TRIP6 antagonizes the recruitment of A20 and CYLD to TRAF6 to promote the LPA2 receptor-mediated TRAF6 activation

The miR-19a/Cylindromatosis Axis Regulates Pituitary Adenoma Bone Invasion by Promoting Osteoclast Differentiation

BACKGROUND

The presence of bone invasion in aggressive pituitary adenoma (PA) was found in our previous study, suggesting that PA cells may be involved in the process of osteoclastogenesis. miR-19a (as a key member of the miR-17-92 cluster) has been reported to activate the nuclear factor-кB (NF-кB) pathway and promote inflammation, which could be involved in the process of the bone invasion of pituitary adenoma.

METHODS

In this work, FISH was applied to detect miR-19a distribution in tissues from patients with PA. A model of bone invasion in PA was established, GH3 cells were transfected with miR-19a mimic, and the grade of osteoclastosis was detected by HE staining. qPCR was performed to determine the expression of miR-19a throughout the course of RANKL-induced osteoclastogenesis. After transfected with a miR-19a mimic, BMMs were treated with RANKL for the indicated time, and the osteoclast marker genes were detected by qPCR and Western Blot. Pit formation and F-actin ring assay were used to evaluate the function of osteoclast. The TargetScan database and GSEA were used to find the potential downstream of miR-19a, which was verified by Co-IP, Western Blot, and EMSA.

RESULTS

Here, we found that miR-19a expression levels were significantly correlated with the bone invasion of PA, both in clinical samples and animal models. The osteoclast formation prior to bone resorption was dramatically enhanced by miR-19, which was mediated by decreased cylindromatosis (CYLD) expression, increasing the K63 ubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6). Consequently, miR-19a promotes osteoclastogenesis by the activation of the downstream NF-кB and mitogen-activated protein kinase (MAPK) pathways.

CONCLUSIONS

To summarize, the results of this study indicate that PA-derived miR-19a promotes osteoclastogenesis by inhibiting CYLD expression and enhancing the activation of the NF-кB and MAPK pathways.

TRIP6 promotes inflammatory damage via the activation of TRAF6 signaling in a murine model of DSS-induced colitis

Background

TRIP6 is a zyxin family member that serves as an adaptor protein to regulate diverse biological processes. In prior reports, TRIP6 was shown to play a role in regulating inflammation. However, its in vivo roles and mechanistic importance in colitis remain largely elusive. Herein, we therefore employed TRIP6-deficient (TRIP6^−/−) mice in order to explore the mechanistic importance of TRIP6 in a dextran sodium sulfate (DSS)-induced model of murine colitis.

Findings

Wild-type (TRIP6^+/+) mice developed more severe colitis following DSS-mediated disease induction relative to TRIP6^−/− mice, as evidenced by more severe colonic inflammation and associated crypt damage. TRIP6 expression in wild-type mice was significantly elevated following DSS treatment. Mechanistically, TRIP6 binds to TRAF6 and enhances oligomerization and autoubiquitination of TRAF6. This leads to the activation of NF-κB signaling and the expression of pro-inflammatory cytokines such as TNFα and IL-6, in the in vivo mouse model of colitis.

Conclusions

These in vivo data demonstrate that TRIP6 serves as a positive regulator of DSS-induced colitis through interactions with TRAF6 resulting in the activation of inflammatory TRAF6 signaling, highlighting its therapeutic promise as a protein that theoretically can be targeted to prevent or treat colitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12950-021-00298-0.

Understanding the regulation of β-catenin expression and activity in colorectal cancer carcinogenesis: beyond destruction complex

Aberrant Wnt/β-catenin signaling is central to colorectal cancer carcinogenesis. The well-known potential of targeting the canonical Wnt signaling pathway for the treatment of CRC is largely attributed to the ability of this pathway to regulate various cellular processes such as cell proliferation, metastasis, drug resistance, immune response, apoptosis, and cellular metabolism. However, with the current approach of targeting this pathway, none of the Wnt-targeted agents have been successfully implicated in clinical practice. Instead of using classical approaches to target this pathway, there is a growing need to find new and modified approaches to achieve the same. For this, a better understanding of the regulation of β-catenin, a major effector of the canonical Wnt pathway is a must. The present review addresses the importance of understanding the regulation of β-catenin beyond the destruction complex. Few recently discovered β-catenin regulators such as ZNF281, TTPAL, AGR2, ARHGAP25, TREM2, and TIPE1 showed significant potential in regulating the development of CRC through modulation of the Wnt/β-catenin signaling pathway in both in vitro and in vivo studies. Although the expression and activity of β-catenin is influenced by many protein regulators, the abovementioned proteins not only influence its expression and activation but are also directly involved in the development of CRC and various other solid tumors. Therefore, we hypothesise that focusing the current research on finding the detailed mechanism of action of these regulators may assist in providing with a better treatment approach or improve the current therapeutic regimens.

Knockdown of TRAF6 inhibits chondrocytes apoptosis and inflammation by suppressing the NF-κB pathway in lumbar facet joint osteoarthritis

Tumor necrosis factor receptor-associated factor 6 (TRAF6), a regulator of NF-κB signaling, has been discovered recently to be probably related to osteoarthritis, while the function of TRAF6 in lumbar facet joint osteoarthritis(FJOA)still remains unknown. The aim of this study was to probe the specific function of TRAF6 in chondrocytes and its connection with the pathophysiology of FJOA. We found upregulation of TRAF6 in FJOA cartilage by western blot analysis. In vitro, we stimulated immortalized human chondrocytes by LPS to establish the cells apoptosis model. Western blot analysis demonstrated that levels of TRAF6 and cleaved caspase-3/8 in the chondrocyte injury model increased significantly. Knockdown of TRAF6 suppressed the expression of matrix metallopeptidase-13 (MMP-13) and interleukin-6 (IL-6) induced by LPS, and alleviated cell apoptosis. Meanwhile, western blot and immunofluorescent staining demonstrated that IκBα degradation and p65 nuclear transportation were also inhibited, revealing that knockdown of TRAF6 suppressed activation of the NF-κB pathway in LPS-induced chondrocytes apoptosis model. Collectively, our findings suggest that TRAF6 plays a crucial role in FJOA development by regulating NF-κB signaling pathway. Knockdown of TRAF6 may supply a potential therapeutic strategy for FJOA.

The Effects of TRAF6 on Growth and Progression in Colorectal Cancer are Regulated by miRNA-140

Background and Aim

Some studies have confirmed that miRNA-140 exhibits a suppressive role in gastric cancer, Wilms’ tumor. However, the function of miRNA-140 in colorectal cancer has not been completely elucidated. The present study aims to verify TRAF6 as the targeted gene by miRNA-140 which was investigated in colorectal cancer tissues and cells, and its effects on the biological characteristics of colorectal cancer cells were determined, in order to provide an experimental and theoretical basis for the application of TRAF6 in the treatment of colorectal cancer.

Methods

qPCR analyzed miRNA-140 expression levels in colorectal cancer tissues, normal colorectal cancer tissues and colorectal cells including SW480 and HCT116 cancer cells and FHC normal colorectal epithetical cells. A serial biological experiment analyzed miRNA-140 effects on cell proliferation, migration and invasion capacities in SW480 and HCT116 cells. miRNA targeting gene prediction and a dual luciferase assay were used to analyze miRNA-140-targeted TRAF6. qPCR and Western blot analyzed miRNA-140 effects on the mRNA and protein expression of TRAF6. Western blot analyzed miRNA-140 effects on NF-κB/c-jun signaling pathways. Animal studies were performed to investigate the effects of miRNA-140 on colorectal cancer implantation tumor growth. Immunohistochemistry analyzed TRAF6 expression in animal experimentation tumors.

Results

miRNA-140 expression is lower in colorectal cancer tissues and colorectal cancer cells. Over-expression of miRNA-140 inhibited the proliferation, migration and invasion capacities of colorectal cancer cells. miRNA-140 targeted the TRAF6 mRNA 3ʹUTR area and decreased TRAF6 protein expression. miRNA-140 suppressed p-NF-κB/p-c-jun proteins expression. miRNA-140 inhibited colorectal cancer implantation tumor growth in the mice model.

Conclusion

miRNA-140 targeting TRAF6 affects the progression and growth of colorectal cancer, the mechanism could be miRNA-140 decreasing the TRAF6 expression effects on the NF-κB/c-jun signaling pathways.

TRAF6-Mediated Inflammatory Cytokines Secretion in LPS-induced Colorectal Cancer Cells Is Regulated by miR-140

BACKGROUND/AIM

Colorectal cancer (CRC) cells secrete inflammatory cytokines that affect CRC progression. The aim of the present study was to determine if micro-RNA-140(miR-140) regulates inflammatory cytokine secretion induced by lipopolysaccharide (LPS) in colorectal cancer cells by targeting tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6).

MATERIALS AND METHODS

Fifty fresh colon-cancer specimens and normal colorectal tissues were collected from patients with CRC and tested for the expression miR-140. Human CRC cell lines SW480 and HCT116 were treated with various concentrations and times with LPS. miR-140 and mRNA expression of potentially related genes were analyzed by qPCR. Protein expression was analyzed using western blot or ELISA. Overexpression plasmids with pcDNA3.1-TRAF6, pGL4.10-wtTRAF6 and pGL4.10-mutTRAF6 were constructed. miRNA target gene prediction and a dual luciferase assay were used to analyze miR-140-targeted TRAF6.

RESULTS

miR-140 expression was up-regulated in CRC tissues. In CRC cells, LPS could increase miR-140 expression in a time- and concentration-dependent manner. LPS increased inflammatory cytokine mRNA expression levels in SW480 and HCT116 human colon-cancer cells. miRNA-140 suppressed TRAF6 expression via targeting the 3'UTR. TRAF6 affected miR-140-mediated inflammatory cytokine expression of SW480 and HCT116 cells under LPS treatment.

CONCLUSION

miR-140 regulates inflammatory cytokine secretion of LPS-induced colorectal cancer cells by targeting TRAF6.

UBL4A Augments Innate Immunity by Promoting the K63-Linked Ubiquitination of TRAF6

Human UBL4A/GdX, encoding an ubiquitin-like protein, was shown in this study to be upregulated by viral infection and IFN stimulation. Then the functions of UBL4A in antiviral immune response were characterized. Overexpression of UBL4A promoted RNA virus-induced ISRE or IFN-β or NF-κB activation, leading to enhanced type I IFN transcription and reduced virus replication. Consistently, knockdown of UBL4A resulted in reduced type I IFN transcription and enhanced virus replication. Additionally, overexpression of UBL4A promoted virus-induced phosphorylation of TBK1, IRF3, and IKKα/β. Knockdown of UBL4A inhibited virus-induced phosphorylation of TBK1, IRF3, and IKKα/β. Coimmunoprecipitation showed that UBL4A interacted with TRAF6, and this interaction was enhanced upon viral infection. Ubiquitination assays showed that UBL4A promoted the K63-linked ubiquitination of TRAF6. Therefore, we reveal a novel positive feedback regulation of UBL4A in innate immune response combating virus invasion by enhancing the K63-linked ubiquitination of TRAF6.

The effects of TRAF6 on proliferation, apoptosis and invasion in osteosarcoma are regulated by miR-124

The present study aimed to verify tumor necrosis factor receptor‑associated factor 6 (TRAF6) as the target gene of microRNA-124 (miR-124). In addition, the expression of miR‑124 was investigated in osteosarcoma tissues and cells, and its effects on the biological characteristics of osteosarcoma cells were determined, in order to provide an experimental and theoretical basis for the application of TRAF6 in the treatment of osteosarcoma. A fluorescence reporter enzyme system was used to verify TRAF6 as a target gene of miR‑124, and western blotting was used to detect the effects of miR‑124 on the protein expression levels of TRAF6 in cells. The expression levels of miR‑124 were detected in osteosarcoma tissues and an osteosarcoma cell line (MG‑63) by quantitative polymerase chain reaction (qPCR). In addition, a total of 48 h post‑transfection of MG‑63 cells with a miR‑124 mimic, qPCR was used to detect the expression levels of miR‑124, and the effects of miR‑124 on the viability of MG‑63 human osteosarcoma cells was determined using the MTT method. The effects of miR‑124 on the cell cycle progression and apoptosis of MG‑63 cells were analyzed by flow cytometry, whereas the effects of miR‑124 on the migration of MG‑63 cells was detected using the Transwell invasion chamber analysis method. A TRAF6 recombinant expression plasmid (pcDNA3.1‑TRAF6) was also constructed, and MG‑63 cells were transfected with the recombinant plasmid and a miR‑124 mimic, in order to further validate the biological role of miR‑124 via the regulation of TRAF6. The results of the present study indicated that, compared with in the normal control group, the expression levels of miR‑124 were significantly increased in MG‑63 cells transfected with a miR‑124 mimic (P<0.01). In addition, the luciferase reporter gene system demonstrated that, compared with in the control group, relative luciferase activity was significantly reduced in the miR‑124 mimic group (P<0.01). The results of MTT analysis indicated that cell viability was also significantly reduced in response to the overexpression of miR‑124 in MG‑63 cells (P<0.01). Flow cytometric analysis demonstrated that the proportion of cells in S phase and G2/M phase was significantly decreased (P<0.01) in cells overexpressing miR‑124, and the number of apoptotic cells was significantly increased (P<0.01). Furthermore, the results of the Transwell invasion assay suggested that the number of invasive cells was significantly decreased following enhanced expression of miR‑124 (P<0.01). In MG‑63 cells overexpressing miR‑124 and TRAF6, the results of MTT, flow cytometric and Transwell assay analyses demonstrated that the overexpression of TRAF6 had the opposite biological effects compared to miR‑124 overexpression. In conclusion, the present study indicated that the expression levels of miR‑124 were downregulated in human osteosarcoma tissues and cells, and that miR‑124 is associated with negative regulation of TRAF6 expression; therefore, the role of TRAF6 in primary osteosarcoma may be regulated by miR‑124. Therapeutic strategies that enhance miR‑124 expression or inhibit TRAF6 expression may be beneficial for the treatment of patients with osteosarcoma.

TRAF molecules in inflammation and inflammatory diseases

Purpose of Review

This review presents an overview of the current knowledge of TRAF molecules in inflammation with an emphasis on available human evidence and direct in vivo evidence of mouse models that demonstrate the contribution of TRAF molecules in the pathogenesis of inflammatory diseases.

Recent Findings

The tumor necrosis factor receptor (TNF-R)-associated factor (TRAF) family of cytoplasmic proteins was initially identified as signaling adaptors that bind directly to the intracellular domains of receptors of the TNF-R superfamily. It is now appreciated that TRAF molecules are widely employed in signaling by a variety of adaptive and innate immune receptors as well as cytokine receptors. TRAF-dependent signaling pathways typically lead to the activation of nuclear factor-κBs (NF-κBs), mitogen-activated protein kinases (MAPKs), or interferon-regulatory factors (IRFs). Most of these signaling pathways have been linked to inflammation, and therefore TRAF molecules were expected to regulate inflammation and inflammatory responses since their discovery in 1990s. However, direct in vivo evidence of TRAFs in inflammation and especially in inflammatory diseases had been lacking for many years, partly due to the difficulty imposed by early lethality of TRAF2^-/-, TRAF3^-/-, and TRAF6^-/- mice. With the creation of conditional knockout and lineage-specific transgenic mice of different TRAF molecules, our understanding about TRAFs in inflammation and inflammatory responses has rapidly advanced during the past decade.

Summary

Increasing evidence indicates that TRAF molecules are versatile and indispensable regulators of inflammation and inflammatory responses and that aberrant expression or function of TRAFs contributes to the pathogenesis of inflammatory diseases.

Deubiquitinases A20 and CYLD modulate costimulatory signaling via CD137 (4-1BB)

TRAF2 dependent K63-polyubiquitinations have been recently shown to connect CD137 (4-1BB) stimulation to NF-κB activation. In a search of deubiquitinase enzymes (DUBs) that could regulate such a signaling route, A20 and CYLD were found to coimmunoprecipitate with CD137 and TRAF2 complexes. Indeed, overexpression of A20 or CYLD downregulated CD137-elicited ubiquitination of TRAF2 and TAK1 upon stimulation with agonist monoclonal antibodies. Moreover, overexpression of A20 or CYLD downregulated CD137-induced NF-κB activation in cultured cells and in gene-transferred hepatocytes in vivo, while silencing these deubiquitinases enhanced CD137 costimulation of primary human CD8 T cells. Therefore A20 and CYLD directly downregulate the signaling from a T and NK-cell costimulatory receptor under exploitation for cancer immunotherapy in clinical trials.

YOD1/TRAF6 association balances p62-dependent IL-1 signaling to NF-κB

The ubiquitin ligase TRAF6 is a key regulator of canonical IκB kinase (IKK)/NF-κB signaling in response to interleukin-1 (IL-1) stimulation. Here, we identified the deubiquitinating enzyme YOD1 (OTUD2) as a novel interactor of TRAF6 in human cells. YOD1 binds to the C-terminal TRAF homology domain of TRAF6 that also serves as the interaction surface for the adaptor p62/Sequestosome-1, which is required for IL-1 signaling to NF-κB. We show that YOD1 competes with p62 for TRAF6 association and abolishes the sequestration of TRAF6 to cytosolic p62 aggregates by a non-catalytic mechanism. YOD1 associates with TRAF6 in unstimulated cells but is released upon IL-1β stimulation, thereby facilitating TRAF6 auto-ubiquitination as well as NEMO/IKKγ substrate ubiquitination. Further, IL-1 triggered IKK/NF-κB signaling and induction of target genes is decreased by YOD1 overexpression and augmented after YOD1 depletion. Hence, our data define that YOD1 antagonizes TRAF6/p62-dependent IL-1 signaling to NF-κB.

DOI:http://dx.doi.org/10.7554/eLife.22416.001

Pubertal development in healthy children is mirrored by DNA methylation patterns in peripheral blood

Puberty marks numerous physiological processes which are initiated by central activation of the hypothalamic–pituitary–gonadal axis, followed by development of secondary sexual characteristics. To a large extent, pubertal timing is heritable, but current knowledge of genetic polymorphisms only explains few months in the large inter-individual variation in the timing of puberty. We have analysed longitudinal genome-wide changes in DNA methylation in peripheral blood samples (n = 102) obtained from 51 healthy children before and after pubertal onset. We show that changes in single methylation sites are tightly associated with physiological pubertal transition and altered reproductive hormone levels. These methylation sites cluster in and around genes enriched for biological functions related to pubertal development. Importantly, we identified that methylation of the genomic region containing the promoter of TRIP6 was co-ordinately regulated as a function of pubertal development. In accordance, immunohistochemistry identified TRIP6 in adult, but not pre-pubertal, testicular Leydig cells and circulating TRIP6 levels doubled during puberty. Using elastic net prediction models, methylation patterns predicted pubertal development more accurately than chronological age. We demonstrate for the first time that pubertal attainment of secondary sexual characteristics is mirrored by changes in DNA methylation patterns in peripheral blood. Thus, modulations of the epigenome seem involved in regulation of the individual pubertal timing.