Emerging Roles of Regulators of G Protein Signaling (RGS) Proteins in the Immune System

Ayurvedic herbal formulations Haridra Khanda and Manjisthadi Kwath (brihat) in the management of allergic rhinitis: A pharmacological study

This study aims to pharmacologically validate Haridra Khanda (HK) and Manjishthadi Kwatham (brihat) (MMK) in allergy management using invivo and invitro studies to rationalize the prescription of these two ayurvedic polyherbal drug formulations, which are currently used in Indian government hospitals. Experimental animals received HK and MMK orally from day 0 to day 14 and histamine (1 mg/kg b.w/i.v) and 1 % evans blue (EB) (0.1 mL) via tail vein on day 14. The compound 48/80 (intracutaneous) challenged mice model followed the same technique. The former mimicked acute anaphylaxis and the latter mast cell degranulation. For both models, EB dye leakage was quantified spectrophotometrically to determine vascular permeability. Plasma histamine was measured in Compound 48/80-induced animals using LC-ESI-MS/MS. The guineapig received HK and MMK p.o. and 0.6 % histamine sprayed in a histamine chamber to simulate allergic rhinitis. Blood eosinophil count and sneeze rate were measured in histamine-challenged guineapigs. Goat R.B.C. membrane stability assay (mammalian cell membrane toxicity) and intracellular histamine-induced cytosolic Ca2+ release assay in Chinese hamster ovary (CHO) cells were performed in vitro. For both histamine and Compound 48/80 challenged animals, HK (22.81 % and 14.58 %) and MMK (19.71 % and 22.40 %) significantly reduced EB dye leakage (p < 0.05). Both formulations, HK and MMK considerably (p < 0.05) decreased plasma histamine (29.62 % and 25.37 % respectively) in mice and eosinophilic count (11.56 % and 9.94 % respectively) and sneeze rate (42.58 % and 29.03 % respectively) in guinea pigs. In membrane stability experiment, HK and MMK reduced RBC lysis. Both HK and MMK raw/dialysate blocked CHO cell cytosolic Ca2+ release. HK and MMK activities mimic mast cell stabilization with possible H1 receptor inactivation seen by decreased Ca2+ efflux and thus indicate potential for allergic rhinitis management. The combination of activities is usually related with curative and prophylactic therapy and might lead future clinical trials and therapies.

Egress of resident memory T cells from tissue with neoadjuvant immunotherapy: Implications for systemic anti-tumor immunity

INTRODUCTION

Resident memory T (TRM) cells are embedded in peripheral tissue and capable of acting as sentinels that can respond quickly to repeat pathogen exposure as part of an endogenous anti-microbial immune response. Recent evidence suggests that chronic antigen exposure and other microenvironment cues may promote the development of TRM cells within solid tumors as well, and that this TRM phenotype can sequester tumor-specific T cells into tumors and out of circulation resulting in limited systemic antitumor immunity. Here, we perform a review of the published English literature and describe tissue-specific mediators of TRM cell differentiation in states of infection and malignancy with special focus on the role of TGF-β and how targeting TGF-β signaling could be used as a therapeutical approach to promote tumor systemic immunity.

DISCUSSION

The presence of TRM cells with antigen specificity to neoepitopes in tumors associates with positive clinical prognosis and greater responsiveness to immunotherapy. Recent evidence indicates that solid tumors may act as reservoirs for tumor specific TRM cells and limit their circulation - possibly resulting in impaired systemic antitumor immunity. TRM cells utilize specific mechanisms to egress from peripheral tissues into circulation and other peripheral sites, and emerging evidence indicates that immunotherapeutic approaches may initiate these processes and increase systemic antitumor immunity.

CONCLUSIONS

Reversing tumor sequestration of tumor-specific T cells prior to surgical removal or radiation of tumor may increase systemic antitumor immunity. This finding may underlie the improved recurrence free survival observed with neoadjuvant immunotherapy in clinical trials.

RGS16 regulates Hippo-YAP activity to promote esophageal cancer cell proliferation and migration

Esophageal Squamous Cell Carcinoma (ESCC) is a common malignant tumor of digestive tract, accounting for 90% of all pathological types of esophageal cancer. Despite the rapid development of multi-disciplinary treatment such as surgery, chemotherapy, radiotherapy and chemoradiotherapy, the prognosis of patients with ESCC is still poor. Regulators of G-protein signaling (RGSs) are involved in the processes of various cancers. The expression levels of its family member RGS16 are abnormally elevated in a variety of tumors, but its role in ESCC is still unclear. We found that RGS16 expression is aberrantly increased in ESCC tissues and correlated with poor prognosis of ESCC patients from The Cancer Genome Atlas (TCGA) database and our collected ESCC tissues. Moreover, knockdown of RGS16 in two ESCC cells could indeed inhibit their proliferation and migration. We further explored the molecular mechanism of RGS16 in ESCC, and the correlation analysis from TCGA database showed that the mRNA levels of RGS16 was positively correlated with that of CTGF and CYR61, two target genes of Hippo-YAP signaling. Consistently, RGS16- knockdown significantly inhibited the expression of CTGF and CYR61 in ESCC cells. We found that the phosphorylation levels of LATS1 and YAP were significantly increased and YAP translocated into the cytoplasm after depletion of RGS16 in ESCC cells. Also, RGS16-knockdown promoted the interaction between LATS1 and upstream kinase MST1. In addition, reintroduction of a constitutive active YAP5A mutant significantly rescued CTGF expression and cell proliferation in RGS16-knockdown cells. Together, our work revealed that RGS16 promoted YAP activity through disrupting the interaction between LATS1 and MST1, thus promoting the proliferation and migration of ESCC cells.

The NF-κB Pathway: a Focus on Inflammatory Responses in Spinal Cord Injury

Spinal cord injury (SCI) is a type of central nervous system trauma that can lead to severe nerve injury. Inflammatory reaction after injury is an important pathological process leading to secondary injury. Long-term stimulation of inflammation can further deteriorate the microenvironment of the injured site, leading to the deterioration of neural function. Understanding the signaling pathways that regulate responses after SCI, especially inflammatory responses, is critical for the development of new therapeutic targets and approaches. Nuclear transfer factor-κB (NF-κB) has long been recognized as a key factor in regulating inflammatory responses. The NF-κB pathway is closely related to the pathological process of SCI. Inhibition of this pathway can improve the inflammatory microenvironment and promote the recovery of neural function after SCI. Therefore, the NF-κB pathway may be a potential therapeutic target for SCI. This article reviews the mechanism of inflammatory response after SCI and the characteristics of NF-κB pathway, emphasizing the effect of inhibiting NF-κB on the inflammatory response of SCI to provide a theoretical basis for the biological treatment of SCI.

Regulator of G-protein signaling 1 critically supports CD8+ TRM cell-mediated intestinal immunity

Members of the Regulator of G-protein signaling (Rgs) family regulate the extent and timing of G protein signaling by increasing the GTPase activity of Gα protein subunits. The Rgs family member Rgs1 is one of the most up-regulated genes in tissue-resident memory (T_RM) T cells when compared to their circulating T cell counterparts. Functionally, Rgs1 preferentially deactivates Gαq, and Gαi protein subunits and can therefore also attenuate chemokine receptor-mediated immune cell trafficking. The impact of Rgs1 expression on tissue-resident T cell generation, their maintenance, and the immunosurveillance of barrier tissues, however, is only incompletely understood. Here we report that Rgs1 expression is readily induced in naïve OT-I T cells in vivo following intestinal infection with Listeria monocytogenes-OVA. In bone marrow chimeras, Rgs1 ^-/- and Rgs1 ^+/+ T cells were generally present in comparable frequencies in distinct T cell subsets of the intestinal mucosa, mesenteric lymph nodes, and spleen. After intestinal infection with Listeria monocytogenes-OVA, however, OT-I Rgs1 ^+/+ T cells outnumbered the co-transferred OT-I Rgs1^{- /-} T cells in the small intestinal mucosa already early after infection. The underrepresentation of the OT-I Rgs1 ^-/- T cells persisted to become even more pronounced during the memory phase (d30 post-infection). Remarkably, upon intestinal reinfection, mice with intestinal OT-I Rgs1 ^+/+ T_RM cells were able to prevent the systemic dissemination of the pathogen more efficiently than those with OT-I Rgs1 ^-/- T_RM cells. While the underlying mechanisms are not fully elucidated yet, these data thus identify Rgs1 as a critical regulator for the generation and maintenance of tissue-resident CD8⁺ T cells as a prerequisite for efficient local immunosurveillance in barrier tissues in case of reinfections with potential pathogens.

Inhibiting RGS1 attenuates secondary inflammation response and tissue degradation via the TLR/TRIF/NF-κB pathway in macrophage post spinal cord injury

Macrophage-dominated inflammation by the activation of Toll-like receptor (TLR) pathway leads to neurological disruption after spinal cord injury (SCI). Regulator of G-protein signaling 1 (RGS1) is reported to be a regulator in inflammation. The present study thus purposes to identify the unknown role of RGS1 mediating TLR on inflammation post SCI. A mouse model of traumatic SCI was established by a mechanical trauma at T10. The mice underwent SCI and a macrophage line activated by lipopolysaccharide (LPS) were treated with shRNA-RGS1 to elucidate the role of RGS1 in inflammatory progression. The inflammatory factors were measured, and the degree of histology and function protection were determined. The expression levels of RGS1, myeloid differentiation primary response protein 88 (Myd88), (TIR-domain-containing adaptor inducing interferon-β (TRIF), p38, metalloproteinase (MMP)-2, and MMP-9 were determined. RGS1 was robustly increased both in LPS-activated macrophage and SCI mice. The TLR signaling pathway-induced inflammation was suppressed by RGS1 knockdown. shRNA-mediated silence of RGS1 was exhibited a prominent decrease in TNF-α, IL-1β and IL-6 via TLR/TRIF/ nuclear factor kappa-B (NF-κB) axis. Depletion of RGS1 also inhibited MMP-induced tissue degradation via MAPK-p38 pathway in SCI mice. Moreover, suppression of RGS1 improved spinal cord histology and function recovery. These findings suggest that RGS1 regulates inflammation and tissue disruption via TLR/TRIF/NF-κB signaling pathway in mice with SCI, thereby explaining a novel target that regulates macrophage inflammation post SCI.

Short stature and combined immunodeficiency associated with mutations in RGS10

We report the clinical and molecular phenotype of three siblings from one family, who presented with short stature and immunodeficiency and carried uncharacterized variants in RGS10 (c.489_491del:p.E163del and c.G511T:p.A171S). This gene encodes regulator of G protein signaling 10 (RGS10), a member of a large family of GTPase-activating proteins (GAPs) that targets heterotrimeric G proteins to constrain the activity of G protein-coupled receptors, including receptors for chemoattractants. The affected individuals exhibited systemic abnormalities directly related to the RGS10 mutations, including recurrent infections, hypergammaglobulinemia, profoundly reduced lymphocyte chemotaxis, abnormal lymph node architecture, and short stature due to growth hormone deficiency. Although the GAP activity of each RGS10 variant was intact, each protein exhibited aberrant patterns of PKA-mediated phosphorylation and increased cytosolic and cell membrane localization and activity compared to the wild-type protein. We propose that the RGS10 p.E163del and p.A171S mutations lead to mislocalization of the RGS10 protein in the cytosol, thereby resulting in attenuated chemokine signaling. This study suggests that RGS10 is critical for both immune competence and normal hormonal metabolism in humans and that rare RGS10 variants may contribute to distinct systemic genetic disorders.

RGS12 Is a Novel Critical NF-κB Activator in Inflammatory Arthritis

Rheumatoid arthritis (RA) is the most common inflammatory disease, which currently lacks effective treatment. Here, we discovered that the Regulator of G Protein Signaling 12 (RGS12) plays a key role in regulating inflammation. Transcriptional and protein analysis revealed that RGS12 was upregulated in human and mouse RA macrophages. Deletion of RGS12 in myeloid lineage or globally inhibits the development of collagen-induced arthritis including joint swelling and bone destruction. Mechanistically, RGS12 associates with NF-κB(p65) to activate its phosphorylation and nuclear translocation through PTB domain, and NF-κB(p65) regulates RGS12 expression in a transcriptional manner. The nuclear translocation ability of NF-κB(p65) and RGS12 can both be enhanced by cyclooxygenase-2 (COX2). Furthermore, ablation of RGS12 via RNA interference significantly blocks the inflammatory process in vivo and in vitro. These results demonstrate that RGS12 plays a critical role in the pathogenesis of inflammatory arthritis.

RGS4 promotes allergen- and aspirin-associated airway hyperresponsiveness by inhibiting PGE2 biosynthesis

BACKGROUND

Allergens elicit host production of mediators acting on G-protein-coupled receptors to regulate airway tone. Among these is prostaglandin E2 (PGE2), which, in addition to its role as a bronchodilator, has anti-inflammatory actions. Some patients with asthma develop bronchospasm after the ingestion of aspirin and other nonsteroidal anti-inflammatory drugs, a disorder termed aspirin-exacerbated respiratory disease. This condition may result in part from abnormal dependence on the bronchoprotective actions of PGE2.

OBJECTIVE

We sought to understand the functions of regulator of G protein signaling 4 (RGS4), a cytoplasmic protein expressed in airway smooth muscle and bronchial epithelium that regulates the activity of G-protein-coupled receptors, in asthma.

METHODS

We examined RGS4 expression in human lung biopsies by immunohistochemistry. We assessed airways hyperresponsiveness (AHR) and lung inflammation in germline and airway smooth muscle-specific Rgs4^-/- mice and in mice treated with an RGS4 antagonist after challenge with Aspergillus fumigatus. We examined the role of RGS4 in nonsteroidal anti-inflammatory drug-associated bronchoconstriction by challenging aspirin-exacerbated respiratory disease-like (ptges1^-/-) mice with aspirin.

RESULTS

RGS4 expression in respiratory epithelium is increased in subjects with severe asthma. Allergen-induced AHR was unexpectedly diminished in Rgs4^-/- mice, a finding associated with increased airway PGE2 levels. RGS4 modulated allergen-induced PGE2 secretion in human bronchial epithelial cells and prostanoid-dependent bronchodilation. The RGS4 antagonist CCG203769 attenuated AHR induced by allergen or aspirin challenge of wild-type or ptges1^-/- mice, respectively, in association with increased airway PGE2 levels.

CONCLUSIONS

RGS4 may contribute to the development of AHR by reducing airway PGE2 biosynthesis in allergen- and aspirin-induced asthma.

Melatonin up-regulates bone marrow mesenchymal stem cells osteogenic action but suppresses their mediated osteoclastogenesis via MT2 -inactivated NF-κB pathway

BACKGROUND AND PURPOSE

Melatonin is a neurohormone involved in bone homeostasis. Melatonin directs bone remodelling and the role of bone marrow mesenchymal stem cells (BMMSCs) in the regulating melatonin-mediated bone formation-resorption balance remains undefined.

EXPERIMENTAL APPROACH

Osteoporosis models were established and bone tissue and serum were collected to test the effects of melatonin on bone homeostasis. Melatonin receptors were knocked down, the NF-κB signalling pathway and receptor activator of NF-κB ligand (RANKL) expression were investigated. Communication between bone marrow mesenchymal stem cells and osteoclasts was detected with direct-contact or indirect-contact system.

KEY RESULTS

Bone loss and microstructure disorder in mice were reversed after melatonin treatment, as a result of anabolic and anti-resorptive effects. In vitro, a physiological (low) concentration of melatonin promoted the bone marrow mesenchymal stem cells, osteogenic lineage commitment and extracellular mineralization but had no impact on extracellular matrix synthesis. After MT knockdown, especially MT₂ , the positive effects of melatonin on osteogenesis were attenuated. The canonical NF-κB signalling pathway was the first discovered downstream signalling pathway after MT receptor activation and was found to be down-regulated by melatonin during osteogenesis. Melatonin suppressed BMMSC-mediated osteoclastogenesis by inhibiting RANKL production in BMMSCs and this effect only occurred when BMMSCs and osteoclast precursors were co-cultured in an indirect-contact manner.

CONCLUSION AND IMPLICATIONS

Our work suggests that melatonin plays a crucial role in bone balance, significantly accelerates the osteogenic differentiation of bone marrow mesenchymal stem cells by suppressing the MT₂ -dependent NF-κB signalling pathway, and down-regulates osteoclastogenesis via RANKL paracrine secretion.

Structural organization of a major neuronal G protein regulator, the RGS7-Gβ5-R7BP complex

Signaling by the G-protein-coupled receptors (GPCRs) plays fundamental role in a vast number of essential physiological functions. Precise control of GPCR signaling requires action of regulators of G protein signaling (RGS) proteins that deactivate heterotrimeric G proteins. RGS proteins are elaborately regulated and comprise multiple domains and subunits, yet structural organization of these assemblies is poorly understood. Here, we report a crystal structure and dynamics analyses of the multisubunit complex of RGS7, a major regulator of neuronal signaling with key roles in controlling a number of drug target GPCRs and links to neuropsychiatric disease, metabolism, and cancer. The crystal structure in combination with molecular dynamics and mass spectrometry analyses reveals unique organizational features of the complex and long-range conformational changes imposed by its constituent subunits during allosteric modulation. Notably, several intermolecular interfaces in the complex work in synergy to provide coordinated modulation of this key GPCR regulator.

Genetics of resistance to photobacteriosis in gilthead sea bream (Sparus aurata) using 2b-RAD sequencing

Background

Photobacteriosis is an infectious disease developed by a Gram-negative bacterium Photobacterium damselae subsp. piscicida (Phdp), which may cause high mortalities (90–100%) in sea bream. Selection and breeding for resistance against infectious diseases is a highly valuable tool to help prevent or diminish disease outbreaks, and currently available advanced selection methods with the application of genomic information could improve the response to selection. An experimental group of sea bream juveniles was derived from a Ferme Marine de Douhet (FMD, Oléron Island, France) selected line using ~ 109 parents (~ 25 females and 84 males). This group of 1187 individuals represented 177 full-sib families with 1–49 sibs per family, which were challenged with virulent Phdp for a duration of 18 days, and mortalities were recorded within this duration. Tissue samples were collected from the parents and the recorded offspring for DNA extraction, library preparation using 2b-RAD and genotyping by sequencing. Genotypic data was used to develop a linkage map, genome wide association analysis and for the estimation of breeding values.

Results

The analysis of genetic variation for resistance against Phdp revealed moderate genomic heritability with estimates of ~ 0.32. A genome-wide association analysis revealed a quantitative trait locus (QTL) including 11 SNPs at linkage group 17 presenting significant association to the trait with p-value crossing genome-wide Bonferroni corrected threshold P ≤ 2.22e-06. The proportion total genetic variance explained by the single top most significant SNP was ranging from 13.28–16.14% depending on the method used to compute the variance. The accuracies of predicting breeding values obtained using genomic vs. pedigree information displayed 19–24% increase when using genomic information.

Conclusion

The current study demonstrates that SNPs-based genotyping of a sea bream population with 2b-RAD approach is effective at capturing the genetic variation for resistance against Phdp. Prediction accuracies obtained using genomic information were significantly higher than the accuracies obtained using pedigree information which highlights the importance and potential of genomic selection in commercial breeding programs.

Electronic supplementary material

The online version of this article (10.1186/s12863-018-0631-x) contains supplementary material, which is available to authorized users.

Regulator of G protein signaling 5 restricts neutrophil chemotaxis and trafficking

Neutrophils are white blood cells that are mobilized to damaged tissues and to sites of pathogen invasion, providing the first line of host defense. Chemokines displayed on the surface of blood vessels promote migration of neutrophils to these sites, and tissue- and pathogen-derived chemoattractant signals, including N-formylmethionylleucylphenylalanine (fMLP), elicit further migration to sites of infection. Although nearly all chemoattractant receptors use heterotrimeric G proteins to transmit signals, many of the mechanisms lying downstream of chemoattractant receptors that either promote or limit neutrophil motility are incompletely defined. Here, we show that regulator of G protein signaling 5 (RGS5), a protein that modulates G protein activity, is expressed in both human and murine neutrophils. We detected significantly more neutrophils in the airways of Rgs5^-/- mice than WT counterparts following acute respiratory virus infection and in the peritoneum in response to injection of thioglycollate, a biochemical proinflammatory stimulus. RGS5-deficient neutrophils responded with increased chemotaxis elicited by the chemokines CXC motif chemokine ligand 1 (CXCL1), CXCL2, and CXCL12 but not fMLP. Moreover, adhesion of these cells was increased in the presence of both CXCL2 and fMLP. In summary, our results indicate that RGS5 deficiency increases chemotaxis and adhesion, leading to more efficient neutrophil mobilization to inflamed tissues in mice. These findings suggest that RGS5 expression and activity in neutrophils determine their migrational patterns in the complex microenvironments characteristic of inflamed tissues.