequently relying on non-specific immunosuppressive drugs. Current efforts aim at reestablishing self tolerance using immune cells with suppressive activity like the regulatory T cells (Treg) or the myeloid-derived suppressor cells (MDSC). We have demonstrated therapeutic efficacy of MDSC in mouse Alopecia Areata (AA). In the same AA model, we now asked whether MDSC exosomes (MDSC-Exo) can replace MDSC. MDSC-Exo from bone marrow cells (BMC) cultures of healthy donors could substantially facilitate treatment. With knowledge on MDSC-Exo being limited, their suitability needs to be verified in advance. Protein marker profiles suggest comparability of BMC- to ex vivo collected inflammatory MDSC/MDSC-Exo in mice with a chronic contact dermatitis, which is a therapeutic option in AA. Proteome analyses substantiated a large overlap of function-relevant molecules in MDSC and MDSC-Exo. Furthermore, MDSC-Exo are taken up by T cells, macrophages, NK, and most avidly by Treg and MDSC-Exo uptake exceeds binding of MDSC themselves. In AA mice, MDSC-Exo preferentially target skin-draining lymph nodes and cells in the vicinity of remnant hair follicles. MDSC-Exo uptake is accompanied by a strong increase in Treg, reduced T helper proliferation, mitigated cytotoxic activity, and a slight increase in lymphocyte apoptosis. Repeated MDSC-Exo application in florid AA prevented progression and sufficed for partial hair regrowth. Deep sequencing of lymphocyte mRNA from these mice revealed a significant increase in immunoregulatory mRNA, including FoxP3 and arginase 1. Downregulated mRNA was preferentially engaged in prohibiting T cell hyperreactivity. Taken together, proteome analysis provided important insights into potential MDSC-Exo activities, these Exo preferentially homing into AA-affected organs. Most importantly, changes in leukocyte mRNA seen after treatment of AA mice with MDSC-Exo sustainably supports the strong impact on the adaptive and the non-adaptive immune system, with Treg expansion being a dominant feature. Thus, MDSC-Exo could potentially serve as therapeutic agents in treating AA and other autoimmune diseases.

Gαi Signaling Promotes Marginal Zone B Cell Development by Enabling Transitional B Cell ADAM10 Expression

The follicular (FO) versus marginal zone (MZ) B cell fate decision in the spleen depends upon BCR, BAFF, and Notch2 signaling. Whether or how G_i signaling affects this fate decision is unknown. Here, we show that direct contact with Notch ligand expressing stromal cells (OP9-Delta-like 1) cannot promote normal MZ B cell development when progenitor B cells lack Gα_i proteins, or if Gi signaling is disabled. Consistent with faulty ADAM10-dependent Notch2 processing, Gα_i-deficient transitional B cells had low ADAM10 membrane expression levels and reduced Notch2 target gene expression. Immunoblotting Gα_i-deficient B cell lysates revealed a reduction in mature, processed ADAM10. Suggesting that Gα_i signaling promotes ADAM10 membrane expression, stimulating normal transitional B cells with CXCL12 raised it, while inhibiting Gα_i nucleotide exchange blocked its upregulation. Surprisingly, inhibiting Gα_i nucleotide exchange in transitional B cells also impaired the upregulation of ADAM10 that occurs following antigen receptor crosslinking. These results indicate that Gα_i signaling supports ADAM10 maturation and activity in transitional B cells, and ultimately Notch2 signaling to promote MZ B cell development.

Adhesion GPCRs in Kidney Development and Disease

Chronic kidney disease (CKD) represents the fastest growing pathology worldwide with a prevalence of >10% in many countries. In addition, kidney cancer represents 5% of all new diagnosed cancers. As currently no effective therapies exist to restore kidney function after CKD- as well as cancer-induced renal damage, it is important to elucidate new regulators of kidney development and disease as new therapeutic targets. G protein-coupled receptors (GPCRs) represent the most successful class of pharmaceutical targets. In recent years adhesion GPCRs (aGPCRs), the second largest GPCR family, gained significant attention as they are present on almost all mammalian cells, are associated to a plethora of diseases and regulate important cellular processes. aGPCRs regulate for example cell polarity, mitotic spindle orientation, cell migration, and cell aggregation; all processes that play important roles in kidney development and/or disease. Moreover, polycystin-1, a major regulator of kidney development and disease, contains a GAIN domain, which is otherwise only found in aGPCRs. In this review, we assess the potential of aGPCRs as therapeutic targets for kidney disease. For this purpose we have summarized the available literature and analyzed data from the databases The Human Protein Atlas, EURExpress, Nephroseq, FireBrowse, cBioPortal for Cancer Genomics and the National Cancer Institute Genomic Data Commons data portal (NCIGDC). Our data indicate that most aGPCRs are expressed in different spatio-temporal patterns during kidney development and that altered aGPCR expression is associated with a variety of kidney diseases including CKD, diabetic nephropathy, lupus nephritis as well as renal cell carcinoma. We conclude that aGPCRs present a promising new class of therapeutic targets and/or might be useful as diagnostic markers in kidney disease.

Ablation of Tacr2 in mice leads to gastric emptying disturbance

BACKGROUND

Tacr2 is one of the G protein-coupled receptors(GPCRs) that mediate the biological actions of tachykinins. It is abundantly expressed in the gastrointestinal (GI) system and is thought to play an important role in GI motility, secretion, and visceral sensitivity. Previously, the physiological and pathophysiological functions of Tacr2 were mainly studied using Tacr2 selective agonists or antagonists. Here, we seek to investigate the effect of Tacr2 disruption in mice to provide further insights.

METHODS

The Tacr2 knockout mice were generated by homologous recombination and the phenotypic changes of the Tacr2-null mice were analyzed and compared with their wild type (wt) littermates.

KEY RESULTS

Increased food retention was detected in Tacr2^-/- mice. The stomach of Tacr2^-/- mice had thinner muscularis externa and less neurons in the myenteric plexus. The stomach and small intestine exhibited longer duration of electrical field stimulation (EFS)-induced inhibition in the gastric fundus and decreased frequency of migrating motor complex (MMC), respectively. Neuronal nitric oxide synthase (nNOS) and vasoactive intestinal polypeptide (VIP) were significantly up-regulated due to Tarc2 deficiency, contributing to enhanced nitric oxide (NO) signaling in the stomach of Tacr2^-/- mice. Intraperitoneal application of 7-nitroindazole (7-NI) to Tacr2^-/- mice effectively relieved the gastric emptying disturbance. Moreover, Creb and NF-κB signalings were involved in the regulation of these physiological changes initiated by Tacr2 deficiency.

CONCLUSIONS & INFERENCES

Tacr2 negatively regulated the expression of nNOS and VIP both in vivo and in vitro. Its ablation in mice elevated the expression of nNOS and VIP, enhanced NO signaling and changed the Creb and NF-κB signalings, finally leading to the gastric emptying disturbance of Tacr2^-/- mice.

Gpr97 is dispensable for metabolic syndrome but is involved in macrophage inflammation in high-fat diet-induced obesity in mice

Local inflammation in tissues is one of primary causes in development of metabolic disorder in obesity. The accumulation of macrophages in some tissues can induce inflammatory reactions in obesity. Gpr97 is highly expressed in some immunocytes, but its potential role in inflammatory regulation has not been revealed clearly. In our research, we investigated Gpr97 in regulating macrophage inflammation and metabolic dysfunction in the high-fat diet (HFD)-induced obese mice. The major metabolic phenotyping were not different after Gpr97 knockout in HFD-fed mice. Similar pathological alterations in adipose tissue, liver, and kidney were observed in Gpr97^−/− HFD mice compared with WT-HFD mice. In white adipose tissue, loss of Gpr97 reduced the ratio of M1-macrophages and increased the M2-macrophage ratio, which was opposite to that seen in the wild-type HFD mice. More macrophages invaded in the liver and kidney after Gpr97 knockout in HFD mice. Furthermore, the levels of TNF-α were higher in the liver and kidney of Gpr97^−/− HFD mice compared to those in wild-type HFD mice. The data indicate that Gpr97 might be required for local inflammation development in obesity-relative tissues, but does not play a role in metabolic disorder in HFD-induced obesity.

Heart Development, Angiogenesis, and Blood-Brain Barrier Function Is Modulated by Adhesion GPCRs

The cardiovascular system in adult organisms forms a network of interconnected endothelial cells, supported by mural cells and displaying a high degree of hierarchy: arteries emerging from the heart ramify into arterioles and then capillaries, which return to the venous systems through venules and veins. The cardiovascular system allows blood circulation, which in turn is essential for hemostasis through gas diffusion, nutrient distribution, and cell trafficking. In this chapter, we have summarized the current knowledge on how adhesion GPCRs (aGPCRs) impact heart development, followed by their role in modulating vascular angiogenesis.

Adhesion GPCRs as Modulators of Immune Cell Function

Immune cells express several adhesion G protein-coupled receptors (aGPCRs), including the ADGRE subfamily members EMR1 (F4/80, ADGRE1), EMR2 (ADGRE2), EMR3 (ADGRE3), EMR4 (FIRE, ADGRE4), and CD97 (ADGRE5), the ADGRB subfamily member BAI1 (ADGRB1), and the ADGRG subfamily members GPR56 (ADGRG1), GPR97 (Pb99, ADGRG3), and GPR114 (ADGRG5). Expression of these molecules in hematopoietic stem and progenitor cells, monocytes/macrophages (Mφs), dendritic cells, granulocytes, and lymphocytes depends on lineage diversification and maturation, making them suitable markers for individual leukocyte subsets (e.g., F4/80 on mouse Mφs). Recent studies revealed intriguing activities of aGPCRs in tolerance induction (EMR1), granulopoiesis (CD97), engulfment of apoptotic cells and bacteria (BAI1), hematopoietic stem cell formation (GPR56), and control of cytotoxicity (GPR56). Here, we review these findings and discuss their biological and translational implications.

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

The Adhesion family forms a large branch of the pharmacologically important superfamily of G protein-coupled receptors (GPCRs). As Adhesion GPCRs increasingly receive attention from a wide spectrum of biomedical fields, the Adhesion GPCR Consortium, together with the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification, proposes a unified nomenclature for Adhesion GPCRs. The new names have ADGR as common dominator followed by a letter and a number to denote each subfamily and subtype, respectively. The new names, with old and alternative names within parentheses, are: ADGRA1 (GPR123), ADGRA2 (GPR124), ADGRA3 (GPR125), ADGRB1 (BAI1), ADGRB2 (BAI2), ADGRB3 (BAI3), ADGRC1 (CELSR1), ADGRC2 (CELSR2), ADGRC3 (CELSR3), ADGRD1 (GPR133), ADGRD2 (GPR144), ADGRE1 (EMR1, F4/80), ADGRE2 (EMR2), ADGRE3 (EMR3), ADGRE4 (EMR4), ADGRE5 (CD97), ADGRF1 (GPR110), ADGRF2 (GPR111), ADGRF3 (GPR113), ADGRF4 (GPR115), ADGRF5 (GPR116, Ig-Hepta), ADGRG1 (GPR56), ADGRG2 (GPR64, HE6), ADGRG3 (GPR97), ADGRG4 (GPR112), ADGRG5 (GPR114), ADGRG6 (GPR126), ADGRG7 (GPR128), ADGRL1 (latrophilin-1, CIRL-1, CL1), ADGRL2 (latrophilin-2, CIRL-2, CL2), ADGRL3 (latrophilin-3, CIRL-3, CL3), ADGRL4 (ELTD1, ETL), and ADGRV1 (VLGR1, GPR98). This review covers all major biologic aspects of Adhesion GPCRs, including evolutionary origins, interaction partners, signaling, expression, physiologic functions, and therapeutic potential.

G Protein-Coupled Receptor 120 Signaling Negatively Regulates Osteoclast Differentiation, Survival, and Function

G protein-coupled receptor 120 (GPR120) plays an important role in the regulation of inflammation and lipid metabolism. In this study, we investigated the role of GPR120 in osteoclast development and found that GPR120 regulates osteoclast differentiation, survival and function. We observed that GPR120 was highly expressed in osteoclasts compared to their precursors, bone marrow-derived macrophages (BMMs). Activation of GPR120 by its ligand GW9508 suppressed receptor activator of NF- κB ligand (RANKL)-induced osteoclast differentiation and the expression of nuclear factor of activated T cells c1 (NFATc1), a key modulator of osteoclastogenesis. GPR120 activation further inhibited the RANKL-stimulated phosphorylation of IκBα and JNK. In addition to osteoclast differentiation, GPR120 activation increased the apoptosis of mature osteoclasts by inducing caspase-3 and Bim expression. Activation of GPR120 also interfered with cell spreading and actin cytoskeletal organization mediated by M-CSF but not by RANKL. Coincident with the impaired cytoskeletal organization, GPR120 activation blocked osteoclast bone resorbing activity. Furthermore, knockdown of GPR120 using small hairpin RNA abrogated all these inhibitory effects on osteoclast differentiation, survival, and function. Together, our findings identify GPR120 as a negative modulator of osteoclast development that may be an attractive therapeutic target for bone-destructive diseases. J. Cell. Physiol. 231: 844-851, 2016. © 2015 Wiley Periodicals, Inc.

Gpr97 Is Dispensable for Inflammation in OVA-Induced Asthmatic Mice

BACKGROUND

Asthma is a complex inflammatory disorder involving the activation and invasion of various immune cells. GPR97 is highly expressed in some immunocytes, including mast cells and eosinophils, which play critical roles in asthma development. However, the role of Gpr97 in regulating airway inflammation in asthma has rarely been reported. In this study, we investigated the potential role of Gpr97 in the development of allergic asthma in mice.

METHODS

Relevant airway asthmatic mouse models were constructed with both wild-type and Gpr97-/- mice sensitized to 250 μg ovalbumin (OVA). The levels of interleukin IL-4, IL-6 and IFN-γ, which are involved in OVA-induced asthma, in the bronchoalveolar lavage fluid (BALF) and the IgE level in the serum were examined by enzyme-linked immunosorbent assay (ELISA). The invasion of mast cells and eosinophils into lung tissues was assessed by immunohistochemical and eosinophil peroxidase activity assays, respectively. Goblet cell hyperplasia and mucus production were morphologically evaluated with periodic acid-Schiff (PAS) staining.

RESULTS

In our study, no obvious alteration in the inflammatory response or airway remodeling was found in the Gpr97-deficient mice with OVA-induced asthma. Neither the secretion of cytokines, including IL-4, IL-6 and IFN-γ, nor inflammatory cell recruitment was altered in the Gpr97-deficient mice. Moreover, Gpr97 deficiency did not affect airway remodeling or mucus production in the asthma mouse model.

CONCLUSION

Our findings imply that Gpr97 might not be required for the development of airway inflammation in OVA-induced allergic asthma in mice.

Hunting for the function of orphan GPCRs - beyond the search for the endogenous ligand

Seven transmembrane-spanning proteins (7TM), also called GPCRs, are among the most versatile and evolutionary successful protein families. Out of the 400 non-odourant members identified in the human genome, approximately 100 remain orphans that have not been matched with an endogenous ligand. Apart from the classical deorphanization strategies, several alternative strategies provided recent new insights into the function of these proteins, which hold promise for high therapeutic potential. These alternative strategies consist of the phenotypical characterization of organisms silenced or overexpressing orphan 7TM proteins, the search for constitutive receptor activity and formation of protein complexes including 7TM proteins as well as the development of synthetic, surrogate ligands. Taken together, a variety of ligand-independent functions can be attributed to orphan 7TM proteins that range from constitutive activity to complex formation with other proteins and include 'true' orphans for which no ligand exist and 'conditional' orphans that behave like orphans in the absence of ligand and as non-orphans in the presence of ligand.