Pellino proteins: novel players in TLR and IL-1R signalling

Post-translational control of NLRP3 inflammasome signaling

Inflammasomes serve as critical sensors for disruptions to cellular homeostasis, with inflammasome assembly leading to inflammatory caspase activation, gasdermin cleavage, and cytokine release. While the canonical pathways leading to priming, assembly, and pyroptosis are well characterized, recent work has begun to focus on the role of post-translational modifications (PTMs) in regulating inflammasome activity. A diverse array of PTMs, including phosphorylation, ubiquitination, SUMOylation, acetylation, and glycosylation, exert both activating and inhibitory influences on members of the inflammasome cascade through effects on protein-protein interactions, stability, and localization. Dysregulation of inflammasome activation is associated with a number of inflammatory diseases, and evidence is emerging that aberrant modification of inflammasome components contributes to this dysregulation. This review provides insight into PTMs within the NLRP3 inflammasome pathway and their functional consequences on the signaling cascade and highlights outstanding questions that remain regarding the complex web of signals at play.

Novel approaches to determine the functional role of cardiomyocyte specific E3 ligase, Pellino-1 following myocardial infarction

OBJECTIVES

Ubiquitination plays a vital role in controlling vascular inflammation, cellular protein quality control, and minimizing misfolded protein toxicity. Pellino-1 (Peli1), a type of E3 ubiquitin ligase, has emerged as a critical regulator of the innate immune response; however, its role in the repair and regeneration of ischemic myocardium remains to be elucidated.

METHODS

Mice (8-12 weeks old, male and females) were divided into (i) Wild type (ii) cardiomyocyte-specific Peli1 overexpressed (AMPEL1Tg/+), (iii) cardiomyocyte-specific Peli1 knockout (CP1KO) and were subjected to sham and left anterior descending artery ligation. The tissues were collected at various time points after surgery for Western blot, and immunohistochemical analyses. Echocardiography is performed 30 days after myocardial infarction. Cardiomyocytes isolated from wild-type, Peli1 overexpressed and knockout mice were used to study the interaction between cardiomyocytes and endothelial cells in vitro under oxidative stress and cells were used for Western blot, flow cytometric analysis, and scratch assay.

RESULTS

We observed faster wound closure and increased expression of angiogenic factors with MCECs treated with conditioned media obtained from the AMPEL1Tg/+ cardiomyocytes compared to CPIKO and WT cardiomyocytes. Again, AMPEL1Tg/+MI mice showed preserved systolic function and reduced fibrosis compared to the CPIKOMI and WTMI groups. Capillary and arteriolar density were found to be increased in AMPEL1Tg/+MI compared to CP1KOMI. Increased survival and angiogenic factors such as p-Akt, p-MK2, p-IkBα, VEGF, cIAP2, and Bcl2 were observed in AMPEL1Tg/+ compared to CP1KO and WT mice subjected to MI.

CONCLUSION

The present study uncovers the crucial role of cardiac Peli1 as a regulator of the repair and regeneration of ischemic myocardium by using multiple genetically engineered mouse models.

A noncanonical IRAK4-IRAK1 pathway counters DNA damage-induced apoptosis independently of TLR/IL-1R signaling

Interleukin-1 receptor (IL-1R)-associated kinases (IRAKs) are core effectors of Toll-like receptors (TLRs) and IL-1R in innate immunity. Here, we found that IRAK4 and IRAK1 together inhibited DNA damage-induced cell death independently of TLR or IL-1R signaling. In human cancer cells, IRAK4 was activated downstream of ATR kinase in response to double-strand breaks (DSBs) induced by ionizing radiation (IR). Activated IRAK4 then formed a complex with and activated IRAK1. The formation of this complex required the E3 ubiquitin ligase Pellino1, acting structurally but not catalytically, and the activation of IRAK1 occurred independently of extracellular signaling, intracellular TLRs, and the TLR/IL-1R signaling adaptor MyD88. Activated IRAK1 translocated to the nucleus in a Pellino2-dependent manner. In the nucleus, IRAK1 bound to the PIDD1 subunit of the proapoptotic PIDDosome and interfered with platform assembly, thus supporting cell survival. This noncanonical IRAK signaling pathway was also activated in response to other DSB-inducing agents. The loss of IRAK4, of IRAK4 kinase activity, of either Pellino protein, or of the nuclear localization sequence in IRAK1 sensitized p53-mutant zebrafish to radiation. Thus, the findings may lead to strategies for overcoming tumor resistance to conventional cancer treatments.

Role of Pellino-1 in Inflammation and Cardioprotection following Severe Sepsis: A Novel Mechanism in a Murine Severe Sepsis Model †

OBJECTIVES

Intra-abdominal sepsis is commonly diagnosed in the surgical population and remains the second most common cause of sepsis overall. Sepsis-related mortality remains a significant burden in the intensive care unit despite advances in critical care. Nearly a quarter of the deaths in people with heart failure are caused by sepsis. We have observed that overexpression of mammalian Pellino-1 (Peli1), an E3 ubiquitin ligase, causes inhibition of apoptosis, oxidative stress, and preservation of cardiac function in a myocardial infarction model. Given these manifold applications, we investigated the role of Peli1 in sepsis using transgenic and knockout mouse models specific to this protein. Therefore, we aimed to explore further the myocardial dysfunction seen in sepsis through its relation to the Peli 1 protein by using the loss of function and gain-of-function strategy.

METHODS

A series of genetic animals were created to understand the role of Peli1 in sepsis and the preservation of heart function. Wild-type, global Peli1 knock out (Peli1-/-), cardiomyocyte-specific Peli1 deletion (CP1KO), and cardiomyocyte-specific Peli1 overexpressing (alpha MHC (αMHC) Peli1; AMPEL1Tg/+) animals were divided into sham and cecal ligation and puncture (CLP) surgical procedure groups. Cardiac function was determined by two-dimensional echocardiography pre-surgery and at 6- and 24-h post-surgery. Serum IL-6 and TNF-alpha levels (ELISA) (6 h), cardiac apoptosis (TUNEL assay), and Bax expression (24 h) post-surgery were measured. Results are expressed as mean ± S.E.M.

RESULTS

AMPEL1Tg/+ prevents sepsis-induced cardiac dysfunction assessed by echocardiographic analysis, whereas global and cardiomyocyte-specific deletion of Peli1 shows significant deterioration of cardiac functions. Cardiac function was similar across the sham groups in all three genetically modified mice. ELISA assay displayed how Peli 1 overexpression decreased cardo-suppressive circulating inflammatory cytokines (TNF-alpha, IL-6) compared to both the knockout groups. The proportion of TUNEL-positive cells varied according to Peli1 expression, with overexpression (AMPEL1Tg/+) leading to a significant reduction and Peli1 gene knockout (Peli1-/- and CP1KO) leading to a significant increase in their presence. A similar trend was also observed with Bax protein expression. The improved cellular survival associated with Peli1 overexpression was again shown with the reduction of oxidative stress marker 4-Hydroxy-2-Nonenal (4-HNE).

CONCLUSION

Our results indicate that overexpression of Peli1 is a novel approach that not only preserved cardiac function but reduced inflammatory markers and apoptosis following severe sepsis in a murine genetic model.

Ubiquitination Links DNA Damage and Repair Signaling to Cancer Metabolism

Changes in the DNA damage response (DDR) and cellular metabolism are two important factors that allow cancer cells to proliferate. DDR is a set of events in which DNA damage is recognized, DNA repair factors are recruited to the site of damage, the lesion is repaired, and cellular responses associated with the damage are processed. In cancer, DDR is commonly dysregulated, and the enzymes associated with DDR are prone to changes in ubiquitination. Additionally, cellular metabolism, especially glycolysis, is upregulated in cancer cells, and enzymes in this metabolic pathway are modulated by ubiquitination. The ubiquitin-proteasome system (UPS), particularly E3 ligases, act as a bridge between cellular metabolism and DDR since they regulate the enzymes associated with the two processes. Hence, the E3 ligases with high substrate specificity are considered potential therapeutic targets for treating cancer. A number of small molecule inhibitors designed to target different components of the UPS have been developed, and several have been tested in clinical trials for human use. In this review, we discuss the role of ubiquitination on overall cellular metabolism and DDR and confirm the link between them through the E3 ligases NEDD4, APC/C^CDH1, FBXW7, and Pellino1. In addition, we present an overview of the clinically important small molecule inhibitors and implications for their practical use.

Role of the Peli1-RIPK1 Signaling Axis in Methamphetamine-Induced Neuroinflammation

Severe neurological inflammation is one of the main symptoms of methamphetamine (meth)-induced brain injury. Studies have demonstrated that meth exposure facilitates neuroinflammation via Pellino E3 ubiquitin protein ligase 1 (Peli1)-mediated signaling. However, the involved mechanisms remain incompletely understood. Herein, we used Peli1^-/- mice and Peli1-knockdown microglial BV2 cells to decipher the roles of Peli1 and downstream signaling in meth-induced neuroinflammation. After meth administration for seven consecutive days, Peli1^-/- mice exhibited better learning and memory behavior and dramatically lower interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 levels than wild-type mice. Moreover, in vitro experiments revealed that Peli1 knockdown significantly attenuated the meth-induced upregulation of cytokines. Besides, meth markedly activated and increased the levels of receptor-interacting protein kinase 1 (RIPK1), and Peli1 knockout or knockdown prevented these effects, indicating that RIPK1 participated in meth-induced Peli1-mediated inflammation. Specifically, treating the cells with necrostatin-1(Nec-1), an antagonist of RIPK1, remarkably inhibited the meth-induced increase in IL-1β, TNF-α, and IL-6 expression, confirming the involvement of RIPK1 in Peli1-mediated neuroinflammation. Finally, meth induced a dramatic transfer of the mixed lineage kinase domain-like protein, a downstream effector of RIRK1, to the cell membrane, disrupting membrane integrity and causing cytokine excretion. Therefore, targeting the Peli1-RIPK1 signaling axis is a potentially valid therapeutic approach against meth-induced neuroinflammation.

A Non-Canonical IRAK Signaling Pathway Triggered by DNA Damage

Interleukin-1 receptor (IL-1R)-associated kinases (IRAKs) are core effectors of Toll-like receptor (TLR) and IL-1R signaling, with no reported roles outside of innate immunity. We find that vertebrate cells exposed to ionizing radiation (IR) sequentially activate IRAK4 and IRAK1 through a phosphorylation cascade mirroring that induced by TLR/IL-1R, resulting in a potent anti-apoptotic response. However, IR-induced IRAK1 activation does not require the receptors or the IRAK4/1 adaptor protein MyD88, and instead of remaining in the cytoplasm, the activated kinase is immediately transported to the nucleus via a conserved nuclear localization signal. We identify: double-strand DNA breaks (DSBs) as the biologic trigger for this pathway; the E3 ubiquitin ligase Pellino1 as the scaffold enabling IRAK4/1 activation in place of TLR/IL-1R-MyD88; and the pro-apoptotic PIDDosome (PIDD1-RAIDD-caspase-2) as a critical downstream target in the nucleus. The data delineate a non-canonical IRAK signaling pathway derived from, or ancestral to, TLR signaling. This DSB detection pathway, which is also activated by genotoxic chemotherapies, provides multiple actionable targets for overcoming tumor resistance to mainstay cancer treatments.

The E3 Ubiquitin Ligase Peli1 Deficiency Promotes Atherosclerosis Progression

Background: Atherosclerosis is a chronic inflammatory vascular disease and the main cause of death and morbidity. Emerging evidence suggests that ubiquitination plays an important role in the pathogenesis of atherosclerosis including control of vascular inflammation, vascular smooth muscle cell (VSMC) function and atherosclerotic plaque stability. Peli1 a type of E3 ubiquitin ligase has emerged as a critical regulator of innate and adaptive immunity, however, its role in atherosclerosis remains to be elucidated. Methods: Apoe^−/− mice and Peli1-deficient Apoe^−/− Peli1^−/− mice were subject to high cholesterol diet. Post sacrifice, serum was collected, and atherosclerotic plaque size and parameters of atherosclerotic plaque stability were evaluated. Immunoprofiling and foam cell quantification were performed. Results: Peli1 deficiency does not affect atherosclerosis lesion burden and cholesterol levels, but promotes VSMCs foam cells formation, necrotic core expansion, collagen, and fibrous cap reduction. Apoe^−/− Peli1^−/− mice exhibit a storm of inflammatory cytokines, expansion of Th1, Th1, Th17, and Tfh cells, a decrease in regulatory T and B cells and induction of pro-atherogenic serum level of IgG2a and IgE. Conclusions: In the present study, we uncover a crucial role for Peli1 in atherosclerosis as an important regulator of inflammation and VSMCs phenotypic modulation and subsequently atherosclerotic plaque destabilization.

Comprehensive molecular profiling of pulmonary pleomorphic carcinoma

Information regarding the molecular features of pulmonary pleomorphic carcinoma (PPC) is insufficient. Here, we performed next-generation sequencing to determine the genomic and transcriptomic profiles of PPC. We sequenced the DNAs and RNAs of 78 specimens from 52 patients with PPC. We analyzed 15 PPC cases to identify intratumoral differences in gene alterations, tumor mutation burden (TMB), RNA expression, and PD-L1 expression between epithelial and sarcomatoid components. The genomic alterations of six cases of primary tumors and corresponding metastatic tumors were analyzed. KRAS mutations (27%) were the most common driver mutations, followed by EGFR (8%), and MET (8%) mutations. Epithelial and sarcomatoid components shared activating driver mutations, and there were no significant differences in CD274 expression or TMB between the two components. However, PD-L1 was highly expressed in the sarcomatoid component of several cases compared with the epithelial component. Primary and metastatic tumors shared oncogenic mutations among genes such as KRAS and TP53, and additional alterations including NOTCH4 mutations were specifically identified in the metastatic regions. Our data suggest that therapies targeting activating driver mutations may be effective for patients with PPC and that immune checkpoint inhibitors of PPC may be recommended after careful assessment of PD-L1 expression in each epithelial and sarcomatoid component.

Ubiquitination as an Important Host-Immune Response Strategy in Penaeid Shrimp: Inferences From Other Species

Shrimp aquaculture is an essential economic venture globally, but the industry faces numerous challenges, especially pathogenic infections. As invertebrates, shrimp rely mainly on their innate immune system for protection. An increasing number of studies have shown that ubiquitination plays a vital role in the innate immune response to microbial pathogens. As an important form of posttranslational modification (PTM), both hosts and pathogens have exploited ubiquitination and the ubiquitin system as an immune response strategy to outwit the other. This short review brings together recent findings on ubiquitination and how this PTM plays a critical role in immune modulation in penaeid shrimps. Key findings inferred from other species would help guide further studies on ubiquitination as an immune response strategy in shrimp-pathogen interactions.

Pellino1 deficiency reprograms cardiomyocytes energy metabolism in lipopolysaccharide-induced myocardial dysfunction

Pellino1 has been shown to regulate proinflammatory genes by activating the nuclear factor kappa B (NF-κB) and Toll-like receptor (TLR) signaling pathways, which are important in the pathological development of lipopolysaccharide (LPS)-induced myocarditis. However, it is still unknown whether silencing Pellino1 (si-Pellino1) has a therapeutic effect on this disease. Here, we showed that silencing Pellino1 can be a potential protective strategy for abnormal myocardial energy metabolism in LPS-induced myocarditis. We used liquid chromatography electrospray–ionization tandem mass spectrometry (LC–MS/MS) to analyze samples from si-Pellino1 neonatal rat cardiac myocytes (NRCMs) treated with LPS or left untreated. After normalization of the data, metabolite interaction analysis of matched KEGG pathway associations following si-Pellino1 treatment was applied, accompanied by interaction analysis of gene and metabolite associations after this treatment. Moreover, we used western blot (WB) and polymerase chain reaction (PCR) analyses to determine the expression of genes involved in regulating cardiac energy and energy metabolism in different groups. LC–MS-based metabolic profiling analysis demonstrated that si-Pellino1 treatment could alleviate or even reverse LPS-induced cellular damage by altering cardiomyocytes energy metabolism accompanied by changes in key genes (Cs, Cpt2, and Acadm) and metabolites (3-oxoocotanoyl-CoA, hydroxypyruvic acid, lauroyl-CoA, and NADPH) in NRCMs. Overall, our study unveiled the promising cardioprotective effect of silencing Pellino1 in LPS-induced myocarditis through fuel and energy metabolic regulation, which can also serve as biomarkers for this disease.

The Post-Translational Regulation of Epithelial-Mesenchymal Transition-Inducing Transcription Factors in Cancer Metastasis

Epithelial-mesenchymal transition (EMT) is generally observed in normal embryogenesis and wound healing. However, this process can occur in cancer cells and lead to metastasis. The contribution of EMT in both development and pathology has been studied widely. This transition requires the up- and down-regulation of specific proteins, both of which are regulated by EMT-inducing transcription factors (EMT-TFs), mainly represented by the families of Snail, Twist, and ZEB proteins. This review highlights the roles of key EMT-TFs and their post-translational regulation in cancer metastasis.

TGR5 activation attenuates neuroinflammation via Pellino3 inhibition of caspase-8/NLRP3 after middle cerebral artery occlusion in rats

BACKGROUND

Nucleotide-binding oligomerization domain-like receptor pyrin domain-containing protein 3 (NLRP3) plays an important role in mediating inflammatory responses during ischemic stroke. Bile acid receptor Takeda-G-protein-receptor-5 (TGR5) has been identified as an important component in regulating brain inflammatory responses. In this study, we investigated the mechanism of TGR5 in alleviating neuroinflammation after middle cerebral artery occlusion (MCAO).

METHODS

Sprague-Dawley rats were subjected to MCAO and TGR5 agonist INT777 was administered intranasally 1 h after MCAO. Small interfering RNAs (siRNA) targeting TGR5 and Pellino3 were administered through intracerebroventricular injection 48 h before MCAO. Infarct volumes and neurologic scores were evaluated, and ELISA, flow cytometry, immunofluorescence staining, immunoblotting, and co-immunoprecipitation were used for the evaluations.

RESULTS

Endogenous TGR5 and Pellino3 levels increased after MCAO. TGR5 activation by INT777 significantly decreased pro-inflammatory cytokine, cleaved caspase-8, and NLRP3 levels, thereby reducing brain infarctions; both short- and long-term neurobehavioral assessments showed improvements. Ischemic damage induced the interaction of TGR5 with Pellino3. Knockdown of either TGR5 or Pellino3 increased the accumulation of cleaved caspase-8 and NLRP3, aggravated cerebral impairments, and abolished the anti-inflammatory effects of INT777 after MCAO.

CONCLUSIONS

TGR5 activation attenuated brain injury by inhibiting neuroinflammation after MCAO, which could be mediated by Pellino3 inhibition of caspase-8/NLRP3.

Data-independent acquisition method for ubiquitinome analysis reveals regulation of circadian biology

Protein ubiquitination is involved in virtually all cellular processes. Enrichment strategies employing antibodies targeting ubiquitin-derived diGly remnants combined with mass spectrometry (MS) have enabled investigations of ubiquitin signaling at a large scale. However, so far the power of data independent acquisition (DIA) with regards to sensitivity in single run analysis and data completeness have not yet been explored. Here, we develop a sensitive workflow combining diGly antibody-based enrichment and optimized Orbitrap-based DIA with comprehensive spectral libraries together containing more than 90,000 diGly peptides. This approach identifies 35,000 diGly peptides in single measurements of proteasome inhibitor-treated cells - double the number and quantitative accuracy of data dependent acquisition. Applied to TNF signaling, the workflow comprehensively captures known sites while adding many novel ones. An in-depth, systems-wide investigation of ubiquitination across the circadian cycle uncovers hundreds of cycling ubiquitination sites and dozens of cycling ubiquitin clusters within individual membrane protein receptors and transporters, highlighting new connections between metabolism and circadian regulation.

MiR-153-3p induces immune dysregulation by inhibiting PELI1 expression in umbilical cord-derived mesenchymal stem cells in patients with systemic lupus erythematosus

Mesenchymal stem cells (MSCs) are identified as a promising tool for the treatment of autoimmune diseases, and several microRNAs (miRNAs) are shown to exhibit vital roles in immune diseases. However, their function and mechanism in systemic lupus erythematosus (SLE) is still unclear. The qRT-PCR analysis was employed to investigate level of miR-153-3p. Subsequently, western blot and luciferase reporter assays were carried out to determine miR-153-3p targets. Cell proliferation and migration were determined using EdU proliferation assays and transwell migration assays. Apoptosis levels were evaluated by annexin V staining and flow cytometry. We used human umbilical cord-derived mesenchymal stem cells (UC-MSCs) transplantation to treat MRL/lpr mice. It was observed that miR-153-3p was upregulated in patients with SLE, and was closely related to SLE disease activity. Overexpression of miR-153-3p decreased UC-MSCs proliferation and migration, and weakened UC-MSCs-mediated decrease of follicular T helper (Tfh) cells and increase of regulatory T (Treg) cells through repressing PELI1 in vitro. We also found that PELI1 overexpression abolished the function of miR-153-3p on UC-MSCs. Furthermore, miR-153-3p overexpression weakened the therapeutic effect of UC-MSCs in MRL/lpr mice in vivo. Taken together, all data suggested that miR-153-3p is a mediator of SLE UC-MSCs regulation and may function as a new therapeutic target for the treatment of lupus.

Pellino1 regulates neuropathic pain as well as microglial activation through the regulation of MAPK/NF-κB signaling in the spinal cord

BACKGROUND

Spinal cord microglia plays a crucial role in the pathogenesis of neuropathic pain. However, the mechanisms underlying spinal microglial activation during neuropathic pain remain incompletely determined. Here, we investigated the role of Pellino1 (Peli1) and its interplay with spinal microglial activation in neuropathic pain.

METHODS

In this study, we examined the effects of Peli1 on pain hypersensitivity and spinal microglial activation after chronic constriction injury (CCI) of the sciatic nerve in mice. The molecular mechanisms involved in Peli1-mediated hyperalgesia were determined by western blot, immunofluorescence, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA). We utilized immunoprecipitation to examine the ubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6) following CCI. In addition, we explored the effect of Peli1 on BV2 microglial cells in response to lipopolysaccharide (LPS) challenge.

RESULTS

We found that CCI induced a significant increase in the levels of Peli1, which was present in the great majority of microglia in the spinal dorsal horn. Our results showed that spinal Peli1 contributed to the induction and maintenance of CCI-induced neuropathic pain. The biochemical data revealed that CCI-induced Peli1 in the spinal cord significantly increased mitogen-activated protein kinase (MAPK) phosphorylation, activated nuclear factor kappa B (NF-κB), and enhanced the production of proinflammatory cytokines, accompanied by spinal microglial activation. Peli1 additionally was able to promote K63-linked ubiquitination of TRAF6 in the ipsilateral spinal cord following CCI. Furthermore, we demonstrated that Peli1 in microglial cells significantly enhanced inflammatory reactions after LPS treatment.

CONCLUSION

These results suggest that the upregulation of spinal Peli1 is essential for the pathogenesis of neuropathic pain via Peli1-dependent mobilization of spinal cord microglia, activation of MAPK/NF-κB signaling, and production of proinflammatory cytokines. Modulation of Peli1 may serve as a potential approach for the treatment of neuropathic pain.

Identification and Molecular Characterization of a Pellino Protein in Kuruma Prawn (Marsupenaeus Japonicus) in Response to White Spot Syndrome Virus and Vibrio Parahaemolyticus Infection

Kuruma prawn, Marsupenaeus japonicus, has the third largest annual yield among shrimp species with vital economic significance in China. White spot syndrome virus (WSSV) is a great threat to the global shrimp farming industry and results in high mortality. Pellino, a highly conserved E3 ubiquitin ligase, has been found to be an important modulator of the Toll-like receptor (TLR) signaling pathways that participate in the innate immune response and ubiquitination. In the present study, the Pellino gene from Marsupenaeus japonicus was identified. A qRT-PCR assay showed the presence of MjPellino in all the tested tissues and revealed that the transcript level of this gene was significantly upregulated in both the gills and hemocytes after challenge with WSSV and Vibrio parahaemolyticus. The function of MjPellino was further verified at the protein level. The results of the three-dimensional modeling and protein-protein docking analyses and a GST pull-down assay revealed that the MjPellino protein was able to bind to the WSSV envelope protein VP26. In addition, the knockdown of MjPellino in vivo significantly decreased the expression of MjAMPs. These results suggest that MjPellino might play an important role in the immune response of kuruma prawn.

Pellino1 Contributes to Morphine Tolerance by Microglia Activation via MAPK Signaling in the Spinal Cord of Mice

Chronic morphine-induced antinociceptive tolerance is a major unresolved issue in clinical practices, which is associated with microglia activation in the spinal cord. E3 ubiquitin ligase Pellino1 (Peli1) is known to be an important microglia-specific regulator. However, it is unclear whether Peli1 is involved in morphine tolerance. Here, we found that Peli1 levels in the spinal cord were significantly elevated in morphine tolerance mouse model. Notably, Peli1 was expressed in a great majority of microglia in the spinal dorsal horn, while downregulation of spinal Peli1 attenuated the development of morphine tolerance and associated hyperalgesia. Our biochemical data revealed that morphine tolerance-induced increase in Peli1 was accompanied by spinal microglia activation, activation of mitogen-activated protein kinase (MAPK) signaling, and production of proinflammatory cytokines. Peli1 additionally was found to promote K63-linked ubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6) in the spinal cord after repeated morphine treatment. Furthermore, knocking down Peli1 in cultured BV2 microglial cells significantly attenuated inflammatory reactions in response to morphine challenge. Therefore, we conclude that the upregulation of Peli1 in the spinal cord plays a curial role in the development of morphine tolerance via Peli1-dependent mobilization of spinal microglia, activation of MAPK signaling, and production of proinflammatory cytokines. Modulation of Peli1 may be a potential strategy for the prevention of morphine tolerance.

Disruption of VEGF Mediated Flk-1 Signaling Leads to a Gradual Loss of Vessel Health and Cardiac Function During Myocardial Infarction: Potential Therapy With Pellino-1

Background

The present study demonstrates that the ubiquitin E3 ligase, Pellino‐1 (Peli1), is an important angiogenic molecule under the control of vascular endothelial growth factor (VEGF) receptor 2/Flk‐1. We have previously reported increased survivability of ischemic skin flap tissue by adenovirus carrying Peli1 (Ad‐Peli1) gene therapy in Flk‐1^+/− mice.

Methods and Results

Two separate experimental groups of mice were subjected to myocardial infarction (MI) followed by the immediate intramyocardial injection of adenovirus carrying LacZ (Ad‐LacZ) (1×10⁹ pfu) or Ad‐Peli1 (1×10⁹ pfu). Heart tissues were collected for analyses. Compared with wild‐type (WTMI) mice, analysis revealed decreased expressions of Peli1, phosphorylated (p‐)Flk‐1, p‐Akt, p‐eNOS, p‐MK2, p‐IκBα, and NF‐κB and decreased vessel densities in Flk‐1^+/− mice subjected to MI (Flk‐1^+/−MI). Mice (CD1) treated with Ad‐Peli1 after the induction of MI showed increased β‐catenin translocation to the nucleus, connexin 43 expression, and phosphorylation of Akt, eNOS, MK2, and IκBα, that was followed by increased vessel densities compared with the Ad‐LacZ–treated group. Echocardiography conducted 30 days after surgery showed decreased function in the Flk1^+/−MI group compared with WTMI, which was restored by Ad‐Peli1 gene therapy. In addition, therapy with Ad‐Peli1 stimulated angiogenic and arteriogenic responses in both CD1 and Flk‐1^+/− mice following MI. Ad‐Peli1 treatment attenuated cardiac fibrosis in Flk‐1^+/−MI mice. Similar positive results were observed in CD1 mice subjected to MI after Ad‐Peli1 therapy.

Conclusion

Our results show for the first time that Peli1 plays a unique role in salvaging impaired collateral blood vessel formation, diminishes fibrosis, and improves myocardial function, thereby offering clinical potential for therapies in humans to mend a damaged heart following MI.

Cardioembolic Ischemic Stroke Gene Expression Fingerprint in Blood: a Systematic Review and Verification Analysis

An accurate etiological classification is key to optimize secondary prevention after ischemic stroke, but the cause remains undetermined in one third of patients. Several studies pointed out the usefulness of circulating gene expression markers to discriminate cardioembolic (CE) strokes, mainly due to atrial fibrillation (AF), while only exploring them in small cohorts. A systematic review of studies analyzing high-throughput gene expression in blood samples to discriminate CE strokes was performed. Significantly dysregulated genes were considered as candidates, and a selection of them was validated by RT-qPCR in 100 patients with defined CE or atherothrombotic (LAA) stroke etiology. Longitudinal performance was evaluated in 12 patients at three time points. Their usefulness as biomarkers for AF was tested in 120 cryptogenic strokes and 100 individuals at high-risk for stroke. Three published studies plus three unpublished datasets were considered for candidate selection. Sixty-seven genes were found dysregulated in CE strokes. CREM, PELI1, and ZAK were verified to be up-regulated in CE vs LAA (p = 0.010, p = 0.003, p < 0.001, respectively), without changes in their expression within the first 24 h after stroke onset. The combined up-regulation of these three biomarkers increased the probability of suffering from CE stroke by 23-fold. In cryptogenic strokes with subsequent AF detection, PELI1 and CREM showed overexpression (p = 0.017, p = 0.059, respectively), whereas in high-risk asymptomatic populations, all three genes showed potential to detect AF (p = 0.007, p = 0.007, p = 0.015). The proved discriminatory capacity of these gene expression markers to detect cardioembolism even in cryptogenic strokes and asymptomatic high-risk populations might bring up their use as biomarkers.

Peli1 induction impairs cardiac microvascular endothelium through Hsp90 dissociation from IRE1α

Ameliorating cardiac microvascular injury is the most effective means to mitigate diabetes-induced cardiovascular complications. Inositol-requiring 1α (IRE1α), a sensor of endoplasmic reticulum stress, is activated by Toll like receptors (TLRs), and then promotes cardiac microvascular injury. Peli1 is a master regulator of TLRs and activates IRE1α. This study aims to investigate whether Peli1 in endothelial cells promotes diabetes-induced cardiac microvascular injury through activating IRE1α. Here we found that Peli1 was markedly up-regulated in cardiac endothelial cells of both diabetic mice and in AGEs-treated cardiac microvascular endothelial cells (CMECs). Peli1 deficiency in endothelial cells significantly alleviated diabetes-induced cardiac microvascular permeability, promoted microvascular regeneration, and suppressed apoptosis, accompanied by the attenuation of adverse cardiac remodeling. Furthermore, Peli1 deletion in CMECs ameliorated AGEs-induced damages in vitro. We identified heat shock protein 90 (Hsp90) as a potential binding partner for Peli1, and the Ring domain of Peli1 directly bound with Hsp90 to enhance IRE1α phosphorylation. Our study suggests that blocking Peli1 in endothelial cells may protect against diabetes-induced cardiac microvascular injury by restraining ER stress.

Identification of a prognostic 28-gene expression signature for gastric cancer with lymphatic metastasis

Gastric cancer (GC) patients have high mortality due to late-stage diagnosis, which is closely associated with lymph node metastasis. Exploring the molecular mechanisms of lymphatic metastasis may inform the research into early diagnostics of GC. In the present study, we obtained RNA-Seq data from The Cancer Genome Altas and used Limma package to identify differentially expressed genes (DEGs) between lymphatic metastases and non-lymphatic metastases in GC tissues. Then, we used an elastic net-regularized COX proportional hazard model for gene selection from the DEGs and constructed a regression model composed of 28-gene signatures. Furthermore, we assessed the prognostic performance of the 28-gene signature by analyzing the receive operating characteristic curves. In addition, we selected the gene PELI2 amongst 28 genes and assessed the roles of this gene in GC cells. The good prognostic performance of the 28-gene signature was confirmed in the testing set, which was also validated by GSE66229 dataset. In addition, the biological experiments showed that PELI2 could promote the growth and metastasis of GC cells by regulating vascular endothelial growth factor C. Our study indicates that the identified 28-gene signature could be considered as a sensitive predictive tool for lymphatic metastasis in GC.

Peli1 controls the survival of dopaminergic neurons through modulating microglia-mediated neuroinflammation

Chronic neuroinflammation is known to contributes to the toxicity of neurodegeneration of Parkinson’s disease (PD). However, the molecular and cellular mechanisms controlling inflammatory responses in the central nervous system remain poorly understood. Here we found that a E3 ubiquitin ligase Peli1 is dramatically induced only in the substantia nigra (SN) of the human and mouse PD brains. The ablation of Peli1 significantly suppressed LPS-induced production of neurotoxic mediators and proinflammatory cytokines in SN and in primary microglia, whereas Peli1 is dispensable for the inflammatory responses in astrocyte. Accordingly, Peli1 deficiency markedly inhibited neuron death induced by the conditioned medium from LPS-stimulated microglia. Mechanistical study suggested that Peli1 acts as a positive regulator of inflammatory response in microglia through activation of NF-κB and MAP kinase. Our results established Peli1 as a critical mediator in the regulation of microglial activation and neuroinflammation-induced death of dopaminergic neurons during PD pathogenesis, suggesting that targeting Peli1 may have therapeutic effect in neuroinflammation.

Pellino1 specifically binds to phospho-Thr18 of p53 and is recruited to sites of DNA damage

Pellino1 is an E3 ubiquitin ligase that plays a key role in positive regulation of innate immunity signaling, specifically required for the production of interferon when induced by viral double-stranded RNA. We report the identification of the tumor suppressor protein, p53, as a binding partner of Pellino1. Their interaction has a K_d of 42 ± 2 μM and requires phosphorylation of Thr18 within p53 and association with the forkhead-associated (FHA) domain of Pellino1. We employed laser micro-irradiation and live cell microscopy to show that Pellino1 is recruited to newly occurring DNA damage sites, via its FHA domain. Mutation of a hitherto unidentified nuclear localization signal within the N-terminus of Pellino1 led to its exclusion from the nucleus. This study provides evidence that Pellino1 translocates to damaged DNA in the nucleus and has a functional role in p53 signaling and the DNA damage response.

Peli1b governs the brain patterning via ERK signaling pathways in zebrafish embryos

Pellino proteins are associated with immune and stress responses through their effects on NF-κB signaling and B-cell development, and through their role as a scaffold in TLR/IL-1R signaling pathways. However, their function during embryonic development is unclear. Here, we report the developmental expression patterns and functions of peli1b, which encodes a zebrafish ortholog of human Pellino1. Maternal peli1b transcripts were present in zebrafish embryos at the 1-cell stage and zygotic transcripts appeared in the shield area at 6 hours post fertilization (hpf), particularly in the neural plate of the dorsal region. peli1b transcripts were concentrated in the somites, lens, myogenic cells, lateral plate mesoderm, and presomitic mesoderm at 12 hpf, but expression shifted to the telencephalon, diencephalon, hindbrain, and rhombomeres (r1-7) at 24 hpf. Distribution of peli1b transcripts was further restricted to the telencephalon, diencephalon, hindbrain, eyes, and pectoral fins at 48 hpf. Knock-down of peli1b with a peli1b antisense morpholino resulted in significant developmental defects and a reduction in size of the telencephalon, diencephalon, rhombomeres (r1-7), and spinal cord at 24 hpf. When peli1b-knock-down embryos were analyzed for zic3, a marker associated with the central nervous system, we found lower levels of zic3 transcripts in the shield area at 6 hpf and in the posterior diencephalon, dorsal neural plate, midbrain, and hindbrain at 14 hpf. Finally, the ERK3/4 inhibitor SB203580 also induced a significant reduction in the level of zic3 transcripts in the neural plate at 6 hpf and in the posterior diencephalon, dorsal neural plate, midbrain, hindbrain, segmental plate, dorsal spinal cord, and dorsal posterior neural plate at 14 hpf. It is thus likely that the association between Peli1b and brain development in zebrafish embryos occurs via ERK3/4 pathways.

Poly IC pretreatment suppresses B cell-mediated lupus-like autoimmunity through induction of Peli1

Noncanonical NF-κB pathway is essential for the B cell activation and antibody production, which centralize the critical role of B cells in regulating the pathogenesis of systemic lupus erythematosus (SLE). We have previously demonstrated that Pellino1 (Peli1) negatively regulates noncanonical NF-κB activation and lupus autoimmunity. Here, we showed that poly IC is a potent inducer of Peli1 protein in mouse splenic B cells in dose- and time-dependent manners, and poly IC-induced Peli1 protein dramatically suppressed the activation of noncanonical NF-κB pathway. In addition, poly IC-pretreated B cells failed to induce lupus-like disease in BM12 CD4+ T cell-immunized mice. Accordingly, the induction of antibody-producing plasma cells and germinal center B cells, as well as the production of autoantibodies were significantly impaired in immunized μMT mice that were transferred with poly IC-pretreated B cells. Our findings demonstrate that poly IC-induced Peli1 negatively regulates the noncanonical NF-κB pathway in the context of restraining the pathogenesis of lupus-like disease.

Pellino 1 is a novel regulator of TNF and TLR signalling in human myometrial and amnion cells

Preterm birth is the primary cause of neonatal deaths and morbidities. Pathological processes causally linked to preterm birth are inflammation and infection. Pellino-1 (Peli1) has previously been found to regulate the inflammatory response in non-gestational tissues in response to toll-like receptor (TLR) ligands and pro-inflammatory cytokines. The aims of this study were to determine the effect of labor on Peli1 expression in myometrium and fetal membranes, and the effect of Peli1 silencing by siRNA (siPELI1) on the production of pro-inflammatory and pro-labor mediators. The expression of Peli1 was found to be higher in myometrium and fetal membranes with term labor, compared to non-laboring samples. Peli1 mRNA and protein expression was also higher in amnion from women with preterm histological chorioamnionitis. In human primary myometrial cells, siPELI1 transfected cells showed a decrease in pro-inflammatory cytokine IL6, chemokines (CXCL8, CCL2) and adhesion molecule ICAM1 when in the presence of pro-inflammatory cytokine TNF, TLR2/6 ligand fsl-1, TLR5 ligand flagellin, and TLR3 ligand poly(I:C). Similarly in primary amnion cells, siPELI1 transfected cells decreased IL1B-induced expression and secretion of IL6 and CXCL8. In siPELI1 transfected myometrial cells, there was a decrease in prostaglandin PGF_2α and its receptor, PTGFR mRNA expression when treated with TNF. There was a decrease in NF-κB RELA transcriptional activity in siPELI1 transfected cells in the presence of TNF, fsl-1 and flagellin, but not poly(I:C). Our study suggests a novel role for Peli1 in regulating pro-inflammatory and pro-labor mediators through TNF and TLR signalling.

Peli1 negatively regulates noncanonical NF-κB signaling to restrain systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by uncontrolled secretion of autoantibodies by plasma cells. Although the functional importance of plasma cells and autoantibodies in SLE has been well established, the underlying molecular mechanisms of controlling autoantibody production remain poorly understood. Here we show that Peli1 has a B cell-intrinsic function to protect against lupus-like autoimmunity in mice. Peli1 deficiency in B cells induces autoantibody production via noncanonical NF-κB signaling. Mechanically, Peli1 functions as an E3 ligase to associate with NF-κB inducing kinase (NIK) and mediates NIK Lys48 ubiquitination and degradation. Overexpression of Peli1 inhibits noncanonical NF-κB activation and alleviates lupus-like disease. In humans, PELI1 levels negatively correlate with disease severity in SLE patients. Our findings establish Peli1 as a negative regulator of the noncanonical NF-κB pathway in the context of restraining the pathogenesis of lupus-like disease.

Pellino-1 confers chemoresistance in lung cancer cells by upregulating cIAP2 through Lys63-mediated polyubiquitination

Pellino-1 is an E3 ubiquitin ligase that mediates immune receptor signaling pathways. The role of Pellino-1 in oncogenesis of lung cancer was investigated in this study. Pellino-1 expression was increased in human lung cancer cell lines compared with non-neoplastic lung cell lines. Pellino-1 overexpression in human lung cancer cells, A549 and H1299 cells, increased the survival and colony forming ability. Pellino-1 overexpression in these cells also conferred resistance to cisplatin- or paclitaxel-induced apoptosis. In contrast, depletion of Pellino-1 decreased the survival of A549 and H1299 cells and sensitized these cells to cisplatin- and paclitaxel-induced apoptosis. Pellino-1 overexpression in A549 and H1299 cells upregulated the expression of inhibitor of apoptosis (IAP) proteins, including cIAP1 and cIAP2, while Pellino-1 depletion downregulated these molecules. Notably, Pellino-1 directly interacted with cIAP2 and stabilized cIAP2 through lysine63-mediated polyubiquitination via its E3 ligase activity. Pellino-1-mediated chemoresistance in lung cancer cells was dependent on the induction of cIAP2. Moreover, a strong positive correlation between Pellino-1 and the cIAP2 expression was observed in human lung adenocarcinoma tissues. Taken together, these results demonstrate that Pellino-1 contributes to lung oncogenesis through the overexpression of cIAP2 and promotion of cell survival and chemoresistance. Pellino-1 might be a novel oncogene and potential therapeutic target in lung cancer.

Peli1 Contributions in Microglial Activation, Neuroinflammatory Responses and Neurological Deficits Following Experimental Subarachnoid Hemorrhage

Early brain injury (EBI) following subarachnoid hemorrhage (SAH) is closely associated with neuroinflammation. Microglial activation is an early event that leads to neuroinflammation after SAH. Peli1 is an E3 ubiquitin ligase that mediates the induction of pro-inflammatory cytokines in microglia. Here we report Peli1 contributions in SAH mediated brain pathology. An SAH model was induced by endovascular perforation in adult male C57BL/6J mice. Peli1 was markedly induced in mice brains in a time-dependent manner and was predominantly expressed in CD16/32-positive microglia after SAH. Using genetic approaches, we demonstrated that decreased Peli1 significantly improved neurological deficits, attenuated brain edema, reduced over-expression of pro-inflammatory cytokine IL-6 and modified apoptotic/antiapoptotic biomarkers. In addition, Peli1 downregulation suppressed ERK and JNK phosphorylation levels via the downregulation of cIAP1/2 expression, subsequently reducing inducible nitric oxide synthase (iNOS) expression after SAH. Therefore, these findings demonstrate that Peli1 contributes to microglia-mediated neuroinflammation in EBI by mediating cIAP1/2 activation, thus promoting the activation of MyD88-dependent MAPK pathway after experimental SAH. Our findings also showed that Peli1 could promote the expression of M1 microglia polarization biomarker CD16/32 and iNOS after SAH. Targeting Peli1 exerts neuroprotective effects during EBI after SAH, thus could provide potential option for prevention-therapy in high-risk individuals.

Toll-like receptor 2: An important immunomodulatory molecule during Helicobacter pylori infection

Toll like receptors (TLRs) are an essential subset of pathogen recognition receptors (PRRs) which identify the microbial components and contribute in the regulation of innate and adaptive immune responses against the infectious agents. The TLRs, especially TLR2, TLR4, TLR5 and TLR9, participate in the induction of immune response against H. pylori. TLR2 is expressed on a number of immune and non-immune cells and recognizes a vast broad of microbial components due to its potential to form heterodimers with other TLRs, including TLR1, TLR6 and TLR10. A number of H. pylori-related molecules may contribute to TLR2-dependent responses, including HP-LPS, HP-HSP60 and HP-NAP. TLR2 plays a pivotal role in regulation of immune response to H. pylori through activation of NF-κB and induction of cytokine expression in epithelial cells, monocytes/macrophages, dendritic cells, neutrophils and B cells. The TLR2-related immune response that is induced by H. pylori-derived components may play an important role regarding the outcome of the infection toward bacterial elimination, persistence or pathological reactions. The immunomodulatory and immunoregulatory roles of TLR2 during H. pylori infection were considered in this review. TLR2 could be considered as an interesting therapeutic target for treatment of H. pylori-related diseases.

Genome-wide analysis identifies colonic genes differentially associated with serum leptin and insulin concentrations in C57BL/6J mice fed a high-fat diet

Obesity-induced chronic inflammation is known to increase the risk of ulcerative colitis, Crohn's disease, and colorectal cancer. Accumulating evidence suggests that leptin and insulin are key molecules linking obesity with diseases of the lower intestine. Here, we identified serum phenotype-associated genes in the colon of diet-induced obese mice as early biomarkers of obesity-associated colonic diseases. C57BL/6J mice were fed with either normal diet (ND, 15% of fat calories) or high-fat diet (HFD, 45% of fat calories) for 8 weeks. Serum concentrations of insulin, insulin-like growth factor-1 (IGF-1), leptin, and adiponectin were measured as obesity-related phenotypic markers. Genome-wide gene expression profiles of colon tissue were determined, followed by statistical analyses to detect differentially expressed and serum phenotype-associated genes. HFD-fed mice showed higher serum concentrations of leptin (P < 0.001) and insulin (P < 0.01) than those in the ND group, whereas serum IGF-1 and adiponectin concentrations did not differ between the two dietary groups. Among differentially expressed genes affected by HFD, 135, 128, 110, and 341 genes were associated with serum levels of leptin, insulin, IGF-1, and adiponectin, respectively. We identified 17 leptin-associated genes and 4 insulin-associated genes that inversely responded to HFD and ND. Among these, leptin-associated Peli3 (Pellino E3 ubiquitin protein ligase family member 3), Creb1 (cAMP responsive element binding protein 1), and Enpp2 (ectonucleotide pyrophosphatase/phosphodiesterase 2, autotaxin) and insulin-associated Centg1 (AGAP2, ArfGAP with GTPase domain) are reported to play a role either in obesity or colonic diseases. mRNA expression of these genes was validated by RT-qPCR. Our data suggest Peli3, Creb1, Enpp2, and Centg1 as potential early biomarker candidates for obesity-induced pathophysiological changes in the colon. Future studies verifying the function of these candidates are needed for the prevention, early detection, and treatment of colon diseases.

Pellino-1 promotes lung carcinogenesis via the stabilization of Slug and Snail through K63-mediated polyubiquitination

Pellino-1 is an E3 ubiquitin ligase acting as a critical mediator for a variety of immune receptor signaling pathways, including Toll-like receptors, interleukin-1 receptor and T-cell receptors. We recently showed that the Pellino-1-transgenic (Tg) mice developed multiple tumors with different subtypes in hematolymphoid and solid organs. However, the molecular mechanism underlying the oncogenic role of Pellino-1 in solid tumors remains unknown. Pellino-1-Tg mice developed adenocarcinoma in the lungs, and Pellino-1 expression was higher in human lung adenocarcinoma cell lines compared with non-neoplastic bronchial epithelial cell lines. Pellino-1 overexpression increased the cell proliferation, survival, colony formation, invasion and migration of lung adenocarcinoma cells, whereas Pellino-1 knock-down showed the opposite effect. Pellino-1 overexpression activated PI3K/Akt and ERK signaling pathways and elicited an epithelial–mesenchymal transition (EMT) phenotype of lung adenocarcinoma cells. Pellino-1-mediated EMT was demonstrated through morphology, the upregulation of Vimentin, Slug and Snail expression and the downregulation of E-cadherin and β-catenin expression. Notably, Pellino-1 had a direct effect on the overexpression of Snail and Slug through Lys63-mediated polyubiquitination and the subsequent stabilization of these proteins. Pellino-1 expression level was significantly correlated with Snail and Slug expression in human lung adenocarcinoma tissues, and lung tumors from Pellino-1-Tg mice showed Snail and Slug overexpression. The Pellino-1-mediated increase in the migration of lung adenocarcinoma cells was mediated by Snail and Slug expression. Taken together, these results show that Pellino-1 contributes to lung tumorigenesis by inducing overexpression of Snail and Slug and promoting EMT. Pellino-1 might be a potential therapeutic target for lung cancer.

MicroRNA expression signatures in lungs of mice infected with Mycobacterium tuberculosis

Tuberculosis (TB) is a major public health concern worldwide; however the factors that account for resistance or susceptibility to disease are not completely understood. Although some studies suggest that the differential expression of miRNAs in peripheral blood of TB patients could be useful as biomarkers of active disease, their involvement during the inflammatory process in lungs of infected individuals is unknown. Here, we evaluated the global expression of miRNAs in the lungs of mice experimentally infected with Mycobacterium tuberculosis on 30 and 60 days post-infection. We observed that several miRNAs were differentially expressed compared to uninfected mice. Furthermore, we verified that the expression of miR-135b, miR-21, miR-155, miR-146a, and miR-146b was significantly altered in distinct leukocyte subsets isolated from lungs of infected mice, while genes potentially targeted by those miRNAs were associated with a diversity of immune related molecular pathways. Importantly, we validated the inhibition of Pellino 1 expression by miR-135b in vitro. Overall, this study contributes to the understanding of the dynamics of miRNA expression in lungs during experimental TB and adds further perspectives into the role of miRNAs on the regulation of immune processes such as leukocyte activation.

E3 ubiquitin ligases Pellinos as regulators of pattern recognition receptor signaling and immune responses

Pellinos are a family of E3 ubiquitin ligases discovered for their role in catalyzing K63-linked polyubiquitination of Pelle, an interleukin-1 (IL-1) receptor-associated kinase homolog in the Drosophila Toll pathway. Subsequent studies have revealed the central and non-redundant roles of mammalian Pellino-1, Pellino-2, and Pelino-3 in signaling pathways emanating from IL-1 receptors, Toll-like receptors, NOD-like receptors, T- and B-cell receptors. While Pellinos ability to interact with many signaling intermediates suggested their scaffolding roles, recent findings in mice expressing ligase-inactive Pellinos demonstrated the importance of Pellino ubiquitin ligase activity. Cell-specific functions of Pellinos have emerged, e.g. Pellino-1 being a negative regulator in T lymphocytes and a positive regulator in myeloid cells, and details of molecular regulation of receptor signaling by various members of the Pellino family have been revealed. In this review, we summarize current information about Pellino-mediated regulation of signaling by pattern recognition receptors, T-cell and B-cell receptors and tumor necrosis factor receptors, and discuss Pellinos roles in sepsis and infectious diseases, as well as in autoimmune, inflammatory, and allergic disorders. We also provide our perspective on the potential of targeting Pellinos with peptide- or small molecule-based drug compounds as a new therapeutic approach for septic shock and autoimmune pathologies.

Study of pathway cross-talk interactions with NF-κB leading to its activation via ubiquitination or phosphorylation: A brief review

NFκB has been known to be a necessary transcription factor for the functioning of nearly all cells in a living organism. For its proper functioning, it talks to several other molecular cofactors and interacts with their functionalities resulting in a convoluted cross talking mesh of signalling networks. To completely understand the working of nuclear factor-kappa B protein, one needs to understand the interactions that occur during its lifecycle, with cofactors from various biological processes. This study attempts to elaborate and bridge the gaps on the cross-talk interactions that NFkB is a part of, during its activation pathway. For this Cytoscape and its various plugins (Cytocopter, Allegro, AgilentLitSearch and Styles) are employed. Other related pathways were also collated and analysed for cross-talk between NfκB and interacting molecules. NFκB was found to mainly interact with E3 ubiquitin ligase, NIK, RIP, TCR, IRAK-1, TLR, TRAF-6, NLR and IL-1, details of which are discussed as a part of this study.

E3 ubiquitin ligases as novel targets for inflammatory diseases

Ubiquitination is one of the post translational modifications which decide the fate of various proteins in the cells, by either directing them towards proteasomal degradation or participation in several cell signalling pathways. Recently, the role of ubiquitination has been unravelled in pathogenesis and progression of various diseases, where inflammation is critical, like obesity, insulin resistance, atherosclerosis, angiotensin-II induced cardiac inflammation and asthma. E3 ligases are known to be instrumental in regulation of the inflammatory cascade. This review focuses on the role of different E3 ligases in the development of inflammatory diseases and thus may help us to target these E3 ligases in future drug discovery to prevent inflammation.

Collembolan Transcriptomes Highlight Molecular Evolution of Hexapods and Provide Clues on the Adaptation to Terrestrial Life

Background

Collembola (springtails) represent a soil-living lineage of hexapods in between insects and crustaceans. Consequently, their genomes may hold key information on the early processes leading to evolution of Hexapoda from a crustacean ancestor.

Method

We assembled and annotated transcriptomes of the Collembola Folsomia candida and Orchesella cincta, and performed comparative analysis with protein-coding gene sequences of three crustaceans and three insects to identify adaptive signatures associated with the evolution of hexapods within the pancrustacean clade.

Results

Assembly of the springtail transcriptomes resulted in 37,730 transcripts with predicted open reading frames for F. candida and 32,154 for O. cincta, of which 34.2% were functionally annotated for F. candida and 38.4% for O. cincta. Subsequently, we predicted orthologous clusters among eight species and applied the branch-site test to detect episodic positive selection in the Hexapoda and Collembola lineages. A subset of 250 genes showed significant positive selection along the Hexapoda branch and 57 in the Collembola lineage. Gene Ontology categories enriched in these genes include metabolism, stress response (i.e. DNA repair, immune response), ion transport, ATP metabolism, regulation and development-related processes (i.e. eye development, neurological development).

Conclusions

We suggest that the identified gene families represent processes that have played a key role in the divergence of hexapods within the pancrustacean clade that eventually evolved into the most species-rich group of all animals, the hexapods. Furthermore, some adaptive signatures in collembolans may provide valuable clues to understand evolution of hexapods on land.

Ubiquitination in the antiviral immune response

Ubiquitination has long been known to regulate fundamental cellular processes through the induction of proteasomal degradation of target proteins. More recently, 'atypical' non-degradative types of polyubiquitin chains have been appreciated as important regulatory moieties by modulating the activity or subcellular localization of key signaling proteins. Intriguingly, many of these non-degradative types of ubiquitination regulate the innate sensing pathways initiated by pattern recognition receptors (PRRs), ultimately coordinating an effective antiviral immune response. Here we discuss recent advances in understanding the functional roles of degradative and atypical types of ubiquitination in innate immunity to viral infections, with a specific focus on the signaling pathways triggered by RIG-I-like receptors, Toll-like receptors, and the intracellular viral DNA sensor cGAS.

Association of PELI1 polymorphisms in systemic lupus erythematosus susceptibility in a Chinese population

Objective

Studies in animal models have indicated that Pellino 1 is involved in inflammatory and autoimmune diseases, such as systemic lupus erythematosus (SLE). The current study was designed to determine whether PELI1 confers genetic susceptibility to SLE in humans, as assessed in a Chinese Han population.

Methods

Blood samples were drawn from patients diagnosed with SLE and healthy volunteers. Three single nucleotide polymorphism (SNP) loci with a minor allele frequency of at least 0.05 were chosen to evaluate the correlation between PELI1 genotype and the incidence of SLE.

Results

There was a significant difference in the frequency distribution of the rs329497 allele between the SLE patients and the healthy controls (A vs. G; Bonferroni corrected p = 0.036, odds ratio = 0.75, 95% confidence interval = 0.60–0.94). No differences in the genotype and allele frequencies of other SNP loci were observed between the two groups. Furthermore, the alleles and genotypes of the three SNPs were not associated with lupus nephritis.

Conclusion

In the Chinese Han population, PELI1 SNPs may be associated with SLE susceptibility.

Pellino1-mediated TGF-β1 synthesis contributes to mechanical stress induced cardiac fibroblast activation

Activation of cardiac fibroblasts is a key event in the progression of cardiac fibrosis that leads to heart failure. However, the molecular mechanisms underlying mechanical stress-induced cardiac fibroblast activation are complex and poorly understood. This study demonstrates that Pellino1, an E3 ubiquitin ligase, was activated in vivo in pressure overloaded rat hearts and in cultured neonatal rat cardiac fibroblasts (NRCFs) exposed to mechanical stretch in vitro. Suppression of the expression and activity of Pellino1 by adenovirus-mediated delivery of shPellino1 (adv-shpeli1) attenuated pressure overload-induced cardiac dysfunction and cardiac hypertrophy and decreased cardiac fibrosis in rat hearts. Transfection of adv-shpeli1 also significantly attenuated mechanical stress-induced proliferation, differentiation and collagen synthesis in NRCFs. Pellino1 silencing also abrogated mechanical stretch-induced polyubiquitination of tumor necrosis factor-alpha receptor association factor-6 (TRAF6) and receptor-interacting protein 1 (RIP1) and consequently decreased the DNA binding activity of nuclear factor-kappa B (NF-κB) in NRCFs. In addition, Pellino1 silencing prevented stretch-induced activation of p38 and activator protein 1 (AP-1) binding activity in NRCFs. Chromatin Immunoprecipitation (ChIP) and luciferase reporter assays showed that Pellino1 silencing prevented the binding of NF-κB and AP-1 to the promoter region of transforming growth factor-β1 (TGF-β1) thus dampening TGF-β1 transactivation. Our data reveal a previously unrecognized role of Pellino1 in extracellular matrix deposition and cardiac fibroblast activation in response to mechanical stress and provides a novel target for treatment of cardiac fibrosis and heart failure.

Pellino 1 promotes lymphomagenesis by deregulating BCL6 polyubiquitination

The signal-responsive E3 ubiquitin ligase pellino 1 (PELI1) regulates TLR and T cell receptor (TCR) signaling and contributes to the maintenance of autoimmunity; however, little is known about the consequence of mutations that result in upregulation of PELI1. Here, we developed transgenic mice that constitutively express human PELI1 and determined that these mice have a shorter lifespan due to tumor formation. Constitutive expression of PELI1 resulted in ligand-independent hyperactivation of B cells and facilitated the development of a wide range of lymphoid tumors, with prominent B cell infiltration observed across multiple organs. PELI1 directly interacted with the oncoprotein B cell chronic lymphocytic leukemia (BCL6) and induced lysine 63-mediated BCL6 polyubiquitination. In samples from patients with diffuse large B cell lymphomas (DLBCLs), PELI1 expression levels positively correlated with BCL6 expression, and PELI1 overexpression was closely associated with poor prognosis in DLBCLs. Together, these results suggest that increased PELI1 expression and subsequent induction of BCL6 promotes lymphomagenesis and that this pathway may be a potential target for therapeutic strategies to treat B cell lymphomas.