COMMD1 promotes the ubiquitination of NF-kappaB subunits through a cullin-containing ubiquitin ligase

Unveiling the Cuproptosis in Colitis and Colitis-Related Carcinogenesis: A Multifaceted Player and Immune Moderator

Cuproptosis represents a novel mechanism of cellular demise characterized by the intracellular buildup of copper ions. Unlike other cell death mechanisms, its distinct process has drawn considerable interest for its promising applications in managing inflammatory bowel disease (IBD) and colorectal cancer (CRC). Emerging evidence indicates that copper metabolism and cuproptosis may exert dual regulatory effects within pathological cellular environments, specifically modulating oxidative stress responses, metabolic reprogramming, and immunotherapeutic efficacy. An appropriate level of copper may promote disease progression and exert synergistic effects, but exceeding a certain threshold, copper can inhibit disease development by inducing cuproptosis in pathological cells. This makes abnormal copper levels a potential new therapeutic target for IBD and CRC. This review emphasizes the dual function of copper metabolism and cuproptosis in the progression of IBD and CRC, while also exploring the potential application of copper-based therapies in disease treatment. The analysis further delineates the modulatory influence of tumor immune microenvironment on cuproptosis dynamics, while establishing the therapeutic potential of cuproptosis-targeted strategies in circumventing resistance to both conventional chemotherapeutic agents and emerging immunotherapies. This provides new research directions for the development of future cuproptosis inducers. Finally, this article discusses the latest advances in potential molecular targets of cuproptosis and their related genes in the treatment of IBD and CRC, highlighting future research priorities and unresolved issues.

Chromatin-associated cullin-RING E3 ubiquitin ligases: keeping transcriptionally active NF-κB in check

Nuclear factor-κB (NF-κB) constitutes a family of transcription factors that serve as a critical regulatory hub, dynamically orchestrating inflammatory and immune responses to maintain homeostasis and protect against pathogenic threats. Persistent activation of NF-κB has been implicated in the pathogenesis of various inflammatory diseases and cancer. A critical mechanism to prevent excessive inflammation and its harmful effects is the timely termination of NF-κB's transcriptional activity on target genes. This termination can be facilitated through the ubiquitination and subsequent proteasomal degradation of chromatin-bound RelA, the most active subunit of NF-κB. Several multi-subunit cullin-RING E3 ubiquitin ligases, composed of elongin B/C, cullin2/5, and SOCS-box proteins, have been identified to target RelA for degradation. These E3s, known as ECS complexes, use SOCS-box proteins as substrate-recognizing subunits to engage RelA. SOCS1 is the first identified SOCS-box member that functions in ECSSOCS1 to target chromatin-bound RelA for ubiquitination. Specifically, SOCS1 collaborates with accessory proteins COMMD1 and GCN5 to preferentially recognize Ser468-phosphorylated RelA. Our recent work demonstrates that WSB1 and WSB2 (WSB1/2), two additional SOCS-box proteins with structurally similar WD40 repeat domains, function as substrate-recognizing subunits of ECSWSB1/2 to specifically mediate the ubiquitination and degradation of chromatin-associated RelA methylated at Lys314/315. In this review, we summarize the discovery and functional importance of ECSSOCS1 and ECSWSB1/2 in terminating NF-κB activity, highlight the distinct molecular mechanisms by which they ubiquitinate chromatin-associated RelA in a modification- and gene-specific manner, and discuss their potential as therapeutic targets for inflammatory diseases and cancer.

A Commander-independent function of COMMD3 in endosomal trafficking

Endosomal recycling is a branch of intracellular membrane trafficking that retrieves endocytosed cargo proteins from early and late endosomes to prevent their degradation in lysosomes. A key player in endosomal recycling is the Commander complex, a 16-subunit protein assembly that cooperates with other endosomal factors to recruit cargo proteins and facilitate the formation of tubulo-vesicular carriers. While the crucial role of Commander in endosomal recycling is well established, its molecular mechanism remains poorly understood. Here, we genetically dissected the Commander complex using unbiased genetic screens and comparative targeted mutations. Unexpectedly, our findings revealed a Commander-independent function for COMMD3, a subunit of the Commander complex, in endosomal recycling. COMMD3 regulates a subset of cargo proteins independently of the other Commander subunits. The Commander-independent function of COMMD3 is mediated by its N-terminal domain (NTD), which binds and stabilizes ADP-ribosylation factor 1 (ARF1), a small GTPase regulating endosomal recycling. Mutations disrupting the COMMD3-ARF1 interaction diminish ARF1 expression and impair COMMD3-dependent cargo recycling. These data provide direct evidence that Commander subunits can function outside the holo-complex and raise the intriguing possibility that components of other membrane trafficking complexes may also possess functions beyond their respective complexes.

Identification of COMMD gene family in large yellow croaker (Larimichthys crocea): Immune response induced by Pseudomonas plecoglossicida infection and acute hypoxia stress

The COMMD (Copper Metabolism gene MURR1 Domain) gene family consists of 10 members, which are involved in various biological processes such as copper and sodium transport, NF-κB activity and cell cycle progression. However, the study of COMMD gene family in large yellow croaker (Larimichthys crocea) is largely unknown. In this study, 10 COMMD gene family members (named LcCOMMDs) were successfully identified from large yellow croaker. The results showed that there were differences in the number of LcCOMMDs exons at the level of gene structure, which reflected that they had adjusted and changed accordingly in the process of evolution to adapt to the environment and achieved functional diversification. Through phylogenetic analysis, we found that the LcCOMMDs was highly conserved, indicating their important functions in organisms. It was worth noting that the expression levels of LcCOMMD1, LcCOMMD2, LcCOMMD3, LcCOMMD5 and LcCOMMD10 in the spleen changed significantly after bacterial stress, which suggested that these genes might be involved in the regulation of innate immune response. In addition, the expression levels of LcCOMMD1, LcCOMMD2, LcCOMMD3, LcCOMMD5, LcCOMMD7, LcCOMMD8, LcCOMMD9 and LcCOMMD10 changed significantly after hypoxia exposure, which further proved the role of LcCOMMDs in immune function. In summary, this study not only revealed the important role of COMMD genes in the innate immune response of large yellow croaker, but also provided valuable information for further understanding the regulatory mechanism of COMMD gene family under different conditions.

Association between dietary copper intake and constipation in US adults

Dietary micronutrients are integral to the development and progression of constipation; however, the specific relationship between dietary copper intake and constipation has not been thoroughly investigated. This study aims to examine the correlation between dietary copper intake and constipation among U.S. adults, thereby offering novel insights and recommendations for the clinical management and prevention of constipation. Bowel health data from the National Health and Nutrition Examination Survey (NHANES) conducted between 2005 and 2010 were analyzed. Subjects' dietary information was collected through questionnaire records. Multivariate logistic regression analysis, subgroup analysis, and curve fitting analysis were used to assess the correlation between dietary copper intake and chronic constipation. After adjusting for all possible confounders, each unit increase in dietary copper intake (converted to natural logarithms) was associated with a 20% reduction in the prevalence of constipation (OR = 0.80; 95% CI 0.65-0.98; P = 0.037). The interaction P-values for all subgroups were greater than 0.05, indicating that the findings were stable and consistent across subgroups. The present study showed a significant negative association between dietary copper intake and chronic constipation in adults. This finding raises clinical and healthcare professionals' awareness of the impact of dietary trace elements on intestinal health and has important implications for the development of personalized meal plans and rational supplementation of trace copper in patients with constipation.

Post-translational modifications of p65: state of the art

P65, a protein subunit of NF-κB, is a widely distributed transcription factor in eukaryotic cells and exerts diverse regulatory functions. Post-translational modifications such as phosphorylation, acetylation, methylation and ubiquitination modulate p65 transcriptional activity and function, impacting various physiological and pathological processes including inflammation, immune response, cell death, proliferation, differentiation and tumorigenesis. The intricate interplay between these modifications can be antagonistic or synergistic. Understanding p65 post-translational modifications not only elucidates NF-κB pathway regulation but also facilitates the identification of therapeutic targets and diagnostic markers for associated clinical conditions.

The impact of copper on bone metabolism

Copper is an essential trace element for the human body. Abnormalities in copper metabolism can lead to bone defects, mainly by directly affecting the viability of osteoblasts and osteoclasts and their bone remodeling function, or indirectly regulating bone metabolism by influencing enzyme activities as cofactors. Copper ions released from biological materials can affect osteoblasts and osteoclasts, either directly or indirectly by modulating the inflammatory response, oxidative stress, and rapamycin signaling. This review presents an overview of recent progress in the impact of copper on bone metabolism. Translational potential of this article: The impact of copper on bone metabolism can provide insights into clinical application of copper-containing supplements and biomaterials.

Structural organization of the retriever-CCC endosomal recycling complex

The recycling of membrane proteins from endosomes to the cell surface is vital for cell signaling and survival. Retriever, a trimeric complex of vacuolar protein-sorting-associated protein (VPS)35L, VPS26C and VPS29, together with the CCC complex comprising coiled-coil domain-containing (CCDC)22, CCDC93 and copper metabolism domain-containing (COMMD) proteins, plays a crucial role in this process. The precise mechanisms underlying retriever assembly and its interaction with CCC have remained elusive. Here, we present a high-resolution structure of retriever in humans determined using cryogenic electron microscopy. The structure reveals a unique assembly mechanism, distinguishing it from its remotely related paralog retromer. By combining AlphaFold predictions and biochemical, cellular and proteomic analyses, we further elucidate the structural organization of the entire retriever-CCC complex across evolution and uncover how cancer-associated mutations in humans disrupt complex formation and impair membrane protein homeostasis. These findings provide a fundamental framework for understanding the biological and pathological implications associated with retriever-CCC-mediated endosomal recycling.

Structure and interactions of the endogenous human Commander complex

The Commander complex, a 16-protein assembly, plays multiple roles in cell homeostasis, cell cycle and immune response. It consists of copper-metabolism Murr1 domain proteins (COMMD1-10), coiled-coil domain-containing proteins (CCDC22 and CCDC93), DENND10 and the Retriever subcomplex (VPS26C, VPS29 and VPS35L), all expressed ubiquitously in the body and linked to various diseases. Here, we report the structure and key interactions of the endogenous human Commander complex by cryogenic-electron microscopy and mass spectrometry-based proteomics. The complex consists of a stable core of COMMD1-10 and an effector containing DENND10 and Retriever, scaffolded together by CCDC22 and CCDC93. We establish the composition of Commander and reveal major interaction interfaces. These findings clarify its roles in intracellular transport, and uncover a strong association with cilium assembly, and centrosome and centriole functions.

WSB1/2 target chromatin-bound lysine-methylated RelA for proteasomal degradation and NF-κB termination

Proteasome-mediated degradation of chromatin-bound NF-κB is critical in terminating the transcription of pro-inflammatory genes and can be triggered by Set9-mediated lysine methylation of the RelA subunit. However, the E3 ligase targeting methylated RelA remains unknown. Here, we find that two structurally similar substrate-recognizing components of Cullin-RING E3 ligases, WSB1 and WSB2, can recognize chromatin-bound methylated RelA for polyubiquitination and proteasomal degradation. We showed that WSB1/2 negatively regulated a subset of NF-κB target genes via associating with chromatin where they targeted methylated RelA for ubiquitination, facilitating the termination of NF-κB-dependent transcription. WSB1/2 specifically interacted with methylated lysines (K) 314 and 315 of RelA via their N-terminal WD-40 repeat (WDR) domains, thereby promoting ubiquitination of RelA. Computational modeling further revealed that a conserved aspartic acid (D) at position 158 within the WDR domain of WSB2 coordinates K314/K315 of RelA, with a higher affinity when either of the lysines is methylated. Mutation of D158 abolished WSB2's ability to bind to and promote ubiquitination of methylated RelA. Together, our study identifies a novel function and the underlying mechanism for WSB1/2 in degrading chromatin-bound methylated RelA and preventing sustained NF-κB activation, providing potential new targets for therapeutic intervention of NF-κB-mediated inflammatory diseases.

PRAMEL7 and CUL2 decrease NuRD stability to establish ground-state pluripotency

Pluripotency is established in E4.5 preimplantation epiblast. Embryonic stem cells (ESCs) represent the immortalization of pluripotency, however, their gene expression signature only partially resembles that of developmental ground-state. Induced PRAMEL7 expression, a protein highly expressed in the ICM but lowly expressed in ESCs, reprograms developmentally advanced ESC+serum into ground-state pluripotency by inducing a gene expression signature close to developmental ground-state. However, how PRAMEL7 reprograms gene expression remains elusive. Here we show that PRAMEL7 associates with Cullin2 (CUL2) and this interaction is required to establish ground-state gene expression. PRAMEL7 recruits CUL2 to chromatin and targets regulators of repressive chromatin, including the NuRD complex, for proteasomal degradation. PRAMEL7 antagonizes NuRD-mediated repression of genes implicated in pluripotency by decreasing NuRD stability and promoter association in a CUL2-dependent manner. Our data link proteasome degradation pathways to ground-state gene expression, offering insights to generate in vitro models to reproduce the in vivo ground-state pluripotency.

Suppression of NF-κB signaling by Pseudorabies virus DNA polymerase processivity factor UL42 via recruiting SOCS1 to promote the ubiquitination degradation of p65

The NF-κB pathway is a critical signaling involved in the regulation of the inflammatory and innate immune responses. Previous studies have shown that Pseudorabies Virus (PRV), a porcine alpha herpesvirus, could lead to the phosphorylation and nucleus translocation of p65 while inhibiting the expression of NF-κB-dependent inflammatory cytokines, which indicated that there may be unknown mechanisms downstream of p65 that downregulate the activation of NF-κB signaling. Here, we found that PRV DNA polymerase factor UL42 inhibited TNFα-, LPS-, IKKα-, IKKβ-, and p65-mediated transactivation of NF-κB signaling, which demonstrated UL42 worked either at or downstream of p65. In addition, it was found that the DNA-binding activity of UL42 was required for inhibition of NF-κB signaling. Importantly, it was revealed that UL42 could induce the ubiquitination degradation of p65 by upregulating the suppressor of cytokine signaling 1 (SOCS1). Additionally, it was found that UL42 could promote the K6/K29-linked ubiquitination of p65. Finally, knockdown of SOCS1 attenuated the replication of PRV and led to a significant increase of the inflammatory cytokines. Taken together, our findings uncovered a novel mechanism that PRV-UL42 could upregulated SOCS1 to promote the ubiquitination degradation of p65 to prevent excessive inflammatory response during PRV infection.

The emerging role and therapeutic implications of bacterial and parasitic deubiquitinating enzymes

Deubiquitinating enzymes (DUBs) are emerging as key factors for the infection of human cells by pathogens such as bacteria and parasites. In this review, we discuss the most recent studies on the role of deubiquitinase activity in exploiting and manipulating ubiquitin (Ub)-dependent host processes during infection. The studies discussed here highlight the importance of DUB host-pathogen research and underscore the therapeutic potential of inhibiting pathogen-specific DUB activity to prevent infectious diseases.

The role and function of CLU in cancer biology and therapy

Clusterin (CLU) is a highly evolutionary conserved glycoprotein with multiple isoform-specific functions and is widely distributed in different species. Accumulated evidence has shown the prominent role of CLU in regulating several essential physiological processes, including programmed cell death, metastasis, invasion, proliferation and cell growth via regulating diverse signaling pathways to mediate cancer progression in various cancers, such as prostate, breast, lung, liver, colon, bladder and pancreatic cancer. Several studies have revealed the potential benefit of inhibiting CLU in CLU inhibition-based targeted cancer therapies in vitro, in vivo or in human, suggesting CLU is a promising therapeutic target. This review discusses the multiple functions and mechanisms of CLU in regulating tumor progression of various cancers and summarizes the inhibitors of CLU used in CLU inhibition-based targeted cancer therapies.

Structural Organization of the Retriever-CCC Endosomal Recycling Complex

The recycling of membrane proteins from endosomes to the cell surface is vital for cell signaling and survival. Retriever, a trimeric complex of VPS35L, VPS26C and VPS29, together with the CCC complex comprising CCDC22, CCDC93, and COMMD proteins, plays a crucial role in this process. The precise mechanisms underlying Retriever assembly and its interaction with CCC have remained elusive. Here, we present the first high-resolution structure of Retriever determined using cryogenic electron microscopy. The structure reveals a unique assembly mechanism, distinguishing it from its remotely related paralog, Retromer. By combining AlphaFold predictions and biochemical, cellular, and proteomic analyses, we further elucidate the structural organization of the entire Retriever-CCC complex and uncover how cancer-associated mutations disrupt complex formation and impair membrane protein homeostasis. These findings provide a fundamental framework for understanding the biological and pathological implications associated with Retriever-CCC-mediated endosomal recycling.

Structural Organization of the Retriever-CCC Endosomal Recycling Complex

The recycling of membrane proteins from endosomes to the cell surface is vital for cell signaling and survival. Retriever, a trimeric complex of VPS35L, VPS26C and VPS29, together with the CCC complex comprising CCDC22, CCDC93, and COMMD proteins, plays a crucial role in this process. The precise mechanisms underlying Retriever assembly and its interaction with CCC have remained elusive. Here, we present the first high-resolution structure of Retriever determined using cryogenic electron microscopy. The structure reveals a unique assembly mechanism, distinguishing it from its remotely related paralog, Retromer. By combining AlphaFold predictions and biochemical, cellular, and proteomic analyses, we further elucidate the structural organization of the entire Retriever-CCC complex and uncover how cancer-associated mutations disrupt complex formation and impair membrane protein homeostasis. These findings provide a fundamental framework for understanding the biological and pathological implications associated with Retriever-CCC-mediated endosomal recycling.

Molecular evolution of Keap1 was essential for adaptation of vertebrates to terrestrial life

Reactive oxygen species (ROS) posed a risk for the transition of vertebrates from aquatic to terrestrial life. How ancestral organisms adapted to such ROS exposure has remained a mystery. Here, we show that attenuation of the activity of the ubiquitin ligase CRL3Keap1 for the transcription factor Nrf2 during evolution was key to development of an efficient response to ROS exposure. The Keap1 gene was duplicated in fish to give rise to Keap1A and the only remaining mammalian paralog Keap1B, the latter of which shows a lower affinity for Cul3 and contributes to robust Nrf2 induction in response to ROS exposure. Mutation of mammalian Keap1 to resemble zebrafish Keap1A resulted in an attenuated Nrf2 response, and most knock-in mice expressing such a Keap1 mutant died on exposure as neonates to sunlight-level ultraviolet radiation. Our results suggest that molecular evolution of Keap1 was essential for adaptation to terrestrial life.

USP7 - a crucial regulator of cancer hallmarks

Over the course of three decades of study, the deubiquitinase Herpesvirus associated Ubiquitin-Specific Protease/Ubiquitin-Specific Protease 7 (HAUSP/USP7) has gradually come to be recognized as a crucially important molecule in cellular physiology. The fact that USP7 is overexpressed in a number of cancers, including breast, prostate, colorectal, and lung cancers, supports the idea that USP7 is also an important regulator of tumorigenesis. In this review, we discuss USP7's function in relation to the cancer hallmarks described by Hanahan and Weinberg. This post-translational modifier can support increased proliferation, block unfavorable growth signals, stop cell death, and support an unstable cellular genome by manipulating key players in the pertinent signalling circuit. It is interesting to note that USP7 also aids in the stabilization of molecules that support angiogenesis and metastasis. Targeting USP7 has now emerged as a crucial component of USP7 research because pharmacological inhibition of USP7 supports p53-mediated cell cycle arrest and apoptosis. Efficacious USP7 inhibition is currently being investigated in both synthetic and natural compounds, but issues with selectivity and a lack of co-crystal structure have hindered USP7 inhibition from being tested in clinical settings. Moreover, the development of new, more effective USP7 inhibitors and their encouraging implications by numerous groups give us a glimmer of hope for USP7-targeting medications as effective substitutes for hazardous cancer chemotherapeutics.

Celastrol suppresses humoral immune responses and autoimmunity by targeting the COMMD3/8 complex

Celastrol, a bioactive molecule extracted from the Tripterygium wilfordii plant, has been shown to exhibit anti-inflammatory properties. However, its mechanism of action has not been fully elucidated. Here, we show that celastrol suppresses humoral immune responses and autoimmunity by disabling a protein complex consisting of copper metabolism MURR1 domain–containing (COMMD) 3 and COMMD8 (COMMD3/8 complex), a signaling adaptor for chemoattractant receptors. Having demonstrated the involvement of the COMMD3/8 complex in a mouse model of rheumatoid arthritis, we identified celastrol as a compound that covalently bound to and dissociated the COMMD3/8 complex. Celastrol inhibited B cell migration, reduced antibody responses, and blocked arthritis progression, recapitulating deficiency of the COMMD3/8 complex. These effects of celastrol were abolished in mice expressing a celastrol-resistant mutant of the COMMD3/8 complex. These findings establish that celastrol exerts immunosuppressive activity by targeting the COMMD3/8 complex. Our study suggests that the COMMD3/8 complex is a potentially druggable target in autoimmune diseases and points to celastrol as a lead pharmacologic candidate in this capacity.

COMMD10 Is Essential for Neural Plate Development during Embryogenesis

The COMMD (copper metabolism MURR1 domain containing) family includes ten structurally conserved proteins (COMMD1 to COMMD10) in eukaryotic multicellular organisms that are involved in a diverse array of cellular and physiological processes, including endosomal trafficking, copper homeostasis, and cholesterol metabolism, among others. To understand the role of COMMD10 in embryonic development, we used Commd10Tg(Vav1-icre)A2Kio/J mice, where the Vav1-cre transgene is integrated into an intron of the Commd10 gene, creating a functional knockout of Commd10 in homozygous mice. Breeding heterozygous mice produced no COMMD10-deficient (Commd10Null) offspring, suggesting that COMMD10 is required for embryogenesis. Analysis of Commd10Null embryos demonstrated that they displayed stalled development by embryonic day 8.5 (E8.5). Transcriptome analysis revealed that numerous neural crest-specific gene markers had lower expression in mutant versus wild-type (WT) embryos. Specifically, Commd10Null embryos displayed significantly lower expression levels of a number of transcription factors, including a major regulator of the neural crest, Sox10. Moreover, several cytokines/growth factors involved in early embryonic neurogenesis were also lower in mutant embryos. On the other hand, Commd10Null embryos demonstrated higher expression of genes involved in tissue remodeling and regression processes. Taken together, our findings show that Commd10Null embryos die by day E8.5 due to COMMD10-dependent neural crest failure, revealing a new and critical role for COMMD10 in neural development.

COMMD proteins function and their regulating roles in tumors

The COMMD proteins are a highly conserved protein family with ten members that play a crucial role in a variety of biological activities, including copper metabolism, endosomal sorting, ion transport, and other processes. Recent research have demonstrated that the COMMD proteins are closely associated with a wide range of disorders, such as hepatitis, myocardial ischemia, cerebral ischemia, HIV infection, and cancer. Among these, the role of COMMD proteins in tumors has been thoroughly explored; they promote or inhibit cancers such as lung cancer, liver cancer, gastric cancer, and prostate cancer. COMMD proteins can influence tumor proliferation, invasion, metastasis, and tumor angiogenesis, which are strongly related to the prognosis of tumors and are possible therapeutic targets for treating tumors. In terms of molecular mechanism, COMMD proteins in tumor cells regulate the oncogenes of NF-κB, HIF, c-MYC, and others, and are related to signaling pathways including apoptosis, autophagy, and ferroptosis. For the clinical diagnosis and therapy of malignancies, additional research into the involvement of COMMD proteins in cancer is beneficial.

ERRα Attenuates Vascular Inflammation via Enhanced NFκB Degradation Pathway

We have previously reported that β-aminoisobutyric acid (BAIBA), a muscle-derived exercise mimetic, had anti-inflammatory and reactive oxygen species (ROS) scavenging effects in vascular endothelial cells through the enhanced expression of peroxisome proliferator-activated receptor gamma coactivator-1β (PGC-1β). Although BAIBA also increased the expression of estrogen-related receptor α (ERRα), the roles of ERRα in vascular endothelial cells have yet to be fully elucidated. Here, we found that human aortic endothelial cells (HAECs) infected with ERRα-expressing adenovirus had significantly decreased mRNA levels of tumor necrosis factor α-stimulated proinflammatory molecules. However, ERRα overexpression had little effect on the mRNA levels of PGC-1β, peroxisome proliferator-activated receptors, and almost all ROS scavenging molecules, except for superoxide dismutase 2. ERRα expression significantly decreased NFκB reporter activities in a dose-dependent manner with unaltered IκBα phosphorylation levels but with a significant increase in the mRNA levels of PDZ and LIM domain protein 2 (PDLIM2) and copper metabolism gene MURR1 domain-containing protein (COMMD1), which enhance the ubiquitination and degradation of NFκB. Also, PDLIM2 and COMMD1 mRNA levels were upregulated in BAIBA-treated HAECs. Finally, we identified the ERRα-response element in the COMMD1 promoter region (-283 to -29 bp). These results indicated that ERRα exerted anti-inflammatory effects in vascular endothelial cells through COMMD1-mediated attenuation of NFκB activity, which could be an atheroprotective mechanism of physical exercise.

Disruption of COMMD1 accelerates diabetic atherosclerosis by promoting glycolysis

AIMS

Diabetes will lead to serious complications, of which atherosclerosis is the most dangerous. This study aimed to explore the mechanisms of diabetic atherosclerosis.

METHODS

ApoE^-/- mice were fed with an high-fat diet diet and injected with streptozotocin to establish an in vivo diabetic atherosclerotic model. RAW 264.7 cells were treated with oxidized low-density lipoprotein particles (ox-LDL) and high glucose to produce an in vitro diabetic atherosclerotic model.

RESULTS

In this study, we showed that diabetes promoted the progression of atherosclerosis in ApoE^-/- mice and that high glucose potentiates macrophage proinflammatory activation and foam cell formation. Mechanistically, Copper metabolism MURR1 domain-containing 1(COMMD1) deficiency increased proinflammatory activation and foam cell formation, characterized by increased glycolysis, and then accelerated the process of atherosclerosis. Furthermore, 2-Deoxy-D-glucose (2-DG) reversed this effect.

CONCLUSION

Taken together, we provided evidence that the lack of COMMD1 accelerates diabetic atherosclerosis via mediating the metabolic reprogramming of macrophages. Our study provides evidence of a protective role for COMMD1 and establishes COMMD1 as a potential therapeutic strategy in patients with diabetic atherosclerosis.

Copper regulation disturbance linked to oxidative stress and cell death during Zika virus infection in human astrocytes

The Zika virus (ZIKV) caused neurological abnormalities in more than 3500 Brazilian newborns between 2015 and 2020. Data have pointed to oxidative stress in astrocytes as well as to dysregulations in neural cell proliferation and cell cycle as important events accounting for the cell death and neurological complications observed in Congenital Zika Syndrome. Copper imbalance has been shown to induce similar alterations in other pathologies, and disturbances in copper homeostasis have already been described in viral infections. Here, we investigated copper homeostasis imbalance as a factor that could contribute to the cytotoxic effects of ZIKV infection in astrocytes. Human induced pluripotent stem cell-derived astrocytes were infected with ZIKV; changes in the gene expression of copper homeostasis proteins were analyzed. The effect of the administration of CuCl₂ or a copper chelator on oxidative stress, cell viability and percentage of infection were also studied. ZIKV infection leads to a downregulation of one of the transporters mediating copper release, ATP7B protein. We also observed the activation of mechanisms that counteract high copper levels, including the synthesis of copper chaperones and the reduction of the copper importer protein CTR1. Finally, we show that chelator-mediated copper sequestration in ZIKV-infected astrocytes reduces the levels of reactive oxygen species and improves cell viability, but does not change the overall percentage of infected cells. In summary, our results show that copper homeostasis imbalance plays a role in the pathology of ZIKV in astrocytes, indicating that it may also be a factor accounting for the developmental abnormalities in the central nervous system following viral infection. Evaluating micronutrient levels and the use of copper chelators in pregnant women susceptible to ZIKV infection may be promising strategies to manage novel cases of congenital ZIKV syndrome.

The positive regulatory loop of TCF4N/p65 promotes glioblastoma tumourigenesis and chemosensitivity

Background

NF‐κB signaling is widely linked to the pathogenesis and treatment resistance in cancers. Increasing attention has been paid to its anti‐oncogenic roles, due to its key functions in cellular senescence and the senescence‐associated secretory phenotype (SASP). Therefore, thoroughly understanding the function and regulation of NF‐κB in cancers is necessary prior to the application of NF‐κB inhibitors.

Methods

We established glioblastoma (GBM) cell lines expressing ectopic TCF4N, an isoform of the β‐catenin interacting transcription factor TCF7L2, and evaluated its functions in GBM tumorigenesis and chemotherapy in vitro and in vivo. In p65 knock‐out or phosphorylation mimic (S536D) cell lines, the dual role and correlation of TCF4N and NF‐κB signaling in promoting tumorigenesis and chemosensitivity was investigated by in vitro and in vivo functional experiments. RNA‐seq and computational analysis, immunoprecipitation and ubiquitination assay, minigene splicing assay and luciferase reporter assay were performed to identify the underlying mechanism of positive feedback regulation loop between TCF4N and the p65 subunit of NF‐κB. A eukaryotic cell‐penetrating peptide targeting TCF4N, 4N, was used to confirm the therapeutic significance.

Results

Our results indicated that p65 subunit phosphorylation at Ser 536 (S536) and nuclear accumulation was a promising prognostic marker for GBM, and endowed the dual functions of NF‐κB in promoting tumorigenesis and chemosensitivity. p65 S536 phosphorylation and nuclear stability in GBM was regulated by TCF4N. TCF4N bound p65, induced p65 phosphorylation and nuclear translocation, inhibited its ubiquitination/degradation, and subsequently promoted NF‐κB activity. p65 S536 phosphorylation was essential for TCF4N‐led senescence‐independent SASP, GBM tumorigenesis, tumor stem‐like cell differentiation and chemosensitivity. Activation of p65 was closely connected to alterative splicing of TCF4N, a likely positive feedback regulation loop between TCF4N and p65 in GBM. 4N increased chemosensitivity, highlighting a novel anti‐cancer strategy.

Conclusion

Our study defined key roles of TCF4N as a novel regulator of NF‐κB through mutual regulation with p65 and provided a new avenue for GBM inhibition.

Neuropathogenesis of HIV-1: insights from across the spectrum of acute through long-term treated infection

This review outlines the neuropathogenesis of HIV, from initial HIV entry into the central nervous system (CNS) to chronic infection, focusing on key advancements in the last 5 years. Discoveries regarding acute HIV infection reveal timing and mechanisms of early HIV entry and replication in the CNS, early inflammatory responses, and establishment of genetically distinct viral reservoirs in the brain. Recent studies additionally explore how chronic HIV infection is maintained in the CNS, examining how the virus remains in a latent "hidden" state in diverse cells in the brain, and how this leads to sustained pathological inflammatory responses. Despite viral suppression with antiretroviral therapy, HIV can persist and even replicate in the CNS, and associate with ongoing neuropathology including CD8 + T-lymphocyte mediated encephalitis. Crucial investigation to advance our understanding of the immune mechanisms that both control viral infection and lead to pathological consequences in the brain is necessary to develop treatments to optimize long-term neurologic health in people living with HIV.

USP48 and A20 synergistically promote cell survival in Helicobacter pylori infection

The human pathogen Helicobacter pylori represents a risk factor for the development of gastric diseases including cancer. The H. pylori-induced transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is involved in the pro-inflammatory response and cell survival in the gastric mucosa, and represents a trailblazer of gastric pathophysiology. Termination of nuclear NF-κB heterodimer RelA/p50 activity is regulated by the ubiquitin-RING-ligase complex elongin-cullin-suppressor of cytokine signalling 1 (ECS^SOCS1), which leads to K48-ubiquitinylation and degradation of RelA. We found that deubiquitinylase (DUB) ubiquitin specific protease 48 (USP48), which interacts with the COP9 signalosome (CSN) subunit CSN1, stabilises RelA by deubiquitinylation and thereby promotes the transcriptional activity of RelA to prolong de novo synthesis of DUB A20 in H. pylori infection. An important role of A20 is the suppression of caspase-8 activity and apoptotic cell death. USP48 thus enhances the activity of A20 to reduce apoptotic cell death in cells infected with H. pylori. Our results, therefore, define a synergistic mechanism by which USP48 and A20 regulate RelA and apoptotic cell death in H. pylori infection.

Hepatitis B virus X protein promotes epithelial-mesenchymal transition of hepatocellular carcinoma cells by regulating SOCS1

Hepatocellular carcinoma (HCC), a primary type of liver cancer, is one of the leading causes of cancer related deaths worldwide. HCC patients have poor prognosis due to intrahepatic and extrahepatic metastasis. Hepatitis B virus (HBV) infection is one of the major causes of various liver diseases including HCC. Among HBV gene products, HBV X protein (HBx) plays an important role in the development and metastasis of HCC. However, the mechanism of HCC metastasis induced by HBx has not been elucidated yet. In this study, for the first time, we report that HBx interacts with the suppressor of cytokine signaling 1 (SOCS1) which negatively controls NF-κB by degrading p65, a subunit of NF-κB. NF-κB activates the transcription of factors associated with epithelial-mesenchymal transition (EMT), a crucial cellular process associated with invasiveness and migration of cancer cells. Here, we report that HBx physically binds to SOCS1, subsequently prevents the ubiquitination of p65, activates the transcription of EMT transcription factors and enhance cell migration and invasiveness, suggesting a new mechanism of HBV-associated HCC metastasis.

Commander Complex-A Multifaceted Operator in Intracellular Signaling and Cargo

Commander complex is a 16-protein complex that plays multiple roles in various intracellular events in endosomal cargo and in the regulation of cell homeostasis, cell cycle and immune response. It consists of COMMD1-10, CCDC22, CCDC93, DENND10, VPS26C, VPS29, and VPS35L. These proteins are expressed ubiquitously in the human body, and they have been linked to diseases including Wilson's disease, atherosclerosis, and several types of cancer. In this review we describe the function of the commander complex in endosomal cargo and summarize the individual known roles of COMMD proteins in cell signaling and cancer. It becomes evident that commander complex might be a much more important player in intracellular regulation than we currently understand, and more systematic research on the role of commander complex is required.

COMMD10 is critical for Kupffer cell survival and controls Ly6Chi monocyte differentiation and inflammation in the injured liver

Liver-resident macrophages Kupffer cells (KCs) and infiltrating Ly6C^hi monocytes both contribute to liver tissue regeneration in various pathologies but also to disease progression upon disruption of orderly consecutive regeneration cascades. Little is known about molecular pathways that regulate their differentiation, maintenance, or inflammatory behavior during injury. Here, we show that copper metabolism MURR1 domain (COMMD)10-deficient KCs adopt liver-specific identity. Strikingly, COMMD10 deficiency in KCs and in other tissue-resident macrophages impedes their homeostatic survival, leading to their continuous replacement by Ly6C^hi monocytes. While COMMD10 deficiency in KCs mildly worsens acetaminophen-induced liver injury (AILI), its deficiency in Ly6C^hi monocytes results in exacerbated and sustained hepatic damage. Monocytes display unleashed inflammasome activation and a reduced type I interferon response and acquire "neutrophil-like" and lipid-associated macrophage differentiation fates. Collectively, COMMD10 appears indispensable for KC and other tissue-resident macrophage survival and is an important regulator of Ly6C^hi monocyte fate decisions and reparative behavior in the diseased liver.

The NF-κB Nucleolar Stress Response Pathway

The nuclear organelle, the nucleolus, plays a critical role in stress response and the regulation of cellular homeostasis. P53 as a downstream effector of nucleolar stress is well defined. However, new data suggests that NF-κB also acts downstream of nucleolar stress to regulate cell growth and death. In this review, we will provide insight into the NF-κB nucleolar stress response pathway. We will discuss apoptosis mediated by nucleolar sequestration of RelA and new data demonstrating a role for p62 (sequestosome (SQSTM1)) in this process. We will also discuss activation of NF-κB signalling by degradation of the RNA polymerase I (PolI) complex component, transcription initiation factor-IA (TIF-IA (RRN3)), and contexts where TIF-IA-NF-κB signalling may be important. Finally, we will discuss how this pathway is targeted by aspirin to mediate apoptosis of colon cancer cells.

The molecular and cellular basis of copper dysregulation and its relationship with human pathologies

Copper (Cu) is an essential micronutrient required for the activity of redox-active enzymes involved in critical metabolic reactions, signaling pathways, and biological functions. Transporters and chaperones control Cu ion levels and bioavailability to ensure proper subcellular and systemic Cu distribution. Intensive research has focused on understanding how mammalian cells maintain Cu homeostasis, and how molecular signals coordinate Cu acquisition and storage within organs. In humans, mutations of genes that regulate Cu homeostasis or facilitate interactions with Cu ions lead to numerous pathologic conditions. Malfunctions of the Cu⁺ -transporting ATPases ATP7A and ATP7B cause Menkes disease and Wilson disease, respectively. Additionally, defects in the mitochondrial and cellular distributions and homeostasis of Cu lead to severe neurodegenerative conditions, mitochondrial myopathies, and metabolic diseases. Cu has a dual nature in carcinogenesis as a promotor of tumor growth and an inducer of redox stress in cancer cells. Cu also plays role in cancer treatment as a component of drugs and a regulator of drug sensitivity and uptake. In this review, we provide an overview of the current knowledge of Cu metabolism and transport and its relation to various human pathologies.

CDC20 promotes bone formation via APC/C dependent ubiquitination and degradation of p65

The E3 ubiquitin ligase complex CDC20‐activated anaphase‐promoting complex/Cyclosome (APC/C^CDC20) plays a critical role in governing mitotic progression by targeting key cell cycle regulators for degradation. Cell division cycle protein 20 homolog (CDC20), the co‐activator of APC/C, is required for full ubiquitin ligase activity. In addition to its well‐known cell cycle‐related functions, we demonstrate that CDC20 plays an essential role in osteogenic commitment of bone marrow mesenchymal stromal/stem cells (BMSCs). Cdc20 conditional knockout mice exhibit decreased bone formation and impaired bone regeneration after injury. Mechanistically, we discovered a functional interaction between the WD40 domain of CDC20 and the DNA‐binding domain of p65. Moreover, CDC20 promotes the ubiquitination and degradation of p65 in an APC11‐dependent manner. More importantly, knockdown of p65 rescues the bone loss in Cdc20 conditional knockout mice. Our current work reveals a cell cycle‐independent function of CDC20, establishes APC11^CDC20 as a pivotal regulator for bone formation by governing the ubiquitination and degradation of p65, and may pave the way for treatment of bone‐related diseases.

HIV-1 persistence in the CNS: Mechanisms of latency, pathogenesis and an update on eradication strategies

Despite four decades of research into the human immunodeficiency virus (HIV-1), a successful strategy to eradicate the virus post-infection is lacking. The major reason for this is the persistence of the virus in certain anatomical reservoirs where it can become latent and remain quiescent for as long as the cellular reservoir is alive. The Central Nervous System (CNS), in particular, is an intriguing anatomical compartment that is tightly regulated by the blood-brain barrier. Targeting the CNS viral reservoir is a major challenge owing to the decreased permeability of drugs into the CNS and the cellular microenvironment that facilitates the compartmentalization and evolution of the virus. Therefore, despite effective antiretroviral (ARV) treatment, virus persists in the CNS, and leads to neurological and neurocognitive deficits. To date, viral eradication strategies fail to eliminate the virus from the CNS. To facilitate the improvement of the existing elimination strategies, as well as the development of potential therapeutic targets, the aim of this review is to provide an in-depth understanding of HIV latency in CNS and the onset of HIV-1 associated neurological disorders.

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.

Cardiomyocyte-Specific COMMD1 Deletion Suppresses Ischemia-Induced Myocardial Apoptosis

Copper metabolism MURR domain 1 (COMMD1) increases in ischemic myocardium along with suppressed contractility. Cardiomyocyte-specific deletion of COMMD1 preserved myocardial contractile function in response to the same ischemic insult. This study was undertaken to test the hypothesis that cardiomyocyte protection in COMMD1 myocardium is responsible for the functional preservation of the heart in response to ischemic insult. After ischemic insult, there were significantly more cardiomyocytes in the cardiomyocyte-specific COMMD1 deletion myocardium than that in WT controls. This preservation of cardiomyocytes was paralleled by a significant suppression of apoptosis in the COMMD1 deletion myocardium compared to controls. In searching for the mechanistic understanding of the anti-apoptotic effect of COMMD1 deletion, we found the anti-apoptotic Bcl-2 mRNA and protein expression were upregulated and the pro-apoptotic Bax mRNA and protein expression were downregulated. The critical transcription factor RelA, maintaining a high ratio between Bcl-2 and Bax for anti-apoptotic action, was suppressed by ischemia, but was rescued in the COMMD1 deletion myocardium. Because COMMD1 is critically involved in RelA ubiquitination and degradation, the data obtained here demonstrate that COMMD1 deletion leads to RelA preservation in ischemic myocardium, promoting the Bcl-2 anti-apoptotic pathway and suppressing the Bax pro-apoptotic pathway, and in combination, leading to protection of cardiomyocytes from ischemia-induced apoptosis.

COMMD1, a multi-potent intracellular protein involved in copper homeostasis, protein trafficking, inflammation, and cancer

Copper is a trace element indispensable for life, but at the same time it is implicated in reactive oxygen species formation. Several inherited copper storage diseases are described of which Wilson disease (copper overload, mutations in ATP7B gene) and Menkes disease (copper deficiency, mutations in ATP7A gene) are the most prominent ones. After the discovery in 2002 of a novel gene product (i.e. COMMD1) involved in hepatic copper handling in Bedlington terriers, studies on the mechanism of action of COMMD1 revealed numerous non-copper related functions. Effects on hepatic copper handling are likely mediated via interactions with ATP7B. In addition, COMMD1 has many more interacting partners which guide their routing to either the plasma membrane or, often in an ubiquitination-dependent fashion, trigger their proteolysis via the S26 proteasome. By stimulating NF-κB ubiquitination, COMMD1 dampens an inflammatory reaction. Finally, targeting COMMD1 function can be a novel approach in the treatment of tumors.

Negative Regulation of the Innate Immune Response through Proteasomal Degradation and Deubiquitination

The rapid and dynamic activation of the innate immune system is achieved through complex signaling networks regulated by post-translational modifications modulating the subcellular localization, activity, and abundance of signaling molecules. Many constitutively expressed signaling molecules are present in the cell in inactive forms, and become functionally activated once they are modified with ubiquitin, and, in turn, inactivated by removal of the same post-translational mark. Moreover, upon infection resolution a rapid remodeling of the proteome needs to occur, ensuring the removal of induced response proteins to prevent hyperactivation. This review discusses the current knowledge on the negative regulation of innate immune signaling pathways by deubiquitinating enzymes, and through degradative ubiquitination. It focusses on spatiotemporal regulation of deubiquitinase and E3 ligase activities, mechanisms for re-establishing proteostasis, and degradation through immune-specific feedback mechanisms vs. general protein quality control pathways.

Regulation of murine copper homeostasis by members of the COMMD protein family

Copper is an essential transition metal for all eukaryotes. In mammals, intestinal copper absorption is mediated by the ATP7A copper transporter, whereas copper excretion occurs predominantly through the biliary route and is mediated by the paralog ATP7B. Both transporters have been shown to be recycled actively between the endosomal network and the plasma membrane by a molecular machinery known as the COMMD/CCDC22/CCDC93 or CCC complex. In fact, mutations in COMMD1 can lead to impaired biliary copper excretion and liver pathology in dogs and in mice with liver-specific Commd1 deficiency, recapitulating aspects of this phenotype. Nonetheless, the role of the CCC complex in intestinal copper absorption in vivo has not been studied, and the potential redundancy of various COMMD family members has not been tested. In this study, we examined copper homeostasis in enterocyte-specific and hepatocyte-specific COMMD gene-deficient mice. We found that, in contrast to effects in cell lines in culture, COMMD protein deficiency induced minimal changes in ATP7A in enterocytes and did not lead to altered copper levels under low- or high-copper diets, suggesting that regulation of ATP7A in enterocytes is not of physiological consequence. By contrast, deficiency of any of three COMMD genes (Commd1, Commd6 or Commd9) resulted in hepatic copper accumulation under high-copper diets. We found that each of these deficiencies caused destabilization of the entire CCC complex and suggest that this might explain their shared phenotype. Overall, we conclude that the CCC complex plays an important role in ATP7B endosomal recycling and function.

Summary: Examination of copper homeostasis in enterocyte-specific and hepatocyte-specific COMMD gene-deficient mice revealed that homologs of COMMD1, which has been linked previously by genetic studies to copper regulation, also regulate copper handling in mammals.

The Anticancer Peptide CIGB-552 Exerts Anti-Inflammatory and Anti-Angiogenic Effects through COMMD1

CIGB-552 is a synthetic anti-tumor peptide capable of reducing tumor size and increasing the lifespan of tumor-bearing mice. Part of its anti-cancer effects consists of inducing apoptosis, modulating NF-kB signaling pathway, and the angiogenesis process. Although one of its major mediators, the COMMD1 protein, has been identified, the mechanism by which CIGB-552 exerts such effects remains elusive. In the present study, we show the role of COMMD1 in CIGB-552 mechanism of action by generating the COMMD1 knock-out from the human lung cancer cell line NCI-H460. A microarray was performed to analyze both wild-type and KO cell lines with regard to CIGB-552 treatment. Additionally, different signaling pathways were studied in both cell lines to validate the results. Furthermore, the interaction between CIGB-552 and COMMD1 was analyzed by confocal microscopy. By signaling pathway analysis we found that genes involved in cell proliferation and apoptosis, oncogenic transformation, angiogenesis and inflammatory response are potentially regulated by the treatment with CIGB-552. We then demonstrated that CIGB-552 is capable of modulating NF-kB in both 2D and 3D cell culture models. Finally, we show that the ability of CIGB-552 to negatively modulate NF-kB and HIF-1 pathways is impaired in the COMMD1 knock-out NCI-H460 cell line, confirming that COMMD1 is essential for the peptide mechanism of action.

An atlas of immune cell exhaustion in HIV-infected individuals revealed by single-cell transcriptomics

Chronic infection with human immunodeficiency virus (HIV) can cause progressive loss of immune cell function, or exhaustion, which impairs control of virus replication. However, little is known about the development and maintenance, as well as heterogeneity of immune cell exhaustion. Here, we investigated the effects of HIV infection on immune cell exhaustion at the transcriptomic level by analyzing single-cell RNA sequencing of peripheral blood mononuclear cells from four healthy subjects (37,847 cells) and six HIV-infected donors (28,610 cells). We identified nine immune cell clusters and eight T cell subclusters, and three of these (exhausted CD4+ and CD8+ T cells and interferon-responsive CD8+ T cells) were detected only in samples from HIV-infected donors. An inhibitory receptor KLRG1 was identified in a HIV-1 specific exhausted CD8+ T cell population expressing KLRG1, TIGIT, and T-betdimEomeshi markers. Ex-vivo antibody blockade of KLRG1 restored the function of HIV-specific exhausted CD8+ T cells demonstrating the contribution of KLRG1+ population to T cell exhaustion and providing an immunotherapy target to treat HIV chronic infection. These data provide a comprehensive analysis of gene signatures associated with immune cell exhaustion during HIV infection, which could be useful in understanding exhaustion mechanisms and developing new cure therapies.

Structure and functions of cellular redox sensor HSCARG/NMRAL1, a linkage among redox status, innate immunity, DNA damage response, and cancer

NmrA-like proteins are NAD(P) (H) interacting molecules whose structures are similar to that of short-chain dehydrogenases. In this review, we focus on an NADP(H) sensor, HSCARG (also named NMRAL1), which is a NmrA-like protein that is widely present in mammals, and provide a comprehensive overview of the current knowledge of its structure and physiological functions. HSCARG selectively binds to the reduced form of type II coenzyme NADPH via its Rossmann fold domain. In response to reduction of intracellular NADPH concentration, HSCARG transforms from homodimer to monomer and exhibits enhanced interactions with its binding partners. In the cytoplasm, HSCARG negatively regulates innate immunity through impairing the activities of NF-κB and RLR pathways. Besides, HSCARG regulates redox homeostasis via suppression of ROS and NO generation. Intensive and persistent oxidative stress leads to translocation of HSCARG from the cytoplasm to the nucleus, where it regulates the DNA damage response. Taken together, HSCARG functions as a linkage between cellular redox status and other signaling pathways and fine-tunes cellular response to redox changes.

The HMGB1-2 Ovarian Cancer Interactome. The Role of HMGB Proteins and Their Interacting Partners MIEN1 and NOP53 in Ovary Cancer and Drug-Response

High mobility group box B (HMGB) proteins are overexpressed in different types of cancers such as epithelial ovarian cancers (EOC). We have determined the first interactome of HMGB1 and HMGB2 in epithelial ovarian cancer (the EOC-HMGB interactome). Libraries from the SKOV-3 cell line and a primary transitional cell carcinoma (TCC) ovarian tumor were tested by the Yeast Two Hybrid (Y2H) approach. The interactome reveals proteins that are related to cancer hallmarks and their expression is altered in EOC. Moreover, some of these proteins have been associated to survival and prognosis of patients. The interaction of MIEN1 and NOP53 with HMGB2 has been validated by co-immunoprecipitation in SKOV-3 and PEO1 cell lines. SKOV-3 cells were treated with different anti-tumoral drugs to evaluate changes in HMGB1, HMGB2, MIEN1 and NOP53 gene expression. Results show that combined treatment of paclitaxel and carboplatin induces a stronger down-regulation of these genes in comparison to individual treatments. Individual treatment with paclitaxel or olaparib up-regulates NOP53, which is expressed at lower levels in EOC than in non-cancerous cells. On the other hand, bevacizumab diminishes the expression of HMGB2 and NOP53. This study also shows that silencing of these genes affects cell-viability after drug exposure. HMGB1 silencing causes loss of response to paclitaxel, whereas silencing of HMGB2 slightly increases sensitivity to olaparib. Silencing of either HMGB1 or HMGB2 increases sensitivity to carboplatin. Lastly, a moderate loss of response to bevacizumab is observed when NOP53 is silenced.

Maturation of the Acute Hepatic TLR4/NF-κB Mediated Innate Immune Response Is p65 Dependent in Mice

Compared to adults, neonates are at increased risk of infection. There is a growing recognition that dynamic qualitative and quantitative differences in immunity over development contribute to these observations. The liver plays a key role as an immunologic organ, but whether its contribution to the acute innate immune response changes over lifetime is unknown. We hypothesized that the liver would activate a developmentally-regulated acute innate immune response to intraperitoneal lipopolysaccharide (LPS). We first assessed the hepatic expression and activity of the NF-κB, a key regulator of the innate immune response, at different developmental ages (p0, p3, p7, p35, and adult). Ontogeny of the NF-κB subunits (p65/p50) revealed a reduction in Rela (p65) and Nfkb1 (p105, precursor to p50) gene expression (p0) and p65 subunit protein levels (p0 and p3) vs. older ages. The acute hepatic innate immune response to LPS was associated by the degradation of the NF-κB inhibitory proteins (IκBα and IκBβ), and nuclear translocation of the NF-κB subunit p50 in all ages, whereas nuclear translocation of the NF-κB subunit p65 was only observed in the p35 and adult mouse. Consistent with these findings, we detected NF-κB subunit p65 nuclear staining exclusively in the LPS-exposed adult liver compared with p7 mouse. We next interrogated the LPS-induced hepatic expression of pro-inflammatory genes (Tnf, Icam1, Ccl3, and Traf1), and observed a gradually increase in gene expression starting from p0. Confirming our results, hepatic NF-κB subunit p65 nuclear translocation was associated with up-regulation of the Icam1 gene in the adult, and was not detected in the p7 mouse. Thus, an inflammatory challenge induces an NF-κB-mediated hepatic innate immune response activation across all developmental ages, but nuclear translocation of the NF-κB subunit p65 and associated induction of pro-inflammatory genes occurred only after the first month of life. Our results demonstrate that the LPS-induced hepatic innate immune response is developmentally regulated by the NF-κB subunit p65 in the mouse.

PDLIM7 Synergizes With PDLIM2 and p62/Sqstm1 to Inhibit Inflammatory Signaling by Promoting Degradation of the p65 Subunit of NF-κB

Activation of NF-κB transcription factors is critical for innate immune cells to induce inflammation and fight against microbial pathogens. On the other hand, the excessive and prolonged activation of NF-κB causes massive inflammatory damage to the host, suggesting that regulatory mechanisms to promptly terminate NF-κB activation are important to prevent immunopathology. We have previously reported that PDLIM2, a PDZ-LIM domain-containing protein, is a nuclear ubiquitin E3 ligase that targets the p65 subunit of NF-κB for degradation, thereby suppressing NF-κB activation. Here we show that PDLIM7, another member of LIM protein family, is also a ubiquitin E3 ligase that inhibits NF-κB-mediated inflammatory responses. PDLIM7 directly polyubiquitinates p65 and promotes its proteasomal degradation. Moreover, PDLIM7 heterodimerizes with PDLIM2 to promote synergistic PDLIM2-mediated degradation of p65. Mechanistically, PDLIM7 promotes K63-linked ubiquitination of PDLIM2 and then the proteasome/autophagosome cargo protein p62/Sqstm1 binds to both polyubiquitinated PDLIM2 and the proteasome, thereby facilitating the delivery of the NF-κB-PDLIM2 complex to the proteasome and subsequent p65 degradation. Consistently, double knockdown of PDLIM7 and either PDLIM2 or p62/Sqstm1 results in augmented proinflammatory cytokine production compared to control cells or single knockdown cells. These data delineate a new role for PDLIM7 and p62/Sqstm1 in the regulation of NF-κB signaling by bridging a ubiquitin E3 ligase and the proteasome.

The COP9 Signalosome: A Multi-DUB Complex

The COP9 signalosome (CSN) is a signaling platform controlling the cellular ubiquitylation status. It determines the activity and remodeling of ~700 cullin-RING ubiquitin ligases (CRLs), which control more than 20% of all ubiquitylation events in cells and thereby influence virtually any cellular pathway. In addition, it is associated with deubiquitylating enzymes (DUBs) protecting CRLs from autoubiquitylation and rescuing ubiquitylated proteins from degradation. The coordination of ubiquitylation and deubiquitylation by the CSN is presumably important for fine-tuning the precise formation of defined ubiquitin chains. Considering its intrinsic DUB activity specific for deneddylation of CRLs and belonging to the JAMM family as well as its associated DUBs, the CSN represents a multi-DUB complex. Two CSN-associated DUBs, the ubiquitin-specific protease 15 (USP15) and USP48 are regulators in the NF-κB signaling pathway. USP15 protects CRL1^β-TrCP responsible for IκBα ubiquitylation, whereas USP48 stabilizes the nuclear pool of the NF-κB transcription factor RelA upon TNF stimulation by counteracting CRL2^SOCS1. Moreover, the CSN controls the neddylation status of cells by its intrinsic DUB activity and by destabilizing the associated deneddylation enzyme 1 (DEN1). Thus, the CSN is a master regulator at the intersection between ubiquitylation and neddylation.

Identification of the COMM-domain containing protein 1 as specific binding partner for the guanine-rich RNA sequence binding factor 1

BACKGROUND

The guanine-rich RNA sequence binding factor 1 (GRSF1) is an RNA-binding protein of the hnRNP H/F family, which has been implicated in erythropoiesis, regulation of the redox homeostasis, embryonic brain development, mitochondrial function and cellular senescence. The molecular basis for GRSF1-RNA interaction has extensively been studied in the past but for the time being GRSF1 binding proteins have not been identified.

METHODS

To search for GRSF1 binding proteins we first employed the yeast two-hybrid system and screened a cDNA library of human fetal brain for potential GRSF1 binding proteins. Subsequently, we explored the protein-protein-interaction of the recombiant proteins, carried out immunoprecipitation experiments to confirm the interaction of the native proteins in living cells and performed truncation studies to identify the protein-binding motif of GRSF1.

RESULTS

Using the yeast two-hybrid system we identified the COMM-domain containing protein 1 (COMMD1) as specific GRSF1 binding protein and in vitro truncation studies suggested that COMMD1 interacts with the alanine-rich domain of GRSF1. Co-immunoprecipitation strategies indicated that COMMD1-GRSF1 interaction was RNA independent and also occurred in living cells expressing the two native proteins.

CONCLUSION

In mammalian cells the COMM-domain containing protein 1 (COMMD1) specifically interacts with the Ala-rich domain of GRSF1 in an RNA-independent manner.

GENERAL SIGNIFICANCE

This is the first report describing a specific GRSF1 binding protein.

Antitumour peptide based on a protein derived from the horseshoe crab: CIGB-552 a promising candidate for cancer therapy

Peptide-based cancer therapy has been of great interest due to the unique advantages of peptides, such as their low MW, the ability to specifically target tumour cells, easily available and low toxicity in normal tissues. Therefore, identifying and synthesizing novel peptides could provide a promising option for cancer patients. The antitumour second generation peptide, CIGB-552 has been developed as a candidate for cancer therapy. Proteomic and genomic studies have identified the intracellular protein COMMD1 as the specific target of CIGB-552. This peptide penetrates to the inside tumour cells to induce the proteasomal degradation of RelA, causing the termination of NF-κB signalling. The antitumour activity of CIGB-552 has been validated in vitro in different human cancer cell lines, as well as in vivo in syngeneic and xenograft tumour mouse models and in dogs with different types of cancers. The aim of this review is to present and discuss the experimental data obtained on the action of CIGB-552, including its mechanism of action and its therapeutic potential in human chronic diseases. This peptide is already in phase I clinical trials as antineoplastic drug and has also possible application for other inflammatory and metabolic conditions.

Mapping DNA interaction landscapes in psoriasis susceptibility loci highlights KLF4 as a target gene in 9q31

BACKGROUND

Genome-wide association studies (GWAS) have uncovered many genetic risk loci for psoriasis, yet many remain uncharacterised in terms of the causal gene and their biological mechanism in disease. This is largely a result of the findings that over 90% of GWAS variants map outside of protein-coding DNA and instead are enriched in cell type- and stimulation-specific gene regulatory regions.

RESULTS

Here, we use a disease-focused Capture Hi-C (CHi-C) experiment to link psoriasis-associated variants with their target genes in psoriasis-relevant cell lines (HaCaT keratinocytes and My-La CD8+ T cells). We confirm previously assigned genes, suggest novel candidates and provide evidence for complexity at psoriasis GWAS loci. For one locus, uniquely, we combine further epigenomic evidence to demonstrate how a psoriasis-associated region forms a functional interaction with the distant (> 500 kb) KLF4 gene. This interaction occurs between the gene and active enhancers in HaCaT cells, but not in My-La cells. We go on to investigate this long-distance interaction further with Cas9 fusion protein-mediated chromatin modification (CRISPR activation) coupled with RNA-seq, demonstrating how activation of the psoriasis-associated enhancer upregulates KLF4 and its downstream targets, relevant to skin cells and apoptosis.

CONCLUSIONS

This approach utilises multiple functional genomic techniques to follow up GWAS-associated variants implicating relevant cell types and causal genes in each locus; these are vital next steps for the translation of genetic findings into clinical benefit.

Microbial Sensing by Intestinal Myeloid Cells Controls Carcinogenesis and Epithelial Differentiation

Physiologic microbe-host interactions in the intestine require the maintenance of the microbiota in a luminal compartment through a complex interplay between epithelial and immune cells. However, the roles of mucosal myeloid cells in this process remain incompletely understood. In this study, we identified that decreased myeloid cell phagocytic activity promotes colon tumorigenesis. We show that this is due to bacterial accumulation in the lamina propria and present evidence that the underlying mechanism is bacterial induction of prostaglandin production by myeloid cells. Moreover, we show that similar events in the normal colonic mucosa lead to reductions in Tuft cells, goblet cells, and the mucus barrier of the colonic epithelium. These alterations are again linked to the induction of prostaglandin production in response to bacterial penetration of the mucosa. Altogether, our work highlights immune cell-epithelial cell interactions triggered by the microbiota that control intestinal immunity, epithelial differentiation, and carcinogenesis.