Brain areas interconnected to ventral pathway circuits are independently able to induce enhancement in object recognition memory and cause reversal in object recognition memory deficit

AIMS

Ventral pathway circuits are constituted by the interconnected brain areas that are distributed throughout the brain. These brain circuits are primarily involved in processing of object related information in brain. However, their role in object recognition memory (ORM) enhancement remains unknown. Here, we have studied on the implication of these circuits in ORM enhancement and in reversal of ORM deficit in aging.

METHODS

The brain areas interconnected to ventral pathway circuits in rat brain were activated by an expression of a protein called regulator of G-protein signaling 14 of 414 amino acids (RGS14414). RGS14414 is an ORM enhancer and therefore used here as a gain-in-function tool. ORM test and immunohistochemistry, lesions, neuronal arborization, and knockdown studies were performed to uncover the novel function of ventral pathway circuits.

RESULTS

An activation of each of the brain areas interconnected to ventral pathway circuits individually induced enhancement in ORM; however, same treatment in brain areas not interconnected to ventral pathway circuits produced no effect. Further study in perirhinal cortex (PRh), area V2 of visual cortex and frontal cortex (FrC), which are brain areas that have been shown to be involved in ORM and are interconnected to ventral pathway circuits, revealed that ORM enhancement seen after the activation of any one of the three brain areas was unaffected by the lesions in other two brain areas either individually in each area or even concurrently in both areas. This ORM enhancement in all three brain areas was associated to increase in structural plasticity of pyramidal neurons where more than 2-fold higher dendritic spines were observed. Additionally, we found that an activation of either PRh, area V2, or FrC not only was adequate but also was sufficient for the reversal of ORM deficit in aging rats, and the blockade of RGS14414 activity led to loss in increase in dendritic spine density and failure in reversal of ORM deficit.

CONCLUSIONS

These results suggest that brain areas interconnected to ventral pathway circuits facilitate ORM enhancement by an increase in synaptic connectivity between the local brain area circuits and the passing by ventral pathway circuits and an upregulation in activity of ventral pathway circuits. In addition, the finding of the reversal of ORM deficit through activation of an interconnected brain area might serve as a platform for developing not only therapy against memory deficits but also strategies for other brain diseases in which neuronal circuits are compromised.

RGS4 Actions in Mouse Prefrontal Cortex Modulate Behavioral and Transcriptomic Responses to Chronic Stress and Ketamine

The signal transduction protein, regulator of G protein signaling 4 (RGS4), plays a prominent role in physiologic and pharmacological responses by controlling multiple intracellular pathways. Our earlier work identified the dynamic but distinct roles of RGS4 in the efficacy of monoamine-targeting versus fast-acting antidepressants. Using a modified chronic variable stress (CVS) paradigm in mice, we demonstrate that stress-induced behavioral abnormalities are associated with the downregulation of RGS4 in the medial prefrontal cortex (mPFC). Knockout of RGS4 (RGS4KO) increases susceptibility to CVS, as mutant mice develop behavioral abnormalities as early as 2 weeks after CVS resting-state functional magnetic resonance imaging I (rs-fMRI) experiments indicate that stress susceptibility in RGS4KO mice is associated with changes in connectivity between the mediodorsal thalamus (MD-THL) and the mPFC. Notably, RGS4KO also paradoxically enhances the antidepressant efficacy of ketamine in the CVS paradigm. RNA-sequencing analysis of naive and CVS samples obtained from mPFC reveals that RGS4KO triggers unique gene expression signatures and affects several intracellular pathways associated with human major depressive disorder. Our analysis suggests that ketamine treatment in the RGS4KO group triggers changes in pathways implicated in synaptic activity and responses to stress, including pathways associated with axonal guidance and myelination. Overall, we show that reducing RGS4 activity triggers unique gene expression adaptations that contribute to chronic stress disorders and that RGS4 is a negative modulator of ketamine actions. SIGNIFICANCE STATEMENT: Chronic stress promotes robust maladaptation in the brain, but the exact intracellular pathways contributing to stress vulnerability and mood disorders have not been thoroughly investigated. In this study, the authors used murine models of chronic stress and multiple methodologies to demonstrate the critical role of the signal transduction modulator regulator of G protein signaling 4 in the medial prefrontal cortex in vulnerability to chronic stress and the efficacy of the fast-acting antidepressant ketamine.

Modulation of Type 5 Metabotropic Glutamate Receptor-Mediated Intracellular Calcium Mobilization by Regulator of G Protein Signaling 4 (RGS4) in Cultured Astrocytes

Acting as GTPase activating proteins promoting the silencing of activated G-proteins, regulators of G protein signaling (RGSs) are generally considered negative modulators of cell signaling. In the CNS, the expression of RGS4 is altered in diverse pathologies and its upregulation was reported in astrocytes exposed to an inflammatory environment. In a model of cultured cortical astrocytes, we herein investigate the influence of RGS4 on intracellular calcium signaling mediated by type 5 metabotropic glutamate receptor (mGluR5), which is known to support the bidirectional communication between neurons and glial cells. RGS4 activity was manipulated by exposure to the inhibitor CCG 63802 or by infecting the cells with lentiviruses designed to achieve the silencing or overexpression of RGS4. The pharmacological inhibition or silencing of RGS4 resulted in a decrease in the percentage of cells responding to the mGluR5 agonist DHPG and in the proportion of cells showing typical calcium oscillations. Conversely, RGS4-lentivirus infection increased the percentage of cells showing calcium oscillations. While the physiological implication of cytosolic calcium oscillations in astrocytes is still under investigation, the fine-tuning of calcium signaling likely determines the coding of diverse biological events. Indirect signaling modulators such as RGS4 inhibitors, used in combination with receptor ligands, could pave the way for new therapeutic approaches for diverse neurological disorders with improved efficacy and selectivity.

Phosphorylation Dynamics in a flg22-Induced, G Protein-Dependent Network Reveals the AtRGS1 Phosphatase

The microbe-associated molecular pattern flg22 is recognized in a flagellin-sensitive 2-dependent manner in root tip cells. Here, we show a rapid and massive change in protein abundance and phosphorylation state of the Arabidopsis root cell proteome in WT and a mutant deficient in heterotrimeric G-protein-coupled signaling. flg22-induced changes fall on proteins comprising a subset of this proteome, the heterotrimeric G protein interactome, and on highly-populated hubs of the immunity network. Approximately 95% of the phosphorylation changes in the heterotrimeric G-protein interactome depend, at least partially, on a functional G protein complex. One member of this interactome is ATBα, a substrate-recognition subunit of a protein phosphatase 2A complex and an interactor to Arabidopsis thaliana Regulator of G Signaling 1 protein (AtRGS1), a flg22-phosphorylated, 7-transmembrane spanning modulator of the nucleotide-binding state of the core G-protein complex. A null mutation of ATBα strongly increases basal endocytosis of AtRGS1. AtRGS1 steady-state protein level is lower in the atbα mutant in a proteasome-dependent manner. We propose that phosphorylation-dependent endocytosis of AtRGS1 is part of the mechanism to degrade AtRGS1, thus sustaining activation of the heterotrimeric G protein complex required for the regulation of system dynamics in innate immunity. The PP2A(ATBα) complex is a critical regulator of this signaling pathway.

Hepatic regulator of G protein signaling 14 ameliorates NAFLD through activating cAMP-AMPK signaling by targeting Giα1/3

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) is an emerging public health threat as the most common chronic liver disease worldwide. However, there remains no effective medication to improve NAFLD. G protein-coupled receptors (GPCRs) are the most frequently investigated drug targets family. The Regulator of G protein signaling 14 (RGS14), as an essential negative modulator of GPCR signaling, plays important regulatory roles in liver damage and inflammatory responses. However, the role of RGS14 in NAFLD remains largely unclear.

METHODS AND RESULTS

In this study, we found that RGS14 was decreased in hepatocytes in NAFLD individuals in a public database. We employed genetic engineering technique to explore the function of RGS14 in NAFLD. We demonstrated that RGS14 overexpression ameliorated lipid accumulation, inflammatory response and liver fibrosis in hepatocytes in vivo and in vitro. Whereas, hepatocyte specific Rgs14-knockout (Rgs14-HKO) exacerbated high fat high cholesterol diet (HFHC) induced NASH. Further molecular experiments demonstrated that RGS14 depended on GDI activity to attenuate HFHC-feeding NASH. More importantly, RGS14 interacted with Guanine nucleotide-binding protein (Gi) alpha 1 and 3 (Giα1/3, gene named GNAI1/3), promoting the generation of cAMP and then activating the subsequent AMPK pathways. GNAI1/3 knockdown abolished the protective role of RGS14, indicating that RGS14 binding to Giα1/3 was required for prevention against hepatic steatosis.

CONCLUSIONS

RGS14 plays a protective role in the progression of NAFLD. RGS14-Giα1/3 interaction accelerated the production of cAMP and then activated cAMP-AMPK signaling. Targeting RGS14 or modulating the RGS14-Giα1/3 interaction may be a potential strategy for the treatment of NAFLD in the future.

RGS10 inhibits proliferation and migration of pulmonary arterial smooth muscle cell in pulmonary hypertension via AKT/mTORC1 signaling

Objective: Excessive proliferation and migration of pulmonary arterial smooth muscle cell (PASMC) is a core event of pulmonary hypertension (PH). Regulators of G protein signaling 10 (RGS10) can regulate cellular proliferation and cardiopulmonary diseases. We demonstrate whether RGS10 also serves as a regulator of PH.Methods: PASMC was challenged by hypoxia to induce proliferation and migration. Adenovirus carrying Rgs10 gene (Ad-Rgs10) was used for external expression of Rgs10. Hypoxia/SU5416 or MCT was used to induce PH. Right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI) were used to validate the establishment of PH model.Results: RGS10 was downregulated in hypoxia-challenged PASMC. Ad-Rgs10 significantly suppressed proliferation and migration of PASMC after hypoxia stimulus, while silencing RGS10 showed contrary effect. Mechanistically, we observed that phosphorylation of S6 and 4E-Binding Protein 1 (4EBP1), the main downstream effectors of mammalian target of rapamycin complex 1 (mTORC1) as well as phosphorylation of AKT, the canonical upstream of mTORC1 in hypoxia-induced PASMC were negatively modulated by RGS10. Both recovering mTORC1 activity and restoring AKT activity abolished these effects of RGS10 on PASMC. More importantly, AKT activation also abolished the inhibitory role of RGS10 in mTORC1 activity in hypoxia-challenged PASMC. Finally, we also observed that overexpression of RGS10 in vivo ameliorated pulmonary vascular wall thickening and reducing RVSP and RVHI in mouse PH model.Conclusion: Our findings reveal the modulatory role of RGS10 in PASMC and PH via AKT/mTORC1 axis. Therefore, targeting RGS10 may serve as a novel potent method for the prevention against PH."

Regulator of G protein signaling protein 6 alleviates acute lung injury by inhibiting inflammation and promoting cell self-renewal in mice

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a disease with high mortality and morbidity. Regulator of G protein signaling protein 6 (RGS6), identified as a tumor suppressor gene, has received increasing attention owing to its close relationship with oxidative stress and inflammation. However, the association between ARDS and RGS6 has not been reported.

METHODS

Congruously regulated G protein-coupled receptor (GPCR)-related genes and differentially expressed genes (DEGs) in an acute lung injury (ALI) model were identified, and functional enrichment analysis was conducted. In an in vivo study, the effects of RGS6 knockout were studied in a mouse model of ALI induced by lipopolysaccharide (LPS). HE staining, ELISA, and immunohistochemistry were used to evaluate pathological changes and the degree of inflammation. In vitro, qRT‒PCR, immunofluorescence staining, and western blotting were used to determine the dynamic changes in RGS6 expression in cells. The RGS6 overexpression plasmid was constructed for transfection. qRT‒PCR was used to assess proinflammatory factors transcription. Western blotting and flow cytometry were used to evaluate apoptosis and reactive oxygen species (ROS) production. Organoid culture was used to assess the stemness and self-renewal capacity of alveolar epithelial type II cells (AEC2s).

RESULTS

A total of 110 congruously regulated genes (61 congruously upregulated and 49 congruously downregulated genes) were identified among GPCR-related genes and DEGs in the ALI model. RGS6 was downregulated in vivo and in vitro in the ALI model. RGS6 was expressed in the cytoplasm and accumulated in the nucleus after LPS stimulation. Compared with the control group, we found higher mortality, more pronounced body weight changes, more serious pulmonary edema and pathological damage, and more neutrophil infiltration in the RGS6 knockout group upon LPS stimulation in vivo. Moreover, AEC2s loss was significantly increased upon RGS6 knockout. Organoid culture assays showed slower alveolar organoid formation, fewer alveolar organoids, and impaired development of new structures after passaging upon RGS6 knockout. In addition, RGS6 overexpression decreased ROS production as well as proinflammatory factor transcription in macrophages and decreased apoptosis in epithelial cells.

CONCLUSIONS

RGS6 plays a protective role in ALI not only in early inflammatory responses but also in endogenous lung stem cell regeneration.

RGS proteins and cardiovascular Angiotensin II Signaling: Novel opportunities for therapeutic targeting

Angiotensin II (AngII), as an octapeptide hormone normally ionized at physiological pH, cannot cross cell membranes and thus, relies on, two (mainly) G protein-coupled receptor (GPCR) types, AT1R and AT2R, to exert its intracellular effects in various organ systems including the cardiovascular one. Although a lot remains to be elucidated about the signaling of the AT2R, AT1R signaling is known to be remarkably versatile, mobilizing a variety of G protein-dependent and independent signal transduction pathways inside cells to produce a biological outcome. Cardiac AT1R signaling leads to hypertrophy, adverse remodeling, fibrosis, while vascular AT1R signaling raises blood pressure via vasoconstriction, but also elicits hypertrophic, vascular growth/proliferation, and pathological remodeling sets of events. In addition, adrenal AT1R is the major physiological stimulus (alongside hyperkalemia) for secretion of aldosterone, a mineralocorticoid hormone that contributes to hypertension, electrolyte abnormalities, and to pathological remodeling of the failing heart. Regulator of G protein Signaling (RGS) proteins, discovered about 25 years ago as GTPase-activating proteins (GAPs) for the Gα subunits of heterotrimeric G proteins, play a central role in silencing G protein signaling from a plethora of GPCRs, including the AngII receptors. Given the importance of AngII and its receptors, but also of several RGS proteins, in cardiovascular homeostasis, the physiological and pathological significance of RGS protein-mediated modulation of cardiovascular AngII signaling comes as no surprise. In the present review, we provide an overview of the current literature on the involvement of RGS proteins in cardiovascular AngII signaling, by discussing their roles in cardiac (cardiomyocyte and cardiofibroblast), vascular (smooth muscle and endothelial cell), and adrenal (medulla and cortex) AngII signaling, separately. Along the way, we also highlight the therapeutic potential of enhancement of, or, in some cases, inhibition of each RGS protein involved in AngII signaling in each one of these cell types.

RGS1 Modulates Autophagic and Metabolic Programs and Is a Critical Mediator of Human Regulatory T Cell Function

Regulatory T cells (Tregs) are critical mediators of immune tolerance and play a diametric role in cancer and autoimmunity. Tumor-infiltrating Tregs are often associated with poor prognosis in solid tumors because their enrichment in the tumor microenvironment contributes to immunosuppression. Conversely, dysregulation in the Treg compartment can disrupt self-tolerance, leading to autoimmunity. In the present study, we describe what is, to our knowledge, a novel regulator of Tregs, the GTPase activator regulator of G protein 1 (RGS1), demonstrating that RGS1-deficient human Tregs show downregulation of Treg-associated genes and are less immunosuppressive. These RGS1-deficient Tregs exhibit perturbations to the FOXP3-c-MYC transcriptional axis and downstream metabolic and autophagy programs by shifting their energy demands toward glycolysis and rendering them less autophagic. Taken together, RGS1 may serve as an apical node of Treg function by regulating the FOXP3-c-MYC transcriptional axis, thereby providing a therapeutic rationale for targeting RGS1 for treatment of cancer and autoimmune diseases.

RGS1 mediates renal interstitial fibrosis through activation of the inflammatory response

Renal interstitial fibrosis (RIF) is considered as a common pathway for all patients with chronic kidney disease (CKD) to progress to end-stage kidney disease (ESRD). The basic pathological manifestation is the increase of matrix component in the tubular interstitium, while the injury of tubular epithelial cells in the renal interstitium and the excessive accumulation of matrix will eventually lead to tubular atrophy and obstruction, loss of effective renal units, and finally impaired renal filtration function. The relevant mechanism of RIF remains unclear. The present study will investigate the function and relevant mechanism of RGS1 in RIF. The RIF-related microarrays GSE22459 and GSE76882 were downloaded and analyzed. Renal parenchymal atrophic calyx tissues were collected from clinical RIF patients. Cellular inflammation, fibrosis and animal RIF models were constructed using Lipopolysaccharide (LPS), TGF-β1 and unilateral ureteral occlusion (UUO). HE and Masson staining were performed to detect morphological alterations of renal tissue samples. qRT-PCR, Western blot and ELISA were carried out to detect the expression of relevant genes/proteins. RGS1 is a gene co-differentially expressed by GSE22459 and GSE76882. RGS1 expression was elevated in renal tissues of RIF patients, cells and animal RIF models. Knockdown of RGS1 inhibited renal cell inflammatory response, fibrosis and renal fibrosis in RIF mice. Overexpression of RGS1 plays the opposite role. Knockdown of RGS1 inhibited the inflammatory response in the RIF cell and mouse model. Targeting RGS1 might be a potential therapeutic strategy for RIF treatment.

A regulatory node involving Gαq, PLCβ, and RGS proteins modulates platelet reactivity to critical agonists

BACKGROUND

Most platelet agonists work through G protein-coupled receptors, activating pathways that involve members of the Gq, Gi, and G12/G13 families of heterotrimeric G proteins. Gq signaling has been shown to be critical for efficient platelet activation. Growing evidence suggests that regulatory mechanisms converge on G protein-coupled receptors and Gq to prevent overly robust platelet reactivity.

OBJECTIVES

To identify and characterize mechanisms by which Gq signaling is regulated in platelets.

METHODS

Based on our prior experience with a Gαi2 variant that escapes regulation by regulator of G protein signaling (RGS) proteins, a Gαq variant was designed with glycine 188 replaced with serine (G188S) and then incorporated into a mouse line so that its effects on platelet activation and thrombus formation could be studied in vitro and in vivo.

RESULTS AND CONCLUSIONS

As predicted, the G188S substitution in Gαq disrupted its interaction with RGS18. Unexpectedly, it also uncoupled PLCβ-3 from activation by platelet agonists as evidenced by a loss rather than a gain of platelet function in vitro and in vivo. Binding studies showed that in addition to preventing the binding of RGS18 to Gαq, the G188S substitution also prevented the binding of PLCβ-3 to Gαq. Structural analysis revealed that G188 resides in the region that is also important for Gαq binding to PLCβ-3 in platelets. We conclude that the Gαq signaling node is more complex than that has been previously understood, suggesting that there is cross-talk between RGS proteins and PLCβ-3 in the context of Gαq signaling.

RGS5 maintaining vascular homeostasis is altered by the tumor microenvironment

BACKGROUND

Regulator of G protein signaling 5 (RGS5), as a negative regulator of G protein-coupled receptor (GPCR) signaling, is highly expressed in arterial VSMCs and pericytes, which is involved in VSMC phenotypic heterogeneity and vascular remodeling in tumors. However, its role in normal and tumor vascular remodeling is controversial.

METHODS

RGS5 knockout (Rgs5-KO) mice and RGS5 overexpression or knockdown in VSMCs in vivo by adeno-associated virus type 9 (AAV) carrying RGS5 cDNA or small hairpin RNA (shRNA) targeting RGS5 were used to determine the functional significance of RGS5 in vascular inflammation. RGS5 expression in the triple-negative (TNBCs) and non-triple-negative breast cancers (Non-TNBCs) was determined by immunofluorescent and immunohistochemical staining. The effect of breast cancer cell-conditioned media (BC-CM) on the pro-inflammatory phenotype of VSMCs was measured by phagocytic activity assays, adhesion assay and Western blot.

RESULTS

We identified that knockout and VSMC-specific knockdown of RGS5 exacerbated accumulation and pyroptosis of pro-inflammatory VSMCs, resulting in vascular remodeling, which was negated by VSMC-specific RGS5 overexpression. In contrast, in the context of breast cancer tissues, the role of RGS5 was completely disrupted. RGS5 expression was increased in the triple-negative breast cancer (TNBC) tissues and in the tumor blood vessels, accompanied with an extensive vascular network. VSMCs treated with BC-CM displayed enhanced pro-inflammatory phenotype and higher adherent with macrophages. Furthermore, tumor-derived RGS5 could be transferred into VSMCs.

CONCLUSIONS

These findings suggest that tumor microenvironment shifts the function of RGS5 from anti-inflammation to pro-inflammation and induces the pro-inflammatory phenotype of VSMCs that is favorable for tumor metastasis.

Function and regulation of RGS family members in solid tumours: a comprehensive review

G protein-coupled receptors (GPCRs) play a key role in regulating the homeostasis of the internal environment and are closely associated with tumour progression as major mediators of cellular signalling. As a diverse and multifunctional group of proteins, the G protein signalling regulator (RGS) family was proven to be involved in the cellular transduction of GPCRs. Growing evidence has revealed dysregulation of RGS proteins as a common phenomenon and highlighted the key roles of these proteins in human cancers. Furthermore, their differential expression may be a potential biomarker for tumour diagnosis, treatment and prognosis. Most importantly, there are few systematic reviews on the functional/mechanistic characteristics and clinical application of RGS family members at present. In this review, we focus on the G-protein signalling regulator (RGS) family, which includes more than 20 family members. We analysed the classification, basic structure, and major functions of the RGS family members. Moreover, we summarize the expression changes of each RGS family member in various human cancers and their important roles in regulating cancer cell proliferation, stem cell maintenance, tumorigenesis and cancer metastasis. On this basis, we outline the molecular signalling pathways in which some RGS family members are involved in tumour progression. Finally, their potential application in the precise diagnosis, prognosis and treatment of different types of cancers and the main possible problems for clinical application at present are discussed. Our review provides a comprehensive understanding of the role and potential mechanisms of RGS in regulating tumour progression. Video Abstract.

RGS5 as a Biomarker of Pericytes, Involvement in Vascular Remodeling and Pulmonary Arterial Hypertension

Introduction

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a sustained rise in mean pulmonary artery pressure. Pulmonary vascular remodeling serves an important role in PAH. Identifying a key driver gene to regulate vascular remodeling of the pulmonary microvasculature is critical for PAH management.

Methods

Differentially expressed genes were identified using the Gene Expression Omnibus (GEO) GSE117261, GSE48149, GSE113439, GSE53408 and GSE16947 datasets. A co-expression network was constructed using weighted gene co-expression network analysis. Novel and key signatures of PAH were screened using four algorithms, including weighted gene co-expression network analysis, GEO2R analysis, support vector machines recursive feature elimination and robust rank aggregation rank analysis. Regulator of G-protein signaling 5 (RGS5), a pro-apoptotic/anti-proliferative protein, which regulate arterial tone and blood pressure in vascular smooth muscle cells. The expression of RGS5 was determined using reverse transcription-quantitative PCR (RT-qPCR) in PAH and normal mice. The location of RGS5 and pericytes was detected using immunofluorescence.

Results

Compared with that in the normal group, RGS5 expression was upregulated in the PAH group based on GEO and RT-qPCR analyses. RGS5 expression in single cells was enriched in pericytes in single-cell RNA sequencing analysis. RGS5 co-localization with pericytes was detected in the pulmonary microvasculature of PAH.

Conclusion

RGS5 regulates vascular remodeling of the pulmonary microvasculature and the occurrence of PAH through pericytes, which has provided novel ideas and strategies regarding the occurrence and innovative treatment of PAH.

Listeria-based vaccination against the pericyte antigen RGS5 elicits anti-vascular effects and colon cancer protection

Colorectal cancer (CRC) remains a leading cause of cancer-related mortality despite efforts to improve standard interventions. As CRC patients can benefit from immunotherapeutic strategies that incite effector T cell action, cancer vaccines represent a safe and promising therapeutic approach to elicit protective and durable immune responses against components of the tumor microenvironment (TME). In this study, we investigate the pre-clinical potential of a Listeria monocytogenes (Lm)-based vaccine targeting the CRC-associated vasculature. CRC survival and progression are reliant on functioning blood vessels to effectively mediate various metabolic processes and oxygenate underlying tissues. We, therefore, advance the strategy of initiating immunity in syngeneic mouse models against the endogenous pericyte antigen RGS5, which is a critical mediator of pathological vascularization. Overall, Lm-based vaccination safely induced potent anti-tumor effects that consisted of recruiting functional Type-1-associated T cells into the TME and reducing tumor blood vessel content. This study underscores the promising clinical potential of targeting RGS5 against vascularized tumors like CRC.

Cardiac RGS7 and RGS11 drive TGFβ1-dependent liver damage following chemotherapy exposure

Off target damage to vital organ systems is an unfortunate side effect of cancer chemotherapy and remains a major limitation to the use of these essential drugs in the clinic. Despite decades of research, the mechanisms conferring susceptibility to chemotherapy driven cardiotoxicity and hepatotoxicity remain unclear. In the livers of patients with a history of chemotherapy, we observed a twofold increase in expression of G protein regulator RGS7 and a corresponding decrease in fellow R7 family member RGS11. Knockdown of RGS7 via introduction of RGS7 shRNA via tail vein injection decreased doxorubicin-induced hepatic collagen and lipid deposition, glycogen accumulation, and elevations in ALT, AST, and triglycerides by approximately 50%. Surprisingly, a similar result could be achieved via introduction of RGS7 shRNA directly to the myocardium without impacting RGS7 levels in the liver directly. Indeed, doxorubicin-treated cardiomyocytes secrete the endocrine factors transforming growth factor β1 (TGFβ1) and TGFβ superfamily binding protein follistatin-related protein 1 (FSTL1). Importantly, RGS7 overexpression in the heart was sufficient to recapitulate the impacts of doxorubicin on the liver and inhibition of TGFβ1 signaling with the receptor blocker GW788388 ameliorated the effect of cardiac RGS7 overexpression on hepatic fibrosis, steatosis, oxidative stress, and cell death as well as the resultant elevation in liver enzymes. Together these data demonstrate that RGS7 controls both the release of TGFβ1 from the heart and the profibrotic and pro-oxidant actions of TGFβ1 in the liver and emphasize the functional significance of endocrine cardiokine signaling in the pathogenesis of chemotherapy drive multiorgan damage.

Mechanisms of mGluR-dependent plasticity in hippocampal area CA2

Pyramidal cells in hippocampal area CA2 have synaptic properties that are distinct from the other CA subregions. Notably, this includes a lack of typical long-term potentiation of stratum radiatum synapses. CA2 neurons express high levels of several known and potential regulators of metabotropic glutamate receptor (mGluR)-dependent signaling including Striatal-Enriched Tyrosine Phosphatase (STEP) and several Regulator of G-protein Signaling (RGS) proteins, yet the functions of these proteins in regulating mGluR-dependent synaptic plasticity in CA2 are completely unknown. Thus, the aim of this study was to examine mGluR-dependent synaptic depression and to determine whether STEP and the RGS proteins RGS4 and RGS14 are involved. Using whole cell voltage-clamp recordings from mouse pyramidal cells, we found that mGluR agonist-induced long-term depression (mGluR-LTD) is more pronounced in CA2 compared with that observed in CA1. This mGluR-LTD in CA2 was found to be protein synthesis and STEP dependent, suggesting that CA2 mGluR-LTD shares mechanistic processes with those seen in CA1, but in addition, RGS14, but not RGS4, was essential for mGluR-LTD in CA2. In addition, we found that exogenous application of STEP could rescue mGluR-LTD in RGS14 KO slices. Supporting a role for CA2 synaptic plasticity in social cognition, we found that RGS14 KO mice had impaired social recognition memory as assessed in a social discrimination task. These results highlight possible roles for mGluRs, RGS14, and STEP in CA2-dependent behaviors, perhaps by biasing the dominant form of synaptic plasticity away from LTP and toward LTD in CA2.

RGS14 limits seizure-induced mitochondrial oxidative stress and pathology in hippocampus

RGS14 is a complex multifunctional scaffolding protein that is highly enriched within pyramidal cells (PCs) of hippocampal area CA2. In these neurons, RGS14 suppresses glutamate-induced calcium influx and related G protein and ERK signaling in dendritic spines to restrain postsynaptic signaling and plasticity. Previous findings show that, unlike PCs of hippocampal areas CA1 and CA3, CA2 PCs are resistant to a number of neurological insults, including degeneration caused by temporal lobe epilepsy (TLE). While RGS14 is protective against peripheral injury, similar roles for RGS14 during pathological injury in hippocampus remain unexplored. Recent studies showed that area CA2 modulates hippocampal excitability, generates epileptiform activity and promotes hippocampal pathology in animal models and patients with TLE. Because RGS14 suppresses CA2 excitability and signaling, we hypothesized that RGS14 would moderate seizure behavior and early hippocampal pathology following seizure activity, possibly affording protection to CA2 PCs. Using kainic acid (KA) to induce status epilepticus (KA-SE) in mice, we show that the loss of RGS14 (RGS14 KO) accelerated onset of limbic motor seizures and mortality compared to wild type (WT) mice, and that KA-SE upregulated RGS14 protein expression in CA2 and CA1 PCs of WT. Our proteomics data show that the loss of RGS14 impacted the expression of a number of proteins at baseline and after KA-SE, many of which associated unexpectedly with mitochondrial function and oxidative stress. RGS14 was shown to localize to the mitochondria in CA2 PCs of mice and reduce mitochondrial respiration in vitro. As a readout of oxidative stress, we found that RGS14 KO dramatically increased 3- nitrotyrosine levels in CA2 PCs, which was greatly exacerbated following KA-SE and correlated with a lack of superoxide dismutase 2 (SOD2) induction. Assessing for hallmarks of seizure pathology in RGS14 KO, we unexpectedly found no differences in neuronal injury in CA2 PCs. However, we observed a striking and surprising lack of microgliosis in CA1 and CA2 of RGS14 KO compared to WT. Together, our data demonstrate a newly appreciated role for RGS14 in limiting intense seizure activity and pathology in hippocampus. Our findings are consistent with a model where RGS14 limits seizure onset and mortality and, after seizure, is upregulated to support mitochondrial function, prevent oxidative stress in CA2 PCs, and promote microglial activation in hippocampus.

Lineage Tracing of RGS5-CreER-Labeled Cells in Long Bones During Homeostasis and Injury

Regulator of G protein signaling 5 (RGS5) is a GTPase activator for heterotrimeric G-protein α-subunits, shown to be a marker of pericytes. Bone marrow stromal cell population (BMSCs) is heterogeneous. Populations of mesenchymal progenitors, cells supportive of hematopoiesis, and stromal cells regulating bone remodeling have been recently identified. Periosteal and bone marrow mesenchymal stem cells (MSCs) are participating in fracture healing, but it is difficult to distinguish the source of cells within the callus. Considering that perivascular cells exert osteoprogenitor potential, we generated an RGS5 transgenic mouse model (Rgs5-CreER) which when crossed with Ai9 reporter animals (Rgs5/Tomato), is suitable for lineage tracing during growth and post-injury. Flow cytometry analysis and histology confirmed the presence of Rgs5/Tomato+ cells within CD31+ endothelial, CD45+ hematopoietic, and CD31-CD45- mesenchymal/perivascular cells. A tamoxifen chase showed expansion of Rgs5/Tomato+ cells expressing osterix within the trabeculae positioned between mineralized matrix and vasculature. Long-term chase showed proportion of Rgs5/Tomato+ cells contributes to mature osteoblasts expressing osteocalcin. Following femoral fracture, Rgs5/Tomato+ cells are observed around newly formed bone within the BM cavity and expressed osterix and osteocalcin, while contribution within periosteum was low and limited to fibroblastic callus with very few positive chondrocytes. In addition, BM injury model confirmed that RGS5-Cre labels population of BMSCs expands during injury and participates in osteogenesis. Under homeostatic conditions, lineage-traced RGS5 cells within the trabecular area demonstrate osteoprogenitor capacity that in an injury model contributes to new bone formation primarily within the BM niche.

Orphan receptor GPR158 serves as a metabotropic glycine receptor: mGlyR

Glycine is a major neurotransmitter involved in several fundamental neuronal processes. The identity of the metabotropic receptor mediating slow neuromodulatory effects of glycine is unknown. We identified an orphan G protein-coupled receptor, GPR158, as a metabotropic glycine receptor (mGlyR). Glycine and a related modulator, taurine, directly bind to a Cache domain of GPR158, and this event inhibits the activity of the intracellular signaling complex regulator of G protein signaling 7-G protein β5 (RGS7-Gβ5), which is associated with the receptor. Glycine signals through mGlyR to inhibit production of the second messenger adenosine 3',5'-monophosphate. We further show that glycine, but not taurine, acts through mGlyR to regulate neuronal excitability in cortical neurons. These results identify a major neuromodulatory system involved in mediating metabotropic effects of glycine, with implications for understanding cognition and affective states.

Non-Ceruloplasmin Copper Identifies a Subtype of Alzheimer’s Disease (CuAD): Characterization of the Cognitive Profile and Case of a CuAD Patient Carrying an RGS7 Stop-Loss Variant

Alzheimer’s disease (AD) is a type of dementia whose cause is incompletely defined. Copper (Cu) involvement in AD etiology was confirmed by a meta-analysis on about 6000 participants, showing that Cu levels were decreased in AD brain specimens, while Cu and non-bound ceruloplasmin Cu (non-Cp Cu) levels were increased in serum/plasma samples. Non-Cp Cu was advocated as a stratification add-on biomarker of a Cu subtype of AD (CuAD subtype). To further circumstantiate this concept, we evaluated non-Cp Cu reliability in classifying subtypes of AD based on the characterization of the cognitive profile. The stratification of the AD patients into normal AD (non-Cp Cu ≤ 1.6 µmol/L) and CuAD (non-Cp Cu > 1.6 µmol/L) showed a significant difference in executive function outcomes, even though patients did not differ in disease duration and severity. Among the Cu-AD patients, a 76-year-old woman showed significantly abnormal levels in the Cu panel and underwent whole exome sequencing. The CuAD patient was detected with possessing the homozygous (c.1486T > C; p.(Ter496Argext*19) stop-loss variant in the RGS7 gene (MIM*602517), which encodes for Regulator of G Protein Signaling 7. Non-Cp Cu as an add-on test in the AD diagnostic pathway can provide relevant information about the underlying pathological processes in subtypes of AD and suggest specific therapeutic options.

RGS14 expression in CA2 hippocampus, amygdala, and basal ganglia: Implications for human brain physiology and disease

RGS14 is a multifunctional scaffolding protein that is highly expressed within postsynaptic spines of pyramidal neurons in hippocampal area CA2. Known roles of RGS14 in CA2 include regulating G protein, H-Ras/ERK, and calcium signaling pathways to serve as a natural suppressor of synaptic plasticity and postsynaptic signaling. RGS14 also shows marked postsynaptic expression in major structures of the limbic system and basal ganglia, including the amygdala and both the ventral and dorsal subdivisions of the striatum. In this review, we discuss the signaling functions of RGS14 and its role in postsynaptic strength (long-term potentiation) and spine structural plasticity in CA2 hippocampal neurons, and how RGS14 suppression of plasticity impacts linked behaviors such as spatial learning, object memory, and fear conditioning. We also review RGS14 expression in the limbic system and basal ganglia and speculate on its possible roles in regulating plasticity in these regions, with a focus on behaviors related to emotion and motivation. Finally, we explore the functional implications of RGS14 in various brain circuits and speculate on its possible roles in certain disease states such as hippocampal seizures, addiction, and anxiety disorders.

Morphological and molecular markers of mouse area CA2 along the proximodistal and dorsoventral hippocampal axes

Hippocampal area CA2 is a molecularly and functionally distinct region of the hippocampus that has classically been defined as the area with large pyramidal neurons lacking input from the dentate gyrus and the thorny excrescences (TEs) characteristic of CA3 neurons. A modern definition of CA2, however, makes use of the expression of several molecular markers that distinguish it from neighboring CA3 and CA1. Using immunohistochemistry, we sought to characterize the staining patterns of commonly used CA2 markers along the dorsal-ventral hippocampal axis and determine how these markers align along the proximodistal axis. We used a region of CA2 that stained for both Regulator of G-protein Signaling 14 (RGS14) and Purkinje Cell Protein 4 (PCP4; "double-labeled zone" [DLZ]) as a reference. Here, we report that certain commonly used CA2 molecular markers may be better suited for drawing distinct boundaries between CA2/3 and CA2/1. For example, RGS14+ and STEP+ neurons showed minimal to no extension into area CA1 while areas stained with VGluT2 and Wisteria Floribunda agglutinin were consistently smaller than the DLZ/CA2 borders by ~100 μ on the CA1 or CA3 sides respectively. In addition, these patterns are dependent on position along the dorsal-ventral hippocampal axis such that PCP4 labeling often extended beyond the distal border of the DLZ into CA1. Finally, we found that, consistent with previous findings, mossy fibers innervate a subset of RGS14 positive neurons (~65%-70%) and that mossy fiber bouton number and relative size in CA2 are less than that of boutons in CA3. Unexpectedly, we did find evidence of some complex spines on apical dendrites in CA2, though much fewer in number than in CA3. Our results indicate that certain molecular markers may be better suited than others when defining the proximal and distal borders of area CA2 and that the presence or absence of complex spines alone may not be suitable as a distinguishing feature differentiating CA3 from CA2 neurons.

Functional Assessment of Cancer-Linked Mutations in Sensitive Regions of Regulators of G Protein Signaling Predicted by Three-Dimensional Missense Tolerance Ratio Analysis

Regulators of G protein signaling (RGS) proteins modulate G protein-coupled receptor (GPCR) signaling by acting as negative regulators of G proteins. Genetic variants in RGS proteins are associated with many diseases, including cancers, although the impact of these mutations on protein function is uncertain. Here we analyze the RGS domains of 15 RGS protein family members using a novel bioinformatic tool that measures the missense tolerance ratio (MTR) using a three-dimensional (3D) structure (3DMTR). Subsequent permutation analysis can define the protein regions that are most significantly intolerant (P < 0.05) in each dataset. We further focused on RGS14, RGS10, and RGS4. RGS14 exhibited seven significantly tolerant and seven significantly intolerant residues, RGS10 had six intolerant residues, and RGS4 had eight tolerant and six intolerant residues. Intolerant and tolerant-control residues that overlap with pathogenic cancer mutations reported in the COSMIC cancer database were selected to define the functional phenotype. Using complimentary cellular and biochemical approaches, proteins were tested for effects on GPCR-Gα activation, Gα binding properties, and downstream cAMP levels. Identified intolerant residues with reported cancer-linked mutations RGS14-R173C/H and RGS4-K125Q/E126K, and tolerant RGS14-S127P and RGS10-S64T resulted in a loss-of-function phenotype in GPCR-G protein signaling activity. In downstream cAMP measurement, tolerant RGS14-D137Y and RGS10-S64T and intolerant RGS10-K89M resulted in change of function phenotypes. These findings show that 3DMTR identified intolerant residues that overlap with cancer-linked mutations cause phenotypic changes that negatively impact GPCR-G protein signaling and suggests that 3DMTR is a potentially useful bioinformatics tool for predicting functionally important protein residues. SIGNIFICANCE STATEMENT: Human genetic variant/mutation information has expanded rapidly in recent years, including cancer-linked mutations in regulator of G protein signaling (RGS) proteins. However, experimental testing of the impact of this vast catalogue of mutations on protein function is not feasible. We used the novel bioinformatics tool three-dimensional missense tolerance ratio (3DMTR) to define regions of genetic intolerance in RGS proteins and prioritize which cancer-linked mutants to test. We found that 3DMTR more accurately classifies loss-of-function mutations in RGS proteins than other databases thereby offering a valuable new research tool.

The therapeutic potential of targeting cardiac RGS4

G protein-coupled receptors (GPCRs) play pivotal roles in regulation of cardiac function and homeostasis. To function properly, every cell needs these receptors to be stimulated only when a specific extracellular stimulus is present, and to be silenced the moment that stimulus is removed. The regulator of G protein signaling (RGS) proteins are crucial for the latter to occur at the cell membrane, where the GPCR normally resides. Perturbations in both activation and termination of G protein signaling underlie numerous heart pathologies. Although more than 30 mammalian RGS proteins have been identified, each RGS protein seems to interact only with a specific set of G protein subunits and GPCR types/subtypes in any given tissue or cell type, and this applies to the myocardium as well. A large number of studies have provided substantial evidence for the roles various RGS proteins expressed in cardiomyocytes play in cardiac physiology and heart disease pathophysiology. This review summarizes the current understanding of the functional roles of cardiac RGS proteins and their implications for the treatment of specific heart diseases, such as heart failure and atrial fibrillation. We focus on cardiac RGS4 in particular, since this isoform appears to be selectively (among the RGS protein family) upregulated in human heart failure and is also the target of ongoing drug discovery efforts for the treatment of a variety of diseases.

ATF3 Modulates the Proliferation, Migration, and Apoptosis of Synovial Fibroblasts after Arthroscopy by Promoting RGS1 Transcription

BACKGROUND

Osteoarthritis (OA) is a degenerative joint disease involving both cartilage and synovium. Activating transcription factor 3 (ATF3) and regulator of G protein signaling 1 (RGS1) have been reported to be up-regulated in OA. However, little is known regarding the relationship between these two genes and the mechanism of this relationship in OA development. Therefore, the present study explores the mechanism of ATF3-mediated RGS1 in the proliferation, migration, and apoptosis of synovial fibroblasts.

METHODS

After the OA cell model was constructed with TGF-β1 induction, human fibroblast-like synoviocytes (HFLSs) were transfected with ATF3 shRNA or RGS1 shRNA alone or co-transfected with ATF3 shRNA and pcDNA3.1-RGS1. Then, proliferation, migration, apoptosis, and the expression of ATF3, RGS1, α-SMA, BCL-2, caspase3, and cleaved-caspase3 were measured. Meanwhile, the potential relationship between ATF3 and RGS1 was predicted and validated.

RESULTS AND DISCUSSION

Analysis of the GSE185059 dataset suggested that RGS1 was up-regulated in OA synovial fluid exosomes. Moreover, ATF3 and RGS1 were both highly expressed in TGF-β1-induced HFLSs. Transfection of ATF3 shRNA or RGS1 shRNA significantly reduced proliferation and migration and promoted apoptosis of TGF- β1-induced HFLSs. Mechanistically, ATF3 bound to the RGS1 promoter and elevated RGS1 expression. Silencing ATF3 repressed proliferation and migration and enhanced apoptosis of TGF-β1-induced HFLSs by down-regulating RGS1.

CONCLUSION

ATF3 binds to the RGS1 promoter and enhances RGS1 expression to accelerate cell proliferation and block cell apoptosis in TGF-β1-induced synovial fibroblasts.

Arabidopsis MPK3 and MPK6 regulates D-glucose signaling and interacts with G-protein, RGS1

Sugar as a signaling molecule has attracted lots of attention. Even though several kinases have been shown to play a crucial role in the sugar signaling and response to exogenous D-glucose (Glc), the information on the involvement of MAP kinase cascade in sugar signaling has remain largely unexplored. In this report we demonstrate that MAP kinase signaling is essential for sensitivity to higher concentrations of D-Glc in Arabidopsis. We found that D-Glc activates MAP kinases, MPK3 and MPK6 in a concentration and time-dependent manner. The mutants of mpk3 and mpk6 display hyposensitivity to 6% D-Glc during seed germination, cotyledon greening and root growth. Interestingly, the altered sensitivity to increased D-Glc is severely enhanced by addition of 1% Sucrose in the media. Our study also deciphered the role of one of the Glc sensor proteins, RGS1 that interacts and gets phosphorylated at its C-terminal domain by MPK3 and MPK6. Overall our study provides a new insight on the involvement of MAP kinases in association with G-proteins that might regulate sugar signaling and sugar responsive growth and development in Arabidopsis.

RGS12 polarizes the GPSM2-GNAI complex to organize and elongate stereocilia in sensory hair cells

Inhibitory G proteins (GNAI/Gαi) bind to the scaffold G protein signaling modulator 2 (GPSM2) to form a conserved polarity complex that regulates cytoskeleton organization. GPSM2 keeps GNAI in a guanosine diphosphate (GDP)-bound state, but how GPSM2-GNAI is generated or relates to heterotrimeric G protein signaling remains unclear. We find that RGS12, a GTPase-activating protein (GAP), is required to polarize GPSM2-GNAI at the hair cell apical membrane and to organize mechanosensory stereocilia in rows of graded heights. Accordingly, RGS12 and the guanine nucleotide exchange factor (GEF) DAPLE are asymmetrically co-enriched at the hair cell apical junction, and Rgs12 mouse mutants are deaf. GPSM2 and RGS12 share GoLoco motifs that stabilize GNAI(GDP), and GPSM2 outcompetes RGS12 to bind GNAI. Our results suggest that polarized GEF/GAP junctional activity might dissociate heterotrimeric G proteins, generating free GNAI(GDP) for GPSM2 at the adjacent apical membrane. GPSM2-GNAI(GDP), in turn, imparts asymmetry to the forming stereocilia to enable sensory function in hair cells.

Clinical and molecular implications of RGS2 promoter genetic variation in severe asthma

BACKGROUND

Regulator of G protein signaling (RGS) 2 terminates bronchoconstrictive Gαq signaling; murine RGS2 knockout demonstrate airway hyperresponsiveness. While RGS2 promoter variants rs2746071 and rs2746072 associate with a clinical mild asthma phenotype, their impact on human airway smooth muscle (HASM) contractility and asthma severity outcomes is unknown.

OBJECTIVE

We sought to determine whether reductions in RGS2 expression seen with these 2 RGS2 promoter variants augment HASM contractility and associate with an asthma severity phenotype.

METHODS

We transfected HASM with a range of RGS2-specific small interfering RNA (siRNA) concentrations and determined RGS2 protein expression by Western blot analysis and intracellular calcium flux induced by histamine (a Gαq-coupled H1 receptor bronchoconstrictive agonist). We conducted regression-based genotype association analyses of RGS2 variants from 611 patients from the National Heart, Lung, and Blood Institute Severe Asthma Research Program 3.

RESULTS

RGS2-specific siRNA caused dose-dependent increases in histamine-stimulated bronchoconstrictive intracellular calcium signaling (2-way ANOVA, P < .0001) with a concomitant decrease in RGS2 protein expression. RGS2-specific siRNA did not affect Gαq-independent ionomycin-induced intracellular calcium signaling (P = .42). The minor allele frequency of rs2746071 and rs2746072 was 0.46 and 0.28 among African American/non-Hispanic Black patients and was 0.28 and 0.27 among non-Hispanic White patients, among whom these single nucleotide polymorphisms were in stronger linkage disequilibrium (r2 = 0.97). Among non-Hispanic White patients, risk allele homozygotes for rs2746072 and rs2746071 each had nearly 2-fold greater asthma exacerbation rates relative to alternative genotypes with wild-type alleles (Padditive = 2.86 × 10-5/Precessive = 5.22 × 10-6 and Padditive = 3.46 × 10-6/Precessive = 6.74 × 10-7, respectively) at baseline, which was confirmed by prospective longitudinal exacerbation data.

CONCLUSION

RGS2 promoter variation associates with a molecular and clinical phenotype characterized by enhanced bronchoconstrictive stimulation in vitro and higher asthma exacerbations rates in non-Hispanic White patients.

Self-activating G protein α subunits engage seven-transmembrane Regulator of G protein Signaling (RGS) proteins and a Rho guanine nucleotide exchange factor effector in the amoeba Naegleria fowleri

The free-living amoeba Naegleria fowleri is a causative agent of primary amoebic meningoencephalitis and is highly resistant to current therapies, resulting in mortality rates >97%. As many therapeutics target G protein-centered signal transduction pathways, further understanding the functional significance of G protein signaling within N. fowleri should aid future drug discovery against this pathogen. Here, we report that the N. fowleri genome encodes numerous transcribed G protein signaling components, including G protein-coupled receptors (GPCRs), heterotrimeric G protein subunits, Regulator of G protein Signaling (RGS) proteins, and candidate Gα effector proteins. We found N. fowleri Gα subunits have diverse nucleotide cycling kinetics; Nf Gα5 and Gα7 exhibit more rapid nucleotide exchange than GTP hydrolysis (i.e. "self-activating" behavior). A crystal structure of Nf Gα7 highlights the stability of its nucleotide-free state, consistent with its rapid nucleotide exchange. Variations in the phosphate binding loop (P-loop) also contribute to nucleotide cycling differences among Gα subunits. Similar to plant G protein signaling pathways, N. fowleri Gα subunits selectively engage members of a large seven-transmembrane RGS protein family, resulting in acceleration of GTP hydrolysis. We show Nf Gα2 and Gα3 directly interact with a candidate Gα effector protein, RGS-RhoGEF, similar to mammalian Gα_12/13 signaling pathways. We demonstrate Nf Gα2 and Gα3 each engage RGS-RhoGEF through a canonical Gα/RGS domain interface, suggesting a shared evolutionary origin with G protein signaling in the enteric pathogen Entamoeba histolytica. These findings further illuminate the evolution of G protein signaling and identify potential targets of pharmacological manipulation in Naegleria fowleri.

Regulator of G protein signaling 2 is inhibited by hypoxia-inducible factor-1α/E1A binding protein P300 complex upon hypoxia in human preeclampsia

BACKGROUND

Preeclampsia is a pregnancy-related complication that causes maternal and fetal mortality. Despite extensive studies showing the role of hypoxia in preeclampsia progression, the specific mechanism remains unclear. The purpose of this study was to explore the possible mechanism underlying hypoxia in preeclampsia.

METHODS

Human trophoblast-like JEG-3 cell line was used to investigate the molecular mechanisms underlying hypoxia contribution to preeclampsia and the expression correlation of key molecules was examined in human placental tissues. Methods include JEG-3 cell culture and hypoxia induction, RNA isolation and quantitative real-time PCR, transient transfection and dual-luciferase assay, western blot, immunoprecipitation, immunofluorescence staining, cell proliferation assay, chromatin immunoprecipitation assay, obtainment of human placental tissue sample and immunohistochemistry staining.

RESULTS

Hypoxia-Inducible Factor-1α is up-regulated in clinical preeclampsia samples, where Regulator of G Protein Signaling 2 is down-regulated. Mechanistically, Hypoxia-Inducible Factor-1α is induced in response to hypoxia, which up-regulates E1A binding protein P300 expression and thereby forms a Hypoxia-Inducible Factor-1α/E1A binding protein P300 protein-protein complex that binds to the promoter of gene Regulator of G Protein Signaling 2 and subsequently inhibits the transcription of Regulator of G Protein Signaling 2, possibly contributing to the preeclampsia development. In addition, the expression of E1A binding protein P300 is increased in preeclampsia samples, and the expression of Regulator of G Protein Signaling 2 in preeclamptic placentas inversely correlates with the levels of E1A binding protein P300.

CONCLUSION

Our findings may provide novel insights into understanding the molecular pathogenesis of preeclampsia and may be a prognostic biomarker and therapeutic target for preeclampsia.

Regulator of G-Protein Signaling-4 Attenuates Cardiac Adverse Remodeling and Neuronal Norepinephrine Release-Promoting Free Fatty Acid Receptor FFAR3 Signaling

Propionic acid is a cell nutrient but also a stimulus for cellular signaling. Free fatty acid receptor (FFAR)-3, also known as GPR41, is a Gi/o protein-coupled receptor (GPCR) that mediates some of the propionate's actions in cells, such as inflammation, fibrosis, and increased firing/norepinephrine release from peripheral sympathetic neurons. The regulator of G-protein Signaling (RGS)-4 inactivates (terminates) both Gi/o- and Gq-protein signaling and, in the heart, protects against atrial fibrillation via calcium signaling attenuation. RGS4 activity is stimulated by β-adrenergic receptors (ARs) via protein kinase A (PKA)-dependent phosphorylation. Herein, we examined whether RGS4 modulates cardiac FFAR3 signaling/function. We report that RGS4 is essential for dampening of FFAR3 signaling in H9c2 cardiomyocytes, since siRNA-mediated RGS4 depletion significantly enhanced propionate-dependent cAMP lowering, Gi/o activation, p38 MAPK activation, pro-inflammatory interleukin (IL)-1β and IL-6 production, and pro-fibrotic transforming growth factor (TGF)-β synthesis. Additionally, catecholamine pretreatment blocked propionic acid/FFAR3 signaling via PKA-dependent activation of RGS4 in H9c2 cardiomyocytes. Finally, RGS4 opposes FFAR3-dependent norepinephrine release from sympathetic-like neurons (differentiated Neuro-2a cells) co-cultured with H9c2 cardiomyocytes, thereby preserving the functional βAR number of the cardiomyocytes. In conclusion, RGS4 appears essential for propionate/FFAR3 signaling attenuation in both cardiomyocytes and sympathetic neurons, leading to cardioprotection against inflammation/adverse remodeling and to sympatholysis, respectively.

Filling in the gaps: SNX-RGS proteins as multiorganelle tethers

SNX-RGS proteins are molecular tethers localized to multiple interorganelle contact sites that exhibit roles in cellular metabolism. Here, we highlight recent findings on these proteins and discuss their emerging roles in metabolism, human disease, and lipid trafficking.

RGS14 regulates PTH- and FGF23-sensitive NPT2A-mediated renal phosphate uptake via binding to the NHERF1 scaffolding protein

Phosphate homeostasis, mediated by dietary intake, renal absorption, and bone deposition, is incompletely understood because of the uncharacterized roles of numerous implicated protein factors. Here, we identified a novel role for one such element, regulator of G protein signaling 14 (RGS14), suggested by genome-wide association studies to associate with dysregulated Pi levels. We show that human RGS14 possesses a carboxy-terminal PDZ ligand required for sodium phosphate cotransporter 2a (NPT2A) and sodium hydrogen exchanger regulatory factor-1 (NHERF1)-mediated renal Pi transport. In addition, we found using isotope uptake measurements combined with bioluminescence resonance energy transfer assays, siRNA knockdown, pull-down and overlay assays, and molecular modeling that secreted proteins parathyroid hormone (PTH) and fibroblast growth factor 23 inhibited Pi uptake by inducing dissociation of the NPT2A-NHERF1 complex. PTH failed to affect Pi transport in cells expressing RGS14, suggesting that it suppresses hormone-sensitive but not basal Pi uptake. Interestingly, RGS14 did not affect PTH-directed G protein activation or cAMP formation, implying a postreceptor site of action. Further pull-down experiments and direct binding assays indicated that NPT2A and RGS14 bind distinct PDZ domains on NHERF1. We showed that RGS14 expression in human renal proximal tubule epithelial cells blocked the effects of PTH and fibroblast growth factor 23 and stabilized the NPT2A-NHERF1 complex. In contrast, RGS14 genetic variants bearing mutations in the PDZ ligand disrupted RGS14 binding to NHERF1 and subsequent PTH-sensitive Pi transport. In conclusion, these findings identify RGS14 as a novel regulator of hormone-sensitive Pi transport. The results suggest that changes in RGS14 function or abundance may contribute to the hormone resistance and hyperphosphatemia observed in kidney diseases.

Effect of Regulator of G Protein Signaling Proteins on Bone

Regulator of G protein signaling (RGS) proteins are critical negative molecules of G protein-coupled receptor (GPCR) signaling, which mediates a variety of biological processes in bone homeostasis and diseases. The RGS proteins are divided into nine subfamilies with a conserved RGS domain which plays an important role in regulating the GTPase activity. Mutations of some RGS proteins change bone development and/or metabolism, causing osteopathy. In this review, we summarize the recent findings of RGS proteins in regulating osteoblasts, chondrocytes, and osteoclasts. We also highlight the impacts of RGS on bone development, bone remodeling, and bone-related diseases. Those studies demonstrate that RGS proteins might be potential drug targets for bone diseases.

Role of RGS2 in sevoflurane-induced cognitive dysfunction in aged rats

After undergoing inhalation anesthesia, some patients, especially elderly patients, experience postoperative cognitive dysfunction, such as personality changes and memory impairment. In the present study, 20-month-old rats were randomly allocated to sevoflurane (Sevo group) and control groups (Con group), and they inhaled 3% sevoflurane or 40% oxygen for 8 hours, respectively. The Morris water maze test found that the cognitive function of rats in the Sevo group were significantly different on 1d and 3d after anesthesia than that of rats in the Con group. The expression of RGS2 mRNA and protein in hippocampus of Sevo group was lower compared to the Con group, while Ca^{2 +} was higher than con group. The expression of CaM and CaMK II in Sevo group was higher compared to the Con group. We found that Bcl-2 reduced, but the expression of Bax and Caspase-3 increased, indicating that apoptosis of hippocampal neurons was increased after sevoflurane inhalation. Both the expression of NGF and BDNF was depressed in the Sevo group. After continuous inhalation of 3% sevoflurane for 8h, the expression of RGS2 in the hippocampi of aged rats is down regulated. RGS2 may be an important factor that leads to cognitive dysfunction in rats.

Single-Cell Transcriptome Analysis Reveals RGS1 as a New Marker and Promoting Factor for T-Cell Exhaustion in Multiple Cancers

T-cell exhaustion is one of the main reasons of tumor immune escape. Using single-cell transcriptome data of CD8+ T cells in multiple cancers, we identified different cell types, in which Pre_exhaust and exhausted T cells participated in negative regulation of immune system process. By analyzing the coexpression network patterns and differentially expressed genes of Pre_exhaust, exhausted, and effector T cells, we identified 35 genes related to T-cell exhaustion, whose high GSVA scores were associated with significantly poor prognosis in various cancers. In the differentially expressed genes, RGS1 showed the greatest fold change in Pre_exhaust and exhausted cells of three cancers compared with effector T cells, and high expression of RGS1 was also associated with poor prognosis in various cancers. Additionally, RGS1 protein was upregulated significantly in tumor tissues in the immunohistochemistry verification. Furthermore, RGS1 displayed positive correlation with the 35 genes, especially highly correlated with PDCD1, CTLA4, HAVCR2, and TNFRSF9 in CD8+ T cells and cancer tissues, indicating the important roles of RGS1 in CD8+ T-cell exhaustion. Considering the GTP-hydrolysis activity of RGS1 and significantly high mRNA and protein expression in cancer tissues, we speculated that RGS1 potentially mediate the T-cell retention to lead to the persistent antigen stimulation, resulting in T-cell exhaustion. In conclusion, our findings suggest that RGS1 is a new marker and promoting factor for CD8+ T-cell exhaustion and provide theoretical basis for research and immunotherapy of exhausted cells.

miR-183-5p Aggravates Breast Cancer Development via Mediation of RGS2

This study mainly explores how miR-183-5p pertains to breast cancer (BC) development. Functional assays were employed to test impacts of miR-183-5p in this cancer. Targeting between RGS2 and miR-183-5p was examined with dual-luciferase assay, and how their interaction pertains to cancer progression was further unraveled. miR-183-5p level was noticeably high in cancer tissue/cells. Overexpressing miR-183-5p could remarkably deteriorate cancer progression. The regulatory gene RGS2 levels was markedly low in BC, and two genes we researched were negatively correlated. It was uncovered by rescue assay that miR-183-5p/RGS2 axis mediated tumor-relevant behaviors in BC. Altogether, miR-183-5p aggravates BC development via mediation of RGS2. miR-183-5p supplies a promising target for BC therapy.

Ex Vivo Intact Tissue Analysis Reveals Alternative Calcium-sensing Behaviors in Parathyroid Adenomas

CONTEXT

The biochemical basis for clinical variability in primary hyperparathyroidism (PHPT) is poorly understood.

OBJECTIVE

This study aimed to define parathyroid tumor biochemical properties associated with calcium-sensing failure in PHPT patients, and to relate differences in these profiles to variations in clinical presentation.

METHODS

Preoperative clinical data from a sequential series of 39 patients undergoing surgery for PHPT at an endocrine surgery referral center in a large, public university hospital were evaluated for correlation to parathyroid tumor biochemical behavior. An intact tissue, ex vivo interrogative assay was employed to evaluate the calcium-sensing capacity of parathyroid adenomas relative to normal donor glands. Tumors were functionally classified based on calcium dose-response curve profiles, and clinical parameters were compared among the respective classes. Changes in the relative expression of 3 key components in the calcium/parathyroid hormone (PTH) signaling axis-CASR, RGS5, and RCAN1-were evaluated as potential mechanisms for calcium-sensing failure.

RESULTS

Parathyroid adenomas grouped into 3 distinct functional classes. Tumors with diminished calcium sensitivity were the most common (18 of 39) and were strongly associated with reduced bone mineral density (P = 0.0009). Tumors with no calcium-sensing deficit (11 of 39) were associated with higher preoperative PTH (P = 0.036). A third group (6/39) displayed a nonsigmoid calcium/PTH response curve; 4 of these 6 tumors expressed elevated RCAN1.

CONCLUSION

Calcium-sensing capacity varies among parathyroid tumors but downregulation of the calcium-sensing receptor (CASR) is not an obligate underlying mechanism. Differences in tumor calcium responsiveness may contribute to variations in PHPT clinical presentation.

The G protein signaling regulator RGS3 enhances the GTPase activity of KRAS

Recently reported to be effective in patients with lung cancer, KRASG12C inhibitors bind to the inactive, or guanosine diphosphate (GDP)–bound, state of the oncoprotein and require guanosine triphosphate (GTP) hydrolysis for inhibition. However, KRAS mutations prevent the catalytic arginine of GTPase-activating proteins (GAPs) from enhancing an otherwise slow hydrolysis rate. If KRAS mutants are indeed insensitive to GAPs, it is unclear how KRASG12C hydrolyzes sufficient GTP to allow inactive state–selective inhibition. Here, we show that RGS3, a GAP previously known for regulating G protein–coupled receptors, can also enhance the GTPase activity of mutant and wild-type KRAS proteins. Our study reveals an unexpected mechanism that inactivates KRAS and explains the vulnerability to emerging clinically effective therapeutics.

Circadian regulation of vertebrate cone photoreceptor function

Eukaryotes generally display a circadian rhythm as an adaption to the reoccurring day/night cycle. This is particularly true for visual physiology that is directly affected by changing light conditions. Here we investigate the influence of the circadian rhythm on the expression and function of visual transduction cascade regulators in diurnal zebrafish and nocturnal mice. We focused on regulators of shut-off kinetics such as Recoverins, Arrestins, Opsin kinases, and Regulator of G-protein signaling that have direct effects on temporal vision. Transcript as well as protein levels of most analyzed genes show a robust circadian rhythm-dependent regulation, which correlates with changes in photoresponse kinetics. Electroretinography demonstrates that photoresponse recovery in zebrafish is delayed in the evening and accelerated in the morning. Functional rhythmicity persists in continuous darkness, and it is reversed by an inverted light cycle and disrupted by constant light. This is in line with our finding that orthologous gene transcripts from diurnal zebrafish and nocturnal mice are often expressed in an anti-phasic daily rhythm.

MicroRNA-3935 promotes human trophoblast cell epithelial-mesenchymal transition through tumor necrosis factor receptor-associated factor 6/regulator of G protein signaling 2 axis

BACKGROUND

Insufficient migration and invasion during trophoblast epithelial-mesenchymal transition (EMT) results in the occurrence and development of preeclampsia (PE), and our previous study has screened 52 miRNAs, whose expression levels are altered in the placental samples from PE patients, compared with the normal group. Among those, miR-3935 is one of the miRNAs being most significantly down-regulated, indicating its involvement in PE. However, the exact effect and molecular mechanisms remain unknown.

METHODS

In the present study, we investigate the roles and underlying mechanisms of miR-3935 in trophoblast EMT by use of the human extra-villous trophoblast cell line HTR-8/SVneo as well as human placental tissues and maternal blood samples obtained from 15 women with normal pregnancies and 15 women with PE. Experimental methods include transfection, quantitative reverse transcription-PCR (qRT-PCR), western blot, immunofluorescence staining, dual-luciferase assays, in vitro invasion and migration assays, RNA-Seq analysis, bisulfite sequencing and immunohistochemistry staining.

RESULTS

MiR-3935 expression is significantly decreased in both placentas and peripheral blood specimens of PE, and functionally, miR-3935 promotes EMT of trophoblast cells. Mechanistically, TRAF6 is identified to be a direct target of miR-3935 and TRAF6 exerts its negative effect on EMT of trophoblast cells by inhibition of RGS2, which down-regulates the methylation status of promoter of CDH1 gene that encodes E-Cadherin protein through induction of ALKBH1, resulting in increase of E-Cadherin and subsequently insufficient trophoblast EMT.

CONCLUSIONS

Together these results uncover a hitherto uncharacterized role of miR-3935/TRAF6/RGS2 axis in the function of human trophoblasts, which may pinpoint the molecular pathogenesis of PE and may be a prognostic biomarker and therapeutic target for such obstetrical diseases as PE.

RGS5 Determines Neutrophil Migration in the Acute Inflammatory Phase of Bleomycin-Induced Lung Injury

The regulator of G protein signaling (RGS) represents a widespread system of controllers of cellular responses. The activities of the R4 subfamily of RGSs have been elucidated in allergic pulmonary diseases. However, the R4 signaling in other inflammatory lung diseases, with a strong cellular immune response, remained unexplored. Thus, our study aimed to discern the functional relevance of the R4 family member, RGS5, as a potential modulating element in this context. Gene profiling of the R4 subfamily showed increased RGS5 expression in human fibrosing lung disease samples. In line with this, RGS5 was markedly increased in murine lungs following bleomycin injury. RGS knock-out mice (RGS-/-) had preserved lung function while control mice showed significant combined ventilatory disorders three days after bleomycin application as compared to untreated control mice. Loss of RGS5 was associated with a significantly reduced neutrophil influx and tissue myeloperoxidase expression. In the LPS lung injury model, RGS5-/- mice also failed to recruit neutrophils into the lung, which was accompanied by reduced tissue myeloperoxidase levels after 24 h. Our in-vitro assays showed impaired migration of RGS5-/- neutrophils towards chemokines despite preserved Ca²⁺ signaling. ERK dephosphorylation might play a role in reduced neutrophil migration in our model. As a conclusion, loss of RGS5 preserves lung function and attenuates hyperinflammation in the acute phase of bleomycin-induced pulmonary fibrosis and LPS-induced lung injury. Targeting RGS5 might alleviate the severity of exacerbations in interstitial lung diseases.

RGS5 Attenuates Baseline Activity of ERK1/2 and Promotes Growth Arrest of Vascular Smooth Muscle Cells

The regulator of G-protein signaling 5 (RGS5) acts as an inhibitor of Gαq/11 and Gαi/o activity in vascular smooth muscle cells (VSMCs), which regulate arterial tone and blood pressure. While RGS5 has been described as a crucial determinant regulating the VSMC responses during various vascular remodeling processes, its regulatory features in resting VSMCs and its impact on their phenotype are still under debate and were subject of this study. While Rgs5 shows a variable expression in mouse arteries, neither global nor SMC-specific genetic ablation of Rgs5 affected the baseline blood pressure yet elevated the phosphorylation level of the MAP kinase ERK1/2. Comparable results were obtained with 3D cultured resting VSMCs. In contrast, overexpression of RGS5 in 2D-cultured proliferating VSMCs promoted their resting state as evidenced by microarray-based expression profiling and attenuated the activity of Akt- and MAP kinase-related signaling cascades. Moreover, RGS5 overexpression attenuated ERK1/2 phosphorylation, VSMC proliferation, and migration, which was mimicked by selectively inhibiting Gαi/o but not Gαq/11 activity. Collectively, the heterogeneous expression of Rgs5 suggests arterial blood vessel type-specific functions in mouse VSMCs. This comprises inhibition of acute agonist-induced Gαq/11/calcium release as well as the support of a resting VSMC phenotype with low ERK1/2 activity by suppressing the activity of Gαi/o.

The Antipsychotic Drug Clozapine Suppresses the RGS4 Polyubiquitylation and Proteasomal Degradation Mediated by the Arg/N-Degron Pathway

Although diverse antipsychotic drugs have been developed for the treatment of schizophrenia, most of their mechanisms of action remain elusive. Regulator of G-protein signaling 4 (RGS4) has been reported to be linked, both genetically and functionally, with schizophrenia and is a physiological substrate of the arginylation branch of the N-degron pathway (Arg/N-degron pathway). Here, we show that the atypical antipsychotic drug clozapine significantly inhibits proteasomal degradation of RGS4 proteins without affecting their transcriptional expression. In addition, the levels of Arg- and Phe-GFP (artificial substrates of the Arg/N-degron pathway) were significantly elevated by clozapine treatment. In silico computational model suggested that clozapine may interact with active sites of N-recognin E3 ubiquitin ligases. Accordingly, treatment with clozapine resulted in reduced polyubiquitylation of RGS4 and Arg-GFP in the test tube and in cultured cells. Clozapine attenuated the activation of downstream effectors of G protein-coupled receptor signaling, such as MEK1 and ERK1, in HEK293 and SH-SY5Y cells. Furthermore, intraperitoneal injection of clozapine into rats significantly stabilized the endogenous RGS4 protein in the prefrontal cortex. Overall, these results reveal an additional therapeutic mechanism of action of clozapine: this drug posttranslationally inhibits the degradation of Arg/N-degron substrates, including RGS4. These findings imply that modulation of protein post-translational modifications, in particular the Arg/N-degron pathway, may be a novel molecular therapeutic strategy against schizophrenia.

Targeting regulator of G protein signaling 1 in tumor-specific T cells enhances their trafficking to breast cancer

Reduced infiltration of anti-tumor lymphocytes remains a major cause of tumor immune evasion and is correlated with poor cancer survival. Here, we found that upregulation of regulator of G protein signaling (RGS)1 in helper TH1 cells and cytotoxic T lymphocytes (CTLs) reduced their trafficking to and survival in tumors and was associated with shorter survival of patients with breast and lung cancer. RGS1 was upregulated by type II interferon (IFN)-signal transducer and activator of transcription (STAT)1 signaling and impaired trafficking of circulating T cells to tumors by inhibiting calcium influx and suppressing activation of the kinases ERK and AKT. RGS1 knockdown in adoptively transferred tumor-specific CTLs significantly increased their infiltration and survival in breast and lung tumor grafts and effectively inhibited tumor growth in vivo, which was further improved when combined with programmed death ligand (PD-L)1 checkpoint inhibition. Our findings reveal RGS1 is important for tumor immune evasion and suggest that targeting RGS1 may provide a new strategy for tumor immunotherapy.

Single Molecule-Based fliFISH Validates Radial and Heterogeneous Gene Expression Patterns in Pancreatic Islet β-Cells

Single-cell RNA-sequencing (scRNA-Seq) technologies have greatly enhanced our understanding of islet cell transcriptomes and have revealed the existence of β-cell heterogeneity. However, comparison of scRNA-Seq data sets from different groups have highlighted inconsistencies in gene expression patterns, primarily due to variable detection of lower abundance transcripts. Furthermore, such analyses are unable to uncover the spatial organization of heterogeneous gene expression. In this study, we used fluctuation localization imaging-based fluorescence in situ hybridization (fliFISH) to quantify transcripts in single cells in mouse pancreatic islet sections. We compared the expression patterns of Insulin 2 (Ins2) with Mafa and Ucn3, two genes expressed in β-cells as they mature, as well as Rgs4, a factor with variably reported expression in the islet. This approach accurately quantified transcripts across a wide range of expression levels, from single copies to >100 copies/cell in one islet. Importantly, fliFISH allowed evaluation of transcript heterogeneity in the spatial context of an intact islet. These studies confirm the existence of a high degree of heterogeneous gene expression levels within the islet and highlight relative and radial expression patterns that likely reflect distinct β-cell maturation states along the radial axis of the islet.

Reported differences in the flg22 response of the null mutation of AtRGS1 correlates with fixed genetic variation in the background of Col-0 isolates

A role for the heterotrimeric G protein complex in the induction of a transient burst of reactive oxygen species (ROS) by the Microbial-Associated Molecular Pattern, flg22, a 22-amino acid peptide derived from bacterial flagella, is well established. However, the evidence for a negative or positive role for one component of the Arabidopsis G protein complex, namely, Regulator of G Signaling 1 (AtRGS1) leads to opposing conclusions. We show that the reason for this difference is due to the isolate of Col-0 ecotype used as the wildtype control in flg22-induced ROS and our data further support the idea that AtRGS1 is a negative regulator of the flg22-induced ROS response. Whole-genome genotyping led to the identification and validation of polymorphism in five genes between two Col-0 isolates that are candidates for the different ROS response relative to the rgs1 null mutant.

Human HINT1 Mutant Proteins that Cause Axonal Motor Neuropathy Exhibit Anomalous Interactions with Partner Proteins

The 14 kDa histidine triad nucleotide-binding protein 1 (HINT1) is critical to maintain the normal function of motor neurons. Thus, a series of human HINT1 mutants cause autosomal recessive axonal neuropathy with neuromyotonia. HINT1 establishes a series of regulatory interactions with signaling proteins, some of which are enriched in motor neurons, such as the type 1 sigma receptor or intracellular domain (ICD) of transmembrane teneurin 1, both of which are also implicated in motor disturbances. In a previous study, we reported the capacity of HINT1 to remove the small ubiquitin-like modifier (SUMO) from a series of substrates and the influence of HINT1 mutants on this activity. We now report how human HINT1 mutations affect the interaction of HINT1 with the regulator of its SUMOylase activity, calcium-activated calmodulin, and its substrate SUMO. Moreover, HINT1 mutants exhibited anomalous interactions with G protein coupled receptors, such as the mu-opioid, and with glutamate N-methyl-D-aspartate receptors as well. Additionally, these HINT1 mutants showed impaired associations with transcriptional regulators such as the regulator of G protein signaling Z2 protein and the cleaved N-terminal ICD of teneurin 1. Thus, the altered enzymatic activity of human HINT1 mutants and their anomalous interactions with partner proteins may disrupt signaling pathways essential to the normal function of human motor neurons.

RGS10 physically and functionally interacts with STIM2 and requires store-operated calcium entry to regulate pro-inflammatory gene expression in microglia

Chronic activation of microglia is a driving factor in the progression of neuroinflammatory diseases, and mechanisms that regulate microglial inflammatory signaling are potential targets for novel therapeutics. Regulator of G protein Signaling 10 is the most abundant RGS protein in microglia, where it suppresses inflammatory gene expression and reduces microglia-mediated neurotoxicity. In particular, microglial RGS10 downregulates the expression of pro-inflammatory mediators including cyclooxygenase 2 (COX-2) following stimulation with lipopolysaccharide (LPS). However, the mechanism by which RGS10 affects inflammatory signaling is unknown and is independent of its canonical G protein targeted mechanism. Here, we sought to identify non-canonical RGS10 interacting partners that mediate its anti-inflammatory mechanism. Through RGS10 co-immunoprecipitation coupled with mass spectrometry, we identified STIM2, an endoplasmic reticulum (ER) localized calcium sensor and a component of the store-operated calcium entry (SOCE) machinery, as a novel RGS10 interacting protein in microglia. Direct immunoprecipitation experiments confirmed RGS10-STIM2 interaction in multiple microglia and macrophage cell lines, as well as in primary cells, with no interaction observed with the homologue STIM1. We further determined that STIM2, Orai channels, and the calcium-dependent phosphatase calcineurin are essential for LPS-induced COX-2 production in microglia, and this pathway is required for the inhibitory effect of RGS10 on COX-2. Additionally, our data demonstrated that RGS10 suppresses SOCE triggered by ER calcium depletion and that ER calcium depletion, which induces SOCE, amplifies pro-inflammatory genes. In addition to COX-2, we also show that RGS10 suppresses the expression of pro-inflammatory cytokines in microglia in response to thrombin and LPS stimulation, and all of these effects require SOCE. Collectively, the physical and functional links between RGS10 and STIM2 suggest a complex regulatory network connecting RGS10, SOCE, and pro-inflammatory gene expression in microglia, with broad implications in the pathogenesis and treatment of chronic neuroinflammation.