The E3 ubiquitin ligase neuregulin receptor degradation protein 1 (Nrdp1) promotes M2 macrophage polarization by ubiquitinating and activating transcription factor CCAAT/enhancer-binding Protein β (C/EBPβ)

Somatic USP8 alteration affects the immune landscape of corticotroph pituitary adenomas- a pilot study

INTRODUCTION

Somatic mutations in ubiquitin-specific protease-8 (USP8), encoding a deubiquinating protein, are found in approximately 30% of corticotroph-derived pituitary adenomas (CPAs). Stratifin, a protein encoded by SFN, inhibits USP8 catalytic activity. USP8 has immunomodulating properties that have been demonstrated in non-tumoral diseases.

METHODS

We assessed the influence of USP8 on the immune landscape of CPA and validated this effect and its dependency on stratifin in large cohorts of non-pituitary tumors. We analyzed data of CPA samples (n = 20) and additional non-pituitary tumors from the TCGA database, using transcriptome signature-recognition algorithms. Immune tumor microenvironment (iTME) was compared both by USP8 and SFN expression levels (n = 843) and by USP8 mutation status and SFN expression (n = 12,389).

RESULTS

CPA with activating USP8 mutations was associated with "cold" iTME compared with wild-type USP8 CPA, as reflected by lower fractions of immune cells, including B cells, CD4, regulatory and gamma/delta T cells, natural killer cells, M0 and M1 macrophages, dendritic cells, and eosinophils (p < 0.05 for all comparisons). Pathways altered by the presence of USP8 mutation, based on the most differentially expressed genes (3061 genes), included microglia pathogen phagocytosis and multiple toll-like receptor signaling pathways (p < 0.0001). In a validation analysis based on large cohorts of non-pituitary tumors, high expression of USP8 was associated with a suppressed iTME effect that was augmented by a low SFN expression.

CONCLUSIONS

Our data demonstrate for the first time, to our knowledge, a distinct immune landscape of tumors based on USP8 status and expression and the dependency of this immunological effect on SFN expression.

RNF41 orchestrates macrophage-driven fibrosis resolution and hepatic regeneration

Hepatic inflammation is a common trigger of chronic liver disease. Macrophage activation is a predictive parameter for survival in patients with cirrhosis. Ring finger protein 41 (RNF41) negatively regulates proinflammatory cytokines and receptors; however, the precise involvement of macrophage RNF41 in liver cirrhosis remains unknown. Here, we sought to understand how RNF41 dictates macrophage fate in hepatic fibrosis and repair within the inflammatory milieu. We found that RNF41 expression is down-regulated in CD11b+ macrophages recruited to mouse fibrotic liver and to patient cirrhotic liver regardless of cirrhosis etiology. Prolonged inflammation with TNF-α progressively reduced macrophage RNF41 expression. We designed a macrophage-selective gene therapy with dendrimer-graphite nanoparticles (DGNPs) to explore the influence of macrophage RNF41 restoration and depletion in liver fibrosis and regeneration. RNF41 expression induced in CD11b+ macrophages by DGNP-conjugated plasmids ameliorated liver fibrosis, reduced liver injury, and stimulated hepatic regeneration in fibrotic mice with or without hepatectomy. This therapeutic effect was mainly mediated by the induction of insulin-like growth factor 1. Conversely, depletion of macrophage RNF41 worsened inflammation, fibrosis, hepatic damage, and survival. Our data reveal implications of macrophage RNF41 in the control of hepatic inflammation, fibrosis, and regeneration and provide a rationale for therapeutic strategies in chronic liver disease and potentially other diseases characterized by inflammation and fibrosis.

Crocin's effect on phenotype switching of J774A.1 macrophages depends on their polarization state during exposure

Objectives

Macrophages exhibit versatile phenotypes, with M1 macrophages releasing inflammatory cytokines and possessing microbicidal activities, while M2 macrophages release anti-inflammatory cytokines and contribute to tissue repair. The M1/M2 imbalance plays a significant role in various pathological processes. Crocin, known for its antioxidant properties and ability to eliminate free radicals, has been investigated for its potential anti-inflammatory effects. We examined the effect of the primary activation state of macrophages on their phenotype switching when exposed to crocin.

Materials and Methods

The crocin impact on macrophage viability was evaluated by MTT. TNF-α, IL-6, and IL-10 secretion, as well as Nos2/Arg1 ratio, were measured in cells treated with crocin or LPS+IFN-γ (M1 inducers), in cells concurrently treated with crocin and LPS+IFN-γ or in cells pretreated with crocin before M1 induction.

Results

Crocin did not show any toxicity at the concentration of 500 µM or lower. When uncommitted macrophages were exposed to crocin (25-100 µM), it elevated certain M1 activity indicators, including Nos2/Arg1 ratio and TNF-α secretion, but not IL-6. Crocin in concurrent treatment with LPS+IFN-γ prevented the increase in M1 indicators, Nos2/Arg1 ratio, and TNF-α secretion. However, pretreatment of cells with crocin before the addition of LPS+IFN-γ did not reverse M1 induction in macrophages; instead, it further increased the Nos2/Arg1 ratio and TNF-α secretion. IL-10 was not detectable in any of the experimental groups.

Conclusion

It appears that the modulatory effects of crocin on macrophage M1/M2 phenotype switching partly depend on the presence or absence of inflammatory mediators and, accordingly, the initial state of macrophage commitment.

Mild Hypothermia Protects Brain Injury After Intracerebral Hemorrhage in Mice Via Enhancing the Nrdp1/MyD88 Signaling Pathway

BACKGROUND

Mild hypothermia has been identified to reduce brain injury following intracerebral hemorrhage (ICH) by protecting neuron cells through several pathways. However, the role of hypothermia in brain function following ICH and the related mechanisms have not been well identified. Ubiquitination-mediated inflammation plays important roles in the pathogenesis of immune diseases. The experiment analyzed anti-inflammatory effects of mild hypothermia following ICH.

METHODS

The model of ICH was induced by injecting autologous blood. Neuregulin receptor degradation protein-1 (Nrdp1) and downstream molecule were analyzed. In addition, brain inflammatory response, brain edema, and neurological functions of ICH mice were also assessed.

RESULTS

We found that mild hypothermia attenuated proinflammatory factors production after ICH. Mild hypothermia significantly inhibited BBB injury, water content, and neurological damage following ICH in vivo. Moreover, mild hypothermia also increased Nrdp1/MyD88 levels and thus affect neuronal apoptosis and inflammation.

CONCLUSIONS

Taken together, these results suggest that mild hypothermia can attenuate the neuroinflammatory response and neuronal apoptosis after ICH through the regulation of the Nrdp1 levels.

Regulation of Glucose, Fatty Acid and Amino Acid Metabolism by Ubiquitination and SUMOylation for Cancer Progression

Ubiquitination and SUMOylation, which are posttranslational modifications, play prominent roles in regulating both protein expression and function in cells, as well as various cellular signal transduction pathways. Metabolic reprogramming often occurs in various diseases, especially cancer, which has become a new entry point for understanding cancer mechanisms and developing treatment methods. Ubiquitination or SUMOylation of protein substrates determines the fate of modified proteins. Through accurate and timely degradation and stabilization of the substrate, ubiquitination and SUMOylation widely control various crucial pathways and different proteins involved in cancer metabolic reprogramming. An understanding of the regulatory mechanisms of ubiquitination and SUMOylation of cell proteins may help us elucidate the molecular mechanism underlying cancer development and provide an important theory for new treatments. In this review, we summarize the processes of ubiquitination and SUMOylation and discuss how ubiquitination and SUMOylation affect cancer metabolism by regulating the key enzymes in the metabolic pathway, including glucose, lipid and amino acid metabolism, to finally reshape cancer metabolism.

Targeting ubiquitin signaling for cancer immunotherapy

Cancer immunotherapy has become an attractive approach of cancer treatment with tremendous success in treating various advanced malignancies. The development and clinical application of immune checkpoint inhibitors represent one of the most extraordinary accomplishments in cancer immunotherapy. In addition, considerable progress is being made in understanding the mechanism of antitumor immunity and characterizing novel targets for developing additional therapeutic approaches. One active area of investigation is protein ubiquitination, a post-translational mechanism of protein modification that regulates the function of diverse immune cells in antitumor immunity. Accumulating studies suggest that E3 ubiquitin ligases and deubiquitinases form a family of potential targets to be exploited for enhancing antitumor immunity in cancer immunotherapy.

E3 ligase FBXW7 restricts M2-like tumor-associated macrophage polarization by targeting c-Myc

FBXW7 functions as an E3 ubiquitin ligase to mediate oncoprotein degradation via the ubiquitin-proteasome system in cancer cells, effectively inhibiting the growth and survival of tumor cells. However, little is known about the functions of FBXW7 in macrophages and the tumor immune microenvironment. In this study, we find that FBXW7 suppresses M2-like tumor-associated macrophage (TAM) polarization to limit tumor progression. We identified a significant increase in the proportion of M2-like TAMs and aggravated tumor growth in mice with myeloid FBXW7 deficiency by subcutaneous inoculation with Lewis lung carcinoma cells (LLCs). When stimulated with LLCs supernatant in vitro, FBXW7-knockout macrophages displayed increased M2 macrophage polarization and enhanced ability of supporting cancer cells growth. In mechanism, we confirmed that FBXW7 inhibited M2-like TAM polarization by mediating c-Myc degradation via the ubiquitin-proteasome system. These findings highlight the role of FBXW7 in M2-like TAM polarization and provide new insights into the potential targets for cancer immunotherapies.

Understanding the complexities of SARS-CoV2 infection and its immunology: A road to immune-based therapeutics

Emerging infectious diseases always pose a threat to humans along with plant and animal life. SARS-CoV2 is the recently emerged viral infection that originated from Wuhan city of the Republic of China in December 2019. Now, it has become a pandemic. Currently, SARS-CoV2 has infected more than 27.74 million people worldwide, and taken 901,928 human lives. It was named first 'WH 1 Human CoV' and later changed to 2019 novel CoV (2019-nCoV). Scientists have established it as a zoonotic viral disease emerged from Chinese horseshoe bats, which do not develop a severe infection. For example, Rhinolophus Chinese horseshoe bats harboring severe acute respiratory syndrome-related coronavirus (SARSr-CoV) or SARSr-Rh-BatCoV appear healthy and clear the virus within 2-4 months period. The article introduces first the concept of EIDs and some past EIDs, which have affected human life. Next section discusses mysteries regarding SARS-CoV2 origin, its evolution, and human transfer. Third section describes COVID-19 clinical symptoms and factors affecting susceptibility or resistance. The fourth section introduces the SARS-CoV2 entry in the host cell, its replication, and the establishment of productive infection. Section five describes the host's immune response associated with asymptomatic, symptomatic, mild to moderate, and severe COVID-19. The subsequent seventh and eighth sections mention the immune status in COVID-19 convalescent patients and re-emergence of COVID-19 in them. Thereafter, the eighth section describes viral strategies to hijack the host antiviral immune response and generate the "cytokine storm". The ninth section describes about transgenic humane ACE2 (hACE2) receptor expressing mice to study immunity, drugs, and vaccines. The article ends with the development of different immunomodulatory and immunotherapeutics strategies, including vaccines waiting for their approval in humans as prophylaxis or treatment measures.

MiRNA-494 enhances M1 macrophage polarization via Nrdp1 in ICH mice model

Background

Ubiquitination-mediated M1/M2 macrophage polarization plays important roles in the pathogenesis of immune disease. However, the regulatory mechanism of ubiquitination during M1/M2 macrophage polarization following intracerebral hemorrhage (ICH) has not been well studied.

Methods

In the experiment, macrophages were administered with erythrocyte lysates, and then miR-494-, Nrdp1-, and M1/M2-related markers were analyzed. Brain inflammatory response, brain edema, and neurological functions of ICH mice were also assessed.

Results

We found that miR-494 levels increased while Nrdp1 levels decreased in macrophages after ICH. We also demonstrated that miR-494 inhibited Nrdp1 expression by directly binding its 3′-untranslated region. MiR-494 attenuated C/EBP-β activation and downstream proinflammatory factor production. Upregulation of Nrdp1 in macrophages significantly promoted M2 macrophage polarization via ubiquitinating and activating C/EBP-β. Moreover, the results indicated that miR-494 could enhance M1 macrophage polarization, promote brain edema, and impair neurological functions in ICH mice.

Conclusions

Taken together, our results demonstrated that Nrdp1 contributed to M1/M2 macrophage polarization and neuroinflammation via ubiquitination and activation of C/EBP-β in ICH. miR-494 may provide a promising therapeutic clue for ICH.

Targeting Degradation of the Transcription Factor C/EBPβ Reduces Lung Fibrosis by Restoring Activity of the Ubiquitin-Editing Enzyme A20 in Macrophages

Although recent progress provides mechanistic insights into the pathogenesis of pulmonary fibrosis (PF), rare anti-PF therapeutics show definitive promise for treating this disease. Repeated lung epithelial injury results in injury-repairing response and inflammation, which drive the development of PF. Here, we report that chronic lung injury inactivated the ubiquitin-editing enzyme A20, causing progressive accumulation of the transcription factor C/EBPβ in alveolar macrophages (AMs) from PF patients and mice, which upregulated a number of immunosuppressive and profibrotic factors promoting PF development. In response to chronic lung injury, elevated glycogen synthase kinase-3β (GSK-3β) interacted with and phosphorylated A20 to suppress C/EBPβ degradation. Ectopic expression of A20 or pharmacological restoration of A20 activity by disturbing the A20-GSK-3β interaction accelerated C/EBPβ degradation and showed potent therapeutic efficacy against experimental PF. Our study indicates that a regulatory mechanism of the GSK-3β-A20-C/EBPβ axis in AMs may be a potential target for treating PF and fibroproliferative lung diseases.

H4 Receptor Inhibits Lipopolysaccharide-induced NF-κB Activation by Interacting with Tumor Necrosis Factor Receptor-Associated Factor 6

Microglia, the resident immune cells of the central nervous system (CNS), are activated at the beginning of the inflammatory response and induce detrimental neuroinflammation by producing excessive pro-inflammatory cytokines. Nuclear factor kappa B (NF-κB) signaling facilitates the onset of microglia activation. However, the molecular mechanisms underlying the negative regulation of NF-κB remain to be fully elucidated. In the present study, our results indicated that H4R expression increased in a rat model of lipopolysaccharide (LPS)-induced CNS inflammation. Knockdown of H4R in microglia HAPI cells enhanced the production of cytokines following LPS stimulation. Co-immunoprecipitation experiments further revealed an interaction between H4R and tumor necrosis factor receptor-associated factor 6 (TRAF6) in microglia, which was verified both in vivo and in vitro. Our experimental results support our hypothesis that H4R interacts with TRAF6 to inhibit the release of inflammatory cytokines in LPS-induced microglia cells by decreasing TRAF6-mediated ubiquitination of K63. These findings provide theoretical and experimental evidence regarding the role of H4R in the microglia inflammatory response, which may aid in the development of novel treatments for inflammation.

High-Confidence Interactome for RNF41 Built on Multiple Orthogonal Assays

Ring finger protein 41 (RNF41) is an E3 ubiquitin ligase involved in the ubiquitination and degradation of many proteins including ErbB3 receptors, BIRC6, and parkin. Next to this, RNF41 regulates the intracellular trafficking of certain JAK2-associated cytokine receptors by ubiquitinating and suppressing USP8, which, in turn, destabilizes the ESCRT-0 complex. To further elucidate the function of RNF41 we used different orthogonal approaches to reveal the RNF41 protein complex: affinity purification-mass spectrometry, BioID, and Virotrap. We combined these results with known data sets for RNF41 obtained with microarray MAPPIT and Y2H screens. This way, we establish a comprehensive high-resolution interactome network comprising 175 candidate protein partners. To remove potential methodological artifacts from this network, we distilled the data into a high-confidence interactome map by retaining a total of 19 protein hits identified in two or more of the orthogonal methods. AP2S1, a novel RNF41 interaction partner, was selected from this high-confidence interactome for further functional validation. We reveal a role for AP2S1 in leptin and LIF receptor signaling and show that RNF41 stabilizes and relocates AP2S1.

Chi3l3: a potential key orchestrator of eosinophil recruitment in meningitis induced by Angiostrongylus cantonensis

BACKGROUND

Angiostrongylus cantonensis, an important foodborne parasite, can induce serious eosinophilic meningitis in non-permissive hosts, such as mouse and human. However, the characteristics and mechanisms of the infection are still poorly understood. This study sought to determine the key molecules and its underlying mechanism in inducing brain eosinophilic infiltration caused by Angiostrongylus cantonensis.

METHODS

Mathematical models were established for prediction of significantly changing genes and the functional associated protein with RNA-seq data in Angiostrongylus cantonensis infection. The expression level of Chi3l3, the predicted key molecule, was verified using Western blotting and real-time quantitative PCR. Critical cell source of Chi3l3 and its relationship with eosinophils were identified with flow cytometry, immunohistochemistry, and further verified by macrophage depletion using liposomal clodronate. The role of soluble antigens of Angiostrongylus cantonensis in eosinophilic response was identified with mice airway allergy model by intranasal administration of Alternaria alternate. The relationship between Chi3l3 and IL-13 was identified with flow cytometry, Western blotting, and Seahorse Bioscience extracellular flux analyzer.

RESULTS

We analyzed the skewed cytokine pattern in brains of Angiostrongylus cantonensis-infected mice and found Chi3l3 to be an important molecule, which increased sharply during the infection. The percentage of inflammatory macrophages, the main source of Chi3l3, also increased, in line with eosinophils percentage in the brain. Network analysis and mathematical modeling predirect a functional association between Chi3l3 and IL-13. Further experiments verified that the soluble antigen of Angiostrongylus cantonensis induce brain eosinophilic meningitis via aggravating a positive feedback loop between IL-13 and Chi3l3.

CONCLUSIONS

We present evidences in favor of a key role for macrophave-derived Chi3l3 molecule in the infection of Angiostrongylus cantonensis, which aggravates eosinophilic meningitis induced by Angiostrongylus cantonensis via a IL-13-mediated positive feedback loop. These reported results constitute a starting point for future research of angiostrongyliasis pathogenesis and imply that targeting chitinases and chitinase-like-proteins may be clinically beneficial in Angiostrongylus cantonensis-induced eosinophilic meningitis.

M2 Macrophage Transplantation Ameliorates Cognitive Dysfunction in Amyloid-β-Treated Rats Through Regulation of Microglial Polarization

Alzheimer's disease (AD) is the most common neurodegenerative disorder in the elderly population. Neuroinflammation induced by amyloid-β (Aβ) aggregation is considered to be the critical factor underlying AD pathological mechanisms. Alternatively activated (M2) macrophages/microglia have been reported to have neuroprotective effects in neurodegenerative disease. In this study, we characterized the neuroprotective effects of M2 macrophage transplantation in AD model rats and investigated the underlying mechanisms. Intracerebroventricular injection of Aβ1 - 42 to rats was used to model AD and resulted in cognitive impairment, neuronal damage, and inflammatory changes in the brain microenvironment. We observed an increased interferon regulatory factor (IRF) 5/IRF4 ratio, resulting in greater production of classically activated (M1) versus M2 microglia. M2 macrophage transplantation attenuated inflammation in the brain, reversed Aβ1 - 42-induced changes in the IRF4-IRF5 ratio, drove endogenous microglial polarization toward the M2 phenotype, and ameliorated cognitive impairment. Nerve growth factor (NGF) treatment reduced the IRF5/IRF4 ratio and induced primary microglial polarization to the M2 phenotype in vitro; these effects were prevented by tyrosine Kinase Receptor A (TrkA) inhibition. M2 macrophage transplantation restored the balance of IRF4-IRF5 by affecting the expression of NGF and inflammatory cytokines in the brains of AD model rats. This drove microglial polarization to the M2 phenotype, promoted termination of neuroinflammation, and resulted in improved cognitive abilities.

CD14/TLR4 priming potentially recalibrates and exerts anti-tumor efficacy in tumor associated macrophages in a mouse model of pancreatic carcinoma

Pancreatic cancer is the fourth major cause of cancer related deaths in the world and 5 year survival is below 5%. Among various tumor directed therapies, stimulation of Toll-like receptors (TLR) has shown promising effects in various tumor models. However, pancreatic cancer cells frequently express these receptors themselves and their stimulation (TLR 2 and/or 4 particularly) within tumor microenvironment is known to potentially enhance tumor cell proliferation and cancer progression. Consistent stimulation of tumor associated macrophages (TAMs), in particular with tumor derived TLR ligand within the tumor microenvironment promotes cancer related inflammation, which is sterile, non-immunogenic and carcinogenic in nature. In view of this, recalibrating of TAM has the potential to induce immunogenic inflammation. Consistent with this, we provide experimental evidence for the first time in this study that priming of TAMs with TLR4 ligend (LPS) alone or in combination with IFN-γ not only recalibrates pancreatic tumor cells induced M2 polarization, but also confers anti-tumor potential in TAMs. Most interestingly, reduced tumor growth in macrophage depleted animals suggests that macrophage directed approaches are important for the management of pancreatic tumors.

Transcriptional Effects of E3 Ligase Nrdp1 on Hypertrophy in Neonatal Rat Cardiomyocytes by Microarray and Integrated Gene Network Analysis

Objective: Neuregulin receptor degradation protein-1 (Nrdp1) is a novel E3 ubiquitin ligase, and we have previously shown that overexpression of Nrdp1 increased cardiomyocyte injury. However, the role of Nrdp1 in myocardial hypertrophy is unclear. In the present study, we clarified the molecular mechanisms of angiotensin II (Ang II)-induced cardiomyocyte hypertrophy regulated by Nrdp1 based on genome-wide transcriptional analysis. Methods: Neonatal rat cardiomyocytes were infected with adenoviruses containing green fluorescent protein (Ad-GFP) or wild-type Nrdp1 (Ad-Nrdp1), and then treated with Ang II for 36 h. Detection of differentially expressed genes was achieved with an Affymetrix Rat Gene 2.0 Array and Cluster and Java TreeView software. Results and Conclusion: Microarray data analysis demonstrated that Nrdp1 overexpression affected the expression of 12,140 mRNA genes in Ang II-induced cardiomyocyte hypertrophy, including the upregulation of 12,044 and the downregulation of 96. Gene ontology and globe signal transduction network analysis showed that Nrdp1 affected the expression of many genes related to stimulus response, the cell receptor pathway, and cell growth. Pathway network analysis identified myocardial metabolism, DNA replication, and the cell cycle as the most important pathways targeted by Nrdp1. lncRNA-mRNA coexpression network analysis showed that two core lncRNAs, NONRATT057160 and NONRATT054243, were involved in cardiomyotrophy regulated by Nrdp1 in cardiomyocytes. Taken together, these data provide compelling clues for further exploration of the function of Nrdp1 in heart disease.

The ER structural protein Rtn4A stabilizes and enhances signaling through the receptor tyrosine kinase ErbB3

ErbB3 and ErbB4 are receptor tyrosine kinases that are activated by the neuregulin (NRG) family of growth factors. These receptors govern various developmental processes, and their dysregulation contributes to several human disease states. The abundance of ErbB3 and ErbB4, and thus signaling through these receptors, is limited by the E3 ubiquitin ligase Nrdp1, which targets ErbB3 and ErbB4 for degradation. Reticulons are proteins that influence the morphology of the endoplasmic reticulum (ER) by promoting the formation of tubules, a response of cells to some stressors. We found that the ER structural protein reticulon 4A (Rtn4A, also known as Nogo-A) increased ErbB3 abundance and proliferative signaling by suppressing Nrdp1 function. Rtn4A interacted with Nrdp1 and stabilized ErbB3 in an Nrdp1-dependent manner. Rtn4A overexpression induced the redistribution of Nrdp1 from a cytosolic or perinuclear localization to ER tubules. Rtn4A knockdown in human breast tumor cells decreased ErbB3 abundance, NRG-stimulated signaling, and cellular proliferation and migration. Because proteins destined for the plasma membrane are primarily synthesized in the sheet portions of the ER, our observations suggest that Rtn4A counteracts the Nrdp1-mediated degradation of ErbB3 by sequestering the ubiquitin ligase into ER tubules. The involvement of a reticulon suggests a molecular link between ER structure and the sensitivity of cells to receptor tyrosine kinase-mediated survival signals at the cell surface.

Toll-Interleukin 1 Receptor domain-containing adaptor protein positively regulates BV2 cell M1 polarization

Microglial activation, including classical (M1) and alternative (M2) activation, plays important roles in the development of several central nervous system disorders and promotes tissue reconstruction. Toll-like receptor (TLR)4 is important for microglial polarization. TIR domain-containing adaptor protein (TIRAP) is an intracellular adaptor protein, which is responsible for the early phase of TLR4 activation. The role of TIRAP in BV2 cell M1 polarization is still unknown. In this study, we showed that TIRAP expression is greatly elevated in lipopolysaccharide (LPS)/interferon (IFN)-γ-treated microglia. TIRAP overexpression promoted BV2 microglial M1 polarization by increasing M1-related marker production (inducible nitric oxide synthase, CD86, interleukin-6, interleukin-1β and tumour necrosis factor-α). In contrast, TIRAP knockdown prevented M1-related marker production. Mechanistically, TIRAP could interact with TNF Receptor-Associated Factor 6 (TRAF6) to increase M1-related marker production in TIRAP overexpressed and LPS/IFN-γ-treated BV2 cells. In addition, silencing of TIRAP effectively inhibited the activation of the Transforming Growth Factor-Beta-Activated Kinase 1/I-Kappa-B Kinase /Nuclear Factor of Kappa Light Polypeptide Gene Enhancer in B-Cells (TAK1/IKK/NF-κB) signalling pathway and the phosphorylation of Akt and mitogen-activated protein kinases, which were activated by LPS/IFN-γ stimulation. Thus, our results suggest that TIRAP positively regulated BV2 microglial M1 polarization through TLR4-mediated TAK1/IKK/NF-κB, mitogen-activated protein kinases and Akt signalling pathways.

Expression profiles and interaction suggest TBK1 can be regulated by Nrdp1 in response to immune stimulation in large yellow croaker Larimichthys crocea

TBK1 has been extensively studied in mammals because of its important roles as a molecular bridge, linking the TLRs (TLR3 and TLR4) and RLRs signals to activate transcriptional factors IRF3 and IRF7 for IFN-I production. However, the information on molecular and functional characteristics of TBK1 in teleosts is limited. In this study, the molecular characterization and immune response of TBK1 in Larimichthys crocea (named as LcTBK1) as well as its interaction with Nrdp1 were investigated. Sequence analysis demonstrated that LcTBK1 included four functional motifs, the N-terminal protein kinase domain and ATP-binding site, middle ULD and C-terminal coiled-coil domain. The tissue expression profiles indicated that LcTBK1 gene was constitutively expressed in the twelve tissues examined, with high expression in brain. Temporal expression analysis showed that LcTBK1 mRNA was obviously increased in the liver after injection of LPS, Poly I:C and inactive Vibrio parahaemolyticus, however, declined at some time points in spleen and head-kidney. Furthermore, we found that LcTBK1 can interact with LcNrdp1, an E3 ubiquitin ligase that involved in immune response to Cryptocaryon irritans infection in L. crocea. The qPCR showed that LcNrdp1 was also significantly up-regulated in liver, down-regualted at some time points in spleen and head-kidney after LPS, Poly I:C and inactive V. parahaemolyticus injection, although the expression patterns of the two genes after the three treatments were different in change magnitude and up-regulation timespan. These results suggested that LcTBK1 was involved in L. crocea defense against the pathogen infection and can be regulated by Nrdp1 in PPRs signaling pathway of fishes.

K33-linked polyubiquitination of Zap70 by Nrdp1 controls CD8(+) T cell activation

The key molecular mechanisms that control signaling via T cell antigen receptors (TCRs) remain to be fully elucidated. Here we found that Nrdp1, a ring finger-type E3 ligase, mediated Lys33 (K33)-linked polyubiquitination of the signaling kinase Zap70 and promoted the dephosphorylation of Zap70 by the acidic phosphatase-like proteins Sts1 and Sts2 and thereby terminated early TCR signaling in CD8(+) T cells. Nrdp1 deficiency significantly promoted the activation of naive CD8(+) T cells but not that of naive CD4(+) T cells after engagement of the TCR. Nrdp1 interacted with Zap70 and with Sts1 and Sts2 and connected K33 linkage of Zap70 to Sts1- and Sts2-mediated dephosphorylation. Our study suggests that Nrdp1 terminates early TCR signaling by inactivating Zap70 and provides new mechanistic insights into the non-proteolytic regulation of TCR signaling by E3 ligases.

Rebamipide suppresses mite-induced asthmatic responses in NC/Nga mice

Allergic asthma caused by continuous allergen exposure evokes allergen-specific Th2 responses and is characterized by chronic airway inflammation and hyperresponsiveness. A previous report showed that rebamipide improved asthmatic symptoms in an ovalbumin/trypsin mice model. However, it is still unclear how rebamipide exerts its effects in asthma. In this study, rebamipide improved the asthmatic responses induced by mite exposure in NC/Nga mice, revealing the mechanism of this therapeutic effect. Rebamipide suppressed the infiltration of eosinophils into the airways and lung as well as attenuating the production of reactive oxygen species in tissues. In addition to these anti-inflammatory effects, rebamipide inhibited the production of IL-33, a member of the IL-1 family that drives the subsequent production of Th2-associated cytokines. These observations identify the point where rebamipide exerts its suppressive action on asthma and suggest that rebamipide has therapeutic potential in preventing mite-induced asthma.

Endogenous prostaglandin E2 potentiates anti-inflammatory phenotype of macrophage through the CREB-C/EBP-β cascade

Macrophages have important functions in tissue homeostasis, but the exact mechanisms regarding wide spectrum of macrophage phenotype remain unresolved. In this study, we report that mouse bone marrow derived naïve macrophages produce prostaglandin E2 (PGE2 ) endogenously, resulting in anti-inflammatory gene expression upon differentiation induced by macrophage colony stimulating factor (M-CSF). Cyclooxygenase (COX) inhibition by indomethacin reduced endogenous PGE2 production of macrophages and subsequently reduced arg1, IL10 and Mrc1, YmI and FizzI gene expressions. Of note, PGE2 phosphorylates CREB via EP2 and EP4 receptor ligation, thereby transcriptionally increasing C/EBP-β expression in BALB/c bone marrow derived macrophages. Activated CREB directly binds to the CREB-responsive element of the C/EBP-β promoter, such that PGE2 ultimately reinforces arg1, IL10 and Mrc1 gene expression. Cyclic AMP activator forskolin also phosphorylated CREB and induced the C/EBP-β cascade, but this was completely blocked by the PKA inhibitor, H89. Consequently, M-CSF grown macrophages inhibited T-cell proliferation but the inhibition ability was reduced when the COX is inhibited by indomethacin or macrophage C/EBP-β expression was decreased by siRNA transduction. Our results collectively describe the molecular basis for homeostatic macrophage differentiation by endogenous PGE2 .

C/EBPβ and C/EBPδ transcription factors: Basic biology and roles in the CNS

CCAAT/enhancer binding protein (C/EBP) β and C/EBPδ are transcription factors of the basic-leucine zipper class which share phylogenetic, structural and functional features. In this review we first describe in depth their basic molecular biology which includes fascinating aspects such as the regulated use of alternative initiation codons in the C/EBPβ mRNA. The physical interactions with multiple transcription factors which greatly opens the number of potentially regulated genes or the presence of at least five different types of post-translational modifications are also remarkable molecular mechanisms that modulate C/EBPβ and C/EBPδ function. In the second part, we review the present knowledge on the localization, expression changes and physiological roles of C/EBPβ and C/EBPδ in neurons, astrocytes and microglia. We conclude that C/EBPβ and C/EBPδ share two unique features related to their role in the CNS: whereas in neurons they participate in memory formation and synaptic plasticity, in glial cells they regulate the pro-inflammatory program. Because of their role in neuroinflammation, C/EBPβ and C/EBPδ in microglia are potential targets for treatment of neurodegenerative disorders. Any strategy to reduce C/EBPβ and C/EBPδ activity in neuroinflammation needs to take into account its potential side-effects in neurons. Therefore, cell-specific treatments will be required for the successful application of this strategy.

Transcription of Nrdp1 by the androgen receptor is regulated by nuclear filamin A in prostate cancer

Prostate cancer (PCa) progression is regulated by the androgen receptor (AR); however, patients undergoing androgen-deprivation therapy (ADT) for disseminated PCa eventually develop castration-resistant PCa (CRPC). Results of previous studies indicated that AR, a transcription factor, occupies distinct genomic loci in CRPC compared with hormone-naïve PCa; however, the cause of this distinction was unknown. The E3 ubiquitin ligase Nrdp1 is a model AR target modulated by androgens in hormone-naïve PCa but not in CRPC. Using Nrdp1, we investigated how AR switches transcription programs during CRPC progression. The proximal Nrdp1 promoter contains an androgen response element (ARE); we demonstrated AR binding to this ARE in androgen-sensitive PCa. Analysis of hormone-naive human prostatectomy specimens revealed correlation between Nrdp1 and AR expression, supporting AR regulation of NRDP1 levels in androgen-sensitive tissue. However, despite sustained AR levels, AR binding to the Nrdp1 promoter and Nrdp1 expression were suppressed in CRPC. Elucidation of the suppression mechanism demonstrated correlation of NRDP1 levels with nuclear localization of the scaffolding protein filamin A (FLNA) which, as we previously showed, is itself repressed following ADT in many CRPC tumors. Restoration of nuclear FLNA in CRPC stimulated AR binding to Nrdp1 ARE, increased its transcription, and augmented NRDP1 protein expression and responsiveness to ADT, indicating that nuclear FLNA controls AR-mediated androgen-sensitive Nrdp1 transcription. Expression of other AR-regulated genes lost in CRPC was also re-established by nuclear FLNA. Thus, our results indicate that nuclear FLNA promotes androgen-dependent AR-regulated transcription in PCa, while loss of nuclear FLNA in CRPC alters the AR-regulated transcription program.

Transcription factors STAT6 and KLF4 implement macrophage polarization via the dual catalytic powers of MCPIP

Macrophage polarization plays a critical role in tissue homeostasis, disease pathogenesis, and inflammation and its resolution. IL-4-induced macrophage polarization involves induction of STAT6 and Krüppel-like factor 4 (KLF4), which induce each other and promote M2 polarization. However, how these transcription factors implement M2 polarization is not understood. We report that in murine macrophages MCP-1-induced protein (MCPIP), induced by KLF4, inhibits M1 polarization by inhibiting NF-κB activation and implements M2 polarization using both its deubiquitinase and RNase activities that cause sequential induction of reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, and autophagy required for M2 polarization. MCPIP also induces C/EBPβ and PPARγ, which promote M2 polarization. Macrophages from mice with myeloid-targeted overexpression of MCPIP show elevated expression of M2 markers and reduced response to LPS, whereas macrophages from mice with myeloid-specific deletion of MCPIP manifest elevated M1 polarization with enhanced phagocytic activity. Thus, both in vivo and in vitro experiments demonstrate that the transcription factors STAT6 and KLF4 implement IL-4-induced M2 polarization via the dual catalytic activities of MCPIP.

Characterization of E3 ubiquitin ligase neuregulin receptor degradation protein-1 (Nrdp1) in the large yellow croaker (Larimichthys crocea) and its immune responses to Cryptocaryon irritans

Neuregulin receptor degradation protein-1 (Nrdp1) was recently identified in humans as an important immune factor responding to the challenge of virus, LPS or cytokine. Its role in fish immune defense and whether it is involved in anti-parasite immunity have not been proven yet. In this report, the full-length cDNA sequence and genomic structure of Nrdp1 in the large yellow croaker Larimichthys crocea (LcNrdp1) were identified and characterized. The full-length cDNA of LcNrdp1 was 1248bp, including a 5' untranslated region (UTR) of 32bp, a 3' UTR of 259bp and an open reading frame (ORF) of 937bp, encoding a polypeptide of 318 amino acid residues. The full-length genomic DNA sequence of LcNrdp1 was composed of 2635 nucleotides, including four exons and three introns. The putative LcNrdp1 protein had no signal peptide sequence and contained a characteristic Nrdp1 consensus motif C3HC3D ring finger and a Coiled-coil domain. Phylogenetic analysis showed that Nrdp1 in fish was closer with that in other vertebrates (79%-90% amino acid identity) than in invertebrates and bacteria (27%-65%). In fishes, Nrdp1 in large yellow croaker was closer with that in Takifugu rubripes. The expression profile showed that LcNrdp1 was constitutively expressed in all tested tissues, especially highly expressed in brain, muscle and kidney. Post-infection (PI) with Cryptocaryon irritans, an increased expression of LcNrdp1 was induced in infection sites (skin and gill), whereas in immune organs, the expression of LcNrdp1 was up-regulated in spleen (except the 1st d and 10th d PI) but suppressed in head kidney. These results suggested that LcNrdp1 might play an important immune role in the finfish L. crocea in the defense against the parasite C. irritans.

Lower expression of Nrdp1 in human glioma contributes tumor progression by reducing apoptosis

Ubiquitin ligase Nrdp1 (neuregulin receptor degradation protein 1) plays important roles in multiple physiological process because it can ubiquitinate various substrates such as ErbB3, BRUCE, MyD88, C/EBPβ, and Parkin, and so forth. In addition to the physiological function, it was also found to be involved in tumor progression. It has been shown that loss of Nrdp1 enhances breast cancer cell growth. Up to now, the role of Nrdp1 in glioma has not been elucidated. Here, we reported that Nrdp1 as well as cleaved caspase 3 was lower expressed in human glioma tissues comparing with the nontumorous. And then we found that the expression of Nrdp1 and cleaved caspase 3 was increased in the treatment of Temozolomide (TMZ), a drug for glioma chemotherapy. Further investigation indicated that transient transfection of Nrdp1 significantly promoted cell apoptosis by aggravating the degradation of BRUCE and activation of caspase 3. In addition, overexpression of Nrdp1 augmented TMZ induced apoptosis by evaluating the degradation of BRUCE and the activation of caspase 3, while silencing of Nrdp1 reduced the sensitivity to the TMZ by inhibiting the degradation of BRUCE and the activation of caspase 3 in human glioma cells. These observations show that Nrdp1 is a pro-apoptotic protein in human glioma and lower expression of Nrdp1 in human glioma may promote tumor progression by reducing apoptosis, suggesting that Nrdp1 may be an important regulator in the development of human glioma.

Inflammatory response of macrophages in infection

BACKGROUND

Macrophages are widely-distributed innate immune cells playing diverse roles in various physiological and pathological processes. The primary function of macrophages is to phagocytize and clear invading pathogens.

DATA SOURCES

A systematic search of PubMed was performed to identify relevant studies in English language literature using the key words such as macrophage and inflammation. A total of 122 articles related to inflammatory response of macrophages in infection were systematically reviewed.

RESULTS

The inflammatory responses of macrophages triggered by infection comprise four interrelated phases: recognition of pathogen-associated molecular patterns by pattern-recognition receptors expressed on/in macrophages; enrichment of quantity of macrophages in local infected tissue by recruitment of circulating monocytes and/or in situ proliferation; macrophage-mediation of microbicidal activity and conversion to anti-inflammatory phenotype to terminate anti-infectious response and to promote tissue repair. Complicated regulation of macrophage activation at molecular level recognized in the past decade is also reviewed, including intracellular multiple signaling molecules, membrane molecules, microRNAs and even epigenetic-associated molecules.

CONCLUSION

The inflammatory response of macrophages in infection is an orderly and complicated process under elaborate regulation at molecular level.

Oligomerization of the Nrdp1 E3 ubiquitin ligase is necessary for efficient autoubiquitination but not ErbB3 ubiquitination

Overexpression of the ErbB3 receptor tyrosine kinase protein in breast and other cancers contributes to tumor malignancy and therapeutic resistance. The RBCC/TRIM family RING finger E3 ubiquitin ligase Nrdp1 mediates the ubiquitination of ErbB3 in normal mammary epithelial cells to facilitate receptor degradation and suppress steady-state receptor levels. Post-transcriptional loss of Nrdp1 in patient breast tumors allows ErbB3 overexpression and receptor contribution to tumor progression, and elevated lability through autoubiquitination contributes to the observed loss of Nrdp1 in tumors relative to normal tissue. To begin to understand the mechanisms underlying Nrdp1 protein self-regulation through lability, we investigated the structural determinants required for efficient autoubiquitination and ErbB3 ubiquitination. Using mutagenesis, chemical cross-linking, size exclusion chromatography, and native polyacrylamide gel electrophoresis, we demonstrate that Nrdp1 self-associates into a stable oligomeric complex in cells. Deletion of its coiled-coil domain abrogates oligomerization but does not affect Nrdp1-mediated ErbB3 ubiquitination or degradation. On the other hand, the presence of the coiled-coil domain is necessary for efficient Nrdp1 autoubiquitination via a trans mechanism, indicating that Nrdp1 ubiquitination of its various targets is functionally separable. Finally, a GFP fusion of the coiled-coil domain stabilizes Nrdp1 and potentiates ErbB3 ubiquitination and degradation. These observations point to a model whereby the coiled-coil domain plays a key role in regulating Nrdp1 lability by promoting its assembly into an oligomeric complex, and raise the possibility that inhibition of ligase oligomerization via its coiled-coil domain could be of therapeutic benefit to breast cancer patients by restoring Nrdp1 protein.