ABINs inhibit EGF receptor-mediated NF-kappaB activation and growth of EGF receptor-overexpressing tumour cells

Association of TNIP1 polymorphisms with hepatocellular carcinoma in a Northwest Chinese Han population

ABSTRACT

Study has demonstrated that TNIP1 polymorphisms are associated with an increased risk of HBV-induced hepatocellular carcinoma (HCC). The purpose of this study was to investigate the correlation between polymorphisms in TNIP1 and HCC risk in a Northwest Chinese Han population.A case-control study was conducted including 473 Hepatocellular carcinoma patients and 564 healthy controls. Three SNPs (rs3792792, rs7708392, and rs10036748) were genotyped with Sequenom MassARRAY technology and their associations with HCC risk were analyzed. These data were evaluated using the Chi-square test/Fisher's exact test, genetic model analysis, and haplotype analysis. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association.Patients with the "G" allele of TNIP1 rs7708392 showed a significantly increased risk of HCC (OR = 1.24, 95%CI: 1.01-1.52, P = .042). Significant association was also shown between TNIP1 rs7708392 and HCC susceptibility in Additive model (OR = 1.25; 95% CI = 1.01-1.54; P = .040). Besides, we also found that the "GC" haplotype of rs7708392 and rs10036748 was significantly associated with higher occurrence of HCC (OR = 1.25, 95% CI: 1.01-1.54, P = .039).These results demonstrate that TNIP1 polymorphisms are associated with increased HCC risk in a Northwest Chinese Han population for the first time, which warrants further investigation in the future.

RNA-Binding Protein HuR Suppresses Inflammation and Promotes Extracellular Matrix Homeostasis via NKRF in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) has been reported to be a major cause of low back pain. Studies have demonstrated that IVDD may be dysregulated at the transcriptional level; however, whether post-transcriptional regulation is involved is still unknown. The current study aimed to illustrate the role of Human antigen R (HuR), an RNA binding protein involved in post-transcriptional regulation, in IVDD. The results showed that the expression of HuR was decreased in degenerative nucleus pulposus (NP) tissues as well as in TNF-α-treated NP cells. Downregulation of HuR may lead to increased inflammation and extracellular matrix (ECM) degradation in TNF-α-treated NP cells; however, these effects were not reversed in HuR overexpressed NP cells. Inhibition of the NF-κB signaling pathway attenuates inflammation and ECM degradation in HuR-deficient NP cells. A mechanism study showed that HuR prompted NKRF mRNA stability via binding to its AU-rich elements, and upregulation of NKRF suppressed inflammation and ECM degradation in HuR-deficient NP cells. Furthermore, we found that NKRF, but not HuR, overexpression ameliorated the process of IVDD in rats in vivo. In conclusion, HuR suppressed inflammation and ECM degradation in NP cells via stabilizing NKRF and inhibiting the NF-κB signaling pathway; NKRF, but not HuR, may serve as a potential therapeutic target for IVDD.

ABIN-1 protects chondrocytes from lipopolysaccharide-induced inflammatory injury through the inactivation of NF-κB signalling

The A20-binding inhibitor of nuclear factor (NF)-κB-1 (ABIN-1) protein has recently been implicated as a key regulator of inflammation with involvement in multiple inflammatory diseases. However, the function of ABIN-1 in osteoarthritis (OA) remains unclear. In the current study, we explored the role of ABIN-1 in the regulation of lipopolysaccharide (LPS)-induced inflammatory injury of chondrocytes, which served as an in vitro model of OA. Results revealed that ABIN-1 expression was induced by chondrocyte exposure to LPS. ABN-1 silencing exacerbated LPS-induced apoptosis and the inflammatory response, while ABIN-1 overexpression alleviated the inflammatory response and LPS-induced apoptosis in chondrocytes. Moreover, ABIN-1 overexpression resulted in significantly decreased LPS-induced NF-κB activation. Notably, activation of NF-κB signalling significantly reversed ABIN-1-mediated inhibitory effects on LPS-induced inflammatory injury in chondrocytes. Taken together, these results demonstrate that ABIN-1 protects chondrocytes against LPS-induced inflammatory injury through the suppression of NF-κB signalling. Our study suggests a potential role for ABIN-1 in OA. Further, we show that ABIN-1 may serve as a potential target for controlling joint inflammation.

miR-423 Promotes Breast Cancer Invasion by Activating NF-κB Signaling

Objective

Breast cancer has become the most common malignancy among women worldwide; therefore, novel diagnostic and prognostic markers and therapeutic targets are urgently required. NF-κB signaling plays a pivotal role in enhancing breast cancer malignant phenotypes, especially cancer invasion and metastasis, which is the main cause of death in cancer patients. TNIP2, an important inhibitor of the NF-κB pathway, is known to involve a negative feedback loop of the NF-κB signaling cascade and to regulate tumor aggressiveness in various cancer types. However, the mRNA level of TNIP2 is barely altered in breast cancer; thus, the mechanism that regulates TNIP2 in breast cancer still needs to be elucidated.

Methods

We analyzed the expression and prognosis of miR-423 in a TCGA BRCA miRNA cohort and in clinical specimens. We detected the invasive capacity through a Matrigel-coated Transwell penetration assay, a three-dimensional (3D) spheroid invasion assay and a wound healing assay. Then, we applied luciferase assays, real-time PCR assays and Western blotting to further study the mechanism.

Results

In this study, analysis of the TCGA BRCA miRNA cohort and clinical specimens demonstrated that miR-423 was upregulated in human breast cancers and was positively correlated with clinical stage, poor overall survival and metastasis classification. Moreover, the invasiveness of breast cancer cells was enhanced by ectopic expression of miR-423 and inhibited by miR-423 downregulation. Mechanistically, upregulation of miR-423 led to activation of the NF-κB signaling pathway and elevated expression of snail and twist, while repression of miR-423 inhibited this pathway. Furthermore, the results indicated that TNIP2 is a target gene of miR-423, and suppression of TNIP2 resulted in increased invasiveness in miR-423-silenced cells.

Conclusion

Our results suggest that miR-423 is a crucial factor that enhances breast cancer cell invasion through the NF-κB signaling pathway and shed light on miR-423 as a promising prognostic and therapeutic marker for metastatic breast cancer.

microRNA-15a-5p participates in sepsis by regulating the inflammatory response of macrophages and targeting TNIP2

The mortality rate for patients experiencing sepsis is decreasing; however, an effective therapeutic strategy requires further investigation. Increasing evidence has supported the idea that dysregulated microRNAs (miR) participate in the development of sepsis. Meanwhile, macrophages are crucial players in various inflammatory responses and diseases. The objective of the current study was to investigate the associated molecular mechanisms of action of miR-15a-5p on inflammatory responses in lipopolysaccharide (LPS)-stimulated mouse macrophages and the macrophage cell line RAW264.7. RAW264.7 macrophages were stimulated with LPS for 4 h, and ELISAs were subsequently used to measure the expression levels of pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, in RAW264.7 macrophages. The expression levels of miR-15a-5p in RAW264.7 macrophages were detected after the stimulation of LPS using reverse transcription quantitative-PCR. The results indicated that the IL-1β, IL-6, TNF-α and miR-15a-5p levels were significantly increased compared with the control group. The Target gene prediction database (TargetScan) and dual-luciferase reporter assays were subsequently employed, and TNF-α induced protein 3-interacting protein 2 (TNIP2) was confirmed as a direct target for miR-15a-5p. Additionally, it was found that the TNIP2 expression levels were decreased in RAW264.7 macrophages following LPS treatment compared with controls. The present study also examined the effects of miR-15a-5p inhibitor on inflammatory cytokine expression levels and the activation of the NF-κ signaling pathway. These results demonstrated that miR-15a-5p inhibitor reduced the secretion of inflammatory cytokines and inhibited NF-κ pathway activation by targeting TNIP2. This may be associated with the progression of sepsis. Meanwhile, a LPS-induced mouse model of sepsis was established to examine the regulation of TNIP2 and miR-15a-5p during inflammation. In the animal model, miR-15a-5p inhibitor significantly suppressed the secretion of inflammatory factors. The levels of creatin, blood urea nitrogen, aspartate aminotransferase and alanine aminotransferase in the serum of LPS-treated mice were also found to be decreased in the miR-15a-5p inhibitor treatment group, while the protective effects of miR-15a-5p inhibitor on sepsis were eliminated by TNIP2-small interfering RNA combination therapy. In conclusion, the present findings indicated that miR-15a-5p may be involved in the inflammatory process during sepsis by activating the NF-κ pathway and targeting TNIP2. This suggests that miR-15a-5p inhibitor may be a novel anti-inflammatory agent and therapeutic strategy for sepsis.

TNIP1 in Autoimmune Diseases: Regulation of Toll-like Receptor Signaling

TNIP1 protein is increasingly being recognized as a key repressor of inflammatory signaling and a potential factor in multiple autoimmune diseases. In addition to earlier foundational reports of TNIP1 SNPs in human autoimmune diseases and TNIP1 protein-protein interaction with receptor regulating proteins, more recent studies have identified new potential interaction partners and signaling pathways likely modulated by TNIP1. Subdomains within the TNIP1 protein as well as how they interact with ubiquitin have not only been mapped but inflammatory cell- and tissue-specific consequences subsequent to their defective function are being recognized and related to human disease states such as lupus, scleroderma, and psoriasis. In this review, we emphasize receptor signaling complexes and regulation of cytoplasmic signaling steps downstream of TLR given their association with some of the same autoimmune diseases where TNIP1 has been implicated. TNIP1 dysfunction or deficiency may predispose healthy cells to the inflammatory response to otherwise innocuous TLR ligand exposure. The recognition of the anti-inflammatory roles of TNIP1 and improved integrated understanding of its physical and functional association with other signaling pathway proteins may position TNIP1 as a candidate target for the design and/or testing of next-generation anti-inflammatory therapeutics.

ZBTB20 regulates EGFR expression and hepatocyte proliferation in mouse liver regeneration

Liver has a unique regenerative capacity, however, its regulatory mechanism is not fully defined. We have established the zinc-finger protein ZBTB20 as a key transcriptional repressor for alpha-fetoprotein (AFP) gene in liver. As a marker of hepatic differentiation, AFP expression is closely associated with hepatocyte proliferation. Unexpectedly, here we showed that ZBTB20 acts as a positive regulator of hepatic replication and is required for efficient liver regeneration. The mice specifically lacking ZBTB20 in hepatocytes exhibited a remarkable defect in liver regeneration after partial hepatectomy, which was characterized by impaired hepatocyte proliferation along with delayed cyclin D1 induction and diminished AKT activation. Furthermore, we found that epithelial growth factor receptor (EGFR) expression was dramatically reduced in the liver in the absence of ZBTB20, thereby substantially attenuating the activation of EGFR signaling pathway in regenerating liver. Adenovirus-mediated EGFR overexpression in ZBTB20-deficient hepatocytes could largely restore AKT activation in response to EGFR ligands in vitro, as well as hepatocyte replication in liver regeneration. Furthermore, ZBTB20 overexpression could significantly restore hepatic EGFR expression and cell proliferation after hepatectomy in ZBTB20-deficient liver. Taken together, our data point to ZBTB20 as a critical regulator of EGFR expression and hepatocyte proliferation in mouse liver regeneration, and may serve as a potential therapeutic target in clinical settings of liver regeneration.

Genetic polymorphisms in TNIP1 increase the risk of gastric carcinoma

The distribution and levels of TNIP1 in malignant and normal gastric mucosa are different, but it is not known whether TNIP1 polymorphisms are related to gastric carcinogenesis. To assess the association between four TNIP1 SNPs (rs3792792, rs4958881, rs7708392, rs10036748) and carcinogenesis, we used Sequenom Mass-ARRAY technology to determine the genotypes of 302 gastric carcinoma patients and 300 healthy controls in a Northwest Chinese Han population. These data were then compared using the Chi-square test/Fisher's exact test, genetic model analysis, and haplotype analysis. Odds ratios (OR) and 95% confidence intervals (CI) were used to evaluate the correlation. We observed that patients with the "G" allele of rs7708392 and the "C" allele of rs10036748 showed an increased risk of gastric carcinoma (OR= 1.335, 95%CI: 1.021-1.745, P= 0.035; OR= 1.358, 95%CI: 1.039-1.774, P= 0.025, respectively). Conversely, the haplotype "CT" of TNIP1 (rs7708392-rs10036748) may act as a genetic protective factor for gastric carcinoma (adjusted OR= 0.731, 95%CI: 0.552-0.970, P= 0.030). Our results are the first to suggest that genetic variation in TNIP1 gene is associated with gastric carcinoma, though, this finding must be confirmed in other populations with larger sample size.

Association between TNIP1, MPHOSPH6 and ZNF208 genetic polymorphisms and the coronary artery disease risk in Chinese Han population

Introduction

Coronary artery disease (CAD) is a common disease and among the leading cause of death in the general population. Inherited factors are involved in the pathogenesis of CAD.

Aims

Our study examined whether SNPs in TNIP1, MPHOSPH6, ZNF208 to be associated with CAD risk in a Chinese Han population. We recruited 596 CAD patients, 603 controls and genotyping fifteen SNPs using Sequenom MassARRAY. For association analysis between TNIP1, MPHOSPH6 and ZNF208 and CAD was determined by Odds ratios (ORs) with 95% confidence intervals (CIs) using Logistic Regression.

Results

The results indicated in allel model, the rs960709 in TNIP1 was associated with CAD risk (OR = 0.78, 95%CI = 0.65-0.94, P=0.010). The genetic model results showed that the rs960709 (A/G) polymorphism was associated with the risk of developing CAD in codominant, Dominant and Log-additive. The rs1056654 A/A allele and CAD patients compared to the healthy controls in recessive model (OR = 0.55, 95%CI = 0.34-0.90; P = 0.018). We also found that three SNPS in ZNF208 associated with CAD, respectively, rs2188971, rs8103163 and rs7248488.

Linkage disequilibrium (LD) and haplotype analyses of the SNPs found that the CTA haplotype (rs1056675, rs1056654, rs11859599) and rs2188972A/rs2188971T/rs8103163A/rs7248488A (ATAA) were associated with CAD.

Conclusion

In conclusion, the present study provided evidence that SNPs in the TNIP1, ZNF208 and MPHOSPH6 were associated with CAD in Chinese Han population. It is possible that these SNPs are CAD risk factors and these data can provide.

USP35 activated by miR let-7a inhibits cell proliferation and NF-κB activation through stabilization of ABIN-2

Ubiquitin specific protease 35 (USP35) is a member of deubiquitylases (DUBs). It remains largely unknown about the biological role and the regulation mechanism of USP35. Here, we first identified miR let-7a as a positive regulator of USP35 expression and showed that USP35 expression positively correlates with miR let-7a expression in different cancer cell lines and tissues. Then, we showed that USP35 expression was decreased dramatically in the tumor tissues compared with the adjacent non-cancerous tissues. USP35 overexpression inhibited cell proliferation in vitro and inhibited xenograft tumor growth in vivo. Furthermore, we revealed that USP35 acts as a functional DUB and stabilizes TNFAIP3 interacting protein 2 (ABIN-2) by promoting its deubiquitination. Functionally, both ABIN-2 and USP35 could inhibit TNFα-induced NF-κB activation and overexpression of ABIN-2 alleviated USP35-loss induced activation of NF-κB. Collectively, our data indicated that miR let-7a-regulated USP35 can inhibit NF-κB activation by deubiquitination and stabilization of ABIN-2 protein and eventually inhibit cell proliferation. Overall, our study provides a novel rationale of targeting miR let-7a-USP35-ABIN-2 pathway for the therapy of cancer patients.

CXCR4 3'UTR functions as a ceRNA in promoting metastasis, proliferation and survival of MCF-7 cells by regulating miR-146a activity

CXCR4 is the most common chemokine receptor expressed on tumor cells, and it is closely correlated with cancer cell stemness. This study was carried out to explore whether CXCR4 could function as a competitive endogenous RNA to promote metastasis, proliferation and survival in MCF-7 breast cancer cells. We validated that CXCR4, together with TRAF6 and EGFR, was directly targeted by miR-146a in MCF-7 cells. Overexpression of CXCR4 3'UTR inhibited the activity of miR-146a, thus elevating the expression of CXCR4, TRAF6 and EGFR. These oncoproteins further activated NF-κB pathway and promoted the proliferation, migration, invasion and anti-apoptotic activity of MCF-7 cells. Collectively, our study provided new insights into the function of CXCR4 in breast cancer: it promotes tumor progression as both a protein-coding gene and a non-coding RNA, complicating the mechanism by which oncogenes promote tumor progression.

Downregulation of TNIP1 Expression Leads to Increased Proliferation of Human Keratinocytes and Severer Psoriasis-Like Conditions in an Imiquimod-Induced Mouse Model of Dermatitis

Psoriasis is a chronic, inflammatory skin disease involving both environmental and genetic factors. According to genome-wide association studies (GWAS), the TNIP1 gene, which encodes the TNF-α–induced protein 3-interacting protein 1 (TNIP1), is strongly linked to the susceptibility of psoriasis. TNIP1 is a widely expressed ubiquitin sensor that binds to the ubiquitin-editing protein A20 and restricts TNF- and TLR-induced signals. In our study, TNIP1 expression decreased in specimens of epidermis affected by psoriasis. Based on previous studies suggesting a role for TNIP1 in modulating cancer cell growth, we investigated its role in keratinocyte proliferation, which is clearly abnormal in psoriasis. To mimic the downregulation or upregulation of TNIP1 in HaCaT cells and primary human keratinocytes (PHKs), we used a TNIP1 specific small interfering hairpin RNA (TNIP1 shRNA) lentiviral vector or a recombinant TNIP1 (rTNIP1) lentiviral vector, respectively. Blocking TNIP1 expression increased keratinocyte proliferation, while overexpression of TNIP1 decreased keratinocyte proliferation. Furthermore, we showed that TNIP1 signaling might involve extracellular signal-regulated kinase1/2 (Erk1/2) and CCAAT/enhancer-binding protein β (C/EBPβ) activity. Intradermal injection of TNIP1 shRNA in BALB/c mice led to exaggerated psoriatic conditions in imiquimod (IMQ)-induced psoriasis-like dermatitis. These findings indicate that TNIP1 has a protective role in psoriasis and therefore could be a promising therapeutic target.

Up-regulation of miR-146a contributes to the inhibition of invasion of pancreatic cancer cells

Pancreatic cancer (PC) is an aggressive malignancy with high mortality and is believed to be in part due to its highly invasive and metastatic behavior, which is associated with over-expression of EGFR and activation of NF-κB. Emerging evidence also suggest critical roles of microRNAs (miRNAs) in the regulation of various pathobiological processes including metastasis in PC and in other human malignancies. In the present study, we found lower expression of miR-146a in PC cells compared to normal human pancreatic duct epithelial (HPDE) cells. Interestingly, re-expression of miR-146a inhibited the invasive capacity of Colo357 and Panc-1 PC cells with concomitant down-regulation of EGFR and IRAK-1. Mechanistic studies including miR-146a re-expression, anti-miR-146 transfection, and EGFR knock-down experiment showed that there was a crosstalk between EGFR, MTA-2, IRAK-1, IκBα and NF-κB. Most importantly, we found that the treatment of PC cells with "natural agents" [3,3'-diinodolylmethane (DIM) or isoflavone] led to an increase in the expression of miR-146a and consequently down-regulated the expression of EGFR, MTA-2, IRAK-1 and NF-κB, resulting in the inhibition of invasion of Colo357 and Panc-1 cells. These results provide experimental evidence in support of the role of DIM and isoflavone as potential non-toxic agents as regulators of miRNA, which could be useful for the inhibition of cancer cell invasion and metastasis, and further suggesting that these agents could be important for designing novel targeted strategy for the treatment of PC.

The biology of A20-binding inhibitors of NF-kappaB activation (ABINs)

The family of A20-Binding Inhibitors of NF-kappaB (ABINs) consists of three proteins, ABIN-1, ABIN-2 and ABIN-3, which were originally identified as A20-binding proteins and inhibitors of cytokines and Lipopolysaccharide (LPS) induced NF-kappaB activation. ABIN family members have limited sequence homology in a number of short regions that mediate A20-binding, ubiquitin-binding, and NF-kappaB inhibition. The functional role of A20 binding to ABINs remains unclear, although an adaptor function has been suggested. ABIN-1 and ABIN-3 expression is upregulated when cells are triggered by NF-kappaB-activating stimuli, suggesting a role for these ABINs in a negative feedback regulation of NF-kappaB signaling. Additional ABIN functions have been reported such as inhibition of TNF-induced hepatocyte apoptosis, regulation of HIV-1 replication for ABIN-1, and Tumor Progression Locus 2 (TPL-2)-mediated Extracellular signal-Regulated Kinase (ERK) activation for ABIN-2. In mice, ABIN-1 overexpression reduces allergic airway inflammation and TNF-mediated liver injury, ABIN-2 overexpression delays liver regeneration, and ABIN-3 overexpression partially protects against LPS-induced acute liver failure. Analysis of mice deficient in ABIN-1 or ABIN-2 demonstrates the important immune regulatory function of ABINs. Future studies should clarify the functional implication of the A20-ABIN interaction in supporting ABINs' mechanisms of action.

A genome-wide scan for breast cancer risk haplotypes among African American women

Genome-wide association studies (GWAS) simultaneously investigating hundreds of thousands of single nucleotide polymorphisms (SNP) have become a powerful tool in the investigation of new disease susceptibility loci. Haplotypes are sometimes thought to be superior to SNPs and are promising in genetic association analyses. The application of genome-wide haplotype analysis, however, is hindered by the complexity of haplotypes themselves and sophistication in computation. We systematically analyzed the haplotype effects for breast cancer risk among 5,761 African American women (3,016 cases and 2,745 controls) using a sliding window approach on the genome-wide scale. Three regions on chromosomes 1, 4 and 18 exhibited moderate haplotype effects. Furthermore, among 21 breast cancer susceptibility loci previously established in European populations, 10p15 and 14q24 are likely to harbor novel haplotype effects. We also proposed a heuristic of determining the significance level and the effective number of independent tests by the permutation analysis on chromosome 22 data. It suggests that the effective number was approximately half of the total (7,794 out of 15,645), thus the half number could serve as a quick reference to evaluating genome-wide significance if a similar sliding window approach of haplotype analysis is adopted in similar populations using similar genotype density.

TGF-β induces miR-182 to sustain NF-κB activation in glioma subsets

The strength and duration of NF-κB signaling are tightly controlled by multiple negative feedback mechanisms. However, in cancer cells, these feedback loops are overridden through unclear mechanisms to sustain oncogenic activation of NF-κB signaling. Previously, we demonstrated that overexpression of miR-30e* directly represses IκBα expression and leads to hyperactivation of NF-κB. Here, we report that miR-182 was overexpressed in a different set of gliomas with relatively lower miR-30e* expression and that miR-182 directly suppressed cylindromatosis (CYLD), an NF-κB negative regulator. This suppression of CYLD promoted ubiquitin conjugation of NF-κB signaling pathway components and induction of an aggressive phenotype of glioma cells both in vitro and in vivo. Furthermore, we found that TGF-β induced miR-182 expression, leading to prolonged NF-κB activation. Importantly, the results of these experiments were consistent with an identified significant correlation between miR-182 levels with TGF-β hyperactivation and activated NF-κB in a cohort of human glioma specimens. These findings uncover a plausible mechanism for sustained NF-κB activation in malignant gliomas and may suggest a new target for clinical intervention in human cancer.

Emerging roles for TNIP1 in regulating post-receptor signaling

A vast number of cellular processes and signaling pathways are regulated by various receptors, ranging from transmembrane to nuclear receptors. These receptor-mediated processes are modulated by a diverse set of regulatory proteins. TNFα-induced protein 3-interacting protein 1 is such a protein that inhibits both transduction by transmembrane receptors, such as TNFα-receptor, EGF-R, and TLR, and nuclear receptors' PPAR and RAR activity. These receptors play key roles in regulating inflammation and inflammatory diseases. A growing number of references have implicated TNIP1 through GWAS and expression studies in chronic inflammatory diseases such as psoriasis and rheumatoid arthritis, although TNIP1s exact role has yet been determined. In this review, we aim to integrate the current knowledge of TNIP1s functions with the diseases in which it has been associated to potentially elucidate the role this regulator has in promoting or alleviating these inflammatory diseases.

A pro-inflammatory role for A20 and ABIN family proteins in human fibroblast-like synoviocytes in rheumatoid arthritis

Circuit of chronic inflammation in the joints of rheumatoid arthritis (RA) starts from the production of inflammatory cytokines by fibroblast-like synoviocytes (FLS) stimulated by TNFα produced by inflammatory cells mainly composed of macrophages. In this context, TNFα/NF-κB pathway plays an essential role for the transcription of pro-inflammatory cytokines. Here we show that the kinetics of pro-inflammatory cytokine genes induced by TNFα in FLS from RA was synchronized with that of A20, ABIN1, and ABIN3 that have been thought as negative regulators for NF-κB activation. Furthermore, based on this finding, we could tentatively categorize the RA-FLS into two groups; TNFα low-responder and high-responder FLS. The high responders that have abundant mRNA levels of NF-κB inhibitory molecules were also accompanied with the marked induction of the pro-inflammatory cytokines by the stimulation with TNFα. The low responders RA-FLS did not show this property, nor did FLS from osteoarthritis. Phosphorylation dependent degradation of IκBα as well as NF-κB activation upon stimulation with TNFα was significantly enhanced in the high-responder FLS lines. Surprisingly, single transfection of each NF-κB inhibitor was enough to facilitate the transcription of pro-inflammatory cytokines, suggesting that there is an unknown pro-inflammatory function for A20 and ABIN family proteins in RA-FLS.

NF-κB, stem cells and breast cancer: the links get stronger

Self-renewing breast cancer stem cells are key actors in perpetuating tumour existence and in treatment resistance and relapse. The molecular pathways required for their maintenance are starting to be elucidated. Among them is the transcription factor NF-κB, which is known to play critical roles in cell survival, inflammation and immunity. Recent studies indicate that mammary epithelial NF-κB regulates the self-renewal of breast cancer stem cells in a model of Her2-dependent tumourigenesis. We will describe here the NF-κB-activating pathways that are involved in this process and in which progenitor cells this transcription factor is actually activated.

A20-binding inhibitor of nuclear factor-kappaB (NF-kappaB)-2 (ABIN-2) is an activator of inhibitor of NF-kappaB (IkappaB) kinase alpha (IKKalpha)-mediated NF-kappaB transcriptional activity

NF-κB transcription factors are pivotal players in controlling inflammatory and immune responses, as well as cell proliferation and apoptosis. Aberrant regulation of NF-κB and the signaling pathways that regulate its activity have been involved in various pathologies, particularly cancers, as well as inflammatory and autoimmune diseases. NF-κB activation is tightly regulated by the IκB kinase (IKK) complex, which is composed of two catalytic subunits IKKα and IKKβ, and a regulatory subunit IKKγ/NEMO. Although IKKα and IKKβ share structural similarities, IKKα has been shown to have distinct biological functions. However, the molecular mechanisms that modulate IKKα activity have not yet been fully elucidated. To understand better the regulation of IKKα activity, we purified IKKα-associated proteins and identified ABIN-2. Here, we demonstrate that IKKα and IKKβ both interact with ABIN-2 and impair its constitutive degradation by the proteasome. Nonetheless, ABIN-2 enhances IKKα- but not IKKβ-mediated NF-κB activation by specifically inducing IKKα autophosphorylation and kinase activity. Furthermore, we found that ABIN-2 serine 146 is critical for the ABIN-2-dependent IKKα transcriptional up-regulation of specific NF-κB target genes. These results imply that ABIN-2 acts as a positive regulator of NF-κB-dependent transcription by activating IKKα.

IGF-I activation of the AKT pathway is impaired in visceral but not subcutaneous preadipocytes from obese subjects

Obesity morbidity is associated with excess visceral adiposity, whereas sc adipose tissue is much less metabolically hazardous. Human abdominal sc preadipocytes have greater capacity for proliferation, differentiation, and survival than omental preadipocytes. IGF-I is a critical mediator of preadipocyte proliferation, differentiation, and survival through multiple signaling pathways. We investigated IGF-I action in primary cultures of human preadipocytes isolated from sc and omental adipose tissue of obese subjects. IGF-I-stimulated DNA synthesis was significantly lower in omental compared with sc preadipocytes. IGF-I phosphorylation of the IGF-I receptor and the ERK pathway was comparable in sc and omental cells. However, omental preadipocytes had decreased insulin receptor substrate (IRS)-1 protein associated with increased IRS-1-serine(636/639) phosphorylation and degradation. IGF-I-stimulated phosphorylation of AKT on serine(473) but not threonine(308) was decreased in omental cells, and activation of downstream targets, including S6Kinase, glycogen synthase kinase-3, and Forkhead box O1 was also impaired. CyclinD1 abundance was decreased in omental cells due to increased degradation. Over-expression of IRS-1 by lentivirus in omental preadipocytes increased IGF-I-stimulated AKT-serine(473) phosphorylation. The mammalian target of rapamycin (mTOR)-Rictor complex regulates phosphorylation of AKT-serine(473) in 3T3-L1 adipocytes, but knockdown of Rictor by lentivirus-delivered short hairpin RNA in sc preadipocytes did not affect AKT-serine(473) phosphorylation by IGF-I. These data reveal an intrinsic defect in IGF-I activation of the AKT pathway in omental preadipocytes from obese subjects that involves IRS-1 but probably not mTOR-Rictor complex. We conclude that impaired cell cycle regulation by AKT contributes to the distinct growth phenotype of preadipocytes in visceral fat of obese subjects.

miR-146a suppresses invasion of pancreatic cancer cells

The aggressive course of pancreatic cancer is believed to reflect its unusually invasive and metastatic nature, which is associated with epidermal growth factor receptor (EGFR) overexpression and NF-kappaB activation. MicroRNAs (miRNA) have been implicated in the regulation of various pathobiological processes in cancer, including metastasis in pancreatic cancer and in other human malignancies. In this study, we report lower expression of miR-146a in pancreatic cancer cells compared with normal human pancreatic duct epithelial cells. Reexpression of miR-146a inhibited the invasive capacity of pancreatic cancer cells with concomitant downregulation of EGFR and the NF-kappaB regulatory kinase interleukin 1 receptor-associated kinase 1 (IRAK-1). Cellular mechanism studies revealed crosstalk between EGFR, IRAK-1, IkappaBalpha, NF-kappaB, and MTA-2, a transcription factor that regulates metastasis. Treatment of pancreatic cancer cells with the natural products 3,3'-diinodolylmethane (DIM) or isoflavone, which increased miR-146a expression, caused a downregulation of EGFR, MTA-2, IRAK-1, and NF-kappaB, resulting in an inhibition of pancreatic cancer cell invasion. Our findings reveal DIM and isoflavone as nontoxic activators of a miRNA that can block pancreatic cancer cell invasion and metastasis, offering starting points to design novel anticancer agents.

DARPin-assisted crystallography of the CC2-LZ domain of NEMO reveals a coupling between dimerization and ubiquitin binding

NEMO is an integral part of the IkappaB kinase complex and serves as a molecular switch by which the NF-kappaB signaling pathway can be regulated. Oligomerization and polyubiquitin (poly-Ub) binding, mediated through the regulatory CC2-LZ domain, were shown to be key features governing NEMO function, but the relationship between these two activities remains unclear. In this study, we solved the structure of this domain in complex with a designed ankyrin repeat protein, which helps its crystallization. We generated several NEMO mutants in this domain, including those associated with human diseases incontinentia pigmenti and immunodeficiency with or without anhidrotic ectodermal dysplasia. Analytical ultracentrifugation and thermal denaturation experiments were used to evaluate the dimerization properties of these mutants. A fluorescence-based assay was developed, as well, to quantify the interaction to monoubiquitin and poly-Ub chains. Moreover, the effect of these mutations was investigated for the full-length protein. We show that a proper folding of the ubiquitin-binding domain, termed NOA/UBAN/NUB, into a stable coiled-coil dimer is required but not sufficient for efficient interaction with poly-Ub. In addition, we show that binding to poly-Ub and, to a lesser extent, to monoubiquitin increases the stability of the NOA coiled-coil dimer. Collectively, these data provide structural insights into how several pathological mutations within and outside of the CC2-LZ's NOA ubiquitin binding site affect IkappaB kinase activation in the NF-kappaB signaling pathway.

ABINs: A20 binding inhibitors of NF-kappa B and apoptosis signaling

ABINs have been described as three different proteins (ABIN-1, ABIN-2, ABIN-3) that bind the ubiquitin-editing nuclear factor-kappaB (NF-kappaB) inhibitor protein A20 and which show limited sequence homology. Overexpression of ABINs inhibits NF-kappaB activation by tumor necrosis factor (TNF) and several other stimuli. Similar to A20, ABIN-1 and ABIN-3 expression is NF-kappaB dependent, implicating a potential role for the A20/ABIN complex in the negative feedback regulation of NF-kappaB activation. Adenoviral gene transfer of ABIN-1 has been shown to reduce NF-kappaB activation in mouse liver and lungs. However, ABIN-1 as well as ABIN-2 deficient mice exhibit only slightly increased or normal NF-kappaB activation, respectively, possibly reflecting redundant NF-kappaB inhibitory activities of multiple ABINs. Other functions of ABINs might be non-redundant. For example, ABIN-1 shares with A20 the ability to inhibit TNF-induced apoptosis and as a result ABIN-1 deficient mice die during embryogenesis due to TNF-dependent fetal liver apoptosis. On the other hand, ABIN-2 is required for optimal TPL-2 dependent extracellularly regulated kinase activation in macrophages treated with TNF or Toll-like receptor ligands. ABINs have recently been shown to contain an ubiquitin-binding domain that is essential for their NF-kappaB inhibitory and anti-apoptotic activities. In this context, ABINs were proposed to function as adaptors between ubiquitinated proteins and other regulatory proteins. Alternatively, ABINs might disrupt signaling complexes by competing with other ubiquitin-binding proteins for the binding to specific ubiquitinated targets. Altogether, these findings implicate an important role for ABINs in the regulation of immunity and tissue homeostasis.