Control of NF-kappa B transcriptional activation by signal induced proteolysis of I kappa B alpha

PCV2 Induced Endothelial Derived IL-8 Affects MoDCs Maturation Mainly via NF-κB Signaling Pathway

Porcine circovirus type 2 (PCV2) infection can cause immunosuppressive diseases in pigs. Vascular endothelial cells (VECs), as the target cells for PCV2, play an important role in the immune response and inflammatory regulation. Endothelial IL-8, which is produced by porcine hip artery endothelial cells (PIECs) infected with PCV2, can inhibit the maturation of monocyte-derived dendritic cells (MoDCs). Here, we established a co-culture system of MoDCs and different groups of PIECs to further investigate the PCV2-induced endothelial IL-8 signaling pathway that drives the inhibition of MoDC maturation. The differentially expressed genes related to MoDC maturation were mainly enriched in the NF-κB and JAK2-STAT3 signaling pathways. Both the NF-κB related factor RELA and JAK2-STAT3 signaling pathway related factors (IL2RA, JAK, STAT2, STAT5, IL23A, IL7, etc.) decreased significantly in the IL-8 up-regulated group, and increased significantly in the down-regulated group. The expression of NF-κB p65 in the IL-8 up-regulated group was reduced significantly, and the expression of IκBα was increased significantly. Nuclear translocation of NF-κB p65 was inhibited, while the nuclear translocation of p-STAT3 was increased in MoDCs in the PCV2-induced endothelial IL-8 group. The results of treatment with NF-κB signaling pathway inhibitors showed that the maturation of MoDCs was inhibited and the expression of IL-12 and GM-CSF at mRNA level were lower. Inhibition of the JAK2-STAT3 signaling pathway had no significant effect on maturation, and the expression of IL-12 and GM-CSF at mRNA level produced no significant change. In summary, the NF-κB signaling pathway is the main signaling pathway of MoDC maturation, and is inhibited by the PCV2-induced up-regulation of endothelial-derived IL-8.

An Analysis of Linker-Dependent Effects on the APC Activation and In Vivo Immunogenicity of an R848-Conjugated Influenza Vaccine

Subunit or inactivated vaccines comprise the majority of vaccines used against viral and bacterial pathogens. However, compared to their live/attenuated counterparts, these vaccines often demonstrate reduced immunogenicity, requiring multiple boosters and or adjuvants to elicit protective immune responses. For this reason, studies of adjuvants and the mechanism through which they can improve inactivated vaccine responses are critical for the development of vaccines with increased efficacy. Studies have shown that the direct conjugation of adjuvant to antigen promotes vaccine immunogenicity, with the advantage of both the adjuvant and antigen targeting the same cell. Using this strategy of direct linkage, we developed an inactivated influenza A (IAV) vaccine that is directly conjugated with the Toll-like receptor 7/8 agonist resiquimod (R848) through a heterobifunctional crosslinker. Previously, we showed that this vaccine resulted in improved protection and viral clearance in newborn nonhuman primates compared to a non-adjuvanted vaccine. We subsequently discovered that the choice of linker used to conjugate R848 to the virus alters the stimulatory activity of the vaccine, promoting increased maturation and proinflammatory cytokine production from DC differentiated in vitro. With this knowledge, we explored how the choice of crosslinker impacts the stimulatory activity of these vaccines. We found that the linker choice alters signaling through the NF-κB pathway in human monocyte-derived dendritic cells (moDCs). Further, we extended our analyses to in vivo differentiated APC present in human peripheral blood, replicating the linker-dependent differences found in in vitro differentiated cells. Finally, we demonstrated in a mouse model that the choice of linker impacts the amount of IAV-specific IgG antibody produced in response to vaccination. These data enhance our understanding of conjugation approaches for improving vaccine immunogenicity.

Toll-like receptor-7 signaling in Kupffer cells exacerbates concanavalin A-induced liver injury in mice

Concanavalin A (ConA) is a plant lectin that can induce immune-mediated liver damage. ConA induced liver damage animal model is a widely accepted model that can mimic clinical acute hepatitis and immune-mediated liver injury in humans. Toll-like receptor-7 (TLR7), a member of the TLR family, plays a key role in pathogen recognition and innate immune activation. The aim of this study was to examine the role of TLR7 in the pathogenesis of ConA-induced liver injury. Acute liver injury was induced by intravenous injection with ConA in WT (wild-type) and TLR7 knockout (KO) mice. Results showed that attenuated liver injury in TLR7-deficient mice, as indicated by increased survival rate, decreased aminotransferase levels, and reduced pathological lesions, was associated with decreased release of pro-inflammatory cytokines in livers. Consistently, significantly decreased proliferation of CD4⁺ T cell was detected in ConA-stimulated TLR7-deficient splenocytes, but not in CD3/CD28 stimulated TLR7-deficient CD4⁺ T cells. Moreover, TLR7 deficiency in KCs specifically suppressed the expression of TNF-α (tumor necrosis factor-α). Depletion of KCs abolished the detrimental role of TLR7 in ConA-induced liver injury. Taken together, these results demonstrate that TLR7 can regulate the expression of TNF-α in KCs, which is necessary for the full progression of ConA-induced liver injury.

The Involvement of Ubiquitination and SUMOylation in Retroviruses Infection and Latency

Retroviruses, especially the pathogenic human immunodeficiency virus type 1 (HIV-1), have severely threatened human health for decades. Retroviruses can form stable latent reservoirs via retroviral DNA integration into the host genome, and then be temporarily transcriptional silencing in infected cells, which makes retroviral infection incurable. Although many cellular restriction factors interfere with various steps of the life cycle of retroviruses and the formation of viral latency, viruses can utilize viral proteins or hijack cellular factors to evade intracellular immunity. Many post-translational modifications play key roles in the cross-talking between the cellular and viral proteins, which has greatly determined the fate of retroviral infection. Here, we reviewed recent advances in the regulation of ubiquitination and SUMOylation in the infection and latency of retroviruses, focusing on both host defense- and virus counterattack-related ubiquitination and SUMOylation system. We also summarized the development of ubiquitination- and SUMOylation-targeted anti-retroviral drugs and discussed their therapeutic potential. Manipulating ubiquitination or SUMOylation pathways by targeted drugs could be a promising strategy to achieve a "sterilizing cure" or "functional cure" of retroviral infection.

Dopamine D2 and Serotonin 5-HT1A Dimeric Receptor-Binding Monomeric Antibody scFv as a Potential Ligand for Carrying Drugs Targeting Selected Areas of the Brain

Targeted therapy uses multiple ways of ensuring that the drug will be delivered to the desired site. One of these ways is an encapsulation of the drug and functionalization of the surface. Among the many molecules that can perform such a task, the present work focused on the antibodies of single-chain variable fragments (scFvs format). We studied scFv, which specifically recognizes the dopamine D₂ and serotonin 5-HT_1A receptor heteromers. The scFv_D2–5-HT1A protein was analyzed biochemically and biologically, and the obtained results indicated that the antibody is properly folded and non-toxic and can be described as low-immunogenic. It is not only able to bind to the D₂–5-HT_1A receptor heteromer, but it also influences the cAMP signaling pathway and—when surfaced on nanogold particles—it can cross the blood–brain barrier in in vitro models. When administered to mice, it decreased locomotor activity, matching the effect induced by clozapine. Thus, we are strongly convinced that scFvD₂–5-HT_1A, which was a subject of the present investigation, is a promising targeting ligand with the potential for the functionalization of nanocarriers targeting selected areas of the brain.

RRS1 knockdown inhibits the proliferation of neuroblastoma cell via PI3K/Akt/NF-κB pathway

BACKGROUND

RRS1 plays an important role in regulating ribosome biogenesis. Recently, RRS1 has emerged as an oncoprotein involved in tumorigenicity of some cancers. However its role in neuroblastoma remains unknown.

METHODS

RRS1 expression was detected in pediatric neuroblastoma patients' tissues and cell lines. The effects of RRS1 knockdown on proliferation, apoptosis, and cell cycle were evaluated in neuroblastoma cell lines. RRS1-related survival pathway was analyzed by co-immunoprecipitation (Co-IP), mass spectrometry, reverse transcription-quantitative real-time PCR (RT-qPCR), and western blot. Protein-protein interaction (PPI) network was constructed using Cytoscape software and the STRING databases.

RESULTS

Increased RRS1 level was found in neuroblastoma cases (35.6%) and cell lines. High RRS1 expression levels were associated with poor prognosis. RRS1 knockdown inhibited cell proliferation, induced apoptosis, and caused cell cycle arrest in SK-N-AS and SH-SY5Y cells. Co-IP and mass spectrometry analysis showed that RRS1 affects PI3K/Akt and nuclear factor κB (NF-κB) pathways. RT-qPCR and western blot results revealed that RRS1 knockdown inhibited the PI3K/Akt/NF-κB pathway through dephosphorylation of key proteins. In PPI network, AKT, PI3K, and P65 connected RRS1 with differentially expressed proteins more closely.

CONCLUSIONS

This study suggests RRS1 knockdown may inhibit neuroblastoma cell proliferation by the PI3K/Akt/NF-κB pathway. Therefore, RRS1 may be a potential target for neuroblastoma treatment.

IMPACT

RRS1 is involved in the progression of neuroblastoma. Knockdown of RRS1 contributes to inhibit the survival of neuroblastoma cells. RRS1 is associated with the PI3K/Akt/NF-κB signaling pathway in neuroblastoma cells. RRS1 may be a promising target for neuroblastoma therapy.

Aplysia Neurons as a Model of Alzheimer's Disease: Shared Genes and Differential Expression

Although Alzheimer’s disease (AD) is the most common form of dementia in the United States, development of therapeutics has proven difficult. Invertebrate alternatives to current mammalian AD models have been successfully employed to study the etiology of the molecular hallmarks of AD. The marine snail Aplysia californica offers a unique and underutilized system in which to study the physiological, behavioral, and molecular impacts of AD. Mapping of the Aplysia proteome to humans and cross-referencing with two databases of genes of interest in AD research identified 898 potential orthologs of interest in Aplysia. Included among these orthologs were alpha, beta and gamma secretases, amyloid-beta, and tau. Comparison of age-associated differential expression in Aplysia sensory neurons with that of late-onset AD in the frontal lobe identified 59 ortholog with concordant differential expression across data sets. The 21 concordantly upregulated genes suggested increased cellular stress and protein dyshomeostasis. The 47 concordantly downregulated genes included important components of diverse neuronal processes, including energy metabolism, mitochondrial homeostasis, synaptic signaling, Ca⁺⁺ regulation, and cellular cargo transport. Compromised functions in these processes are known hallmarks of both human aging and AD, the ramifications of which are suggested to underpin cognitive declines in aging and neurodegenerative disease.

Novel insights into the immune regulatory effects of Megalobrama amblycephala intelectin on the phagocytosis and killing activity of macrophages

Previous studies have found that the expression level of Megalobrama amblycephala intelectin (MaINTL) increased significantly post Aeromonas hydrophila infection, and recombinant MaINTL (rMaINTL) protein could activate macrophages and enhance the phagocytosis and killing activity of macrophages. In order to reveal the immune regulatory mechanisms of MaINTL, primary M. amblycephala macrophages were treated with endotoxin-removed rMaINTL and GST-tag proteins, then total RNA were extracted and used for comparative Digital Gene Expression Profiling (DGE). 1247 differentially expressed genes were identified by comparing rMaINTL and GST-tag treated macrophage groups, including 482 up-regulated unigenes and 765 down-regulated unigenes. In addition, eleven randomly selected differentially expressed genes were verified by qRT-PCR, and most of them shared the similar expression patterns as that of DGE results. GO enrichment revealed that the differentially expressed genes were mainly concentrated in the membrane part and cytoskeleton of cellular component, the binding and signal transducer activity of molecular function, the cellular process, regulation of biological process, signaling and localization of biological process, most of which might related with the phagocytosis and killing activity of macrophages. KEGG analysis revealed the activation and involvement of differentially expressed genes in immune related pathways, such as Tumor necrosis factor (TNF) signaling pathway, Interleukin 17 (IL-17) signaling pathway, Toll-like receptor signaling pathway, and NOD like receptor signaling pathway, etc. In these pathways, TNF-ɑ, Activator protein-1 (AP-1), Myeloid differentiation primary response protein MyD88 (MyD88), NF-kappa-B inhibitor alpha (ikBɑ) and other key signaling factors were significantly up-regulated. These results will be helpful to clarify the immune regulatory mechanisms of fish intelectin on macrophages, thus providing a theoretical basis for the prevention and control of fish bacterial diseases.

A Novel Protein-Protein Interaction between RSK3 and IκBα and a New Binding Inhibitor That Suppresses Breast Cancer Tumorigenesis

Multiple cancer-related biological processes are mediated by protein-protein interactions (PPIs). Through interactions with a variety of factors, members of the ribosomal S6 kinase (RSK) family play roles in cell cycle progression and cell proliferation. In particular, RSK3 contributes to cancer viability, but the underlying mechanisms remain unknown. We performed a kinase library screen to find IκBα PPI binding partners and identified RSK3 as a novel IκBα binding partner using a cell-based distribution assay. In addition, we discovered a new PPI inhibitor using mammalian two-hybrid (MTH) analysis. We assessed the antitumor effects of the new inhibitor using cell proliferation and colony formation assays and monitored the rate of cell death by FACS apoptosis assay. IκBα is phosphorylated by the active form of the RSK3 kinase. A small-molecule inhibitor that targets the RSK3/IκBα complex exhibited antitumor activity in breast cancer cells and increased their rate of apoptosis. RSK3 phosphorylation and RSK3/IκBα complex formation might be functionally important in breast tumorigenesis. The RSK3/IκBα-specific binding inhibitor identified in this study represents a lead compound for the development of new anticancer drugs.

Co-expression analysis identifies neuro-inflammation as a driver of sensory neuron aging in Aplysia californica

Aging of the nervous system is typified by depressed metabolism, compromised proteostasis, and increased inflammation that results in cognitive impairment. Differential expression analysis is a popular technique for exploring the molecular underpinnings of neural aging, but technical drawbacks of the methodology often obscure larger expression patterns. Co-expression analysis offers a robust alternative that allows for identification of networks of genes and their putative central regulators. In an effort to expand upon previous work exploring neural aging in the marine model Aplysia californica, we used weighted gene correlation network analysis to identify co-expression networks in a targeted set of aging sensory neurons in these animals. We identified twelve modules, six of which were strongly positively or negatively associated with aging. Kyoto Encyclopedia of Genes analysis and investigation of central module transcripts identified signatures of metabolic impairment, increased reactive oxygen species, compromised proteostasis, disrupted signaling, and increased inflammation. Although modules with immune character were identified, there was no correlation between genes in Aplysia that increased in expression with aging and the orthologous genes in oyster displaying long-term increases in expression after a virus-like challenge. This suggests anti-viral response is not a driver of Aplysia sensory neuron aging.

Post-translational Modifications of IκBα: The State of the Art

The nuclear factor-kappa B (NF-κB) signaling pathway regulates a variety of biological functions in the body, and its abnormal activation contributes to the pathogenesis of many diseases, such as cardiovascular and respiratory diseases and cancers. Therefore, to ensure physiological homeostasis of body systems, this pathway is strictly regulated by IκBα transcription, IκBα synthesis, and the IκBα-dependent nuclear transport of NF-κB. Particularly, the post-translational modifications of IκBα including phosphorylation, ubiquitination, SUMOylation, glutathionylation and hydroxylation are crucial in the abovementioned regulatory process. Because of the importance of the NF-κB pathway in maintaining body homeostasis, understanding the post-translational modifications of IκBα can not only provide deeper insights into the regulation of NF-κB pathway but also contribute to the development of new drug targets and biomarkers for the diseases.

Proteasome, a Promising Therapeutic Target for Multiple Diseases Beyond Cancer

Proteasome is vital for intracellular protein homeostasis as it eliminates misfolded and damaged protein. Inhibition of proteasome has been validated as a powerful strategy for anti-cancer therapy, and several drugs have been approved for treatment of multiple myeloma. Recent studies indicate that proteasome has potent therapeutic effects on a variety of diseases besides cancer, including parasite infectious diseases, bacterial/fungal infections diseases, neurodegenerative diseases and autoimmune diseases. In this review, recent developments of proteasome inhibitors for various diseases and related structure activity relationships are going to be summarized.

CP-25 improves nephropathy in collagen-induced arthritis rats by inhibiting the renal inflammatory response

Paeoniflorin-6'-O-benzene sulfonate (CP-25) is a derivative of paeoniflorin. We previously confirmed that CP-25 inhibits inflammatory responses in several arthritis animal models. The aim of the present study was to investigate the beneficial effects of CP-25 on renal damage in rats with collagen-induced arthritis (CIA). CIA was induced in rats, which were orally administered CP-25 (25, 50 and 100 mg/kg/day) for 24 days. The levels of plasma blood urea nitrogen (BUN) and urine protein in CIA rats were measured. Pathological changes in renal tissues and joints were observed, and inflammatory cell infiltration was evaluated by immunohistochemistry. Moreover, renal inflammatory mediators and transporters were measured by western blotting. We found that CP-25 not only inhibited arthritis manifestations but also improved renal pathological manifestations and kidney injury by decreasing serum BUN and urine protein levels. Further study revealed that CP-25 treatment reduced the number of renal CD68+ cells and downregulated the levels of MCP-1, TNF-α and IL-6 in CIA rats. On the other hand, we noted that CP-25 decreased the ratios of phosphorylated NF-κB p65 (p-p65) to total p65 and p-IκBα to total IκBα in CIA rats, suggesting that CP-25 blocked NF-κB activation. Finally, we observed that CP-25 restored the abnormal expression of OAT1 and OCT1 in the renal tissues of CIA rat. Our data indicate that CP-25 ameliorates kidney damage in CIA rats, and this beneficial effect is closely related to inhibiting renal inflammation and the abnormal expression of transporters.

Inflammation Triggered by Saturated Fat Ingestion Is Linked to Insulin Resistance and Hyperandrogenism in Polycystic Ovary Syndrome

CONTEXT

Inflammation and insulin resistance are often present in polycystic ovary syndrome (PCOS).

OBJECTIVE

We determined the effect of saturated fat ingestion on mononuclear cell (MNC) nuclear factor-κB (NFκB) activation; NFκB, inhibitory-κBα (IκBα), and tumor necrosis factor-α (TNFα) gene expression; and circulating C-reactive protein (CRP) in women with PCOS.

DESIGN

Cross-sectional study.

SETTING

Academic medical center.

PATIENTS

Twenty reproductive-age women with PCOS (10 lean, 10 with obesity) and 20 ovulatory controls (10 lean, 10 with obesity).

MAIN OUTCOME MEASURES

Activated NFκB, NFκB heterodimer subunits, IκBα and TNFα messenger ribonucleic acid content and NFκB p65 and IκBα protein content were quantified in mononuclear cells (MNC), and CRP was measured in plasma from blood drawn fasting and 2, 3, and 5 h after saturated fat ingestion. Insulin sensitivity was derived from oral glucose tolerance testing (ISOGTT). Androgen secretion was assessed from blood drawn fasting and 24, 48, and 72 h after human chorionic gonadotropin (HCG) administration.

RESULTS

In response to saturated fat ingestion, women with PCOS regardless of weight class exhibited lipid-induced increases in activated NFκB, NFκB, and TNFα gene expression and plasma CRP and decreases in IκBα protein compared with lean control subjects. Both PCOS groups exhibited lower ISOGTT and greater HCG-stimulated androgen secretion compared with control subjects. Lipid-stimulated NFκB activation was negatively correlated with ISOGTT, and positively correlated with HCG-stimulated androgen secretion.

CONCLUSION

In PCOS, increases in NFκB activation and circulating CRP and decreases in IκBα protein following saturated fat ingestion are independent of obesity. Circulating MNC and excess adipose tissue are separate and distinct contributors to inflammation in this disorder.

Reversible inhibitor of CRM1 sensitizes glioblastoma cells to radiation by blocking the NF-κB signaling pathway

Background

Activation of nuclear factor-kappa B (NF-κΒ) through DNA damage is one of the causes of tumor cell resistance to radiotherapy. Chromosome region 1 (CRM1) regulates tumor cell proliferation, drug resistance, and radiation resistance by regulating the nuclear-cytoplasmic translocation of important tumor suppressor proteins or proto-oncoproteins. A large number of studies have reported that inhibition of CRM1 suppresses the activation of NF-κΒ. Thus, we hypothesize that the reversible CRM1 inhibitor S109 may induce radiosensitivity in glioblastoma (GBM) by regulating the NF-κΒ signaling pathway.

Methods

This study utilized the cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and colony formation assay to evaluate the effect of S109 combined with radiotherapy on the proliferation and survival of GBM cells. The therapeutic efficacy of S109 combined with radiotherapy was evaluated in vivo to explore the therapeutic mechanism of S109-induced GBM radiosensitization.

Results

We found that S109 combined with radiotherapy significantly inhibited GBM cell proliferation and colony formation. By regulating the levels of multiple cell cycle- and apoptosis-related proteins, the combination therapy induced G1 cell cycle arrest in GBM cells. In vivo studies showed that S109 combined with radiotherapy significantly inhibited the growth of intracranial GBM and prolonged survival. Importantly, we found that S109 combined with radiotherapy promoted the nuclear accumulation of IκΒα, and inhibited phosphorylation of p65 and the transcriptional activation of NF-κΒ.

Conclusion

Our findings provide a new therapeutic regimen for improving GBM radiosensitivity as well as a scientific basis for further clinical trials to evaluate this combination therapy.

SUMO conjugation regulates immune signalling

Post-translational modifications (PTMs) are critical drivers and attenuators for proteins that regulate immune signalling cascades in host defence. In this review, we explore functional roles for one such PTM, the small ubiquitin-like modifier (SUMO). Very few of the SUMO conjugation targets identified by proteomic studies have been validated in terms of their roles in host defence. Here, we compare and contrast potential SUMO substrate proteins in immune signalling for flies and mammals, with an emphasis on NFκB pathways. We discuss, using the few mechanistic studies that exist for validated targets, the effect of SUMO conjugation on signalling and also explore current molecular models that explain regulation by SUMO. We also discuss in detail roles of evolutionary conservation of mechanisms, SUMO interaction motifs, crosstalk of SUMO with other PTMs, emerging concepts such as group SUMOylation and finally, the potentially transforming roles for genome-editing technologies in studying the effect of PTMs.

Ubiquitination and SUMOylation in HIV Infection: Friends and Foes

As intracellular parasites, viruses hijack the cellular machinery to facilitate their replication and spread. This includes favouring the expression of their viral genes over host genes, appropriation of cellular molecules, and manipulation of signalling pathways, including the post-translational machinery. HIV, the causative agent of AIDS, is notorious for using post-translational modifications to generate infectious particles. Here, we discuss the mechanisms by which HIV usurps the ubiquitin and SUMO pathways to modify both viral and host factors to achieve a productive infection, and also how the host innate sensing system uses these post-translational modifications to hinder HIV replication.

Anti-inflammatory Effect of Ghrelin in Lymphoblastoid Cell Lines From Children With Autism Spectrum Disorder

The gut hormone ghrelin has been implicated in a variety of functional roles in the central nervous system through the brain-gut axis, one of which is an anti-inflammatory effect. An aberrant brain-gut axis producing immune dysfunction has been implicated in the pathobiology of autism spectrum disorder (ASD), and elevated expression of inflammatory markers has been shown in blood and brain tissue from subjects with ASD. We hypothesized that ghrelin may mitigate this effect. Lymphoblastoid cell lines from typically developed children (TD-C) (N = 20) and children with ASD (ASD-C) (N = 20) were cultured with PBS or human ghrelin (0.01 μM) for 24 h, and mRNA expression levels of the inflammation-related molecules interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and nuclear factor kappa B (NF-κB) were measured to examine the effects of ghrelin as an anti-inflammatory agent. Expression levels of TNF-α and NF-κB mRNA, but not IL-1β or IL-6, were significantly elevated in ASD-C compared to TD-C. Ghrelin showed a tendency to reduce the expression of TNF-α and NF-κB, but this was not statistically significant. Considering the heterogenous pathobiology of ASD, we examined the effects of ghrelin on TD-C and ASD-C with expression levels of TNF-α and NF-κB in the highest and lowest quartiles. We found that ghrelin markedly reduced mRNA expression of TNF-α and NF-κB s in ASD-C with highest-quartile expression, but there were no effects in ASD-C with lowest-quartile expression, TD-C with highest quartile expression, or TD-C with lowest quartile expression. Together, these findings suggest that ghrelin has potential as a novel therapeutic agent for ASD with inflammation and/or immune dysfunction.

Barriers for HIV Cure: The Latent Reservoir

Thirty-five years after the identification of HIV-1 as the causative agent of AIDS, we are still in search of vaccines and treatments to eradicate this devastating infectious disease. Progress has been made in understanding the molecular pathogenesis of this infection, which has been crucial for the development of the current therapy regimens. However, despite their efficacy at limiting active viral replication, these drugs are unable to purge the latent reservoir: a pool of cells that harbor transcriptionally inactive, but replication-competent HIV-1 proviruses, and that represent the main barrier to eradicate HIV-1 from affected individuals. In this review, we discuss advances in the field that have allowed a better understanding of HIV-1 latency, including the diverse cell types that constitute the latent reservoir, factors influencing latency, tools to study HIV-1 latency, as well as current and prospective therapeutic approaches to target these latently infected cells, so a functional cure for HIV/AIDS can become a reality.

BCA2/Rabring7 Interferes with HIV-1 Proviral Transcription by Enhancing the SUMOylation of IκBα

BCA2/Rabring7 is a BST2 cofactor that promotes the lysosomal degradation of trapped HIV-1 virions but also functions as a BST2-independent anti-HIV factor by targeting Gag for lysosomal degradation. Since many antiviral factors regulate the NF-κB innate signaling pathway, we investigated whether BCA2 is also connected to this proinflammatory cascade. Here, we show for the first time that BCA2 is induced by NF-κB-activating proinflammatory cytokines and that upregulation of BCA2 provides regulatory negative feedback on NF-κB. Specifically, BCA2 serves as an E3 SUMO ligase in the SUMOylation of IκBα, which in turn enhances the sequestration of NF-κB components in the cytoplasm. Since HIV-1 utilizes NF-κB to promote proviral transcription, the BCA2-mediated inhibition of NF-κB significantly decreases the transcriptional activity of HIV-1 (up to 4.4-fold in CD4⁺ T cells). Therefore, our findings indicate that BCA2 poses an additional barrier to HIV-1 infection: not only does BCA2 prevent assembly and release of nascent virions, it also significantly restricts HIV-1 transcription by inhibiting the NF-κB pathway.IMPORTANCE Understanding the interactions between HIV-1 and its host cells is highly relevant to the design of new drugs aimed at eliminating HIV-1 from infected individuals. We have previously shown that BCA2, a cofactor of BST2 in the restriction of HIV-1, also prevents virion assembly in a BST2-independent manner. In this study, we found that BCA2 negatively regulates the NF-κB pathway-a signaling cascade necessary for HIV-1 replication and infectivity-which in turn detrimentally affects proviral transcription and virus propagation. Thus, our results indicate that, besides its previously described functions as an antiviral factor, BCA2 poses an additional barrier to HIV-1 replication at the transcriptional level.

Selinexor, a Selective Inhibitor of Nuclear Export (SINE) compound, acts through NF-κB deactivation and combines with proteasome inhibitors to synergistically induce tumor cell death

The nuclear export protein, exportin-1 (XPO1/CRM1), is overexpressed in many cancers and correlates with poor prognosis. Selinexor, a first-in-class Selective Inhibitor of Nuclear Export (SINE) compound, binds covalently to XPO1 and blocks its function. Treatment of cancer cells with selinexor results in nuclear retention of major tumor suppressor proteins and cell cycle regulators, leading to growth arrest and apoptosis. Recently, we described the selection of SINE compound resistant cells and reported elevated expression of inflammation-related genes in these cells. Here, we demonstrated that NF-κB transcriptional activity is up-regulated in cells that are naturally resistant or have acquired resistance to SINE compounds. Resistance to SINE compounds was created by knockdown of the cellular NF-κB inhibitor, IκB-α. Combination treatment of selinexor with proteasome inhibitors decreased NF-κB activity, sensitized SINE compound resistant cells and showed synergistic cytotoxicity in vitro and in vivo. Furthermore, we showed that selinexor inhibited NF-κB activity by blocking phosphorylation of the IκB-α and the NF-κB p65 subunits, protecting IκB-α from proteasome degradation and trapping IκB-α in the nucleus to suppress NF-κB activity. Therefore, combination treatment of selinexor with a proteasome inhibitor may be beneficial to patients with resistance to either single-agent.

Inhibition of nuclear factor-kappa B enhances the tumor growth of ovarian cancer cell line derived from a low-grade papillary serous carcinoma in p53-independent pathway

Background

NF-kB can function as an oncogene or tumor suppressor depending on cancer types. The role of NF-kB in low-grade serous ovarian cancer, however, has never been tested. We sought to elucidate the function of NF-kB in the low-grade serous ovarian cancer.

Methods

The ovarian cancer cell line, HOC-7, derived from a low-grade papillary serous carcinoma. Introduction of a dominant negative mutant, IkBαM, which resulted in decrease of NF-kB function in ovarian cancer cell lines. The transcription ability, tumorigenesis, cell proliferation and apoptosis were observed in derivative cell lines in comparison with parental cells.

Results

Western blot analysis indicated increased expression of the anti-apoptotic proteins Bcl-xL and reduced expression of the pro-apoptotic proteins Bax, Bad, and Bid in HOC-7/IĸBαM cell. Further investigations validate this conclusion in KRAS wildtype cell line SKOV3. Interesting, NF-kB can exert its pro-apoptotic effect by activating mitogen-activated protein kinase (MAPK) phosphorylation in SKOV3 ovarian cancer cell, whereas opposite changes detected in p-MEK in HOC-7 ovarian cancer cell, the same as some chemoresistant ovarian cancer cell lines. In vivo animal assay performed on BALB/athymic mice showed that injection of HOC-7 induced subcutaneous tumor growth, which was completely regressed within 7 weeks. In comparison, HOC-7/IĸBαM cells caused sustained tumor growth and abrogated tumor regression, suggesting that knock-down of NF-kB by IĸBαM promoted sustained tumor growth and delayed tumor regression in HOC-7 cells.

Conclusion

Our results demonstrated that NF-kB may function as a tumor suppressor by facilitating regression of low grade ovarian serous carcinoma through activating pro-apoptotic pathways.

SUMOylation and Potassium Channels: Links to Epilepsy and Sudden Death

Neuronal potassium ion channels play an essential role in the generation of the action potential and excitability of neurons. The dysfunction of ion channel subunits can cause channelopathies, which are associated in some cases with sudden unexplained death in epilepsy SUDEP. The physiological roles of neuronal ion channels have been largely determined, but little is known about the molecular mechanisms underlying neurological channelopathies, especially the determinants of the channels' regulation. SUMO (small ubiquitin-like modifier) proteins covalently conjugate lysine residues in a large number of target proteins and modify their functions. SUMO modification (SUMOylation) has emerged as an important regulatory mechanism for protein stability, function, subcellular localization, and protein-protein interactions. Since SUMO was discovered almost 20 years ago, the biological contribution of SUMOylation has not fully understood. It is until recently that the physiological impacts of SUMOylation on the regulation of neuronal potassium ion channels have been investigated. It is well established that SUMOylation controls many aspects of nuclear function, but it is now clear that it is also a key determinant in the function of potassium channels, and SUMOylation has also been implicated in a wide range of channelopathies, including epilepsy and sudden death.

Role of RSUME in inflammation and cancer

RSUME (for RWD-domain-containing sumoylation enhancer), RWDD3 gene, was identified from a pituitary tumor cell with increased tumorigenic and angiogenic potential, and has higher expression in cerebellum, pituitary, heart, kidney, liver, pancreas, adrenal gland and prostate. RSUME is induced by cellular stress like hypoxia and heat shock, and is increased in pituitary tumors, in gliomas and in VHL tumors. Seven splicing forms have been described. Two of them correspond to non-coding RNAs and the other five possess an RWD domain in the N-terminus and differ in their C-terminal end. RSUME enhances SUMO conjugation by interacting with the SUMO conjugase Ubc9, increases Ubc9 thioester formation and therefore favors sumoylation of specific targets. RSUME increases IκB levels and stabilizes HIF-1α during hypoxia, leading to inhibition of NF-κB and increased HIF-1 transcriptional activity. RSUME inhibits pVHL function, thus suppressing HIF-1 and 2α ubiquitination and degradation. Disruption of the RWD domain structure of RSUME indicated that this domain is critical for RSUME action. The findings point to an important role of RSUME in the regulation and stability of specific targets, which are key regulatory mediators in cancer and inflammation.

Modification by ubiquitin-like proteins: significance in apoptosis and autophagy pathways

Ubiquitin-like proteins (Ubls) confer diverse functions on their target proteins. The modified proteins are involved in various biological processes, including DNA replication, signal transduction, cell cycle control, embryogenesis, cytoskeletal regulation, metabolism, stress response, homeostasis and mRNA processing. Modifiers such as SUMO, ATG12, ISG15, FAT10, URM1, and UFM have been shown to modify proteins thus conferring functions related to programmed cell death, autophagy and regulation of the immune system. Putative modifiers such as Domain With No Name (DWNN) have been identified in recent times but not fully characterized. In this review, we focus on cellular processes involving human Ubls and their targets. We review current progress in targeting these modifiers for drug design strategies.

Reactive Oxygen Species, SUMOylation, and Endothelial Inflammation

Although the exact mechanism through which NADPH oxidases (Nox's) generate reactive oxygen species (ROS) is still not completely understood, it is widely considered that ROS accumulation is the cause of oxidative stress in endothelial cells. Increasing pieces of evidence strongly indicate the role for ROS in endothelial inflammation and dysfunction and subsequent development of atherosclerotic plaques, which are causes of various pathological cardiac events. An overview for a causative relationship between ROS and endothelial inflammation will be provided in this review. Particularly, a crucial role for specific protein SUMOylation in endothelial inflammation will be presented. Given that SUMOylation of specific proteins leads to increased endothelial inflammation, targeting specific SUMOylated proteins may be an elegant, effective strategy to control inflammation. In addition, the involvement of ROS production in increasing the risk of recurrent coronary events in a sub-group of non-diabetic, post-infarction patients with elevated levels of HDL-cholesterol will be presented with the emphasis that elevated HDL-cholesterol under certain inflammatory conditions can lead to increased incidence of cardiovascular events.

Regulation and function of nuclear IκBα in inflammation and cancer

The nuclear translocation and accumulation of IκBα represents an important mechanism regulating transcription of NFκB-dependent pro-inflammatory and anti-apoptotic genes. The nuclear accumulation of IκBα can be induced by post-induction repression in stimulated cells, inhibition of the CRM1-dependent nuclear IκBα export by leptomycin B, and by the inhibition of the 26S proteasome. In addition, IκBα is constitutively localized in the nucleus of human neutrophils, likely contributing to the high rate of spontaneous apoptosis in these cells. In the nucleus, IκBα suppresses transcription of NFκB-dependent pro-inflammatory and anti-apoptotic genes, representing an attractive therapeutic target. However, the inhibition of NFκB-dependent genes by nuclear IκBα is promoter specific, and depends on the subunit composition of NFκB dimers and post-translational modifications of the recruited NFκB proteins. In addition, several recent studies have demonstrated an NFκB-independent role of the nuclear IκBα. In this review, we discuss the mechanisms leading to the nuclear accumulation of IκBα and its nuclear functions as potential targets for anti-inflammatory and anti-cancer therapies.

Novel roles of SUMO in pancreatic β-cells: thinking outside the nucleus

The endocrine pancreas is critically important in the regulation of energy metabolism, with defective insulin secretion from pancreatic islet β-cells a major contributing factor to the development of type 2 diabetes. Small ubiquitin-like modifier (SUMO) proteins have been demonstrated to covalently modify a wide range of target proteins, mediating a broad range of cellular processes. While the effects of SUMOylation on β-cell gene transcription have been previously reviewed, recent reports indicate roles for SUMO outside of the nucleus. In this review we shall focus on the reported non-nuclear roles of SUMOylation in the regulation of β-cells, including SUMOylation as a novel signaling pathway in the acute regulation of insulin secretion.

Anergic CD8+ T lymphocytes have impaired NF-κB activation with defects in p65 phosphorylation and acetylation

Because of the cytotoxic potential of CD8(+) T cells, maintenance of CD8(+) peripheral tolerance is extremely important. A major peripheral tolerance mechanism is the induction of anergy, a refractory state in which proliferation and IL-2 production are inhibited. We used a TCR transgenic mouse model to investigate the signaling defects in CD8(+) T cells rendered anergic in vivo. In addition to a previously reported alteration in calcium/NFAT signaling, we also found a defect in NF-κB-mediated gene transcription. This was not due to blockade of early NF-κB activation events, including IκB degradation and NF-κB nuclear translocation, as these occurred normally in tolerant T cells. However, we discovered that anergic cells failed to phosphorylate the NF-κB p65 subunit at Ser(311) and also failed to acetylate p65 at Lys(310). Both of these modifications have been implicated as critical for NF-κB transactivation capacity, and thus, our results suggest that defects in key phosphorylation and acetylation events are important for the inhibition of NF-κB activity (and subsequent T cell function) in anergic CD8(+) T cells.

Euonymus alatus extract attenuates LPS-induced NF-κB activation via IKKβ inhibition in RAW 264.7 cells

AIM OF THE STUDY

The present study was performed to investigate the underlying mechanisms of anti-inflammatory effects with the extract of Euonymus alatus (EEA), and specially focused on nuclear factor κB (NF-κB) signaling pathway by targeting the IκB kinase β (IKKβ).

MATERIALS AND METHODS

The effect of EEA for IKKβ activity was analyzed using an immobilized metal affinity for phosphochemicals (IMAP)-based time-resolved fluorescence resonance energy transfer (TR-FRET) assay. The effect of EEA on lipopolysaccharide (LPS)-induced NF-κB activation in murine macrophage RAW 264.7 cells with western blotting and immunofluorescent staining was evaluated.

RESULTS

IKKβ studies based on IMAP-TR-FRET showed that EEA possesses a potent IKKβ inhibitory activity with IC(50) value of 11.83μg/ml. EEA (10, 30μg/ml) also attenuated the LPS-induced IκBα phosphorylation/degradation, NF-κB translocation and subsequent NO synthesis in RAW 264.7 cells.

CONCLUSIONS

These results suggest that EEA abrogates LPS-induced NF-κB signaling pathway by targeting the IKKβ in RAW 264.7 cells and these properties may provide a molecular basis for understanding the inhibitory effects of EEA on LPS-mediated inflammation.

Transcriptomic and innate immune responses to Yersinia pestis in the lymph node during bubonic plague

A delayed inflammatory response is a prominent feature of infection with Yersinia pestis, the agent of bubonic and pneumonic plague. Using a rat model of bubonic plague, we examined lymph node histopathology, transcriptome, and extracellular cytokine levels to broadly characterize the kinetics and extent of the host response to Y. pestis and how it is influenced by the Yersinia virulence plasmid (pYV). Remarkably, dissemination and multiplication of wild-type Y. pestis during the bubonic stage of disease did not induce any detectable gene expression or cytokine response by host lymph node cells in the developing bubo. Only after systemic spread had led to terminal septicemic plague was a transcriptomic response detected, which included upregulation of several cytokine, chemokine, and other immune response genes. Although an initial intracellular phase of Y. pestis infection has been postulated, a Th1-type cytokine response associated with classical activation of macrophages was not observed during the bubonic stage of disease. However, elevated levels of interleukin-17 (IL-17) were present in infected lymph nodes. In the absence of pYV, sustained recruitment to the lymph node of polymorphonuclear leukocytes (PMN, or neutrophils), the major IL-17 effector cells, correlated with clearance of infection. Thus, the ability to counteract a PMN response in the lymph node appears to be a major in vivo function of the Y. pestis virulence plasmid.

A short-hairpin RNA targeting osteopontin downregulates MMP-2 and MMP-9 expressions in prostate cancer PC-3 cells

Osteopontin (OPN), a secreted phosphoglycoprotein, is frequently associated with cell proliferation and tumor metastatic spread in a variety of cancers. It has been reported that OPN induce matrix metalloproteinase (MMP)-2 and MMP-9 activations through nuclear factor kappaB (NF-kappaB)-mediated signaling pathways. In this study, we investigated the roles of OPN in human prostate cancer cells and provided clues about the possible functions of IkappaB kinase (IKK) in NF-kappaB-mediated OPN-induced activations of MMP-2 and MMP-9. Short-hairpin RNA (shRNA) expression vectors were used to inhibit OPN expression in PC-3 cells, human prostate cancer cell line, and IKK inhibitor VII were applied to inhibit the activities of IKK-1 and IKK-2. The results showed that OPN shRNA-mediated RNA interference can downregulate OPN, MMP-2 and MMP-9 expressions, thereby resulting in suppression of the proliferation, migration and invasion of PC-3 cells in vitro and tumor growth in vivo. Moreover, the inhibition of IKK-2 can suppress MMP-2 and MMP-9 expressions, in contrast, the inhibition of IKK-1 has no effects on the OPN, MMP-2 and MMP-9 expression levels. Thus, this study demonstrated that OPN knockdown could downregulate MMP-2 and MMP-9 expressions result in inhibiting the malignant physiological behaviors of PC-3 cell and that IKK-2 may play a crucial role in OPN-induced MMP-2 and MMP-9 expressions via NF-kappaB-mediated signaling pathways.

Transcriptional regulation of hepatic stellate cells

Hepatic stellate cell (HSC) activation is a process of cellular transdifferentiation in which, upon liver injury, the quiescent vitamin A storing perisinusoidal HSC is converted into a wound-healing myofibroblast and acquires potent pro-inflammatory and pro-fibrogenic activities. This remarkable phenotypic transformation is underpinned by changes in the expression of a vast number of genes. In this review we survey current knowledge of the transcription factors that either control HSC activation or which regulate specific fibrogenic functions of the activated HSC such as collagen expression, proliferation and resistance to apoptosis.

SUMO proteases: redox regulation and biological consequences

Small-ubiquitin modifier (SUMO) has emerged as a novel modification system that governs the activities of a wide spectrum of protein substrates. SUMO-specific proteases (SENP) are of particular interest, as they are responsible for both the maturation of SUMO precursors and for their deconjugation. The interruption of SENPs has been implicated in embryonic defects and carcinoma cells, indicating that a proper balance of SUMO conjugation and deconjugation is crucial. Recent advances in molecular and cellular biology have highlighted the distinct subcellular localization, and endopeptidase and isopeptidase activities of SENPs, suggesting that they are nonredundant. A better understanding of the molecular basis of SUMO recognition and hydrolytic cleavage has been obtained from the crystal structures of SENP-substrate complexes. While a number of proteomic studies have shown an upregulation of sumoylation, attention is now increasingly being directed towards the regulatory mechanism of sumoylation, in particular the oxidative effect. Findings on the oxidation-induced intermolecular disulfide of E1-E2 ligases and SENP1/2 have improved our understanding of the mechanism by which modification is switched up or down. More intriguingly, a growing body of evidence suggests that sumoylation cross-talks with other modifications, and that the upstream and downstream signaling pathway is co-regulated by more than one modifier.

Adenosine signaling mediates SUMO-1 modification of IkappaBalpha during hypoxia and reoxygenation

Small ubiquitin-like modifier 1 (SUMO-1) modification of IkappaBalpha has been described to actively participate in NFkappaB regulation. Following proteosomal degradation of IkappaBalpha, an auto-regulatory loop consisting of transcriptional activation of IkappaBalpha gene and SUMO-1 modification of newly synthesized IkappaBalpha proceeds. The SUMOylated IkappaBalpha form is resistant to signal-induced degradation, consequently halting NFkappaB activation. We describe a mechanistic model by which adenosine (Ado) signaling results in significant accumulation of SUMO-1 modified IkappaBalpha with subsequent attenuation of NFkappaB activation. Using models of hypoxia followed by reoxygenation (H/R), we have documented an H/R cycle-dependent increase in extracellular Ado correlating with increases in the cytoplasmic pool of IkappaBalpha/SUMO-1. We demonstrate a dose-dependent increase in IkappaBalpha/SUMO in cells treated with the general Ado receptor agonist NECA and abolished by Ado receptor antagonists. Experiments in cells exposed to cycles of H/R followed by hypoxia demonstrated differential patterns of SUMOylation and phosphorylation of IkappaBalpha, greatly impacting its proteosomal degradation by the 26 S proteasome. Assays targeting knockdown and overexpression of SUMO-1 demonstrated significant regulation of NFkappaB activation and NFkappaB-mediated gene transcription (interleukin-6). These results were confirmed in vivo using wild type and cd73 null mouse lung tissue. In summary, we present an endogenous mechanism by which cells and tissues acquire anti-inflammatory properties by recruiting a nondegradable form of IkappaBalpha, a major control point for NFkappaB activation via Ado signaling.

Mechanisms underlying the control of progesterone receptor transcriptional activity by SUMOylation

Posttranslational modification by small ubiquitin-like modifier (SUMO) is a major regulator of transcription. We previously showed that progesterone receptors (PR) have a single consensus psiKXE SUMO-conjugation motif centered at Lys-388 in the N-terminal domain of PR-B and a homologous site of PR-A. SUMOylation of the PR is hormone-dependent and has a suppressive effect on transcription of an exogenous promoter. Here we show that repression of PR activity by SUMOylation at Lys-388 is uncoupled from phosphorylation, involves synergy between tandem progesterone response elements, and is associated with lowered ligand sensitivity and slowed ligand-dependent down-regulation. However, paradoxically, cellular overexpression of SUMO-1 increases PR transcriptional activity even if Lys-388 is mutated, suggesting that the receptors are activated indirectly by other SUMOylated proteins. One of these is the coactivator SRC-1, whose binding to PR and enhancement of agonist-dependent N-/C-terminal interactions is augmented by the presence of SUMO-1. Increased transcription due to SRC-1 is independent of PR SUMOylation based on assays with the Lys-388 mutants and the pure antiprogestin ZK98299, which blocks N-/C-terminal interactions. In summary, SUMOylation tightly regulates the transcriptional activity of PR by repressing the receptors directly while activating them indirectly through augmented SRC-1 coactivation.

Molecular understanding of cytokine-steroid hormone dialogue: implications for human diseases

Highly sophisticated mechanisms confer upon the immune system the capacity to respond with a certain degree of autonomy. However, the final outcome of an adaptative immune response depends on the interaction with other systems of the organism. The immune-neuroendocrine systems have an intimate cross-communication, making possible a satisfactory response to environmental changes. Part of this interaction occurs through cytokines and steroid hormones. The last step of this crosstalk is at the molecular level. In this article we will focus on the physical and functional interrelationship between cytokine signaling pathway-activated transcription factors (TFs) and steroid receptors in different cell models, where the signals triggered by cytokines and steroid hormones have major roles: (1) the ligand-dependent-activated glucocorticoid receptor (GR) influence the genetic program that specifies lineage commitment in T helper (Th) cell differentiation. How posttranslational modifications of several TFs as well as nuclear hormone receptors could be implicated in the molecular crosstalk between the immune-neuroendocrine messengers is discussed. (2) glucocorticoid (GC) antagonism on the TCR-induced T cell apoptosis. (3) estrogen receptor/TGF-beta family proteins molecular interaction implicated on pituitary prolactinomas pathogenesis. The functional crosstalk at the molecular level between immune and steroids signals is essential to determine an integrative response to both mediators (which in the last instance results in a new gene activation/repression profile) and constitutes the ultimate integrative level of interaction between the immune and neuroendocrine systems.

Role of desumoylation in the development of prostate cancer

SUMO is a novel ubiquitin-like protein that can covalently modify a large number of nuclear proteins. SUMO modification has emerged as an important regulatory mechanism for protein function and localization. Sumoylation is a dynamic process that is mediated by activating (E1), conjugating (E2), and ligating (E3) enzymes and is readily reversed by a family of SUMO-specific proteases (SENPs). Since SUMO was discovered 10 years ago, the biologic contribution of this posttranslational modification has remained unclear. In this review, we report that SENP1, a member of the SENP family, is overexpressed in human prostate cancer specimens. The induction of SENP1 is observed with the chronic exposure of prostate cancer cells to androgen and/or interleukin (IL) 6. SENP1 upregulation modulates the transcriptional activity of androgen receptors (ARs) and c-Jun, as well as cyclin D1 expression. Initial in vivo data from transgenic mice indicate that overexpression of SENP1 in the prostate leads to the development of prostatic intraepithelial neoplasia at an early age. Collectively, these studies indicate that overexpression of SENP1 is associated with prostate cancer development.

Higher expression of transcription targets and components of the nuclear factor-kappaB pathway is a distinctive feature of umbilical cord blood CD34+ precursors

Delayed engraftment, better reconstitution of progenitors, higher thymic function, and a lower incidence of the graft-versus-host disease are characteristics associated with umbilical cord blood (UCB) transplants, compared with bone marrow (BM). To understand the molecular mechanisms causing these intrinsic differences, we analyzed the differentially expressed genes between BM and UCB hematopoietic stem and progenitor cells (HSPCs). The expressions of approximately 10,000 genes were compared by serial analysis of gene expression of magnetically sorted CD34(+) cells from BM and UCB. Differential expression of selected genes was evaluated by real-time polymerase chain reaction on additional CD34(+) samples from BM (n = 22), UCB (n = 9), and granulocyte colony stimulating factor-mobilized peripheral blood (n = 6). The overrepresentation of nuclear factor-kappaB (NF-kappaB) pathway components and targets was found to be a major characteristic of UCB HSPCs. Additional promoter analysis of 41 UCB-overrepresented genes revealed a significantly higher number of NF-kappaB cis-regulatory elements (present in 22 genes) than would be expected by chance. Our results point to an important role of the NF-kappaB pathway on the molecular and functional differences observed between BM and UCB HSPCs. Our study forms the basis for future studies and potentially for new strategies to stem cell graft manipulation, by specific NF-kappaB pathway modulation on stem cells, prior to transplant.

Role of ubiquitin-like proteins in transcriptional regulation

Conjugation of ubiquitin-like proteins (Ubls) to components of the transcriptional machinery represents an important mechanism to allow switching between different activity states. While ubiquitin modification of transcription factors is associated with transcriptional activation, SUMO modification of transcription factors is most often associated with transcriptional repression. Recent experiments indicate that another Ubl, NEDD8, can also influence transcription. One of the characteristics of Ubl modification is that the biological consequences of conjugation do not appear proportionate to the small fraction of substrate that is modified. The low steady state levels of Ubl-modified substrates can be attributed to a highly dynamic situation in which proteins are conjugated to a particular Ubl only for the modification to be removed by Ubl-specific proteases. It therefore appears that an unmodified protein with a history of Ubl modification may have different properties from a protein that never has been modified. Here the diverse effects of Ubl modification are discussed and models proposed to explain Ubl actions.

SUMOylation attenuates sensitivity toward hypoxia- or desferroxamine-induced injury by modulating adaptive responses in salivary epithelial cells

Hypoxic stress activates various signal transduction pathways including posttranslational modification with the ubiquitin-like SUMO protein (SUMOylation). However, the molecular mechanisms by which SUMOylation regulates hypoxic responses remain unclear. Here, we investigated the ability of rat salivary Pa-4 epithelial cells to resist cell injury elicited by 1% O(2)- or hypoxia-mimetic desferroxamine (DFO)-stimulated SUMOylation processes. By using Pa-4 cells stably transduced with lenti-SUMO-1 and a cell-permeant peptide harboring SUMO-binding motif to interfere with SUMO-dependent protein-protein interactions, we demonstrate that SUMOylation augments cell survival against DFO treatment. This appeared to be partly mediated through attenuation of Protein Kinase C (PKC)-delta activation and caspase-3 cleavage, hallmarks of pro-apoptotic signaling. Intriguingly, DFO-induced phosphorylation of DNA damage marker ataxia-telangiectasia-mutated protein S1981 preceded activation of PKCdelta and caspase-3. Constitutive SUMOylation facilitated 1% O(2)- or DFO-induced nuclear factor kappaB transactivation, possibly via activation of genotoxic signaling cascade. In addition, we observed transient preservation of transepithelial electrical resistance during the early stage of hypoxia (1% O(2)) as well as enhanced transepithelial electrical resistance recovery after prolonged hypoxia in SUMO-1-expressing cell monolayers. In conclusion, our results unveil a previously unrecognized mechanism by which SUMOylation and activation of ataxia-telangiectasia-mutated protein, PKCdelta, caspase-3, and nuclear factor kappaB signaling pathways modulate salivary adaptive responses to stress in cells exposed to either 1% O(2) or DFO.

Peroxynitrite induces an alternative NF-kappaB activation pathway in L8 rat myoblasts

The role of peroxynitrite in NF-kappaB activation remains controversial. This study investigated NF-kappaB activation by peroxynitrite in skeletal myocytes. Myocytes were treated with NO and peroxynitrite donors. Both NO and peroxynitrite caused NF-kappaB activation (measured by p65 nuclear translocation and luciferase expression). NO donor-induced NF-kappaB activation was transient, dependent on I-kappaB alpha degradation, and was decreased in the presence of I-kappaB alpha super-repressor. Conversely, peroxynitrite donors induced NF-kappaB activation that was dependent on tyrosine nitration of I-kappaB alpha, but independent of its serine phosphorylation and degradation. This activation did not decrease in the presence of I-kappaB alpha super-repressor. Prolonged exposure to peroxynitrite resulted in nontransient NF-kappaB activation and high iNOS expression. Proteasome inhibitor MG-132 did not diminish SIN-1-induced NF-kappaB activation. Tyrosine nitration inhibitor EGCG re-established transient NF-kappaB activation with I-kappaB alpha degradation after SIN-1 treatment. EGCG, but not MG-132 decreased SIN-1- dependent iNOS expression. Peroxynitrite activates NF-kappaB in skeletal myocytes through an alternative mechanism, in which I-kappaB alpha is nitrated on tyrosine and dissociated from NF-kappaB, thus enabling its nontransient activation. This resulted in prolonged iNOS expression. Hence, peroxynitrite may exacerbate inflammatory responses mediated by NF-kappaB.

SIZ1/SIZ2 control of chromosome transmission fidelity is mediated by the sumoylation of topoisomerase II

The Smt3 (SUMO) protein is conjugated to substrate proteins through a cascade of E1, E2, and E3 enzymes. In budding yeast, the E3 step in sumoylation is largely controlled by Siz1p and Siz2p. Analysis of Siz- cells shows that SUMO E3 is required for minichromosome segregation and thus has a positive role in maintaining the fidelity of mitotic transmission of genetic information. Sumoylation of the carboxy-terminus of Top2p, a known SUMO target, is mediated by Siz1p and Siz2p both in vivo and in vitro. Sumoylation in vitro reveals that Top2p is an extremely potent substrate for Smt3p conjugation and that chromatin-bound Top2p can still be sumoylated, unlike many other SUMO substrates. By combining mutations in the TOP2 sumoylation sites and the SIZ1 and SIZ2 genes we demonstrate that the minichromosome segregation defect and dicentric minichromosome stabilization, both characteristic for Smt3p-E3-deficient cells, are mediated by the lack of Top2p sumoylation in these cells. A role for Smt3p-modification as a signal for Top2p targeting to pericentromeric regions was suggested by an analysis of Top2p-Smt3p fusion. We propose a model for the positive control of the centromeric pool of Top2p, required for high segregation fidelity, by Smt3p modification.

The ubiquitin-proteasome system at the crossroads of stress-response and ageing pathways: a handle for skin care?

The regulation of gene expression at the transcriptional level has been considered for long as the main mechanism of cellular adaptive responses. Since the turn of the century, however, it is becoming clear that higher organisms developed a complex, sensitive and maybe equally important network of regulatory pathways, relying largely on protein interactions, post-translational modifications and proteolysis. Here we review the involvement of the ubiquitin-proteasome pathway of protein degradation at different levels of cellular life in relation with ageing, and with a special focus on skin. It comes out that the ubiquitin system plays a major role in signal transduction associated with stress and ageing, in skin in particular through the control of retinoid and NF-kappaB pathways. The understanding of specific proteolytic targeting by E3 ubiquitin-ligases paves the way for a new generation of active molecules that may control particular steps of normal and pathological ageing.

dUbc9 negatively regulates the Toll-NF-kappa B pathways in larval hematopoiesis and drosomycin activation in Drosophila

Highly conserved during evolution, the enzyme Ubc9 activates the small ubiquitin-like modifier (SUMO) prior to its covalent ligation to target proteins. We have used mutations in the Drosophila Ubc9 (dUbc9) gene to understand Ubc9 functions in vivo. Loss-of-function mutations in dUbc9 cause strong mitotic defects in larval hematopoietic tissues, an increase in the number of hematopoietic precursors in the lymph gland and of mature blood cells in circulation, and an increase in the proportion of cyclin-B-positive cells. Some blood cells are polyploid and multinucleate, exhibiting signs of genomic instability. We also observe an overabundance of highly differentiated blood cells (lamellocytes), normally not found in healthy larvae. Lamellocytes in mutants are either free in circulation or recruited to form tumorous masses. Hematopoietic defects of dUbc9 mutants are strongly suppressed in the absence of the Rel/NF-kappaB-family transcription factors Dorsal and Dif or in the presence of a non-signaling allele of Cactus, the IkappaB protein in Drosophila. In the larval fat body, dUbc9 negatively regulates the expression of the antifungal peptide gene drosomycin, which is constitutively expressed in dUbc9 mutants in the absence of immune challenge. dUbc9-mediated drosomycin expression requires Dorsal and Dif. Together, our results support a role for dUbc9 in the negative regulation of the Drosophila NF-kappaB signaling pathways in larval hematopoiesis and humoral immunity.

Amorphous silica particles promote inflammatory gene expression through the redox sensitive transcription factor, AP-1, in alveolar epithelial cells

Ultrafine particulate (UFP) matter, from environmental or industrial exposure, can induce expression of inflammatory mediators and promote production of reactive oxygen species. Previous studies showed various cellular stresses activate signaling pathways operating through specific transcription factors (TFs), activator protein (AP)-1 and nuclear factor (NF)-kappaB, known to regulate inflammatory gene expression. Exposing MLE15 cells to inflammatory, or UFP, stimuli increased macrophage inflammatory protein (MIP)-2 protein, in the absence of the NF = kappaB inhibitor IkappaBc degradation, synergistically increasing in the presence of proteosomal inhibition. Although thiol antioxidants attenuate MIP-2 induction, mitogen-activated protein kinase (MAPK) inhibitors significantly inhibit MIP-2 protein production. This suggests UFP promote inflammatory gene expression through the redox responsive TF AP-1.

A genome-wide analysis of sumoylation-related biological processes and functions in human nucleus

Protein sumoylation is an important reversible post-translational modification of proteins in the nucleus, and it orchestrates a variety of the cellular processes. Genome-wide analysis of functional abundance and distribution of Small Ubiquitin-related MOdifier (SUMO) substrates may shed a light on how sumoylation is involved in nuclear biological processes and functions. Two interesting questions about sumoylation have emerged: (1) how many SUMO substrates exist in mammalian proteomes, such as human and mouse, (2) and what are their functions and how are they involved in a variety of biological processes? To address these two questions,we present an in silico genome-scale analysis for SUMO substrates in human. Based on the pattern recognition and phylogenetic conservation, we retrieved a list of 2683 potential SUMO substrates conserved in both human and mouse. Then, by functional enrichment analysis, we surveyed the over-represented GO terms and functional domains of them against the whole human proteome. Besides the consistence between our analyses and in vivo or in vitro work, the in silico predicted candidates also point to several potential roles of sumoylation, e.g., perception of sound. These potential SUMO substrates in human are of great value for further in vivo or in vitro experimental analysis.