Perturbation of neddylation-dependent NF-κB responses in the intestinal epithelium drives apoptosis and inhibits resolution of mucosal inflammation

The blockade of neddylation alleviates ventilator-induced lung injury by reducing stretch-induced damage to pulmonary epithelial cells

Ventilator-induced lung injury is a serious complication in mechanically ventilated patients. Neddylation, the post-translational modification of neural precursor cell-expressed developmentally down-regulated 8 (NEDD8) conjugation, regulates numerous biological functions. However, its involvement and therapeutic significance in ventilator-induced lung injury remains unknown. Therefore, this study aimed to examine the kinetics and contribution of activated neddylation and the impact of neddylation inhibition in mice subjected to high tidal volume (HTV) ventilation in vivo and human pulmonary alveolar epithelial cells stimulated through cyclic stretching (CS) in vitro. The neddylation and expression of ubiquitin conjugating enzyme 3 (UBA3), a NEDD8-activating enzyme (NAE) catalytic subunit, were time-dependently upregulated in HTV-ventilated mice. Additionally, the NAE inhibitor MLN4924 considerably attenuated acute lung injury induced by HTV ventilation, manifesting as reduced inflammation and oxidative stress. Furthermore, MLN4924 effectively reduced the secretion of inflammatory cytokines from Ly6Chigh monocytes and neutrophils, subsequently decreasing endothelial permeability. Moreover, our study revealed an upregulation of the neddylation pathway, oxidative stress, and apoptosis during CS of alveolar epithelial cells. However, blockade of neddylation via MLN4924 or through UBA3 knockdown suppressed this upregulation. Overall, the inhibition of neddylation may alleviate HTV-induced acute lung injury by preventing CS-induced damage to alveolar epithelial cells. This indicates that the neddylation pathway plays a critical role in the progression of ventilator-induced lung injury. These findings may provide a new therapeutic target for treating ventilator-induced lung injury.

Inhibition of DCUN1D1 attenuates periodontitis by suppressing NF-κB signaling

Nuclear factor kappa-B (NF-κB) signaling-mediated inflammation contributes greatly to the pathogenesis of periodontitis. Neddylation, a ubiquitin-like posttranslational modification, is known to regulate NF-κB signaling. DCUN1D1 (defective in cullin neddylation 1 domain containing 1) is a critical factor in neddylation and has been shown to regulate NF-κB activation. However, the previse roles of DCUN1D1 in periodontitis are not fully elucidated. To explore the roles of DCUN1D1 in periodontitis, the expression of DCUN1D1 was measured in gingival tissues of patients with periodontitis. We inhibited DCUN1D1 by siRNA knocking down or using inhibitor in gingival fibroblasts and the lipopolysaccharides (LPS)-induced expression of IL-6 and TNF-α, and activation of NF-κB were measured. The expression of DCUN1D1 was increased in gingival tissues of patients with periodontitis. Knocking down or inhibiting DCUN1D1 suppressed LPS-induced production of IL-6 and TNF-α, decreased NF-κB activity, and inhibited LPS-induced activation of NF-κB. Inhibiting DCUN1D1 ameliorates periodontitis by suppressing NF-κB signaling.

MLN4924 alleviates autoimmune myocarditis by promoting Act1 degradation and blocking Act1-mediated mRNA stability

BACKGROUND

Prolonged exposure to interleukin-17A (IL-17A) can induce autoimmune myocarditis, and MLN4924, an inhibitor of NEDD8 activating enzyme (NAE), has been reported to effectively suppress various inflammatory reactions. However, the effects of MLN4924 in IL-17A-mediated inflammation associated with autoimmune myocarditis remain uncertain.

METHODS

An experimental autoimmune myocarditis (EAM) model was established and treated with MLN4924. The inflammation degree of heart tissues was assessed histopathologically. The expression levels of inflammatory cytokines and chemokines were measured using ELISA and RT-qPCR, respectively. Additionally, the interaction of biomacromolecules was detected through co-immunoprecipitation (Co-IP) and RNA immunoprecipitation (RIP).

RESULTS

MLN4924 could attenuate IL-17A-induced inflammation. In the in vivo studies, MLN4924 treatment improved inflammatory responses, diminished immune cell infiltration and tissue fibrosis, and reduced the secretion of various inflammatory cytokines in serum, including IL-1β, IL-6, TNF-α, and MCP-1. In vitro experiments further corroborated these findings, showing that MLN4924 treatment reduced the secretion and transcription of pro-inflammatory factors, particularly MCP-1. Mechanistically, we confirmed that MLN4924 promoted Act1 ubiquitination degradation and disrupted Act1's interaction with IL-17R, thereby impeding the formation of the IL-17R/Act1/TRAF6 complex and subsequent activation of TAK1, c-Jun, and p65. Moreover, MLN4924 interfered with Act1's binding to mRNA, resulting in mRNA instability.

CONCLUSIONS

In conclusion, MLN4924 effectively alleviated inflammatory symptoms in EAM by disrupting the interaction between IL and 17R and Act1, thereby reducing Act1-mediated mRNA stability and resulting in decreased expression of pro-inflammatory factors.

Neddylation Regulation of Immune Responses

Neddylation plays a vital role in post-translational modification, intricately shaping the regulation of diverse biological processes, including those related to cellular immune responses. In fact, neddylation exerts control over both innate and adaptive immune systems via various mechanisms. Specifically, neddylation influences the function and survival of innate immune cells, activation of pattern recognition receptors and GMP-AMP synthase-stimulator of interferon genes pathways, as well as the release of various cytokines in innate immune reactions. Moreover, neddylation also governs the function and survival of antigen-presenting cells, which are crucial for initiating adaptive immune reactions. In addition, neddylation regulates T cell activation, proliferation, differentiation, survival, and their effector functions, thereby ensuring an appropriate adaptive immune response. In this review, we summarize the most recent findings in these aspects and delve into the connection between dysregulated neddylation events and immunological disorders, especially inflammatory diseases. Lastly, we propose future directions and potential treatments for these diseases by targeting neddylation.

Pevonedistat, a first-in-class NEDD8-activating enzyme inhibitor, sensitizes cancer cells to VSVΔ51 oncolytic virotherapy

The clinical efficacy of VSVΔ51 oncolytic virotherapy has been limited by tumor resistance to viral infection, so strategies to transiently repress antiviral defenses are warranted. Pevonedistat is a first-in-class NEDD8-activating enzyme (NAE) inhibitor currently being tested in clinical trials for its antitumor potential. In this study, we demonstrate that pevonedistat sensitizes human and murine cancer cells to increase oncolytic VSVΔ51 infection, increase tumor cell death, and improve therapeutic outcomes in resistant syngeneic murine cancer models. Increased VSVΔ51 infectivity was also observed in clinical human tumor samples. We further identify the mechanism of this effect to operate via blockade of the type 1 interferon (IFN-1) response through neddylation-dependent interferon-stimulated growth factor 3 (ISGF3) repression and neddylation-independent inhibition of NF-κB nuclear translocation. Together, our results identify a role for neddylation in regulating the innate immune response and demonstrate that pevonedistat can improve the therapeutic outcomes of strategies using oncolytic virotherapy.

Bi-allelic variants in NAE1 cause intellectual disability, ischiopubic hypoplasia, stress-mediated lymphopenia and neurodegeneration

Neddylation has been implicated in various cellular pathways and in the pathophysiology of numerous diseases. We identified four individuals with bi-allelic variants in NAE1, which encodes the neddylation E1 enzyme. Pathogenicity was supported by decreased NAE1 abundance and overlapping clinical and cellular phenotypes. To delineate how cellular consequences of NAE1 deficiency would lead to the clinical phenotype, we focused primarily on the rarest phenotypic features, based on the assumption that these would best reflect the pathophysiology at stake. Two of the rarest features, neuronal loss and lymphopenia worsening during infections, suggest that NAE1 is required during cellular stress caused by infections to protect against cell death. In support, we found that stressing the proteasome system with MG132-requiring upregulation of neddylation to restore proteasomal function and proteasomal stress-led to increased cell death in fibroblasts of individuals with NAE1 genetic variants. Additionally, we found decreased lymphocyte counts after CD3/CD28 stimulation and decreased NF-κB translocation in individuals with NAE1 variants. The rarest phenotypic feature-delayed closure of the ischiopubic rami-correlated with significant downregulation of RUN2X and SOX9 expression in transcriptomic data of fibroblasts. Both genes are involved in the pathophysiology of ischiopubic hypoplasia. Thus, we show that NAE1 plays a major role in (skeletal) development and cellular homeostasis during stress. Our approach suggests that a focus on rare phenotypic features is able to provide significant pathophysiological insights in diseases caused by mutations in genes with pleiotropic effects.

Emerging role of protein modification in inflammatory bowel disease

The onset of inflammatory bowel disease (IBD) involves many factors, including environmental parameters, microorganisms, and the immune system. Although research on IBD continues to expand, the specific pathogenesis mechanism is still unclear. Protein modification refers to chemical modification after protein biosynthesis, also known as post-translational modification (PTM), which causes changes in the properties and functions of proteins. Since proteins can be modified in different ways, such as acetylation, methylation, and phosphorylation, the functions of proteins in different modified states will also be different. Transitions between different states of protein or changes in modification sites can regulate protein properties and functions. Such modifications like neddylation, sumoylation, glycosylation, and acetylation can activate or inhibit various signaling pathways (e.g., nuclear factor-‍κB (NF-‍κB), extracellular signal-regulated kinase (ERK), and protein kinase B (AKT)) by changing the intestinal flora, regulating immune cells, modulating the release of cytokines such as interleukin-1β (IL-‍‍1β), tumor necrosis factor-α (TNF‍-‍α), and interferon-‍γ (IFN-‍γ), and ultimately leading to the maintenance of the stability of the intestinal epithelial barrier. In this review, we focus on the current understanding of PTM and describe its regulatory role in the pathogenesis of IBD.

The Cellular and Developmental Roles of Cullins, Neddylation, and the COP9 Signalosome in Dictyostelium discoideum

Cullins (CULs) are a core component of cullin-RING E3 ubiquitin ligases (CRLs), which regulate the degradation, function, and subcellular trafficking of proteins. CULs are post-translationally regulated through neddylation, a process that conjugates the ubiquitin-like modifier protein neural precursor cell expressed developmentally downregulated protein 8 (NEDD8) to target cullins, as well as non-cullin proteins. Counteracting neddylation is the deneddylase, COP9 signalosome (CSN), which removes NEDD8 from target proteins. Recent comparative genomics studies revealed that CRLs and the CSN are highly conserved in Amoebozoa. A well-studied representative of Amoebozoa, the social amoeba Dictyostelium discoideum, has been used for close to 100 years as a model organism for studying conserved cellular and developmental processes owing to its unique life cycle comprised of unicellular and multicellular phases. The organism is also recognized as an exceptional model system for studying cellular processes impacted by human diseases, including but not limited to, cancer and neurodegeneration. Recent work shows that the neddylation inhibitor, MLN4924 (Pevonedistat), inhibits growth and multicellular development in D. discoideum, which supports previous work that revealed the cullin interactome in D. discoideum and the roles of cullins and the CSN in regulating cellular and developmental processes during the D. discoideum life cycle. Here, we review the roles of cullins, neddylation, and the CSN in D. discoideum to guide future work on using this biomedical model system to further explore the evolutionarily conserved functions of cullins and neddylation.

Cardioprotective effect of MLN4924 on ameliorating autophagic flux impairment in myocardial ischemia-reperfusion injury by Sirt1

Neddylation is essential for cardiomyocyte survival in the presence of oxidative stress, and it participates in autophagy regulation. However, whether MLN4924-an inhibitor of neddylation-exerts cardioprotective effects against myocardial ischemia/reperfusion (MI/R) remains unknown. In the present study, MLN4924 exerted strong cardioprotective effects, demonstrated by significantly elevated cell viability, a decreased LDH leakage rate, and improved cell morphology following H₂O₂-induced injury in vitro. MLN4924 also markedly decreased the serum myocardial zymogram level, ameliorated cardiac histopathological alterations, and alleviated left ventricular contractile dysfunction, thus limiting the cardiac infarct size in vivo compared with those in MI/R mice. Amazingly, such action of MLN4924 was abrogated by a combined treatment with the autophagic flux inhibitor, chloroquine. The mRFP-GFP-LC3 assay illustrated that MLN4924 restored the defective autophagic flux via enhancing the autolysosome formation. Notably, the expression levels of Rab7 and Atg5 were markedly up-regulated in MLN4924 treated cells and mice subjected to H₂O₂ or MI/R, respectively, while knockdown of Sirt1 in cells and heart tissue largely blocked such effect and induced autophagosome accumulation by inhibiting its fusion with lysosomes. Transmission electron microscopic analysis, histopathological assay and TUNEL detection of the heart tissues showed that the absence of Sirt1 blocked the cardioprotective effect of MLN4924 by further exacerbating the impaired autophagic flux during MI/R injury in vivo. Taken together, MLN4924 exhibited the strong cardioprotective action via restoring the impaired autophagic flux in H₂O₂-induced injury in vitro and in MI/R mice. Our work implicated that Sirt1 played a critical role in autophagosome clearance, likely through up-regulating Rab7 in MI/R.

Diverse and pivotal roles of neddylation in metabolism and immunity

Neddylation is one type of protein post-translational modification by conjugating a ubiquitin-like protein neural precursor cell-expressed developmentally downregulated protein 8 to substrate proteins via a cascade involving E1, E2, and E3 enzymes. The best-characterized substrates of neddylation are cullins, essential components of cullin-RING E3 ubiquitin-ligase complexes. The discovery of noncullin neddylation targets indicates that neddylation may have diverse biological functions. Indeed, neddylation has been implicated in various cellular processes including cell cycle progression, metabolism, immunity, and tumorigenesis. Here, we summarized the reported neddylation substrates and also discuss the functions of neddylation in the immune system and metabolism.

The pivotal roles of neddylation pathway in immunoregulation

Introduction

Protein neddylation, one of the most important posttranslational modifications that tagging neuronal precursor cell‐expressed developmentally downregulated protein 8 onto substrate proteins, plays fundamental roles in the process of many cellular functions. A number of studies have demonstrated the critical roles of neddylation modification in multiple pathophysiological processes, but its regulatory role in the immune system has only been finitely unveiled.

Methods

In this review, the latest advances in the field of neddylation modification in regulating the immune responses are succinctly discussed.

Results

Neddylation modification acts as a crucial modulator of innate immune cells (neutrophils, macrophages, and dendritic cells) and lymphocytes. Dysregulation of neddylation alters characteristics and functions of those cells due to abnormal degradation of key signaling molecules involved in immunoregulation. Furthermore, the ectopic immune responses caused by the abnormal neddylation play pivotal roles in a variety of immune‐related diseases, such as infection, inflammation, and cancer.

Conclusions

The pivotal roles of neddylation pathway in immunoregulation are attracted more and more attention, which may provide new insights into the pathogenesis of a variety of immune‐related diseases and help to indicate new therapeutic targets and potential treatment strategies.

HucMSC-exosomes carrying miR-326 inhibit neddylation to relieve inflammatory bowel disease in mice

Background

Inflammatory bowel disease (IBD) is a group of chronic intestinal inflammation that is a risk factor for many gastrointestinal cancers. Exosomes are gradually gaining attention as an emerging treatment method for IBD due to their important biological characteristics. NF‐κB is an important pro‐inflammatory transcription factor kept inactive by IκB protein in the cytoplasm by masking the nuclear localization signal of NF‐κB. The deterioration of IκB is mainly ubiquitination, and this depends on neddylation.

Methods

In this study, we established a dextran sulfate sodium (DSS)‐induced IBD model in BABL/C mice to evaluate the effect of human umbilical cord mesenchymal stem cell‐derived exosomes (hucMSC‐exosomes, hucMSC‐Ex) on the repair of IBD. At the same time, human colorectal mucosa cells (FHC) were stimulated by LPS (lipopolysaccharide) in vitro to activate the inflammatory environment to study the mechanism of hucMSC‐Ex regulating neddylation. The microRNA (miRNA) obtained by sequencing and transfection with hucMSC‐Ex was used to verify the role of miR‐326/neddylation/IκB/NF‐κB signaling pathway in IBD repair.

Results

HucMSC‐Ex inhibited the process of neddylation in relieving DSS‐induced IBD in mice. The binding of NEDD8 (neural precursor cell‐expressed, developmentally downregulated gene 8) to cullin 1 and the activation of NF‐κB signaling pathway were suppressed along with reduced expression levels of neddylation‐related enzyme molecules. The same phenomenon was observed in FHC cells. The miRNA comparison results showed that miR‐326 was highly expressed in hucMSC‐Ex and played an important role in inhibiting the neddylation process. The therapeutic effect of hucMSC‐Ex with high expression of miR‐326 on IBD mice was significantly stronger than that of ordinary hucMSC‐Ex.

Conclusions

HucMSC‐Ex relieves DSS‐induced IBD in a mouse model by inhibiting neddylation through miR‐326.

Microbiota-derived butyrate dynamically regulates intestinal homeostasis through regulation of actin-associated protein synaptopodin

The intestinal mucosa exists in dynamic balance with trillions of luminal microbes. Disruption of the intestinal epithelial barrier, commonly observed in mucosal inflammation and diseases such as inflammatory bowel diseases (IBDs), is often associated with dysbiosis, particularly decreases in species producing short-chain fatty acids (SCFAs), such as butyrate. It remains unclear to what extent microbiota-derived factors contribute to the overall maintenance of intestinal homeostasis. Initial studies revealed that butyrate selectively promotes epithelial barrier function and wound healing. We aimed to define the specific mechanism(s) through which butyrate contributes to these epithelial responses. Guided by an unbiased profiling approach, we identified the dominant regulation of the actin-binding protein synaptopodin (SYNPO). Extensions of this work revealed a role for SYNPO in intestinal epithelial barrier function and wound healing. SYNPO was localized to the intestinal epithelial tight junction and within F-actin stress fibers where it is critical for barrier integrity and cell motility. Butyrate, but not other SCFAs, induced SYNPO in epithelial cell lines and murine colonic enteroids through mechanisms possibly involving histone deacetylase inhibition. Moreover, depletion of the microbiota abrogated expression of SYNPO in the mouse colon, which was rescued with butyrate repletion. Studies in Synpo-deficient mice demonstrated exacerbated disease susceptibility and increased intestinal permeability in a dextran sulfate sodium colitis model. These findings establish a critical role for the microbiota and their products, specifically butyrate, in the regulated expression of SYNPO for intestinal homeostasis and reveal a direct mechanistic link between microbiota-derived butyrate and barrier restoration.

Hypoxia and Innate Immunity: Keeping Up with the HIFsters

Recent years have witnessed an emergence of interest in understanding metabolic changes associated with immune responses, termed immunometabolism. As oxygen is central to all aerobic metabolism, hypoxia is now recognized to contribute fundamentally to inflammatory and immune responses. Studies from a number of groups have implicated a prominent role for oxygen metabolism and hypoxia in innate immunity of healthy tissue (physiologic hypoxia) and during active inflammation (inflammatory hypoxia). This inflammatory hypoxia emanates from a combination of recruited inflammatory cells (e.g., neutrophils, eosinophils, and monocytes), high rates of oxidative metabolism, and the activation of multiple oxygen-consuming enzymes during inflammation. These localized shifts toward hypoxia have identified a prominent role for the transcription factor hypoxia-inducible factor (HIF) in the regulation of innate immunity. Such studies have provided new and enlightening insight into our basic understanding of immune mechanisms, and extensions of these findings have identified potential therapeutic targets. In this review, we summarize recent literature around the topic of innate immunity and mucosal hypoxia with a focus on transcriptional responses mediated by HIF.

TRAF6 neddylation drives inflammatory arthritis by increasing NF-κB activation

Neddylation is a process similar to ubiquitination, and is critical in various inflammatory diseases; however, its importance in the pathogenesis of inflammatory arthritis is not well understood. Here, we investigated the role of neddylation in collagen-induced arthritis (CIA) and its clinical relevance. We showed that neddylation-related genes, including NEDD8 and CULLIN-1, were significantly upregulated in inflamed arthritic synovia. Functionally, neddylation activation was crucial for synovitis of CIA, as the inhibition of neddylation by MLN4924 significantly suppressed synovial cell proliferation and inflammatory responses. Mechanistically, neddylation mediated inflammatory arthritis by regulating NF-κB activation in fibroblast-like synovial cells (FLSs). Furthermore, TNF receptor-associated factor 6 (TRAF6) neddylation at Lys124 was essential for IL-17A-induced NF-κB activation. Replacing the Lys-124 residue with Arg (K124R) resulted in significantly impaired conjugation of NEDD8 to TRAF6, as well as markedly attenuated IL-17A-induced NF-κB activity. Therefore, the pathogenic role of neddylation in CIA as well as its mechanism of action demonstrated here provides a new insight into understanding the role of post-transcriptional modifications in the arthritis inflammatory response.

A Central Role for Heme Oxygenase-1 in the Control of Intestinal Epithelial Chemokine Expression

In mucosal inflammatory disorders, the protective influence of heme oxygenase-1 (HO-1) and its metabolic byproducts, carbon monoxide (CO) and biliverdin, is a topic of significant interest. Mechanisms under investigation include the regulation of macrophage function and mucosal cytokine expression. While there is an increasing recognition of the importance of epithelial-derived factors in the maintenance of intestinal mucosal homeostasis, the contribution of intestinal epithelial cell (IEC) HO-1 on inflammatory responses has not previously been investigated. We examined the influence of modulating HO-1 expression on the inflammatory response of human IECs. Engineered deficiency of HO-1 in Caco-2 and T84 IECs led to increased proinflammatory chemokine expression in response to pathogenic bacteria and inflammatory cytokine stimulation. Crosstalk with activated leukocytes also led to increased chemokine expression in HO-1-deficient cells in an IL-1β dependent manner. Treatment of Caco-2 cells with a pharmacological inducer of HO-1 led to the inhibition of chemokine expression. Mechanistic studies suggest that HO-1 and HO-1-related transcription factors, but not HO-1 metabolic products, are partly responsible for the influence of HO-1 on chemokine expression. In conclusion, our data identify HO-1 as a central regulator of IEC chemokine expression that may contribute to homeo-stasis in the intestinal mucosa.

Protein neddylation and its alterations in human cancers for targeted therapy

Neddylation, a post-translational modification that conjugates an ubiquitin-like protein NEDD8 to substrate proteins, is an important biochemical process that regulates protein function. The best-characterized substrates of neddylation are the cullin subunits of Cullin-RING ligases (CRLs), which, as the largest family of E3 ubiquitin ligases, control many important biological processes, including tumorigenesis, through promoting ubiquitylation and subsequent degradation of a variety of key regulatory proteins. Recently, increasing pieces of experimental evidence strongly indicate that the process of protein neddylation modification is elevated in multiple human cancers, providing sound rationale for its targeting as an attractive anticancer therapeutic strategy. Indeed, neddylation inactivation by MLN4924 (also known as pevonedistat), a small molecule inhibitor of E1 NEDD8-activating enzyme currently in phase I/II clinical trials, exerts significant anticancer effects by inducing cell cycle arrest, apoptosis, senescence and autophagy in a cell-type and context dependent manner. Here, we summarize the latest progresses in the field with a major focus on preclinical studies in validation of neddylation modification as a promising anticancer target.