The Research Progress in Physiological and Pathological Functions of TRAF4

Fine particulate matter‑induced cardiac developmental toxicity (Review)

Fine particulate matter (PM2.5) has become an important risk factor threatening human health. Epidemiological and toxicological investigations have revealed that PM2.5 not only leads to cardiovascular dysfunction, but it also gives rise to various adverse health effects on the human body, such as cardiovascular and cerebrovascular diseases, cancers, neurodevelopmental disorders, depression and autism. PM2.5 is able to penetrate both respiratory and placental barriers, thereby resulting in negative effects on fetal development. A large body of epidemiological evidences has suggested that gestational exposure to PM2.5 increases the incidence of congenital diseases in offspring, including congenital heart defects. In addition, animal model studies have revealed that gestational exposure to PM2.5 can disrupt normal heart development in offspring, although the potential molecular mechanisms have yet to be fully elucidated. The aim of the present review was to provide a brief overview of what is currently known regarding the molecular mechanisms underlying cardiac developmental toxicity in offspring induced by gestational exposure to PM2.5.

CircWDR37 promotes hepatocellular carcinoma tumorigenesis by mediating the miR-646/TRAF4 regulatory pathway

BACKGROUND

CircRNA has emerged as a significant player in human malignancies, including hepatocellular carcinoma (HCC). Hsa_circ_0004277 (circWDR37) is abnormally up-regulated in HCC. But, its function and underlying mechanism in HCC progression are largely unknown.

METHODS

qRT-PCR and western blot assays were used to measure the expression of circWDR37, miR-646, and TRAF4. Cell malignant phenotypes were assessed via CCK-8, EdU, colony formation, flow cytometry, transwell, and tube formation experiments. The intermolecular interaction between miR-646 and circWDR37 or TRAF4 was confirmed by dual-luciferase reporter and RNA immunoprecipitation (RIP) assay. The in vivo effect of circWDR37 on xenograft tumor growth was also investigated in mice.

RESULTS

Increased CircWDR37 and TRAF4 and decreased miR-646 were found in HCC tissues and cells. Scilencing circWDR37 impeded cell proliferation, migration, invasion, and tube formation, while accelerated apoptosis. CircWDR37 directly bind to miR-646 to suppress miR-646 expression and up-regulate TRAF4 expression. MiR-646 inhibitor partially abated the cell phenotype changes caused by circWDR37 knockdown. Moreover, miR-646 exerted an inhibitory effect on cell malignant phenotypes, which were attenuated due to the increase of TRAF4. Additionally, circWDR37 knockdown blocked HCC tumor growth in vivo.

CONCLUSION

CircWDR37 exerted an oncogenic effect in HCC by sponging miR-646 to up-regulate TRAF4 expression. Our finding elucidates a novel 'circWDR37-miR-646-TRAF4' regulatory axis in HCC and provides a promising target for HCC treatment.

Genome-wide association study for high-temperature tolerance in the Japanese flounder

This study addresses the critical issue of high-temperature stress in Japanese flounder (Paralichthys olivaceus), a factor threatening both their survival and the growth of the aquaculture industry. The research aims to identify genetic markers associated with high-temperature tolerance, unravel the genetic regulatory mechanisms, and lay the foundation for breeding Japanese flounder with increased resistance to high temperatures. In this study, using a genome-wide association study was performed to identify single nucleotide polymorphisms (SNPs) and genes associated with high-temperature tolerance for Japanese flounder using 280 individuals with 342 311 high-quality SNPs. The traits of high-temperature tolerance were defined as the survival time and survival status of Japanese flounder at high water temperature (31℃) for 15 days cultivate. A genome-wide association study identified six loci on six chromosomes significantly correlated with survival time under high-temperature stress. Six candidate genes were successfully annotated. Additionally, 34 loci associated with survival status were identified and mapped to 15 chromosomes, with 22 candidate genes annotated. Functional analysis highlighted the potential importance of genes like traf4 and ppm1l in regulating apoptosis, impacting high-temperature tolerance in Japanese flounder. These findings provide a valuable theoretical framework for integrating molecular markers into Japanese flounder breeding programmes, serving as a molecular tool to enhance genetic traits linked to high-temperature tolerance in cultured Japanese flounder.

Gene regulatory network topology governs resistance and treatment escape in glioma stem-like cells

Poor prognosis and drug resistance in glioblastoma (GBM) can result from cellular heterogeneity and treatment-induced shifts in phenotypic states of tumor cells, including dedifferentiation into glioma stem-like cells (GSCs). This rare tumorigenic cell subpopulation resists temozolomide, undergoes proneural-to-mesenchymal transition (PMT) to evade therapy, and drives recurrence. Through inference of transcriptional regulatory networks (TRNs) of patient-derived GSCs (PD-GSCs) at single-cell resolution, we demonstrate how the topology of transcription factor interaction networks drives distinct trajectories of cell-state transitions in PD-GSCs resistant or susceptible to cytotoxic drug treatment. By experimentally testing predictions based on TRN simulations, we show that drug treatment drives surviving PD-GSCs along a trajectory of intermediate states, exposing vulnerability to potentiated killing by siRNA or a second drug targeting treatment-induced transcriptional programs governing nongenetic cell plasticity. Our findings demonstrate an approach to uncover TRN topology and use it to rationally predict combinatorial treatments that disrupt acquired resistance in GBM.

TRAF4-Mediated LAMTOR1 Ubiquitination Promotes mTORC1 Activation and Inhibits the Inflammation-Induced Colorectal Cancer Progression

Mechanistic target of rapamycin complex 1 (mTORC1) is a conserved serine/threonine kinase that integrates various environmental signals to regulate cell growth and metabolism. mTORC1 activation requires tethering to lysosomes by the Ragulator-Rag complex. However, the dynamic regulation of the interaction between Ragulator and Rag guanosine triphosphatase (GTPase) remains unclear. In this study, that LAMTOR1, an essential component of Ragulator, is dynamically ubiquitinated depending on amino acid abundance is reported. It is found that the E3 ligase TRAF4 directly interacts with LAMTOR1 and catalyzes the K63-linked polyubiquitination of LAMTOR1 at K151. Ubiquitination of LAMTOR1 by TRAF4 promoted its binding to Rag GTPases and enhanced mTORC1 activation, K151R knock-in or TRAF4 knock-out blocks amino acid-induced mTORC1 activation and accelerates the development of inflammation-induced colon cancer. This study revealed that TRAF4-mediated LAMTOR1 ubiquitination is a regulatory mechanism for mTORC1 activation and provides a therapeutic target for diseases involving mTORC1 dysregulation.

Vesicular Stomatitis Virus Elicits Early Transcriptome Response in Culicoides sonorensis Cells

Viruses that are transmitted by arthropods, or arboviruses, have evolved to successfully navigate both the invertebrate and vertebrate hosts, including their immune systems. Biting midges transmit several arboviruses including vesicular stomatitis virus (VSV). To study the interaction between VSV and midges, we characterized the transcriptomic responses of VSV-infected and mock-infected Culicoides sonorensis cells at 1, 8, 24, and 96 h post inoculation (HPI). The transcriptomic response of VSV-infected cells at 1 HPI was significant, but by 8 HPI there were no detectable differences between the transcriptome profiles of VSV-infected and mock-infected cells. Several genes involved in immunity were upregulated (ATG2B and TRAF4) or downregulated (SMAD6 and TOLL7) in VSV-treated cells at 1 HPI. These results indicate that VSV infection in midge cells produces an early immune response that quickly wanes, giving insight into in vivo C. sonorensis VSV tolerance that may underlie their permissiveness as vectors for this virus.

TRAF Family Member 4 Promotes Cardiac Hypertrophy Through the Activation of the AKT Pathway

Background Pathological cardiac hypertrophy is a major cause of heart failure morbidity. The complex mechanism of intermolecular interactions underlying the pathogenesis of cardiac hypertrophy has led to a lack of development and application of therapeutic methods. Methods and Results Our study provides the first evidence that TRAF4, a member of the tumor necrosis factor receptor-associated factor (TRAF) family, acts as a promoter of cardiac hypertrophy. Here, Western blotting assays demonstrated that TRAF4 is upregulated in cardiac hypertrophy. Additionally, TRAF4 deletion inhibits the development of cardiac hypertrophy in a mouse model after transverse aortic constriction surgery, whereas its overexpression promotes phenylephrine stimulation-induced cardiomyocyte hypertrophy in primary neonatal rat cardiomyocytes. Mechanistically, RNA-seq analysis revealed that TRAF4 promoted the activation of the protein kinase B pathway during cardiac hypertrophy. Moreover, we found that inhibition of protein kinase B phosphorylation rescued the aggravated cardiomyocyte hypertrophic phenotypes caused by TRAF4 overexpression in phenylephrine-treated neonatal rat cardiomyocytes, suggesting that TRAF4 may regulate cardiac hypertrophy in a protein kinase B-dependent manner. Conclusions Our results revealed the regulatory function of TRAF4 in cardiac hypertrophy, which may provide new insights into developing therapeutic and preventive targets for this disease.

TRAF inhibition drives cancer cell apoptosis and improves retinoic acid sensitivity in multiple cancers models

TNF receptor-associated factors (TRAFs) are signaling adaptor proteins that play a crucial role in regulating cellular receptors' signaling transduction to downstream pathways and exert multifaceted roles in regulating signaling pathways, cell survival, and carcinogenesis. The 13-cis-retinoic acid (RA), an active metabolite of vitamin A, exhibits anti-cancer properties, but the development of retinoic acid resistance poses a challenge in clinical application. This study aimed to investigate the relationship between TRAFs and retinoic acid sensitivity in various cancers. Here, we revealed that TRAFs' expression varied significantly across The Cancer Genome Atlas (TCGA) cancer cohorts and human cancer cell lines. Additionally, inhibiting TRAF4, TRAF5, or TRAF6 improved retinoic acid sensitivity and reduced colony formation in ovarian cancer and melanoma cells. Mechanistically, knocking down TRAF4, TRAF5, or TRAF6 in retinoic acid-treated cancer cell lines increased the levels of procaspase 9 and induced cell apoptosis. Further in vivo studies using the SK-OV-3 and MeWo xenograft models confirmed the anti-tumor effects of TRAF knockdown combined with retinoic acid treatment. These findings support that combination therapy with retinoic acid and TRAF silencing may offer significant therapeutic advantages in treating melanoma and ovarian cancers.

AHR-mediated m6A RNA methylation contributes to PM2.5-induced cardiac malformations in zebrafish larvae

A growing body of evidence indicates that ambient fine particle matter (PM_2.5) exposure inhibits heart development, but the underlying mechanisms remain elusive. We hypothesized that m⁶A RNA methylation plays an important role in the cardiac developmental toxicity of PM_2.5. In this study, we demonstrated that extractable organic matter (EOM) from PM2.5 significantly decreased global m⁶A RNA methylation levels in the heart of zebrafish larvae, which were restored by the methyl donor, betaine. Betaine also attenuated EOM-induced ROS overgeneration, mitochondrial damage, apoptosis and heart defects. Furthermore, we found that the aryl hydrocarbon receptor (AHR), which was activated by EOM_, directly repressed the transcription of methyltransferases mettl14 and mettl3. EOM also induced genome-wide m⁶A RNA methylation changes, which led us to focus more on the aberrant m⁶A methylation changes that were subsequently alleviated by the AHR inhibitor, CH223191. In addition, we found that the expression levels of traf4a and bbc3, two apoptosis related genes, were upregulated by EOM but restored to control levels by the forced expression of mettl14. Moreover, knockdown of either traf4a or bbc3 attenuated EOM-induced ROS overproduction and apoptosis. In conclusion, our results indicate that PM_2.5 induces m⁶A RNA methylation changes via AHR-mediated mettl14 downregulation, which upregulates traf4a and bbc3, leading to apoptosis and cardiac malformations.

TRAF4-mediated nonproteolytic ubiquitination of androgen receptor promotes castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) poses a major clinical challenge with the androgen receptor (AR) remaining to be a critical oncogenic player. Several lines of evidence indicate that AR induces a distinct transcriptional program after androgen deprivation in CRPCs. However, the mechanism triggering AR binding to a distinct set of genomic loci in CRPC and how it promotes CRPC development remain unclear. We demonstrate here that atypical ubiquitination of AR mediated by an E3 ubiquitin ligase TRAF4 plays an important role in this process. TRAF4 is highly expressed in CRPCs and promotes CRPC development. It mediates K27-linked ubiquitination at the C-terminal tail of AR and increases its association with the pioneer factor FOXA1. Consequently, AR binds to a distinct set of genomic loci enriched with FOXA1- and HOXB13-binding motifs to drive different transcriptional programs including an olfactory transduction pathway. Through the surprising upregulation of olfactory receptor gene transcription, TRAF4 increases intracellular cAMP levels and boosts E2F transcription factor activity to promote cell proliferation under androgen deprivation conditions. Altogether, these findings reveal a posttranslational mechanism driving AR-regulated transcriptional reprogramming to provide survival advantages for prostate cancer cells under castration conditions.

TRAF4 Silencing Induces Cell Apoptosis and Improves Retinoic Acid Sensitivity in Human Neuroblastoma

Neuroblastoma (NB) is a pediatric malignancy that arises in the peripheral nervous system, and the prognosis in the high-risk group remains dismal, despite the breakthroughs in multidisciplinary treatments. The oral treatment with 13-cis-retinoic acid (RA) after high-dose chemotherapy and stem cell transplant has been proven to reduce the incidence of tumor relapse in children with high-risk neuroblastoma. However, many patients still have tumors relapsed following retinoid therapy, highlighting the need for the identification of resistant factors and the development of more effective treatments. Herein, we sought to investigate the potential oncogenic roles of the tumor necrosis factor (TNF) receptor-associated factor (TRAF) family in neuroblastoma and explore the correlation between TRAFs and retinoic acid sensitivity. We discovered that all TRAFs were efficiently expressed in neuroblastoma, but TRAF4, in particular, was found to be strongly expressed. The high expression of TRAF4 was associated with a poor prognosis in human neuroblastoma. The inhibition of TRAF4, rather than other TRAFs, improved retinoic acid sensitivity in two human neuroblastoma cell lines, SH-SY5Y and SK-N-AS cells. Further in vitro studies indicated that TRAF4 suppression induced retinoic acid-induced cell apoptosis in neuroblastoma cells, probably by upregulating the expression of Caspase 9 and AP1 while downregulating Bcl-2, Survivin, and IRF-1. Notably, the improved anti-tumor effects from the combination of TRAF4 knockdown and retinoic acid were confirmed in vivo using the SK-N-AS human neuroblastoma xenograft model. In conclusion, the highly expressed TRAF4 might be implicated in developing resistance to retinoic acid treatment in neuroblastoma, and the combination therapy with retinoic acid and TRAF4 inhibition may offer significant therapeutic advantages in the treatment of relapsed neuroblastoma.

TRAF4-mediated ubiquitination-dependent activation of JNK/Bcl-xL drives radioresistance

The E3 ligase TNF receptor-associated factor 4 (TRAF4) is upregulated and closely associated with tumorigenesis and the progression of multiple human malignancies. However, its effect on radiosensitivity in colorectal cancer (CRC) has not been elucidated. The present study found that TRAF4 was significantly increased in CRC clinical tumor samples. Depletion of TRAF4 impaired the malignant phenotype of CRC cells and sensitized irradiation-induced cell death. Irradiation activated the c-Jun N-terminal kinases (JNKs)/c-Jun signaling via increasing JNKs K63-linked ubiquitination and phosphorylation. Furthermore, c-Jun activation triggered the transcription of the antiapoptotic protein Bcl-xL, thus contributing to the radioresistance of CRC cells. TRAF4 was positively correlated with c-Jun and Bcl-xL, and blocking TRAF4 or inhibiting Bcl-xL with inhibitor markedly promoted ionizing radiation (IR)-induced intrinsic apoptosis and sensitized CRC cells to radiotherapy in vitro and in vivo. Our findings illustrate a potential mechanism of radioresistance, emphasizing the clinical value of targeting the TRAF4/Bcl-xL axis in CRC therapy.