Negative regulation of NF-kappaB signaling by PIAS1

Coinfection with bacterial pathogens and genetic modification of PRRSV-2 for suppression of NF-κB and attenuation of proinflammatory responses

Porcine reproductive and respiratory syndrome virus (PRRSV) infects pulmonary alveolar macrophages and induces inflammation in the respiratory system. In swine farms, coinfection with PRRSV and bacterial pathogens is common and can result in clinically complicated outcomes, including porcine respiratory disease complex. Coinfection can cause excessive expressions of proinflammatory mediators and may lead to cytokine-storm-like syndrome. An immunological hallmark of PRRSV-2 is the bidirectional regulation of NF-κB with the nucleocapsid (N) protein identified as the NF-κB activator. We generated an NF-κB-silencing mutant PRRSV-2 by mutating the N gene to block its binding to PIAS1 [protein inhibitor of activated STAT-1 (signal transducer and activator of transcription 1)]. PIAS1 functions as an NF-κB repressor, and thus, the PIAS1-binding modified N-mutant PRRSV-2 became NF-κB activation-resistant in its phenotype. During coinfection of pigs with PRRSV-2 and Streptococcus suis, the N-mutant PRRSV-2 decreased the expression of proinflammatory cytokines and showed clinical attenuation. This review describes the coinfection of pigs with various pathogens, the generation of mutant PRRSV for NF-κB suppression, inflammatory profiles during bacterial coinfection, and the potential application of these findings to designing a new vaccine candidate for PRRSV-2.

DOC2b enrichment mitigates proinflammatory cytokine-induced CXCL10 expression by attenuating IKKβ and STAT-1 signaling in human islets

INTRODUCTION

Type 1 diabetic human islet β-cells are deficient in double C 2 like domain beta (DOC2b) protein. Further, DOC2b protects against cytokine-induced pancreatic islet β-cell stress and apoptosis. However, the mechanisms underpinning the protective effects of DOC2b remain unknown.

METHODS

Biochemical studies, qPCR, proteomics, and immuno-confocal microscopy were conducted to determine the underlying protective mechanisms of DOC2b in β-cells. DOC2b-enriched or -depleted primary islets (human and mouse) and β-cell lines challenged with or without proinflammatory cytokines, global DOC2b heterozygous knockout mice subjected to multiple-low-dose-streptozotocin (MLD-STZ), were used for these studies.

RESULTS

A significant elevation of stress-induced CXCL10 mRNA was observed in DOC2b-depleted β-cells and primary mouse islets. Further, DOC2b enrichment markedly attenuated cytokine-induced CXCL10 levels in primary non-diabetic human islets and β-cells. DOC2b enrichment also reduced total-NF-κB p65 protein levels in human islets challenged with T1D mimicking proinflammatory cytokines. IKKβ, NF-κB p65, and STAT-1 are capable of associating with DOC2b in cytokine-challenged β-cells. DOC2b enrichment in cytokine-stressed human islets and β-cells corresponded with a significant reduction in activated and total IKKβ protein levels. Total IκBβ protein was increased in DOC2b-enriched human islets subjected to acute cytokine challenge. Cytokine-induced activated and total STAT-1 protein and mRNA levels were markedly reduced in DOC2b-enriched human islets. Intriguingly, DOC2b also prevents ER-stress-IKKβ and STAT-1 crosstalk in the rat INS1-832/13 β-cell line.

CONCLUSION

The mechanisms underpinning the protective effects of DOC2b involve attenuation of IKKβ-NF-κB p65 and STAT-1 signaling, and reduced CXCL10 expression.

DOC2b enrichment mitigates proinflammatory cytokine-induced CXCL10 expression by attenuating IKKβ and STAT-1 signaling in human islets

Introduction

Type 1 diabetic human islet β-cells are deficient in double C 2 like domain beta (DOC2b) protein. Further, DOC2b protects against cytokine-induced pancreatic islet β-cell stress and apoptosis. However, the mechanisms underpinning the protective effects of DOC2b remain unknown.

Methods

Biochemical studies, qPCR, proteomics, and immuno-confocal microscopy were conducted to determine the underlying protective mechanisms of DOC2b in β-cells. DOC2b- enriched or-depleted primary islets (human and mouse) and β-cell lines challenged with or without proinflammatory cytokines, global DOC2b heterozygous knockout mice subjected to multiple-low-dose-streptozotocin (MLD-STZ), were used for these studies.

Results

A significant elevation of stress-induced CXCL10 mRNA was observed in DOC2b- depleted β-cells and primary mouse islets. Further, DOC2b enrichment markedly attenuated cytokine-induced CXCL10 levels in primary non-diabetic human islets and β-cells. DOC2b enrichment also reduced total-NF-κB p65 protein levels in human islets challenged with T1D mimicking proinflammatory cytokines. IKKβ, NF-κB p65, and STAT-1 are capable of associating with DOC2b in cytokine-challenged β-cells. DOC2b enrichment in cytokine-stressed human islets and β-cells corresponded with a significant reduction in activated and total IKKβ protein levels. Total IκBβ protein was increased in DOC2b-enriched human islets subjected to acute cytokine challenge. Cytokine-induced activated and total STAT-1 protein and mRNA levels were markedly reduced in DOC2b-enriched human islets. Intriguingly, DOC2b also prevents ER-stress-IKKβ and STAT-1 crosstalk in the rat INS1-832/13 β-cell line.

Conclusion

The mechanisms underpinning the protective effects of DOC2b involve attenuation of IKKβ-NF-κB p65 and STAT-1 signaling, and reduced CXCL10 expression.

Graphical abstract

SUMOylation at the crossroads of gut health: insights into physiology and pathology

SUMOylation, a post-translational modification involving the covalent attachment of small ubiquitin-like modifier (SUMO) proteins to target substrates, plays a pivotal role at the intersection of gut health and disease, influencing various aspects of intestinal physiology and pathology. This review provides a comprehensive examination of SUMOylation's diverse roles within the gut microenvironment. We examine its critical roles in maintaining epithelial barrier integrity, regulating immune responses, and mediating host-microbe interactions, thereby highlighting the complex molecular mechanisms that underpin gut homeostasis. Furthermore, we explore the impact of SUMOylation dysregulation in various intestinal disorders, including inflammatory bowel diseases and colorectal cancer, highlighting its implications as a potential diagnostic biomarker and therapeutic target. By integrating current research findings, this review offers valuable insights into the dynamic interplay between SUMOylation and gut health, paving the way for novel therapeutic strategies aimed at restoring intestinal equilibrium and combating associated pathologies.

A UL26-PIAS1 complex antagonizes anti-viral gene expression during Human Cytomegalovirus infection

Viral disruption of innate immune signaling is a critical determinant of productive infection. The Human Cytomegalovirus (HCMV) UL26 protein prevents anti-viral gene expression during infection, yet the mechanisms involved are unclear. We used TurboID-driven proximity proteomics to identify putative UL26 interacting proteins during infection to address this issue. We find that UL26 forms a complex with several immuno-regulatory proteins, including several STAT family members and various PIAS proteins, a family of E3 SUMO ligases. Our results indicate that UL26 prevents STAT phosphorylation during infection and antagonizes transcriptional activation induced by either interferon α (IFNA) or tumor necrosis factor α (TNFα). Additionally, we find that the inactivation of PIAS1 sensitizes cells to inflammatory stimulation, resulting in an anti-viral transcriptional environment similar to ΔUL26 infection. Further, PIAS1 is important for HCMV cell-to-cell spread, which depends on the presence of UL26, suggesting that the UL26-PIAS1 interaction is vital for modulating intrinsic anti-viral defense.

Protein inhibitor of activated STAT1 (PIAS1) alleviates cerebral infarction and inflammation after cerebral ischemia in rats

Background

Ischemic stroke is a severe disorder with high incidence, disability rate and mortality. Multiple pathogenesis mechanisms are involved in ischemic stroke, such as inflammation and neuronal cell apoptosis. Protein inhibitor of activated signal transducer and activators of transcription 1 (PIAS1) plays a crucial role in various biological processes, including inflammation. PIAS1 is also downregulated in ischemia-reperfusion injury and involved in the disease processes. However, the role of PIAS1 in cerebral ischemia is unclear.

Methods

Sprague-Dawley (SD) rats were induced with middle cerebral artery occlusion (MCAO). The role and mechanisms of PIAS1 in ischemic cerebral infarction were explored by Longa test, 2,3,5-triphenyltetrazolium chloride (TTC) staining, Morris water maze (MWM) test, hematoxylin-eosin (HE) staining, quantification of brain water content, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL), Western blot and immunofluorescence assays.

Results

The expression of PIAS1 in MCAO-induced rat was declined compared to sham rats. Overexpression of PIAS1 reduced the Longa neurological scores, the percent of infarction area, the pathological abnormality, the escape latency of swimming and the percent of brain water content, and increased the number of platform crossings and time in the target quadrant in the MCAO-induced rats. Besides, overexpression of PIAS1 decreased the MCAO-induced the contents of IL-1β, IL-6 and TNF-α, but further elevated the concentrations of IL-10 in both sera and brain tissues. Moreover, overexpression of PIAS1 reversed the MCAO-induced apoptosis rate and the relative protein level of Bax, cleaved caspase3 and Bcl-2. Overexpression of PIAS1 also reversed the level of proteins involved in NF-κB pathway.

Conclusion

PIAS1 reduced inflammation and apoptosis, thereby alleviating ischemic cerebral infarction in MCAO-induced rats through regulation NF-κB pathway.

PIAS family in cancer: from basic mechanisms to clinical applications

Protein inhibitors of activated STATs (PIAS) are proteins for cytokine signaling that activate activator-mediated gene transcription. These proteins, as versatile cellular regulators, have been described as regulators of approximately 60 proteins. Dysregulation of PIAS is associated with inappropriate gene expression that promotes oncogenic signaling in multiple cancers. Multiple lines of evidence have revealed that PIAS family members show modulated expressions in cancer cells. Most frequently reported PIAS family members in cancer development are PIAS1 and PIAS3. SUMOylation as post-translational modifier regulates several cellular machineries. PIAS proteins as SUMO E3 ligase factor promotes SUMOylation of transcription factors tangled cancer cells for survival, proliferation, and differentiation. Attenuated PIAS-mediated SUMOylation mechanism is involved in tumorigenesis. This review article provides the PIAS/SUMO role in the modulation of transcriptional factor control, provides brief update on their antagonistic function in different cancer types with particular focus on PIAS proteins as a bonafide therapeutic target to inhibit STAT pathway in cancers, and summarizes natural activators that may have the ability to cure cancer.

The Identification of Host Proteins That Interact with Non-Structural Proteins-1α and -1β of Porcine Reproductive and Respiratory Syndrome Virus-1

Porcine reproductive and respiratory syndrome viruses (PRRSV-1 and -2) are the causative agents of one of the most important infectious diseases affecting the global pig industry. Previous studies, largely focused on PRRSV-2, have shown that non-structural protein-1α (NSP1α) and NSP1β modulate host cell responses; however, the underlying molecular mechanisms remain to be fully elucidated. Therefore, we aimed to identify novel PRRSV-1 NSP1-host protein interactions to improve our knowledge of NSP1-mediated immunomodulation. NSP1α and NSP1β from a representative western European PRRSV-1 subtype 1 field strain (215-06) were used to screen a cDNA library generated from porcine alveolar macrophages (PAMs), the primary target cell of PRRSV, using the yeast-2-hybrid system. This identified 60 putative binding partners for NSP1α and 115 putative binding partners for NSP1β. Of those taken forward for further investigation, 3 interactions with NSP1α and 27 with NSP1β were confirmed. These proteins are involved in the immune response, ubiquitination, nuclear transport, or protein expression. Increasing the stringency of the system revealed NSP1α interacts more strongly with PIAS1 than PIAS2, whereas NSP1β interacts more weakly with TAB3 and CPSF4. Our study has increased our knowledge of the PRRSV-1 NSP1α and NSP1β interactomes, further investigation of which could provide detailed insight into PRRSV immunomodulation and aid vaccine development.

Methylation Levels in the Promoter Region of FHIT and PIAS1 Genes Associated with Mastitis Resistance in Xinjiang Brown Cattle

Mastitis causes serious economic losses in the dairy industry, but there are no effective treatments or preventive measures. In this study, the ZRANB3, PIAS1, ACTR3, LPCAT2, MGAT5, and SLC37A2 genes in Xinjiang brown cattle, which are associated with mastitis resistance, were identified using a GWAS. Pyrosequencing analysis showed that the promoter methylation levels of the FHIT and PIAS1 genes in the mastitis group were higher and lower, respectively, than those in the healthy group (65.97 ± 19.82% and 58.00 ± 23.52%). However, the methylation level of the PIAS1 gene promoter region in the mastitis group was lower than that in the healthy group (11.48 ± 4.12% and 12.17 ± 4.25%). Meanwhile, the methylation levels of CpG3, CpG5, CpG8, and CpG15 in the promoter region of the FHIT and PIAS1 genes in the mastitis group were significantly higher than those in the healthy group (p < 0.01), respectively. RT-qPCR showed that the expression levels of the FHIT and PIAS1 genes were significantly higher in the healthy group than those in the mastitis group (p < 0.01). Correlation analysis showed that the promoter methylation level of the FHIT gene was negatively correlated with its expression. Hence, increased methylation in the promoter of the FHIT gene reduces the mastitis resistance in Xinjiang brown cattle. Finally, this study provides a reference for the molecular-marker-assisted selection of mastitis resistance in dairy cattle.

Human DUX4 and mouse Dux interact with STAT1 and broadly inhibit interferon-stimulated gene induction

DUX4 activates the first wave of zygotic gene expression in the early embryo. Mis-expression of DUX4 in skeletal muscle causes facioscapulohumeral dystrophy (FSHD), whereas expression in cancers suppresses IFNγ induction of major histocompatibility complex class I (MHC class I) and contributes to immune evasion. We show that the DUX4 protein interacts with STAT1 and broadly suppresses expression of IFNγ-stimulated genes by decreasing bound STAT1 and Pol-II recruitment. Transcriptional suppression of interferon-stimulated genes (ISGs) requires conserved (L)LxxL(L) motifs in the carboxyterminal region of DUX4 and phosphorylation of STAT1 Y701 enhances interaction with DUX4. Consistent with these findings, expression of endogenous DUX4 in FSHD muscle cells and the CIC-DUX4 fusion containing the DUX4 CTD in a sarcoma cell line inhibit IFNγ induction of ISGs. Mouse Dux similarly interacted with STAT1 and suppressed IFNγ induction of ISGs. These findings identify an evolved role of the DUXC family in modulating immune signaling pathways with implications for development, cancers, and FSHD.

SUMO and PIAS repress NF-κB activation in a basal chordate

Small ubiquitin-like modifier (SUMO) regulates various biological processes, including the MyD88/TICAMs-IRAKs-TRAF6-NF-κB pathway, one of the core immune pathways. However, its functions are inconsistent between invertebrates and vertebrates and have rarely been investigated in lower chordates, including amphioxus and fishes. Here, we investigated the SUMOylation gene system in the amphioxus, a living basal chordate. We found that amphioxus has a SUMOylation system that has a complete set of genes and preserves several ancestral traits. We proceeded to study their molecular functions using the mammal cell lines. Both amphioxus SUMO1 and SUMO2 were shown to be able to attach to NF-κB Rel and to inhibit NF-κB activation by 50-75% in a dose-dependent fashion. The inhibition by SUMO2 could be further enhanced by the addition of the SUMO E2 ligase UBC9. In comparison, while human SUMO2 inhibited RelA, human SUMO1 slightly activated RelA. We also showed that, similar to human PIAS1-4, amphioxus PIAS could serve as a SUMO E3 ligase and promote its self-SUMOylation. This suggests that amphioxus PIAS is functionally compatible in human cells. Moreover, we showed that amphioxus PIAS is not only able to inhibit NF-κB activation induced by MyD88, TICAM-like, TRAF6 and IRAK4 but also able to suppress NF-κB Rel completely in the presence of SUMO1/2 in a dose-insensitive manner. This suggests that PIAS could effectively block Rel by promoting Rel SUMOylation. In comparison, in humans, only PIAS3, but not PIAS1/2/4, has been reported to promote NF-κB SUMOylation. Taken together, the findings from amphioxus, together with those from mammals and other species, not only offer insights into the functional volatility of the animal SUMO system, but also shed light on its evolutionary transitions from amphioxus to fish, and ultimately to humans.

Reprogramming viral immune evasion for a rational design of next-generation vaccines for RNA viruses

Type I interferons (IFNs-α/β) are antiviral cytokines that constitute the innate immunity of hosts to fight against viral infections. Recent studies, however, have revealed the pleiotropic functions of IFNs, in addition to their antiviral activities, for the priming of activation and maturation of adaptive immunity. In turn, many viruses have developed various strategies to counteract the IFN response and to evade the host immune system for their benefits. The inefficient innate immunity and delayed adaptive response fail to clear of invading viruses and negatively affect the efficacy of vaccines. A better understanding of evasion strategies will provide opportunities to revert the viral IFN antagonism. Furthermore, IFN antagonism-deficient viruses can be generated by reverse genetics technology. Such viruses can potentially serve as next-generation vaccines that can induce effective and broad-spectrum responses for both innate and adaptive immunities for various pathogens. This review describes the recent advances in developing IFN antagonism-deficient viruses, their immune evasion and attenuated phenotypes in natural host animal species, and future potential as veterinary vaccines.

A protein inhibitor of activated STAT (CgPIAS) negatively regulates the expression of ISGs by inhibiting STAT activation in oyster Crassostrea gigas

The protein inhibitor of activated STAT (PIAS) family proteins act as the important negative regulators in janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway, which can be also involved in regulating the expression of interferon-stimulated genes (ISGs). In the present study, a PIAS homologue (designated as CgPIAS) was identified from oyster Crassostrea gigas. The open reading frame (ORF) of CgPIAS cDNA was of 1887 bp encoding a peptide of 628 amino acid residues. The CgPIAS protein contains a conserved scaffold attachment factor A/B/acinus/PIAS (SAP) domain, a Pro-Ile-Asn-Ile-Thr (PINIT) motif, a RING-finger-like zinc-binding domain (RLD) and two SUMO-interaction Motifs (SIMs). The deduced amino acid sequence of CgPIAS shared 74.58-81.36% similarity with other PIAS family members in the RLD domain. The mRNA transcripts of CgPIAS were detected in all the tested tissues with highest level in haemocytes (32.98-fold of mantles, p < 0.001). After poly (I:C) and recombinant Interferon-like protein (rCgIFNLP) stimulation, the mRNA expression of CgPIAS in haemocytes significantly up-regulated to the highest level at 48 h (7.38-fold, p < 0.001) and at 24 h (13.08-fold, p < 0.01), respectively. Moreover, the nuclear translocation of CgPIAS was observed in haemocytes after poly (I:C) stimulation. Biolayer Interferometry (BLI) assay revealed that the recombinant protein CgPIAS-RLD could interact with the recombinant protein CgSTAT in vitro with the K_D value of 3.88 × 10^-8 M. In the CgPIAS-RNAi oysters, the green signals of CgSTAT protein in nucleus of haemocytes increased compared with that in NC-RNAi group, and the mRNA expression of myxovirus resistance (CgMx1), oligoadenylate synthase-like proteins (CgOASL), CgViperin and IFN-induced protein 44-like (CgIFI44L-1) in haemocytes significantly increased at 12 h after poly (I:C) stimulation, which were 2.39-fold (p < 0.05), 2.18-fold (p < 0.001), 1.74-fold (p < 0.05), and 2.89-fold (p < 0.01) of that in control group, respectively. The above results indicated that CgPIAS negatively regulated the ISG expression by inhibiting STAT activation in oyster C. gigas.

The SUMO components in rheumatoid arthritis

Small ubiquitin-like modifier (SUMO) proteins can reversibly attach covalently or non-covalently to lysine residues of various substrates. The processes are named SUMOylation and de-SUMOylation, which maintain a dynamic balance in the physiological state, and are regulated by SUMO components. However, the dysregulation of components disturbs the balance and alters the functions of target proteins, which causes the occurrence of diseases. To date, certain SUMO components, including SUMO-1, SUMO-2/3, SAE1/Uba2, Ubc9, PIASs (protein inhibitors of activated signal transducer and activator of transcription) and SENPs (SUMO-specific proteases), have been found to participate in the pathogenesis of RA and their potential value as therapeutic targets also have been highlighted. In addition, single nucleotide polymorphisms (SNPs) in the SUMO components have been reported to be associated with disease susceptibility. Until now, only the SNP site of SUMO-4 has been reported in RA. Here we provided a systematic overview of the general characteristics of SUMO components and highlighted a summary of their impact on RA.

SENP1 prevents steatohepatitis by suppressing RIPK1-driven apoptosis and inflammation

Activation of RIPK1-driven cell death and inflammation play important roles in the progression of nonalcoholic steatohepatitis (NASH). However, the mechanism underlying RIPK1 activation in NASH remains unclear. Here we identified SENP1, a SUMO-specific protease, as a key endogenous inhibitor of RIPK1. SENP1 is progressively reduced in proportion to NASH severity in patients. Hepatocyte-specific SENP1-knockout mice develop spontaneous NASH-related phenotypes in a RIPK1 kinase-dependent manner. We demonstrate that SENP1 deficiency sensitizes cells to RIPK1 kinase-dependent apoptosis by promoting RIPK1 activation following TNFα stimulation. Mechanistically, SENP1 deSUMOylates RIPK1 in TNF-R1 signaling complex (TNF-RSC), keeping RIPK1 in check. Loss of SENP1 leads to SUMOylation of RIPK1, which re-orchestrates TNF-RSC and modulates the ubiquitination patterns and activity of RIPK1. Notably, genetic inhibition of RIPK1 effectively reverses disease progression in hepatocyte-specific SENP1-knockout male mice with high-fat-diet-induced nonalcoholic fatty liver. We propose that deSUMOylation of RIPK1 by SENP1 provides a pathophysiologically relevant cell death-restricting checkpoint that modulates RIPK1 activation in the pathogenesis of nonalcoholic steatohepatitis.

Analysis of Tumor-Infiltrating T-Cell Transcriptomes Reveal a Unique Genetic Signature across Different Types of Cancer

CD8+ and CD4+ T-cells play a key role in cellular immune responses against cancer by cytotoxic responses and effector lineages differentiation, respectively. These subsets have been found in different types of cancer; however, it is unclear whether tumor-infiltrating T-cell subsets exhibit similar transcriptome profiling across different types of cancer in comparison with healthy tissue-resident T-cells. Thus, we analyzed the single cell transcriptome of five tumor-infiltrating CD4-T, CD8-T and Treg cells obtained from different types of cancer to identify specific pathways for each subset in malignant environments. An in silico analysis was performed from single-cell RNA-sequencing data available in public repositories (Gene Expression Omnibus) including breast cancer, melanoma, colorectal cancer, lung cancer and head and neck cancer. After dimensionality reduction, clustering and selection of the different subpopulations from malignant and nonmalignant datasets, common genes across different types of cancer were identified and compared to nonmalignant genes for each T-cell subset to identify specific pathways. Exclusive pathways in CD4+ cells, CD8+ cells and Tregs, and common pathways for the tumor-infiltrating T-cell subsets were identified. Finally, the identified pathways were compared with RNAseq and proteomic data obtained from T-cell subsets cultured under malignant environments and we observed that cytokine signaling, especially Th2-type cytokine, was the top overrepresented pathway in Tregs from malignant samples.

The Interplay Between Coronavirus and Type I IFN Response

In the past few decades, newly evolved coronaviruses have posed a global threat to public health and animal breeding. To control and prevent the coronavirus-related diseases, understanding the interaction of the coronavirus and the host immune system is the top priority. Coronaviruses have evolved multiple mechanisms to evade or antagonize the host immune response to ensure their replication. As the first line and main component of innate immune response, type I IFN response is able to restrict virus in the initial infection stage; it is thus not surprising that the primary aim of the virus is to evade or antagonize the IFN response. Gaining a profound understanding of the interaction between coronaviruses and type I IFN response will shed light on vaccine development and therapeutics. In this review, we provide an update on the current knowledge on strategies employed by coronaviruses to evade type I IFN response.

Chicory: Understanding the Effects and Effectors of This Functional Food

Industrial chicory has been the subject of numerous studies, most of which provide clinical observations on its health effects. Whether it is the roasted root, the flour obtained from the roots or the different classes of molecules that enter into the composition of this plant, understanding the molecular mechanisms of action on the human organism remains incomplete. In this study, we were interested in three molecules or classes of molecules present in chicory root: fructose, chlorogenic acids, and sesquiterpene lactones. We conducted experiments on the murine model and performed a nutrigenomic analysis, a metabolic hormone assay and a gut microbiota analysis, associated with in vitro observations for different responses. We have highlighted a large number of effects of all these classes of molecules that suggest a pro-apoptotic activity, an anti-inflammatory, antimicrobial, antioxidant, hypolipidemic and hypoglycemic effect and also an important role in appetite regulation. A significant prebiotic activity was also identified. Fructose seems to be the most involved in these activities, contributing to approximately 83% of recorded responses, but the other classes of tested molecules have shown a specific role for these different effects, with an estimated contribution of 23-24%.

Liver and Kidney Surgical Anatomy to Verify the Effect of miR-221 on Organ Damage in Septic Rats

Background

Related studies have shown that miR-221 has the ability to promote inflammatory response. This experiment mainly discusses the effect of miR-221 on acute liver and kidney injury in septic rats.

Method

Thirty Sprague Dawley (SD) rats were randomly divided into a (1) control group, (2) sepsis group, (3) miR-221 overexpression group, (4) miR-221 inhibition group, (5) HECTD2 inhibition group, and (6) miR-221 overexpression + HECTD2 inhibition group. The sepsis rat model was prepared by cecal ligation and puncture (CLP). The expression levels of miR-221 and HECTD2 were detected by RT-qPCR. The levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the liver were detected by the IFCC method. The levels of blood urea nitrogen (BUN) were detected by the creatine oxidase method. The levels of inflammatory factors were detected by ELISA. The apoptosis rate of liver and kidney cells was detected by flow cytometry. The expression of p65 protein was detected by western blotting.

Result

RT-qPCR results showed that the expressions of miR-221 and HECTD2 were upregulated in septic rats (P < 0.05). Compared with group 1, the liver function index, kidney function index, liver and kidney apoptosis rate, serum inflammatory factor level, and p65 protein expression in each group were increased (P < 0.05). Compared with group 2, the liver function index, kidney function index, liver and kidney apoptosis rate, serum inflammatory factor level, and p65 protein expression in groups 4 and 5 were decreased (P < 0.05). Compared with group 2, the expression of HECTD2 was upregulated in group 3 (P < 0.05). Compared with group 3, the liver function index, renal function index, liver and kidney apoptosis rate, serum inflammatory factor level, and p65 protein expression were decreased in group 6 (P < 0.05).

Conclusion

MiR-221 promotes the expression of HECTD2 in septic rats, and inhibition of miR-221 expression can reduce the degree of liver and kidney injury in septic rats.

Exploring the Relationship of Perivascular Adipose Tissue Inflammation and the Development of Vascular Pathologies

Initially thought to only provide mechanical support for the underlying blood vessels, perivascular adipose tissue (PVAT) has now emerged as a regulator of vascular function. A healthy PVAT exerts anticontractile and anti-inflammatory actions on the underlying vasculature via the release of adipocytokines such as adiponectin, nitric oxide, and omentin. However, dysfunctional PVAT produces more proinflammatory adipocytokines such as leptin, resistin, interleukin- (IL-) 6, IL-1β, and tumor necrosis factor-alpha, thus inducing an inflammatory response that contributes to the pathogenesis of vascular diseases. In this review, current knowledge on the role of PVAT inflammation in the development of vascular pathologies such as atherosclerosis and hypertension was discussed.

A PIAS1 Protective Variant S510G Delays polyQ Disease Onset by Modifying Protein Homeostasis

BACKGROUND

Polyglutamine (polyQ) diseases are dominant neurodegenerative diseases caused by an expansion of the polyQ-encoding CAG repeats in the disease-causing gene. The length of the CAG repeats is the major determiner of the age at onset (AO) of polyQ diseases, including Huntington's disease (HD) and spinocerebellar ataxia type 3 (SCA3).

OBJECTIVE

We set out to identify common genetic variant(s) that may affect the AO of polyQ diseases.

METHODS

Three hundred thirty-seven patients with HD or SCA3 were enrolled for targeted sequencing of 583 genes implicated in proteinopathies. In total, 16 genes were identified as containing variants that are associated with late AO of polyQ diseases. For validation, we further investigate the variants of PIAS1 because PIAS1 is an E3 SUMO (small ubiquitin-like modifier) ligase for huntingtin (HTT), the protein linked to HD.

RESULTS

Biochemical analyses revealed that the ability of PIAS1^S510G to interact with mutant huntingtin (mHTT) was less than that of PIAS1^WT , resulting in lower SUMOylation of mHTT and lower accumulation of insoluble mHTT. Genetic knock-in of PIAS1^S510G in a HD mouse model (R6/2) ameliorated several HD-like deficits (including shortened life spans, poor grip strength and motor coordination) and reduced neuronal accumulation of mHTT.

CONCLUSIONS

Our findings suggest that PIAS1 is a genetic modifier of polyQ diseases. The naturally occurring variant, PIAS1^S510G , is associated with late AO in polyQ disease patients and milder disease severity in HD mice. Our study highlights the possibility of targeting PIAS1 or pathways governing protein homeostasis as a disease-modifying approach for treating patients with HD.

NF-κB signaling in inflammation and cancer

Since nuclear factor of κ-light chain of enhancer-activated B cells (NF-κB) was discovered in 1986, extraordinary efforts have been made to understand the function and regulating mechanism of NF-κB for 35 years, which lead to significant progress. Meanwhile, the molecular mechanisms regulating NF-κB activation have also been illuminated, the cascades of signaling events leading to NF-κB activity and key components of the NF-κB pathway are also identified. It has been suggested NF-κB plays an important role in human diseases, especially inflammation-related diseases. These studies make the NF-κB an attractive target for disease treatment. This review aims to summarize the knowledge of the family members of NF-κB, as well as the basic mechanisms of NF-κB signaling pathway activation. We will also review the effects of dysregulated NF-κB on inflammation, tumorigenesis, and tumor microenvironment. The progression of the translational study and drug development targeting NF-κB for inflammatory diseases and cancer treatment and the potential obstacles will be discussed. Further investigations on the precise functions of NF-κB in the physiological and pathological settings and underlying mechanisms are in the urgent need to develop drugs targeting NF-κB for inflammatory diseases and cancer treatment, with minimal side effects.

PIAS Factors from Rainbow Trout Control NF-κB- and STAT-Dependent Gene Expression

Four ‘protein inhibitors of activated STAT’ (PIAS) control STAT-dependent and NF-κB-dependent immune signalling in humans. The genome of rainbow trout (Oncorhynchus mykiss) contains eight pias genes, which encode at least 14 different pias transcripts that are differentially expressed in a tissue- and cell-specific manner. Pias1a2 was the most strongly expressed variant among the analysed pias genes in most tissues, while pias4a2 was commonly low or absent. Since the knock-out of Pias factors in salmonid CHSE cells using CRISPR/Cas9 technology failed, three structurally different Pias protein variants were selected for overexpression studies in CHSE-214 cells. All three factors quenched the basal activity of an NF-κB promoter in a dose-dependent fashion, while the activity of an Mx promoter remained unaffected. Nevertheless, all three overexpressed Pias variants from trout strongly reduced the transcript level of the antiviral Stat-dependent mx gene in ifnγ-expressing CHSE-214 cells. Unlike mx, the overexpressed Pias factors modulated the transcript levels of NF-κB-dependent immune genes (mainly il6, il10, ifna3, and stat4) in ifnγ-expressing CHSE-214 cells in different ways. This dissimilar modulation of expression may result from the physical cooperation of the Pias proteins from trout with differential sets of interacting factors bound to distinct nuclear structures, as reflected by the differential nuclear localisation of trout Pias factors. In conclusion, this study provides evidence for the multiplication of pias genes and their sub-functionalisation during salmonid evolution.

Genetic profiles of subcutaneous panniculitis-like T-cell lymphoma and clinicopathological impact of HAVCR2 mutations

Recent studies identified germline mutations in HAVCR2 (encoding T-cell immunoglobulin mucin 3) as a genetic factor that predisposes to subcutaneous panniculitis-like T-cell lymphoma (SPTCL). However, the differences between HAVCR2-mutated (HAVCR2MUT) and HAVCR2 wild-type (HAVCR2WT) SPTCLs remain unclear. A nationwide cohort of 53 patients with SPTCL diagnosed at 8 Korean institutions was established. Whole-exome sequencing and RNA-sequencing were performed on 8 patients in the discovery set. In the validation set, targeted gene sequencing or direct sequencing of HAVCR2 was performed. Of 49 patients with available HAVCR2 status, 25 (51.0%) were HAVCR2Y82C. HAVCR2Y82C was associated with younger age (P = .001), development of hemophagocytic lymphohistiocytosis or hemophagocytic lymphohistiocytosis-like systemic illness (P < .001), and short relapse-free survival (RFS) (P = .023). Most mutated genes in SPTCLs were involved in immune responses, epigenetic modifications, and cell signaling. Mutations in UNC13D, PIAS3, and KMT2D were more frequent in HAVCR2WT SPTCLs. At the gene expression level, HAVCR2Y82C SPTCLs were enriched in genes involved in IL6-JAK-STAT3 signaling and in tumor necrosis factor-α signaling via NF-κB. CCR4 was significantly upregulated in HAVCR2WT SPTCLs both at the messenger RNA level and at the protein level. We established a risk stratification system for SPTCL by integrating clinical and histopathological features, including age and HAVCR2 mutation status. This risk stratification system was strongly associated with RFS (P = .031). In conclusion, the HAVCR2Y82C mutation was common in Korean patients with SPTCL and was associated with unique clinicopathological and genetic features. Combining clinicopathological parameters could aid in predicting prognosis for patients with SPTCL.

Viruses, SUMO, and immunity: the interplay between viruses and the host SUMOylation system

The conjugation of small ubiquitin-like modifier (SUMO) proteins to substrates is a well-described post-translational modification that regulates protein activity, subcellular localization, and protein-protein interactions for a variety of downstream cellular activities. Several studies describe SUMOylation as an essential post-translational modification for successful viral infection across a broad range of viruses, including RNA and DNA viruses, both enveloped and un-enveloped. These viruses include but are not limited to herpes viruses, human immunodeficiency virus-1, and coronaviruses. In addition to the SUMOylation of viral proteins during infection, evidence shows that viruses manipulate the SUMO pathway for host protein SUMOylation. SUMOylation of host and viral proteins greatly impacts host innate immunity through viral manipulation of the host SUMOylation machinery to promote viral replication and pathogenesis. Other post-translational modifications like phosphorylation can also modulate SUMO function. For example, phosphorylation of COUP-TF interacting protein 2 (CTIP2) leads to its SUMOylation and subsequent proteasomal degradation. The SUMOylation of CTIP2 and subsequent degradation prevents CTIP2-mediated recruitment of a multi-enzymatic complex to the HIV-1 promoter that usually prevents the transcription of integrated viral DNA. Thus, the "SUMO switch" could have implications for CTIP2-mediated transcriptional repression of HIV-1 in latency and viral persistence. In this review, we describe the consequences of SUMO in innate immunity and then focus on the various ways that viral pathogens have evolved to hijack the conserved SUMO machinery. Increased understanding of the many roles of SUMOylation in viral infections can lead to novel insight into the regulation of viral pathogenesis with the potential to uncover new targets for antiviral therapies.

Inhibitory feedback control of NF-κB signalling in health and disease

Cells must adapt to changes in their environment to maintain cell, tissue and organismal integrity in the face of mechanical, chemical or microbiological stress. Nuclear factor-κB (NF-κB) is one of the most important transcription factors that controls inducible gene expression as cells attempt to restore homeostasis. It plays critical roles in the immune system, from acute inflammation to the development of secondary lymphoid organs, and also has roles in cell survival, proliferation and differentiation. Given its role in such critical processes, NF-κB signalling must be subject to strict spatiotemporal control to ensure measured and context-specific cellular responses. Indeed, deregulation of NF-κB signalling can result in debilitating and even lethal inflammation and also underpins some forms of cancer. In this review, we describe the homeostatic feedback mechanisms that limit and ‘re-set’ inducible activation of NF-κB. We first describe the key components of the signalling pathways leading to activation of NF-κB, including the prominent role of protein phosphorylation and protein ubiquitylation, before briefly introducing the key features of feedback control mechanisms. We then describe the array of negative feedback loops targeting different components of the NF-κB signalling cascade including controls at the receptor level, post-receptor signalosome complexes, direct regulation of the critical ‘inhibitor of κB kinases’ (IKKs) and inhibitory feedforward regulation of NF-κB-dependent transcriptional responses. We also review post-transcriptional feedback controls affecting RNA stability and translation. Finally, we describe the deregulation of these feedback controls in human disease and consider how feedback may be a challenge to the efficacy of inhibitors.

Functional genomics study of protein inhibitor of activated STAT1 in mouse hippocampal neuronal cells revealed by RNA sequencing

Protein inhibitor of activated STAT1 (PIAS1), a small ubiquitin-like modifier (SUMO) E3 ligase, was considered to be an inhibitor of STAT1 by inhibiting the DNA-binding activity of STAT1 and blocking STAT1-mediated gene transcription in response to cytokine stimulation. PIAS1 has been determined to be involved in modulating several biological processes such as cell proliferation, DNA damage responses, and inflammatory responses, both in vivo and in vitro. However, the role played by PIAS1 in regulating neurodegenerative diseases, including Alzheimer’s disease (AD), has not been determined. In our study, significantly different expression levels of PIAS1 between normal controls and AD patients were detected in four regions of the human brain. Based on a functional analysis of Pias1 in undifferentiated mouse hippocampal neuronal HT-22 cells, we observed that the expression levels of several AD marker genes could be inhibited by Pias1 overexpression. Moreover, the proliferation ability of HT-22 cells could be promoted by the overexpression of Pias1. Furthermore, we performed RNA sequencing (RNA-seq) to evaluate and quantify the gene expression profiles in response to Pias1 overexpression in HT-22 cells. As a result, 285 significantly dysregulated genes, including 79 upregulated genes and 206 downregulated genes, were identified by the comparison of Pias1/+ cells with WT cells. Among these genes, five overlapping genes, including early growth response 1 (Egr1), early growth response 2 (Egr2), early growth response 3 (Egr3), FBJ osteosarcoma oncogene (Fos) and fos-like antigen 1 (Fosl1), were identified by comparison of the transcription factor binding site (TFBS) prediction results for STAT1, whose expression was evaluated by qPCR. Three cell cycle inhibitors, p53, p18 and p21, were significantly downregulated with the overexpression of Pias1. Analysis of functional enrichment and expression levels showed that basic region leucine zipper domain-containing transcription factors including zinc finger C2H2 (zf-C2H2), homeobox and basic/helix-loop-helix (bHLH) in several signaling pathways were significantly involved in PIAS1 regulation in HT-22 cells. A reconstructed regulatory network under PIAS1 overexpression demonstrated that there were 43 related proteins, notably Nr3c2, that directly interacted with PIAS1.

SUMOylation Connects Cell Stress Responses and Inflammatory Control: Lessons From the Gut as a Model Organ

Conjugation with the small ubiquitin-like modifier (SUMO) constitutes a key post-translational modification regulating the stability, activity, and subcellular localization of its target proteins. However, the vast numbers of identified SUMO substrates obscure a clear view on the function of SUMOylation in health and disease. This article presents a comprehensive review on the physiological relevance of SUMOylation by discussing how global SUMOylation levels—rather than specific protein SUMOylation—shapes the immune response. In particular, we highlight the growing body of work on SUMOylation in intestinal pathologies, because of the unique metabolic, infectious, and inflammatory challenges of this organ. Recent studies show that global SUMOylation can help restrain detrimental inflammation while maintaining immune defenses and tissue integrity. These results warrant further efforts to develop new therapeutic tools and strategies to control SUMOylation in infectious and inflammatory disorders.

Exploring the "Other" subfamily of HECT E3-ligases for therapeutic intervention

The HECT E3 ligase family regulates key cellular signaling pathways, with its 28 members divided into three subfamilies: NEDD4 subfamily (9 members), HERC subfamily (6 members) and "Other" subfamily (13 members). Here, we focus on the less-explored "Other" subfamily and discuss the recent findings pertaining to their biological roles. The N-terminal regions preceding the conserved HECT domains are significantly diverse in length and sequence composition, and are mostly unstructured, except for short regions that incorporate known substrate-binding domains. In some of the better-characterized "Other" members (e.g., HUWE1, AREL1 and UBE3C), structure analysis shows that the extended region (~ aa 50) adjacent to the HECT domain affects the stability and activity of the protein. The enzymatic activity is also influenced by interactions with different adaptor proteins and inter/intramolecular interactions. Primarily, the "Other" subfamily members assemble atypical ubiquitin linkages, with some cooperating with E3 ligases from the other subfamilies to form branched ubiquitin chains on substrates. Viruses and pathogenic bacteria target and hijack the activities of "Other" subfamily members to evade host immune responses and cause diseases. As such, these HECT E3 ligases have emerged as potential candidates for therapeutic drug development.

PIAS1 modulates striatal transcription, DNA damage repair, and SUMOylation with relevance to Huntington's disease

DNA damage repair genes are modifiers of disease onset in Huntington's disease (HD), but how this process intersects with associated disease pathways remains unclear. Here we evaluated the mechanistic contributions of protein inhibitor of activated STAT-1 (PIAS1) in HD mice and HD patient-derived induced pluripotent stem cells (iPSCs) and find a link between PIAS1 and DNA damage repair pathways. We show that PIAS1 is a component of the transcription-coupled repair complex, that includes the DNA damage end processing enzyme polynucleotide kinase-phosphatase (PNKP), and that PIAS1 is a SUMO E3 ligase for PNKP. Pias1 knockdown (KD) in HD mice had a normalizing effect on HD transcriptional dysregulation associated with synaptic function and disease-associated transcriptional coexpression modules enriched for DNA damage repair mechanisms as did reduction of PIAS1 in HD iPSC-derived neurons. KD also restored mutant HTT-perturbed enzymatic activity of PNKP and modulated genomic integrity of several transcriptionally normalized genes. The findings here now link SUMO modifying machinery to DNA damage repair responses and transcriptional modulation in neurodegenerative disease.

Targeting NF-κB pathway for the therapy of diseases: mechanism and clinical study

NF-κB pathway consists of canonical and non-canonical pathways. The canonical NF-κB is activated by various stimuli, transducing a quick but transient transcriptional activity, to regulate the expression of various proinflammatory genes and also serve as the critical mediator for inflammatory response. Meanwhile, the activation of the non-canonical NF-κB pathway occurs through a handful of TNF receptor superfamily members. Since the activation of this pathway involves protein synthesis, the kinetics of non-canonical NF-κB activation is slow but persistent, in concordance with its biological functions in the development of immune cell and lymphoid organ, immune homeostasis and immune response. The activation of the canonical and non-canonical NF-κB pathway is tightly controlled, highlighting the vital roles of ubiquitination in these pathways. Emerging studies indicate that dysregulated NF-κB activity causes inflammation-related diseases as well as cancers, and NF-κB has been long proposed as the potential target for therapy of diseases. This review attempts to summarize our current knowledge and updates on the mechanisms of NF-κB pathway regulation and the potential therapeutic application of inhibition of NF-κB signaling in cancer and inflammatory diseases.

Non-proteolytic ubiquitination of OTULIN regulates NF-κB signaling pathway

NF-κB signaling regulates diverse processes such as cell death, inflammation, immunity, and cancer. The activity of NF-κB is controlled by methionine 1-linked linear polyubiquitin, which is assembled by the linear ubiquitin chain assembly complex (LUBAC) and the ubiquitin-conjugating enzyme UBE2L3. Recent studies found that the deubiquitinase OTULIN breaks the linear ubiquitin chain, thus inhibiting NF-κB signaling. Despite the essential role of OTULIN in NF-κB signaling has been established, the regulatory mechanism for OTULIN is not well elucidated. To discover the potential regulators of OTULIN, we analyzed the OTULIN protein complex by proteomics and revealed several OTULIN-binding proteins, including LUBAC and tripartite motif-containing protein 32 (TRIM32). TRIM32 is known to activate NF-κB signaling, but the mechanism is not clear. Genetic complement experiments found that TRIM32 is upstream of OTULIN and TRIM32-mediated NF-κB activation is dependent on OTULIN. Mutagenesis of the E3 ligase domain showed that the E3 ligase activity is essential for TRIM32-mediated NF-κB activation. Further experiments found that TRIM32 conjugates polyubiquitin onto OTULIN and the polyubiquitin blocks the interaction between HOIP and OTULIN, thereby activating NF-κB signaling. Taken together, we report a novel regulatory mechanism by which TRIM32-mediated non-proteolytic ubiquitination of OTULIN impedes the access of OTULIN to the LUBAC and promotes NF-κB activation.

Chordate PIAS proteins act as conserved repressors of the TRAF6 self-polyubiquitination

In mammals, PIAS proteins are important SUMO E3 ligases and act as versatile regulators of over sixty different proteins, including components from the NF-κB pathways. But the PIAS functions are not well-understood due to complicated molecular mechanisms and multiple gene paralogs with overlapping roles, which is especially true in lower vertebrates where dedicated studies are scarce. As a basal chordate with a single PIAS gene, amphioxus is a convenient model to study PIAS from the evolutionary perspective. TRAF6 is a critical adaptor of the NF-κB pathways but it is not known whether TRAF6 is regulated by PIAS. Here we discover that in mammalian cells, amphioxus PIAS inhibited NF-κB activation by co-localizing and binding with TRAF6. The interaction relied on the N-terminal SAP and PINIT domains of PIAS. TRAF6 is an E3 ubiquitin ligase, which initiates downstream NF-κB signaling by promoting its self-ubiquitination. Both amphioxus SUMO1 and Ubc9 (SUMO E2 ligase) could suppress TRAF6 self-ubiquitination and NF-κB activation, suggesting that the SUMOylation activity competed away the ubiquitination activity of TRAF6. However, we show that the wild-type PIAS and the mutant PIAS without SUMO E3 ligase activity both could inhibit TRAF6-mediated NF-κB activation by reducing TRAF6 self-ubiquitination. This implies that SUMO ligase activity is not the only mechanism for PIAS to negatively regulate TRAF6. Finally, we tested the interactions between human PIAS1-4 and TRAF6. It reveals that human PIAS1, 3 and 4, but not 2, were able to repress NF-κB activation by reducing TRAF6 self-ubiquitination. Taken together, our study discovers a conserved regulatory interaction between chordate PIAS and TRAF6. It therefore sheds light on the complicated role of PIAS in immune regulation, and may help to understand the PIAS functions in other lower chordate taxa, such as jawless and jawed fishes.

Age-Dependent and -Independent Effects of Perivascular Adipose Tissue and Its Paracrine Activities during Neointima Formation

Cardiovascular risk factors may act by modulating the composition and function of the adventitia. Here we examine how age affects perivascular adipose tissue (PVAT) and its paracrine activities during neointima formation. Aortic tissue and PVAT or primary aortic smooth muscle cells from male C57BL/6JRj mice aged 52 weeks (“middle-aged”) were compared to tissue or cells from mice aged 16 weeks (“adult”). Vascular injury was induced at the carotid artery using 10% ferric chloride. Carotid arteries from the middle-aged mice exhibited smooth muscle de-differentiation and elevated senescence marker expression, and vascular injury further aggravated media and adventitia thickening. Perivascular transplantation of PVAT had no effect on these parameters, but age-independently reduced neointima formation and lumen stenosis. Quantitative PCR analysis revealed a blunted increase in senescence-associated proinflammatory changes in perivascular tissue compared to visceral adipose tissue and higher expression of mediators attenuating neointima formation. Elevated levels of protein inhibitor of activated STAT1 (PIAS1) and lower expression of STAT1- or NFκB-regulated genes involved in adipocyte differentiation, inflammation, and apoptosis/senescence were present in mouse PVAT, whereas PIAS1 was reduced in the PVAT of patients with atherosclerotic vessel disease. Our findings suggest that age affects adipose tissue and its paracrine vascular activities in a depot-specific manner. PIAS1 may mediate the age-independent vasculoprotective effects of perivascular fat.

Downregulation of Protein Inhibitor of Activated STAT (PIAS) 1 Is Possibly Involved in the Process of Allograft Rejection

BACKGROUND

Protein inhibitors of activated STAT (PIAS) proteins are regarded as negative regulators of cytokine-signaling and potent immunosuppressive proteins. However, their role in the process of organ transplant rejection has not been elucidated.

METHODS

In the current study, we compared transcript levels of PIAS1 to 4 in the peripheral blood of renal transplant recipients who experienced transplant rejection with those having normal transplant functions. Expression of PIAS1 was significantly higher in nonrejected group compared with the rejected group among male recipients; however, differences were insignificant among female recipients. Expressions of other PIAS genes were not different between study groups. Significant pairwise correlations were found between expression levels of PIAS genes in all study subgroups. The current investigation highlights the role of PIAS1 downregulation in the evolution of graft rejection and potentiates this gene as a predictive marker for transplant fate.

Protein inhibitor of activated STAT1 (PIAS1) inhibits IRF8 activation of Epstein-Barr virus lytic gene expression

Epstein-Barr virus (EBV), a major human oncogenic pathogen, establishes life-long persistent infections. In latently infected B lymphocytes, the virus persists as an episome in the nucleus. Periodic reactivation of latent virus is controlled by both viral and cellular factors. Our recent studies showed that interferon regulatory factor 8 (IRF8) is required for EBV lytic reactivation while protein inhibitor of activated STAT1 (PIAS1) functions as an EBV restriction factor to block viral reactivation. Here, we show that IRF8 directly binds to the EBV genome and regulates EBV lytic gene expression together with PU.1 and EBV transactivator RTA. Furthermore, our study reveals that PIAS1 antagonizes IRF8/PU.1-mediated lytic gene activation through binding to and inhibiting IRF8. Together, our study establishes IRF8 as a transcriptional activator in promoting EBV reactivation and defines PIAS1 as an inhibitor of IRF8 to limit lytic gene expression.

Functional characterization of a protein inhibitor of activated STAT (PIAS) gene in Litopenaeus vannamei

Protein inhibitor of activated STAT (PIAS) plays a critical role in the feedback modulation of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway as a negative regulator in mammals and Drosophila, but the function of PIAS in crustaceans is still unclear. In this study, a PIAS termed LvPIAS was cloned and characterized from Litopenaeus vannamei. The full length of LvPIAS was 3065 bp, including a 2361 bp open reading frame (ORF) coding for a protein of 786 aa. LvPIAS expression was most abundant in muscle and could respond to the challenge of LPS, Vibrio parahaemolyticus, Staphhylococcus aureus, Poly I: C and white spot syndrome virus (WSSV). LvPIAS could be induced by the transcription factor LvSTAT, but LvPIAS could inhibit the transcriptional activity of LvSTAT to the LvPIAS promoter conversely, which indicated that there was a negative feedback loop between LvSTAT and LvPIAS. Furthermore, RNAi-mediated knockdown of LvPIAS shrimps showed higher survival rate to WSSV infection than those in the control group (dsGFP injection), suggesting that LvPIAS may play a negatively role against WSSV infection.

Suppressors of Cytokine Signaling and Protein Inhibitors of Activated Signal Transducer and Activator of Transcriptions As Therapeutic Targets in Flavivirus Infections

Flaviviruses cause significant human diseases putting more than 400 million people at risk annually worldwide. Because of migration and improved transportation, these viruses can be found on all continents (except Antarctica). Although a majority of the viruses are endemic in the tropics, a few [West Nile virus (WNV) and tick-borne encephalitis virus (TBEV)] have shown endemicity in Europe and North America. Currently, there are vaccines for the Yellow fever virus, Japanese encephalitis virus, and TBEV, but there is no effective vaccine and/or therapy against all other flaviviruses. Although there are intensive efforts to develop vaccines for Zika viruses, dengue viruses, and WNVs, there is the need for alternative or parallel antiviral therapeutic approaches. Suppressors of cytokine signaling (SOCS) and protein inhibitors of activated signal transducer and activator of transcription (STATs; PIAS), both regulatory proteins of the Janus kinase/STAT signaling pathway, have been explored as therapeutic targets in herpes simplex and vaccinia viruses, as well as in cancer therapy. In this review, we briefly describe the function of SOCS and PIAS and their therapeutic potential in flaviviral infections. [Figure: see text].

NCoR1: Putting the Brakes on the Dendritic Cell Immune Tolerance

Understanding the mechanisms fine-tuning immunogenic versus tolerogenic balance in dendritic cells (DCs) is of high importance for therapeutic approaches. We found that NCoR1-mediated direct repression of the tolerogenic program in conventional DCs is essential for induction of an optimal immunogenic response. NCoR1 depletion upregulated a wide variety of tolerogenic genes in activated DCs, which consequently resulted in increased frequency of FoxP3⁺ regulatory T cells. Mechanistically, NCoR1 masks the PU.1-bound super-enhancers on major tolerogenic genes after DC activation that are subsequently bound by nuclear factor-κB. NCoR1 knockdown (KD) reduced RelA nuclear translocation and activity, whereas RelB was unaffected, providing activated DCs a tolerogenic advantage. Moreover, NCoR1^DC−/- mice depicted enhanced Tregs in draining lymph nodes with increased disease burden upon bacterial and parasitic infections. Besides, adoptive transfer of activated NCoR1 KD DCs in infected animals showed a similar phenotype. Collectively, our results demonstrated NCoR1 as a promising target to control DC-mediated immune tolerance.

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NCoR1 directly represses tolerogenic program in mouse cDCs

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Depletion of NCoR1 in cDCs enhanced Treg development ex vivo and in vivo

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NCoR1 masks PU.1-bound super-enhancers on tolerogenic genes in cDCs

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NCoR1^DC−/− animals depicted enhanced Treg frequency and infection load

Interaction of PIAS1 with PRRS virus nucleocapsid protein mediates NF-κB activation and triggers proinflammatory mediators during viral infection

Porcine reproductive and respiratory syndrome virus (PRRSV) activates NF-κB during infection. We examined the ability of all 22 PRRSV genes for NF-κB regulation and determined the nucleocapsid (N) protein as the NF-κB activator. Protein inhibitor of activated STAT1 (signal transducer and activator of transcription 1) (PIAS1) was identified as a cellular protein binding to N. PIAS1 is known to bind to p65 (RelA) in the nucleus and blocks its DNA binding, thus functions as a repressor of NF-κB. Binding of N to PIAS1 released p65 for NF-κB activation. The N-terminal half of PIAS1 was mapped as the N-binding domain, and this region overlapped its p65-binding domain. For N, the region between 37 and 72 aa was identified as the binding domain to PIAS1, and this domain alone was able to activate NF-κB. A nuclear localization signal (NLS) knock-out mutant N did not activate NF-κB, and this is mostly likely due to the lack of its interaction with PIAS1 in the nucleus, demonstrating the positive correlation between the binding of N to PIAS1 and the NF-κB activation. Our study reveals a role of N in the nucleus for NF-κB activation and proinflammatory cytokine production during infection.

Protein inhibitor of activated STAT1 Ser503 phosphorylation-mediated Elk-1 SUMOylation promotes neuronal survival in APP/PS1 mice

BACKGROUND AND PURPOSE

Protein inhibitor of activated STAT1 (PIAS1) is phosphorylated by IKKα at Ser⁹⁰ in a PIAS1 E3 ligase activity-dependent manner. Whether PIAS1 is also phosphorylated at other residues and the functional significance of these additional phosphorylation events are not known. The transcription factor Elk-1 remains SUMOylated under basal conditions, but the role of Elk-1 SUMOylation in brain is unknown. Here, we examined the functional significance of PIAS1-mediated Elk-1 SUMOylation in Alzheimer's disease (AD) using the APP/PS1 mouse model of AD and amyloid β (Aβ) microinjections in vivo.

EXPERIMENTAL APPROACH

Novel phosphorylation site(s) on PIAS1 were identified by LC-MS/MS, and MAPK/ERK-mediated phosphorylation of Elk-1 demonstrated using in vitro kinase assays. Elk-1 SUMOylation by PIAS1 in brain was determined using in vitro SUMOylation assays. Apoptosis in hippocampus was assessed by measuring GADD45α expression by western blotting, and apoptosis of hippocampal neurons in APP/PS1 mice was assessed by TUNEL assay.

KEY RESULTS

Using LC-MS/MS, we identified a novel MAPK/ERK-mediated phosphorylation site on PIAS1 at Ser⁵⁰³ and showed this phosphorylation determines PIAS1 E3 ligase activity. In rat brain, Elk-1 was SUMOylated by PIAS1, which decreased Elk-1 phosphorylation and down-regulated GADD45α expression. Moreover, lentiviral-mediated transduction of Elk-1-SUMO1 reduced the number of hippocampal apoptotic neurons in APP/PS1 mice.

CONCLUSIONS AND IMPLICATIONS

MAPK/ERK-mediated phosphorylation of PIAS1 at Ser⁵⁰³ determines PIAS1 E3 ligase activity. Moreover, PIAS1 mediates SUMOylation of Elk-1, which functions as an endogenous defence mechanism against Aβ toxicity in vivo. Targeting Elk-1 SUMOylation could be considered a novel therapeutic strategy against AD.

A NIK-SIX signalling axis controls inflammation by targeted silencing of non-canonical NF-κB

The non-canonical NF-κB signalling cascade is essential for lymphoid organogenesis, B cell maturation, osteoclast differentiation, and inflammation in mammals1,2; dysfunction of this system is associated with human diseases, including immunological disorders and cancer3-6. Although expression of NF-κB-inducing kinase (NIK, also known as MAP3K14) is the rate-limiting step in non-canonical NF-κB pathway activation2,7, the mechanisms by which transcriptional responses are regulated remain largely unknown. Here we show that the sine oculis homeobox (SIX) homologue family transcription factors SIX1 and SIX2 are integral components of the non-canonical NF-κB signalling cascade. The developmentally silenced SIX proteins are reactivated in differentiated macrophages by NIK-mediated suppression of the ubiquitin proteasome pathway. Consequently, SIX1 and SIX2 target a subset of inflammatory gene promoters and directly inhibit the trans-activation function of the transcription factors RELA and RELB in a negative feedback circuit. In support of a physiologically pivotal role for SIX proteins in host immunity, a human SIX1 transgene suppressed inflammation and promoted the recovery of mice from endotoxic shock. In addition, SIX1 and SIX2 protected RAS/P53-driven non-small-cell lung carcinomas from inflammatory cell death induced by SMAC-mimetic chemotherapeutic agents (small-molecule activators of the non-canonical NF-κB pathway). Our findings identify a NIK-SIX signalling axis that fine-tunes inflammatory gene expression programs under both physiological and pathological conditions.

A Threshold Model for T-Cell Activation in the Era of Checkpoint Blockade Immunotherapy

Continued discoveries of negative regulators of inflammatory signaling provide detailed molecular insights into peripheral tolerance and anti-tumor immunity. Accumulating evidence indicates that peripheral tolerance is maintained at multiple levels of immune responses by negative regulators of proinflammatory signaling, soluble anti-inflammatory factors, inhibitory surface receptors & ligands, and regulatory cell subsets. This review provides a global overview of these regulatory machineries that work in concert to maintain peripheral tolerance at cellular and host levels, focusing on the direct and indirect regulation of T cells. The recent success of checkpoint blockade immunotherapy (CBI) has initiated a dramatic shift in the paradigm of cancer treatment. Unprecedented responses to CBI have highlighted the central role of T cells in both anti-tumor immunity and peripheral tolerance and underscored the importance of T cell exhaustion in cancer. We discuss the therapeutic implications of modulating the negative regulators of T cell function for tumor immunotherapy with an emphasis on inhibitory surface receptors & ligands—central players in T cell exhaustion and targets of checkpoint blockade immunotherapies. We then introduce a Threshold Model for Immune Activation—the concept that these regulatory mechanisms contribute to defining a set threshold of immunogenic (proinflammatory) signaling required to elicit an anti-tumor or autoimmune response. We demonstrate the value of the Threshold Model in understanding clinical responses and immune related adverse events in the context of peripheral tolerance, tumor immunity, and the era of Checkpoint Blockade Immunotherapy.

A nanogel based oral gene delivery system targeting SUMOylation machinery to combat gut inflammation

Poor success rates and challenges associated with the current therapeutic strategies of inflammatory bowel disease (IBD) have accelerated the emergence of gene therapy as an alternative treatment option with great promise. However, oral delivery of nucleic acids (NAs) to an inflamed colon is challenged by multiple barriers presented by the gastrointestinal, extracellular and intracellular compartments. Therefore, we screened a series of polyaspartic acid-derived amphiphilic cationic polymers with varied hydrophobicity for their ability to deliver NAs into mammalian cells. Using the most effective TAC6 polymer, we then engineered biocompatible and stable nanogels composed of polyplexes (TAC6, NA) and an anionic polymer, sodium polyaspartate, that were able to deliver the NAs across mammalian cells using caveolae-mediated cellular uptake. We then utilized these nanogels for oral delivery of PIAS1 (protein inhibitor of activated STAT1), a SUMO 3 ligase, encoding plasmid DNA since PIAS1 is a key nodal therapeutic target for IBD due to its ability to control NF-κB-mediated inflammatory signaling. We show that plasmid delivery using TAC6-derived nanogels diminished gut inflammation in a murine colitis model. Therefore, our study presents engineering of orally deliverable nanogels that can target SUMOylation machinery to combat gut inflammation with very high efficacy.

B Cell Receptor Activation and Chemical Induction Trigger Caspase-Mediated Cleavage of PIAS1 to Facilitate Epstein-Barr Virus Reactivation

Epstein-Barr virus (EBV) in tumor cells is predominately in the latent phase, but the virus can undergo lytic reactivation in response to various stimuli. However, the cellular factors that control latency and lytic replication are poorly defined. In this study, we demonstrated that a cellular factor, PIAS1, restricts EBV lytic replication. PIAS1 depletion significantly facilitated EBV reactivation, while PIAS1 reconstitution had the opposite effect. Remarkably, we found that various lytic triggers promote caspase-dependent cleavage of PIAS1 to antagonize PIAS1-mediated restriction and that caspase inhibition suppresses EBV replication through blocking PIAS1 cleavage. We further demonstrated that a cleavage-resistant PIAS1 mutant suppresses EBV replication upon B cell receptor activation. Mechanistically, we demonstrated that PIAS1 acts as an inhibitor for transcription factors involved in lytic gene expression. Collectively, these results establish PIAS1 as a key regulator of EBV lytic replication and uncover a mechanism by which EBV exploits apoptotic caspases to antagonize PIAS1-mediated restriction.

The Direct and Indirect Roles of NF-κB in Cancer: Lessons from Oncogenic Fusion Proteins and Knock-in Mice

NF-κB signaling pathways play an important role in the regulation of cellular immune and stress responses. Aberrant NF-κB activity has been implicated in almost all the steps of cancer development and many of the direct and indirect contributions of this transcription factor system for oncogenesis were revealed in the recent years. The indirect contributions affect almost all hallmarks and enabling characteristics of cancer, but NF-κB can either promote or antagonize these tumor-supportive functions, thus prohibiting global NF-κB inhibition. The direct effects are due to mutations of members of the NF-κB system itself. These mutations typically occur in upstream components that lead to the activation of NF-κB together with further oncogenesis-promoting signaling pathways. In contrast, mutations of the downstream components, such as the DNA-binding subunits, contribute to oncogenic transformation by affecting NF-κB-driven transcriptional output programs. Here, we discuss the features of recently identified oncogenic RelA fusion proteins and the characterization of pathways that are regulating the transcriptional activity of NF-κB by regulatory phosphorylations. As NF-κB’s central role in human physiology prohibits its global inhibition, these auxiliary or cell type-specific NF-κB regulating pathways are potential therapeutic targets.

The conserved ancient role of chordate PIAS as a multilevel repressor of the NF-κB pathway

In vertebrates, PIAS genes encode versatile cellular regulators, with functions extremely complex and redundant. Here we try to understand their functions from an evolutionary perspective. we evaluate the sequences, expression and molecular functions of amphioxus PIAS genes and compare them with their vertebrate counterparts. Phylogenetic analysis suggests a single PIAS gene in ancestral chordates, which has been duplicated into four families (PIAS1-4) in vertebrates by 2R-WGD but remained single in a basal chordate (amphioxus). Amphioxus PIAS encodes two variants with and without a Serine/Threonine-rich tail, which are retained in human PIAS1-3 but lost in PIAS4. We show that amphioxus PIAS binds C-terminus of NF-κB Rel and blocks the DNA binding activity. In humans, such function is retained in PIAS1, altered in PIAS4, and lost in PIAS2-3. Instead, PIAS3 has evolved new ability to inhibit Rel by binding RHD and promoting SUMOylation. We show that amphioxus PIAS also inhibits NF-κB by binding with upstream signalling adaptor TICAM-like and MyD88. Finally, we verify that human PIAS1, 3 and 4, but not 2, were capable of these newly-discovered functions. Our study offers insight into the sub- and neo-functionalization of PIAS genes and suggests a conserved ancient role for chordate PIAS in NF-κB signalling.

N-Myc-Interacting Protein Negatively Regulates TNF-α-Induced NF-κB Transcriptional Activity by Sequestering NF-κB/p65 in the Cytoplasm

NF-κB is a major regulator of gene transcription involved in immune, inflammation, apoptosis and stress responses. However, the regulation of NF-κB is not completely understood. Here, we report that the N-Myc and STATs Interactor (NMI), an IFN-inducible protein, is an important negative regulator of NF-κB activity. We found that NMI negatively regulates TNF-α-induced IL-6 and IL-1β production in HeLa cells. Overexpression of NMI inhibits NF-κB transcriptional activity, in contrast, depletion of NMI by shRNA increases NF-κB transcriptional activity. Mechanistically, NMI associates with NF-κB/p65 and inhibits NF-κB/p65 nuclear translocation and thereby negatively regulates NF-κB/p65 transcriptional activity. Taken together, our results demonstrate that NMI modulates the NF-κB signaling pathway by sequestering NF-κB/p65 in the cytoplasm, resulting in reduced IL-6 and IL-1β production after TNF-α stimulation. Treatment with IFNα in the presence of NMI leads to increased apoptosis in tumor cells. These findings reveal a novel mechanism by which NMI regulates NF-κB activity.

Identification of novel NF-κB transcriptional targets in TNFα-treated HeLa and HepG2 cells

Identification of target genes of NF-κB is critical for deeply understanding its biological functions. Here, we identified five novel NF-κB target genes. Firstly, we found that 20 NF-κB potential target genes (PTGs) identified by ChIP-Seq and Genechip assay were enriched into the KEGG term of Pathways in cancer, 16 of them were enriched into the KEGG pathways of small cell lung cancer, chronic myeloid leukemia, basal cell carcinoma, pancreatic cancer, and colorectal cancer. Among these PTGs, there are many documented NF-κB target genes. Therefore, NF-κB may play important role in cancer progression by transcriptionally regulating these genes. Apart from the known target genes, we also found some novel PTGs including CYCS, MITF, FZD1, FZD8, and PIAS1. We subsequently demonstrated whether NF-κB transcriptionally control the five PTGs. The ChIP-Seq assay revealed that NF-κB/p65 bound to these genes in TNFα-treated HeLa. The bioinformatic analysis indicated that the NF-κB binding regions (i.e., ChIP-Seq peaks) contained κB sites and NF-κB/RelA DNA-binding motif. The ChIP-qPCR assay also confirmed that NF-κB bound to these regions in both TNFα-treated HeLa and HepG2 cells. The reporter construct showed that NF-κB could regulate luciferase expression via its binding region. Finally, qPCR and Western blot assay demonstrated that NF-κB indeed regulated the expression of these genes in the TNFα-treated HeLa and HepG2 cells. In a word, CYCS, MITF, FZD1, FZD8, and PIAS1 were identified as bona fide NF-κB target genes. These findings provide more insights into the role of NF-κB in cancers.