TRIM8 modulates STAT3 activity through negative regulation of PIAS3

E3 ligase TRIM8 suppresses lung cancer metastasis by targeting MYOF degradation through K48-linked polyubiquitination

Ubiquitination is a posttranslational modification that regulates tumour progression-associated proteins through the ubiquitin‒proteasome system, making E3 ligases potential antitumour targets. Here, we report that TRIM8, a member of the TRIM family and an E3 ligase, can act as a tumour suppressor in non-small cell lung cancer (NSCLC). Both gain- and loss-of-function experiments revealed that TRIM8 inhibits the proliferation, colony formation, migration and invasion of NSCLC cells. Experiments with a xenograft model showed that TRIM8 expression suppresses tumour metastasis in vivo. Moreover, low expression of TRIM8 was associated with poor overall survival in both the Taiwanese and GEO lung cancer cohorts. TRIM8 overexpression in lung cancer cells reduced MYOF expression, and restoring MYOF rescued cell migration in TRIM8-overexpressing cells. TRIM8 targeted MYOF for K48-linked ubiquitination, facilitating proteasome-mediated degradation and subsequently suppressing the extracellular secretion of MMPs. Our results provide new insights into the contribution of TRIM8 to lung cancer progression, suggesting that TRIM8 is a new biomarker and a novel therapeutic target for lung cancer.

Effects of dietary curcumin on gene expression: An analysis of transcriptomic data in mice

BACKGROUND

Curcumin, a ubiquitous polyphenol in turmeric, possesses many anti-cancer and anti-inflammatory properties. These therapeutic effects are largely resultant of curcumin's ability to modulate global gene expression. Bioinformatics-based approaches for analyzing differential gene expression are effective tools in gaining a more profound understanding of the underlying mechanisms of action.

AIM

In this study, we aimed to identify key genes that were differentially regulated by curcumin treatment of mice.

METHODS

We downloaded GSE10684 and GSE13705 microarray profiles from the GEO database. Differentially expressed genes were identified and compared in both data sets. Twenty-seven genes that are significantly differentially regulated in both datasets were considered as key genes.

RESULTS

Gene ontology (GO) enrichment indicates these key genes were mostly enriched in GO Process of regulation of immune response and immune system process. The KEGG pathways of Cytokine-cytokine receptor interaction and TISSUES of Immune system were the top enriched terms of key genes base on strength and false discovery rate. The protein-protein interactions were analyzed by the STRING. PPI clustering showed that cluster 1 with Csf1, Cxcl16, Cxcr3, Fas, Il7r, Rassf2, and Rp2h was the most significant cluster. GO enrichment analysis for this cluster also showed the roles of these genes in immune system regulation.

CONCLUSIONS

Overall, the microarray datasets to identify the key genes and the related pathways which were affected by curcumin treatments show that curcumin has a significant impact on immune system regulation through the modulation of gene expression.

Tripartite motif 8 promotes the progression of hepatocellular carcinoma via mediating ubiquitination of HNF1α

Tripartite motif 8 (TRIM8) is an E3 ligase that plays dual roles in various tumor types. The biological effects and underlying mechanism of TRIM8 in hepatocellular carcinoma (HCC) remain unknown. Hepatocyte nuclear factor 1α (HNF1α) is a key transcriptional factor that plays a significant role in regulating hepatocyte differentiation and liver function. The reduced expression of HNF1α is a critical event in the development of HCC, but the underlying mechanism for its degradation remains elusive. In this study, we discovered that the expression of TRIM8 was upregulated in HCC tissues, and was positively correlated with aggressive tumor behavior of HCC and shorter survival of HCC patients. Overexpression of TRIM8 promoted the proliferation, colony formation, invasion, and migration of HCC cells, while TRIM8 knockdown or knockout exerted the opposite effects. RNA sequencing revealed that TRIM8 knockout suppresses several cancer-related pathways, including Wnt/β-catenin and TGF-β signaling in HepG2 cells. TRIM8 directly interacts with HNF1α, promoting its degradation by catalyzing polyubiquitination on lysine 197 in HCC cells. Moreover, the cancer-promoting effects of TRIM8 in HCC were abolished by the HNF1α-K197R mutant in vitro and in vivo. These data demonstrated that TRIM8 plays an oncogenic role in HCC progression through mediating the ubiquitination of HNF1α and promoting its protein degradation, and suggests targeting TRIM8-HNF1α may provide a promising therapeutic strategy of HCC.

Mutual regulation between TRIM21 and TRIM8 via K48-linked ubiquitination

Tripartite motif (TRIM)-containing proteins, one of the largest subfamilies of the RING type E3 ubiquitin ligases, control important biological processes such as cell apoptosis, autophagy, signal transduction, innate immunity and tumorigenesis. So far, the mutual regulation between TRIM family members has rarely been reported. Here, we found for the first time that there was a direct mutual regulation between TRIM21 and TRIM8 in lung and renal cancer cells, mechanistically by activating their proteasome pathway via Lys48 (K48)- linked ubiquitination. Subsequent studies verified that negatively correlated expressions existed in clinical non-small cell lung cancer (NSCLC) and renal cell carcinoma (RCC) tissues, which were closely related to tumor progression. Our findings highlighted a possible homeostasis between TRIM21 and TRIM8 that might possibly affect cell stemness and was expected to provide a new idea for cancer therapy.

Intricate confrontation: Research progress and application potential of TRIM family proteins in tumor immune escape

BACKGROUND

Tripartite motif (TRIM) family proteins have more than 80 members and are widely found in various eukaryotic cells. Most TRIM family proteins participate in the ubiquitin-proteasome degradation system as E3-ubiquitin ligases; therefore, they play pivotal regulatory roles in the occurrence and development of tumors, including tumor immune escape. Due to the diversity of functional domains of TRIM family proteins, they can extensively participate in multiple signaling pathways of tumor immune escape through different substrates. In current research and clinical contexts, immune escape has become an urgent problem. The extensive participation of TRIM family proteins in curing tumors or preventing postoperative recurrence and metastasis makes them promising targets.

AIM OF REVIEW

The aim of the review is to make up for the gap in the current research on TRIM family proteins and tumor immune escape and propose future development directions according to the current progress and problems.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This up-to-date review summarizes the characteristics and biological functions of TRIM family proteins, discusses the mechanisms of TRIM family proteins involved in tumor immune escape, and highlights the specific mechanism from the level of structure-function-molecule-pathway-phenotype, including mechanisms at the level of protein domains and functions, at the level of molecules and signaling pathways, and at the level of cells and microenvironments. We also discuss the application potential of TRIM family proteins in tumor immunotherapy, such as possible treatment strategies for combination targeting TRIM family protein drugs and checkpoint inhibitors for improving cancer treatment.

The role of TRIM family in metabolic associated fatty liver disease

Metabolic associated fatty liver disease (MAFLD) ranks among the most prevalent chronic liver conditions globally. At present, the mechanism of MAFLD has not been fully elucidated. Tripartite motif (TRIM) protein is a kind of protein with E3 ubiquitin ligase activity, which participates in highly diversified cell activities and processes. It not only plays an important role in innate immunity, but also participates in liver steatosis, insulin resistance and other processes. In this review, we focused on the role of TRIM family in metabolic associated fatty liver disease. We also introduced the structure and functions of TRIM proteins. We summarized the TRIM family's regulation involved in the occurrence and development of metabolic associated fatty liver disease, as well as insulin resistance. We deeply discussed the potential of TRIM proteins as targets for the treatment of metabolic associated fatty liver disease.

The Molecular and Function Characterization of Porcine MID2

Midline2 (MID2/TRIM1) is a member of the tripartite motif-containing (TRIM) family, which is involved in a wide range of cellular processes. However, fundamental studies on porcine MID2 (pMID2) are still lacking. In this study, we identified and characterized the full length MID2 gene of pig (Sus scrofa). The sequence alignment analysis results showed that pMID2 had an N-terminal RING zinc-finger domain, BBC domain, and C-terminal COS box, FN3 motif, and PRY-SPRY domain that were conserved and similar to those of other vertebrates. Furthermore, pMID2 had the highest expression levels in porcine lung and spleen. Serial deletion and site-directed mutagenesis showed that the putative nuclear factor-κB (NF-κB) binding site may be an essential transcription factor for regulating the transcription expression of pMID2. Furthermore, the immunofluorescence assay indicated that pMID2 presented in the cell membrane and cytoplasm. To further study the functions of pMID2, we identified and determined its potential ability to perceive poly (I:C) and IFN-α stimulation. Stimulation experiments showed pMID2 enhanced poly (I:C)-/IFN-α-induced JAK-STAT signaling pathway, indicating that pMID2 might participate in the immune responses. In conclusion, we systematically and comprehensively analyzed the characterizations and functions of pMID2, which provide valuable information to explore the pMID2 functions in innate immunity. Our findings not only enrich the current knowledge of MID2 in IFN signaling regulation but also offer the basis for future research of pig MID2 gene.

TRIM8: a double-edged sword in glioblastoma with the power to heal or hurt

Glioblastoma multiforme (GBM) is an aggressive primary brain tumor and one of the most lethal central nervous system tumors in adults. Despite significant breakthroughs in standard treatment, only about 5% of patients survive 5 years or longer. Therefore, much effort has been put into the search for identifying new glioma-associated genes. Tripartite motif-containing (TRIM) family proteins are essential regulators of carcinogenesis. TRIM8, a member of the TRIM superfamily, is abnormally expressed in high-grade gliomas and is associated with poor clinical prognosis in patients with glioma. Recent research has shown that TRIM8 is a molecule of duality (MoD) that can function as both an oncogene and a tumor suppressor gene, making it a "double-edged sword" in glioblastoma development. This characteristic is due to its role in selectively regulating three major cellular signaling pathways: the TP53/p53-mediated tumor suppression pathway, NFKB/NF-κB, and the JAK-STAT pathway essential for stem cell property support in glioma stem cells. In this review, TRIM8 is analyzed in detail in the context of GBM and its involvement in essential signaling and stem cell-related pathways. We also discuss the basic biological activities of TRIM8 in macroautophagy/autophagy, regulation of bipolar spindle formation and chromosomal stability, and regulation of chemoresistance, and as a trigger of inflammation.

TRIM family contribute to tumorigenesis, cancer development, and drug resistance

The tripartite-motif (TRIM) family represents one of the largest classes of putative single protein RING-finger E3 ubiquitin ligases. TRIM family is involved in a variety of cellular signaling transductions and biological processes. TRIM family also contributes to cancer initiation, progress, and therapy resistance, exhibiting oncogenic and tumor-suppressive functions in different human cancer types. Moreover, TRIM family members have great potential to serve as biomarkers for cancer diagnosis and prognosis. In this review, we focus on the specific mechanisms of the participation of TRIM family members in tumorigenesis, and cancer development including interacting with dysregulated signaling pathways such as JAK/STAT, PI3K/AKT, TGF-β, NF-κB, Wnt/β-catenin, and p53 hub. In addition, many studies have demonstrated that the TRIM family are related to tumor resistance; modulate the epithelial–mesenchymal transition (EMT) process, and guarantee the acquisition of cancer stem cells (CSCs) phenotype. In the end, we havediscussed the potential of TRIM family members for cancer therapeutic targets.

Knockdown of TRIM27 alleviated sepsis-induced inflammation, apoptosis, and oxidative stress via suppressing ubiquitination of PPARγ and reducing NOX4 expression

BACKGROUND

Sepsis is a global fatal disease and leads to severe lung injury due to dysfunction of inflammation response. TRIM27 is closely related to the diseased with dysfunction of inflammation response. The aim of this study was to clarify the role and mechanism of TRIM27 in sepsis-induced lung injury.

METHODS

The lipopolysaccharide (LPS)-induced septic mouse model was successfully established. The lung injury was evaluated by lung wet/dry (W/D) ratio and hematoxylin-eosin (H&E) staining. The cell apoptosis was evaluated by TUNEL assay. The inflammatory cytokines were measured by quantitative real time-PCR (qRT-PCR) assay and commercial enzyme-linked immunosorbent assay (ELISA). The oxidative stress was assessed by the contents of superoxide dismutase (SOD) and malondialdehyde (MDA), and the expression of dihydroethidium (DHE).

RESULTS

In this study, we demonstrated that TRIM27 was up-regulated in LPS-induced septic mice. In loss-of-function experiments, knockdown of TRIM27 alleviated sepsis-induced lung injury, inflammation, apoptosis, and oxidative stress. More importantly, knockdown of TRIM27 was observed to reduce p-p65/NOX4 expression via suppressing ubiquitination of PPARγ. In rescue experiments, overexpression of NOX4 abolished the effect of sh-TRIM27 on alleviating sepsis-induced inflammation, apoptosis, and oxidative stress.

CONCLUSION

These findings highlighted that knockdown of TRIM27 alleviated sepsis-induced inflammation, oxidative stress and apoptosis via suppressing ubiquitination of PPARγ and reducing NOX4 expression, which supports the potential utility of TRIM27 as a therapeutic target in septic lung injury.

Defective STAT5 Activation and Aberrant Expression of BCL6 in Naive CD4 T Cells Enhances Follicular Th Cell-like Differentiation in Patients with Granulomatosis with Polyangiitis

Granulomatosis with polyangiitis (GPA) is a potentially fatal small vessel vasculitis of unknown etiology, characterized by anti-neutrophil cytoplasmic autoantibodies, chronic inflammation, and granulomatous tissue damage. T cell dysregulation, comprising decreased regulatory T cell function and increased circulating effector memory follicular Th cells (TFH), is strongly associated with disease pathogenesis, but the mechanisms driving these observations are unknown. We undertook transcriptomic and functional analysis of naive CD4 T cells from patients with GPA to identify underlying functional defects that could manifest in the pathogenic profiles observed in GPA. Gene expression studies revealed a dysregulation of the IL-2 receptor β/JAK-STAT signaling pathway and higher expression of BCL6 and BCL6-regulated genes in GPA naive CD4 T cells. IL-2-induced STAT5 activation in GPA naive CD4 T cells was decreased, whereas STAT3 activation by IL-6 and IL-2 was unperturbed. Consistently, BCL6 expression was sustained following T cell activation of GPA naive CD4 T cells and in vitro TFH differentiation of these cells resulted in significant increases in the production TFH-related cytokines IL-21 and IL-6. Thus, naive CD4 T cells are dysregulated in patients with GPA, resulting from an imbalance in signaling equilibrium and transcriptional changes that drives the skewed pathogenic CD4 effector immune response in GPA.

Regulation of Tripartite Motif-Containing Proteins on Immune Response and Viral Evasion

Tripartite motif-containing proteins (TRIMs), exhibiting ubiquitin E3 ligase activity, are involved in regulation of not only autophagy and apoptosis but also pyrotosis and antiviral immune responses of host cells. TRIMs play important roles in modulating signaling pathways of antiviral immune responses via type I interferon, NF-κB, Janus kinase/signal transducer and activator of transcription (JAK/STAT), and Nrf2. However, viruses are able to antagonize TRIM activity or evenly utilize TRIMs for viral replication. This communication presents the current understanding of TRIMs exploited by viruses to evade host immune response.

TNF-α-induced E3 ligase, TRIM15 inhibits TNF-α-regulated NF-κB pathway by promoting turnover of K63 linked ubiquitination of TAK1

Ubiquitin E3-ligases are recruited at different steps of TNF-α-induced NF-κB activation; however, their role in temporal regulation of the pathway remains elusive. The study systematically identified TRIMs as potential feedback regulators of the TNF-α-induced NF-κB pathway. We further observed that TRIM15 is "late" response TNF-α-induced gene and inhibits the TNF-α-induced NF-κB pathway in several human cell lines. TRIM15 promotes turnover of K63-linked ubiquitin chains in a PRY/SPRY domain-dependent manner. TRIM15 interacts with TAK1 and inhibits its K63-linked ubiquitination, thus NF-κB activity. Further, TRIM15 interacts with TRIM8 and inhibits cytosolic translocation to antagonize TRIM8 modualted NF-κB. TRIM8 and TRIM15 also show functionally inverse correlation in psoriasis condition. In conclusion, TRIM15 is TNF-α-induced late response gene and inhibits TNF-α induced NF-κB pathway hence a feedback modulator to keep the proinflammatory NF-κB pathway under control.

ZSWIM8 is a myogenic protein that partly prevents C2C12 differentiation

Cell adhesion molecule-related/downregulated by oncogenes (Cdon) is a cell-surface receptor that mediates cell–cell interactions and positively regulates myogenesis. The cytoplasmic region of Cdon interacts with other proteins to form a Cdon/JLP/Bnip-2/CDC42 complex that activates p38 mitogen-activated protein kinase (MAPK) and induces myogenesis. However, Cdon complex may include other proteins during myogenesis. In this study, we found that Cullin 2-interacting protein zinc finger SWIM type containing 8 (ZSWIM8) ubiquitin ligase is induced during C2C12 differentiation and is included in the Cdon complex. We knocked-down Zswim8 in C2C12 cells to determine the effect of ZSWIM8 on differentiation. However, we detected neither ZSWIM8-dependent ubiquitination nor the degradation of Bnip2, Cdon, or JLP. In contrast, ZSWIM8 knockdown accelerated C2C12 differentiation. These results suggest that ZSWIM8 is a Cdon complex-included myogenic protein that prevents C2C12 differentiation without affecting the stability of Bnip2, Cdon, and JLP.

A tripartite motif protein (CgTRIM1) involved in CgIFNLP mediated antiviral immunity in the Pacific oyster Crassostrea gigas

Tripartite motif (TRIM) proteins are a large family of E3 ubiquitin ligases involved in many biological processes, such as inflammation and antiviral immunity. In the present study, a novel TRIM protein homolog named CgTRIM1 was identified from Pacific oyster Crassostrea gigas. The open reading frame (ORF) of CgTRIM1 was of 1914 bp encoding a putative polypeptide of 637 amino acid residues. There were three classical domains in the predicted CgTRIM1 protein, including one RING domain, two b-box domains and one coiled-coil domain in N-terminal. For the lack of C-terminal domains, the CgTRIM1 was classified as the member of C-V TRIM subfamily. The mRNA transcripts of CgTRIM1 were detected in all the tested tissues and haemocytes, with the highest expression level in gill. The mRNA and protein levels of CgTRIM1 in gill were significantly up-regulated at 6 h after poly (I:C) stimulation. Moreover, the nuclear translocation of CgTRIM1 was observed in haemocytes of oysters after poly (I:C) stimulation. After IFN-like protein (CgIFNLP) was knocked down by RNA interference (RNAi), the expression of CgTRIM1 in gill was markedly inhibited in both mRNA (0.14-fold, p < 0.001) and protein levels after poly (I:C) stimulation. Furthermore, after knocking down of CgTRIM1, the mRNA expression levels of IFN-stimulated genes, including myxovirus resistance of oyster (CgMx) and Interferon-induced protein 44 (CgIFI44) were significantly down-regulated post poly (I:C) stimulation, while no significant change of the CgIFNLP expression was observed. These results indicated that CgTRIM1 participated in the antiviral response of C. gigas by regulating the mRNA expressions of IFN-stimulated genes.

TRIM8 modulates the EWS/FLI oncoprotein to promote survival in Ewing sarcoma

Fusion-transcription factors (fusion-TFs) represent a class of driver oncoproteins that are difficult to therapeutically target. Recently, protein degradation has emerged as a strategy to target these challenging oncoproteins. The mechanisms that regulate fusion-TF stability, however, are generally unknown. Using CRISPR-Cas9 screening, we discovered tripartite motif-containing 8 (TRIM8) as an E3 ubiquitin ligase that ubiquitinates and degrades EWS/FLI, a driver fusion-TF in Ewing sarcoma. Moreover, we identified TRIM8 as a selective dependency in Ewing sarcoma compared with >700 other cancer cell lines. Mechanistically, TRIM8 knockout led to an increase in EWS/FLI protein levels that was not tolerated. EWS/FLI acts as a neomorphic substrate for TRIM8, defining the selective nature of the dependency. Our results demonstrate that fusion-TF protein stability is tightly regulated and highlight fusion oncoprotein-specific regulators as selective therapeutic targets. This study provides a tractable strategy to therapeutically exploit oncogene overdose in Ewing sarcoma and potentially other fusion-TF-driven cancers.

Unraveling the origin of glucose mediated disparate proliferation dynamics of cancer stem cells

Cancer stem cells (CSCs) often switch on their self-renewal programming aggressively to cause a relapse of cancer. Intriguingly, glucose triggers the proliferation propensities in CSCs by controlling the expression of the key transcription factor-like Nanog. However, the factors that critically govern this glucose-stimulated proliferation dynamics of CSCs remain elusive. Herein, by proposing a mathematical model of glucose-mediated Nanog regulation, we showed that the differential proliferation behavior of CSCs and cell-type similar to CSCs can be explained by considering the experimentally observed varied expression levels of key positive (STAT3) and negative (p53) regulators of Nanog. Our model reconciles various experimental observations and predicts ways to fine-tune the proliferation dynamics of these cell types in a context-dependent manner. In future, these modeling insights will be useful in developing improved therapeutic strategies to get rid of harmful CSCs.

Ubiquitination, Biotech Startups, and the Future of TRIM Family Proteins: A TRIM-Endous Opportunity

Ubiquitination is a post-translational modification that has pivotal roles in protein degradation and diversified cellular processes, and for more than two decades it has been a subject of interest in the biotech or biopharmaceutical industry. Tripartite motif (TRIM) family proteins are known to have proven E3 ubiquitin ligase activities and are involved in a multitude of cellular and physiological events and pathophysiological conditions ranging from cancers to rare genetic disorders. Although in recent years many kinds of E3 ubiquitin ligases have emerged as the preferred choices of big pharma and biotech startups in the context of protein degradation and disease biology, from a surface overview it appears that TRIM E3 ubiquitin ligases are not very well recognized yet in the realm of drug discovery. This article will review some of the blockbuster scientific discoveries and technological innovations from the world of ubiquitination and E3 ubiquitin ligases that have impacted the biopharma community, from biotech colossuses to startups, and will attempt to evaluate the future of TRIM family proteins in the province of E3 ubiquitin ligase-based drug discovery.

MicroRNA-665 facilitates cell proliferation and represses apoptosis through modulating Wnt5a/β-Catenin and Caspase-3 signaling pathways by targeting TRIM8 in LUSC

Background

MicroRNAs (miRNAs) are involved in the oncogenesis, development and transformation of lung squamous cell carcinoma (LUSC). miR-665 is clinically significant and acts as a pivotal function in some cancers. Nevertheless, the effects and the potential mechanisms of miR-665 in human LUSC are still unknown.

Methods

To analyse the clinical significant of miR-665 in human LUSC, quantitative real-time PCR (qRT-PCR) was use to measure miR-665 expression in LUSC specimen tissues and cell lines. Tripartite motif 8 (TRIM8) was verified a target of miR-665 by performing bioinformatic prediction and luciferase reporter assay. The expression levels of TRIM8 were examined through qRT-PCR and Western blotting in LUSC specimen tissues. CCK8 assay was fulfilled for analyzing the function in LUSC cell proliferation. Flow cytometry was used to detect cell and apoptosis. TRIM8 silencing and overexpression further verified the biological effects as those caused by miR-665.

Results

Here we reported that miR-665 expression was upregulated in LUSC specimen tissues and cell lines. High miR-665 levels were related to differentiation, tumor size and TNM stage. miR-665 mimics facilitated LUSC cell growth and cell cycle G1-S transition and repressed apoptosis. miR-665 inhibitor suppressed cell proliferation and G1-S transition and promoted apoptosis. miR-665 expression was negatively correlated with TRIM8 mRNA expression in LUSC. Luciferase reporter assay confirmed that TRIM8 was a direct target gene of miR-665. miR-665 mimics downregulated the TRIM8 levels, and miR-665 inhibitor upregulated the TRIM8 levels in LUSC cells. Particularly, silencing TRIM8 led to the similar effects of miR-665 mimics in LUSC cells. Overexpression of TRIM8 inhibited LUSC cell proliferation in vitro and in vivo. Furthermore, miR-665 promoted LUSC cell proliferation through facilitating the Wnt5a/β-catenin signaling pathway and restrained apoptosis via inhibiting Caspase-3 signaling pathway, whereas TRIM8 suppressed cell growth by repressing the Wnt5a/β-catenin signaling pathway and induced apoptosis through activating Caspase-3 signaling pathway.

Conclusions

The current study demonstrates that miR-665 facilitates LUSC cell proliferation and cell cycle transition by regulation of the Wnt5a/β-Catenin signaling pathway and represses cell apoptosis via modulation of Caspase-3 signaling pathway by directly targeting TRIM8. These findings suggest that miR-665 might be a potential new target for LUSC therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01913-z.

Emerging Roles of TRIM8 in Health and Disease

The superfamily of TRIM (TRIpartite Motif-containing) proteins is one of the largest groups of E3 ubiquitin ligases. Among them, interest in TRIM8 has greatly increased in recent years. In this review, we analyze the regulation of TRIM8 gene expression and how it is involved in many cell reactions in response to different stimuli such as genotoxic stress and attacks by viruses or bacteria, playing a central role in the immune response and orchestrating various fundamental biological processes such as cell survival, carcinogenesis, autophagy, apoptosis, differentiation and inflammation. Moreover, we show how TRIM8 functions are not limited to ubiquitination, and contrasting data highlight its role either as an oncogene or as a tumor suppressor gene, acting as a “double-edged weapon”. This is linked to its involvement in the selective regulation of three pivotal cellular signaling pathways: the p53 tumor suppressor, NF-κB and JAK-STAT pathways. Lastly, we describe how TRIM8 dysfunctions are linked to inflammatory processes, autoimmune disorders, rare developmental and cardiovascular diseases, ischemia, intellectual disability and cancer.

TRIM9 is involved in facilitating Vibrio parahaemolyticus infection by inhibition of relish pathway in Penaeus monodon

Tripartite motif-containing 9 (TRIM9) has been demonstrated to exert important roles in regulation of innate immune signaling. In this study, a novel TRIM9 homolog was identified from Penaeus monodon (named PmTRIM9). The open reading frame (ORF) of PmTRIM9 was 2064 bp, which encoding a 687-amino-acid polypeptide. Following Vibrio parahaemolyticus challenge, the expression levels of PmTRIM9 mRNA were significantly down-regulated in tested tissues. RNA interference and recombinant protein injection experiments were performed to explore the function of PmTRIM9, and the results showed it could facilitate V. parahaemolyticus replication and lead P. monodon more vulnerable to V. parahaemolyticus challenge. The dual-luciferase reporter assay showed that PmTRIM9 possessed the ability to inhibit the promoter activity in HEK293 T cells. Silencing of PmTRIM9 could increase the expression of the major NF-κB transcription factor, PmRelish. Further studies showed that knockdown of PmRelish promoted the V. parahaemolyticus infection and decreased the expression of specific antimicrobial peptides (AMPs), including PmCRU5, PmCRU7, PmALF6, PmALF3, PmLYZ and PmPEN5. However, knockdown of PmTRIM9 increased expression levels of the same AMPs, but except for PmCRU5, indicating that PmTRIM9 may negatively regulate the PmRelish-mediated expression of AMPs. All these results suggest that PmTRIM9 was involved in facilitating V. parahaemolyticus infection by inhibition of Relish pathway in P. monodon.

TRIMming Type I Interferon-Mediated Innate Immune Response in Antiviral and Antitumor Defense

The tripartite motif (TRIM) family comprises at least 80 members in humans, with most having ubiquitin or SUMO E3 ligase activity conferred by their N-terminal RING domain. TRIMs regulate a wide range of processes in ubiquitination- or sumoylation-dependent manners in most cases, and fewer as adaptors. Their roles in the regulation of viral infections, autophagy, cell cycle progression, DNA damage and other stress responses, and carcinogenesis are being increasingly appreciated, and their E3 ligase activities are attractive targets for developing specific immunotherapeutic strategies for immune diseases and cancers. Given their importance in antiviral immune response, viruses have evolved sophisticated immune escape strategies to subvert TRIM-mediated mechanisms. In this review, we focus on their regulation of IFN-I-mediated innate immune response, which plays key roles in antiviral and antitumor defense.

De novo TRIM8 variants impair its protein localization to nuclear bodies and cause developmental delay, epilepsy, and focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is the main pathology underlying steroid-resistant nephrotic syndrome (SRNS) and a leading cause of chronic kidney disease. Monogenic forms of pediatric SRNS are predominantly caused by recessive mutations, while the contribution of de novo variants (DNVs) to this trait is poorly understood. Using exome sequencing (ES) in a proband with FSGS/SRNS, developmental delay, and epilepsy, we discovered a nonsense DNV in TRIM8, which encodes the E3 ubiquitin ligase tripartite motif containing 8. To establish whether TRIM8 variants represent a cause of FSGS, we aggregated exome/genome-sequencing data for 2,501 pediatric FSGS/SRNS-affected individuals and 48,556 control subjects, detecting eight heterozygous TRIM8 truncating variants in affected subjects but none in control subjects (p = 3.28 × 10-11). In all six cases with available parental DNA, we demonstrated de novo inheritance (p = 2.21 × 10-15). Reverse phenotyping revealed neurodevelopmental disease in all eight families. We next analyzed ES from 9,067 individuals with epilepsy, yielding three additional families with truncating TRIM8 variants. Clinical review revealed FSGS in all. All TRIM8 variants cause protein truncation clustering within the last exon between residues 390 and 487 of the 551 amino acid protein, indicating a correlation between this syndrome and loss of the TRIM8 C-terminal region. Wild-type TRIM8 overexpressed in immortalized human podocytes and neuronal cells localized to nuclear bodies, while constructs harboring patient-specific variants mislocalized diffusely to the nucleoplasm. Co-localization studies demonstrated that Gemini and Cajal bodies frequently abut a TRIM8 nuclear body. Truncating TRIM8 DNVs cause a neuro-renal syndrome via aberrant TRIM8 localization, implicating nuclear bodies in FSGS and developmental brain disease.

Tripartite-motif family genes associated with cancer stem cells affect tumor progression and can assist in the clinical prognosis of kidney renal clear cell carcinoma

Ubiquitination is presently a hot topic in the field of oncology. The tripartite-motif (TRIM) family of proteins represents one of the largest classes of putative single protein RING-finger E3 ubiquitin ligases, which play an essential role in the ubiquitination of proteins in the body. At the same time, research related to cancer stem cells (CSCs) is increasing in popularity in the field of oncology. CSCs are potentially chemically resistant and can be selectively enriched in patients receiving chemotherapy, ultimately leading to adverse outcomes, such as treatment failure and cancer recurrence. There is a close relationship between multiple TRIM family genes and CSCs. Accumulating evidence suggests that TRIM family proteins are expressed in diverse human cancers and act as regulators of oncoproteins or tumor suppressor proteins. In this study, we used biological information to explore the potential function of TRIM family genes related to CSCs in the development of pan-cancer. Kidney renal clear cell carcinoma (KIRC) is one of the deadliest malignant tumors in the world. Owing to its complex molecular and cellular heterogeneity, the effectiveness of existing KIRC-related risk prediction models is not satisfactory at present. Therefore, we focused on the potential role of these TRIM family genes in KIRC and used seven TRIM family genes to establish a prognostic risk model. This model includes TRIM16, TRIM32, TRIM24, TRIM8, TRIM27, PML, and TRIM11. In conclusion, this study provides further insight into the prognosis of KIRC, which may guide treatment.

Focal segmental glomerulosclerosis and mild intellectual disability in a patient with a novel de novo truncating TRIM8 mutation

Mutations in the TRIM8 gene have been described in patients with severe developmental delay, intellectual disability and epilepsy. Only six patients have been described to date. All the previous mutations were truncating variants clustered in the C-terminus of the protein. A previous patient with TRIM8-related epileptic encephalopathy was reported to have nephrotic syndrome. Here we describe the clinical, radiological and histological features of an 8-year-old male patient with a TRIM8 mutation who, in contrast to previous patients, had only mild intellectual disability and well-controlled epilepsy. The patient was found to have proteinuria at 2 years of age. Renal biopsy findings were suggestive of focal segmental glomerulosclerosis. His kidney function declined and peritoneal dialysis was started at 5 years of age. He underwent renal transplant at 7 years of age. Trio-based whole genome sequencing identified a novel de novo heterozygous frameshift mutation in TRIM8 (NM_030912.2) c.1198_1220del, p.(Tyr400ArgfsTer2). This patient is further evidence that TRIM8 mutations cause a syndrome with both neurological and renal features. Our findings suggest the spectrum of TRIM8-related disease may be wider than previously thought with the possibility of milder neurodevelopmental problems and/or a more severe, progressive renal phenotype. We highlight the need for proteinuria screening in patients with TRIM8 mutations.

TRIM27 promotes IL-6-induced proliferation and inflammation factor production by activating STAT3 signaling in HaCaT cells

The IL-6/STAT3 signaling pathway is required for the development of psoriatic lesions, and tripartite motif-containing 27 (TRIM27) is a protein inhibitor of activated STAT3 (PIAS3)-interacting protein that could modulate IL-6-induced STAT3 activation. However, whether TRIM27 is associated with the IL-6/STAT3 signaling pathway in psoriasis remains enigmatic. TRIM27 expression and gene set enrichment analysis in patients with psoriasis were determined using bioinformatics. Human keratinocyte HaCaT cells treated with recombinant protein IL-6 (rh-IL-6) were transduced with lentivirus silencing TRIM27 and/or PIAS3 or, otherwise, transduced with lentivirus expressing TRIM27 and/or lentivirus silencing STAT3, or MG132, a proteasome-specific protease inhibitor. Cell proliferation and inflammation factor production were measured using Cell Counting Kit-8 and ELISA, respectively. TRIM27, proliferation marker protein Ki-67 (Ki67), phospho-STAT3 (p-STAT3), STAT3, and PIAS3 expressions were determined using real-time quantitative PCR, immunofluorescence staining, or Western blot analysis. Coimmunoprecipitation combined with ubiquitination analysis was performed to explore the interaction between TRIM27 and PIAS3. In the present study, TRIM27 expression was increased in psoriatic lesions, associated with the IL-6 signaling pathway, and induced by rh-IL-6 in a time-dependent manner. The increased cell proliferation, inflammation factor production, and expression of Ki67 and of p-STAT3 relative to STAT3 induced by rh-IL-6 and TRIM27 overexpression were significantly inhibited by TRIM27 silencing and STAT3 silencing, respectively. More importantly, TRIM27 interacted with PIAS3, and its overexpression promoted PIAS3 ubiquitination in HaCaT cells. PIAS3 silencing also significantly promoted TRIM27-dependent and IL6-induced STAT3 activation, cell proliferation, and inflammation factor production. In conclusion, our results highlight that TRIM27 expression is significantly increased by IL-6 and suggest a TRIM27/STAT3-dependent mechanism for regulation of inflammation and proliferation-associated development of psoriasis.

The role of TRIM family proteins in the regulation of cancer stem cell self-renewal

The tripartite-motif (TRIM) family of proteins represents one of the largest classes of putative single protein RING-finger E3 ubiquitin ligases. The members of this family are characterized by an N-terminal TRIM motif containing one RING-finger domain, one or two zinc-finger domains called B boxes (B1 box and B2 box), and a coiled-coil region. The TRIM motif can be found in isolation or in combination with a variety of C-terminal domains, and based on C-terminus, TRIM proteins are classified into 11 distinct groups. Because of the complex nature of TRIM proteins, they are implicated in a variety of cellular functions and biological processes, including regulation of cell proliferation, cell division and developmental processes, cancer transformation, regulation of cell metabolism, autophagocytosis, modification of chromatin status, regulation of gene transcription, post-translational modifications, and interactions with pathogens. Here, we demonstrate the specific activities of TRIM family proteins that contribute to the cancer stem cell phenotype. A growing body of evidence demonstrates that several TRIM members guarantee the acquisition of stem cell properties and the ability to sustain stem-like phenotype by cancer cells using distinct mechanisms. For other members, further work is needed to understand their full contribution to stem cell self-renewal. Identification of TRIM proteins that possess the potential to serve as therapeutic targets may result in the development of new therapeutic strategies. Finally, these strategies may result in the disruption of the machinery of stemness acquisition, which may prevent tumor growth, progression, and overcome the resistance to anticancer therapies.

TRIM8 is required for virus-induced IFN response in human plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) play a crucial role in antiviral innate immunity through their unique capacity to produce large amounts of type I interferons (IFNs) upon viral detection. Tripartite motif (TRIM) proteins have recently come forth as important modulators of innate signaling, but their involvement in pDCs has not been investigated. Here, we performed a rationally streamlined small interfering RNA (siRNA)-based screen of TRIM proteins in human primary pDCs to identify those that are critical for the IFN response. Among candidate hits, TRIM8 emerged as an essential regulator of IFN regulatory factor 7 (IRF7) function. Mechanistically, TRIM8 protects phosphorylated IRF7 (pIRF7) from proteasomal degradation in an E3 ubiquitin ligase-independent manner by preventing its recognition by the peptidyl-prolyl isomerase Pin1. Our findings uncover a previously unknown regulatory mechanism of type I IFN production in pDCs by which TRIM8 and Pin1 oppositely regulate the stability of pIRF7.

Targeting Chemoresistant Tumors: Could TRIM Proteins-p53 Axis Be a Possible Answer?

Chemosensitivity is a crucial feature for all tumours so that they can be successfully treated, but the huge heterogeneity of these diseases, to be intended both inter- and intra-tumour, makes it a hard-to-win battle. Indeed, this genotypic and phenotypic variety, together with the adaptability of tumours, results in a plethora of chemoresistance acquisition mechanisms strongly affecting the effectiveness of treatments at different levels. Tripartite motif (TRIM) proteins are shown to be involved in some of these mechanisms thanks to their E3-ubiquitin ligase activity, but also to other activities they can exert in several cellular pathways. Undoubtedly, the ability to regulate the stability and activity of the p53 tumour suppressor protein, shared by many of the TRIMs, represents the preeminent link between this protein family and chemoresistance. Indeed, they can modulate p53 degradation, localization and subset of transactivated target genes, shifting the cellular response towards a cytoprotective or cytotoxic reaction to whatever damage induced by therapy, sometimes in a cellular-dependent way. The involvement in other chemoresistance acquisition mechanisms, independent by p53, is known, affecting pivotal processes like PI3K/Akt/NF-κB signalling transduction or Wnt/beta catenin pathway, to name a few. Hence, the inhibition or the enhancement of TRIM proteins functionality could be worth investigating to better understand chemoresistance and as a strategy to increase effectiveness of anticancer therapies.

TRIM52 promotes colorectal cancer cell proliferation through the STAT3 signaling

Background

The tripartite motif (TRIM) family proteins are implicated in the pathogenesis of various human malignancies. The up-regulation and oncogenic roles of TRIM52 have been reported in hepatocellular carcinoma. In the current study, we aimed to examine its expression and possible function in colorectal cancer (CRC).

Method

Immunohistochemical staining or immunoblotting analysis was carried out to detect protein expression. Cell proliferation and apoptosis was evaluated by Cell Counting Kit-8 (CCK-8) and flow cytometry assay, respectively.

Results

TRIM52 expression was increased in 67.5% of CRC tissues (54/80) compared to matched normal colonic mucosa. TRIM52 expression was closely related with tumor size (p = 0.0376), tumor stage (p = 0.0227) and overall survival (p = 0.0177). Short hairpin RNAs (shRNAs) targeting TRIM52 had the potential anti-proliferative effects on CRC cell lines, SW480 and LoVo, by inducing cell apoptosis. In addition, an in vivo xenograft experiment confirmed the in vitro results. In addition, TRIM52 shRNAs decreased the phosphorylation of STAT3, but increased the protein expression of SHP2, a negative regulator of STAT3 phosphorylation. TRIM52 formed a complex with SHP2 and promoted the ubiquitination of SHP2. Furthermore, inhibition of the STAT3 signaling by AG490 in RKO cells significantly abolished the effects of TRIM52 overexpression on cell proliferation, apoptosis and STAT3 activation.

Conclusions

TRIM52 might exert oncogenic role in CRC via regulating the STAT3 signaling pathway.

TRIM14 promotes colorectal cancer cell migration and invasion through the SPHK1/STAT3 pathway

Background

Colorectal cancer (CRC) is one of the most lethal malignancies. Tripartite Motif Containing 14 (TRIM14) is a member of TRIM family proteins, which are involved in the pathogenesis of various cancers. This study aimed to investigate TRIM14 expression in CRC tissues, and its effects on the migration and invasion of CRC cell lines.

Methods

TRIM14 mRNA expression was detected by real-time PCR analysis. Cell migration and invasion were measured by Transwell assays. Protein expression was assessed by western blot analysis.

Results

The expression of TRIM14 was significantly higher in CRC tissues than in matched non-cancerous tissues. TRIM14 knockdown by specific short hairpin RNA (shRNA) attenuated CRC cell migration and invasion, whereas TRIM14 overexpression caused reverse effect. Moreover, TRIM14 positively regulated the protein levels of sphingosine kinase 1 (SPHK1) and phosphorylated STAT3 (p-STAT3), as well as the mRNA and protein expression of matrix metalloproteinase 2, MMP9 and vascular endothelial growth factor, which are transcriptional targets of the STAT3 signaling pathway. Importantly, the blockage of the SPHK1/STAT3 signaling pathway by SKI-II or AG490 could reverse the TRIM14-promoted CRC cell migration and invasion.

Conclusions

Our results reveal a critical role for TRIM14 in promoting migration and invasion of CRC cells, and suggest TRIM14 may serve as a potential molecular target to prevent CRC metastasis.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0701-1) contains supplementary material, which is available to authorized users.

TRIM8-driven transcriptomic profile of neural stem cells identified glioma-related nodal genes and pathways

BACKGROUND

We recently reported TRIM8, encoding an E3 ubiquitin ligase, as a gene aberrantly expressed in glioblastoma whose expression suppresses cell growth and induces a significant reduction of clonogenic potential in glioblastoma cell lines.

METHODS

we provided novel insights on TRIM8 functions by profiling the transcriptome of TRIM8-expressing primary mouse embryonal neural stem cells by RNA-sequencing and bioinformatic analysis. Functional analysis including luciferase assay, western blot, PCR arrays, Real time quantitative PCR were performed to validate the transcriptomic data.

RESULTS

Our study identified enriched pathways related to the neurotransmission and to the central nervous system (CNS) functions, including axonal guidance, GABA receptor, Ephrin B, synaptic long-term potentiation/depression, and glutamate receptor signalling pathways. Finally, we provided additional evidence about the existence of a functional interactive crosstalk between TRIM8 and STAT3.

CONCLUSIONS

Our results substantiate the role of TRIM8 in the brain functions through the dysregulation of genes involved in different CNS-related pathways, including JAK-STAT.

GENERAL SIGNIFICANCE

This study provides novel insights on the physiological TRIM8 function by profiling for the first time the primary Neural Stem Cell over-expressing TRIM8 by using RNA-Sequencing methodology.

Expression and the potential functions of TRIM32 in lung cancer tumorigenesis

TRIM32 is a member of the tripartite motif (TRIM) family, which has been associated with tumorigenesis. However, its expression and potential functional role(s) in lung cancer progression have not been fully understood. To evaluate the relationship between the expression of TRIM32 and the prognosis of patients with lung cancer, an independent data set (The Human Protein Atlas website) was introduced. The expression and function analysis of TRIM32 in lung cancer cell lines were also performed by using cell counting kit-8, flow cytometry, transwell, real-time polymerase chain reaction and Western blot analysis. Our data showed that TRIM32 was overexpressed in lung cancer tissues and cell lines and was associated with a poor prognosis. TRIM32 silencing inhibited cell proliferation, migration, invasion, adhesion, and the activation of janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling. The results showed knockdown of TRIM32 in NCI-H446 cells also inhibited cell growth in nude mice in the xenograft model. Additionally, TRIM32 overexpression promoted lung cancer cell proliferation and motility and mediated the expression of Bax, Bcl-2, cleaved caspase-3, matrix metalloproteinase-2 (MMP-2) and MMP-9 were inhibited by JAK2/STAT3 signaling inhibitor (AG490). Taken together, our findings suggest that TRIM32 may regulate lung cancer cell proliferation, apoptosis, and motility through activating the JAK2/STAT3-signaling pathway and may be a novel and promising target for lung cancer.

Post-transcriptional regulation of PIAS3 expression by miR-18a in malignant mesothelioma

Protein inhibitor of activated STAT3 (PIAS3) is an endogenous suppressor of signal transducer and activator of transcription 3 (STAT3) signaling. By directly interacting with phosphorylated STAT3, PIAS3 can block the downstream transcriptional activity of STAT3, which is hyper-activated in various cancers. We previously reported that in malignant mesothelioma (MM), low PIAS3 expression is associated with increased STAT3 activation and correlates with poor patient survival, yet the regulatory mechanism(s) governing PIAS3 expression in MM remain unclear. Here, we demonstrate that PIAS3 protein expression does not correlate with its mRNA level in MM cell lines, indicating that PIAS3 expression is regulated at a post-transcriptional level. Inhibition of proteasomal degradation with MG132 (10 μm) or bortezomib (1 μm), alone and in combination, did not increase PIAS3 protein levels; furthermore, inhibition of protein synthesis by cycloheximide treatment did not decrease PIAS3 levels within 48 h, suggesting that PIAS3 expression is not actively regulated at a post-translational level. To determine whether miRNA (miRs) can translationally regulate PIAS3 expression, we combined miR microarray analysis with bioinformatic screening to identify candidate miRs, in MM cell lines with low PIAS3 expression, followed by luciferase reporter assays to validate miR regulation of the PIAS3 3'UTR. We identified miR-18a as a suppressor of PIAS3 expression that is upregulated in MM cells and whose inhibition can increase PIAS3 expression and suppress STAT3 activity. Moreover, we showed that miR-18a inhibition can decrease MM cell viability and that its expression is negatively correlated with MM patient survival. Taken together, these results suggest that targeting miR-18a may have therapeutic benefit in MM.

Nuclear Smad6 promotes gliomagenesis by negatively regulating PIAS3-mediated STAT3 inhibition

To date, the molecular mechanism underlying constitutive signal transducer and activator of transcription 3 (STAT3) activation in gliomas is largely unclear. In this study, we report that Smad6 is overexpressed in nuclei of glioma cells, which correlates with poor patient survival and regulates STAT3 activity via negatively regulating the Protein Inhibitors of Activated STAT3 (PIAS3). Mechanically, Smad6 interacts directly with PIAS3, and this interaction is mediated through the Mad homology 2 (MH2) domain of Smad6 and the Ring domain of PIAS3. Smad6 recruits Smurf1 to facilitate PIAS3 ubiquitination and degradation, which also depends on the MH2 domain and the PY motif of Smad6. Consequently, Smad6 reduces PIAS3-mediated STAT3 inhibition and promotes glioma cell growth and stem-like cell initiation. Moreover, the Smad6 MH2 transducible protein restores PIAS3 expression and subsequently reduces gliomagenesis. Collectively, we conclude that nuclear-Smad6 enhances glioma development by inducing PIAS3 degradation and subsequent STAT3 activity upregulation.

Intracellular Antiviral Immunity

Innate immunity is traditionally thought of as the first line of defense against pathogens that enter the body. It is typically characterized as a rather weak defense mechanism, designed to restrict pathogen replication until the adaptive immune response generates a tailored response and eliminates the infectious agent. However, intensive research in recent years has resulted in better understanding of innate immunity as well as the discovery of many effector proteins, revealing its numerous powerful mechanisms to defend the host. Furthermore, this research has demonstrated that it is simplistic to strictly separate adaptive and innate immune functions since these two systems often work synergistically rather than sequentially. Here, we provide a broad overview of innate pattern recognition receptors in antiviral defense, with a focus on the TRIM family, and discuss their signaling pathways and mechanisms of action with special emphasis on the intracellular antibody receptor TRIM21.

TRIM8: Making the Right Decision between the Oncogene and Tumour Suppressor Role

The TRIM8/GERP protein is a member of the TRIM family defined by the presence of a common domain structure composed of a tripartite motif including a RING-finger, one or two B-box domains, and a coiled-coil motif. The TRIM8 gene maps on chromosome 10 within a region frequently found deleted and rearranged in tumours and transcribes a 3.0-kB mRNA. Its expression is mostly ubiquitously in murine and human tissues, and in epithelial and lymphoid cells, it can be induced by IFNγ. The protein spans 551 aa and is highly conserved during evolution. TRIM8 plays divergent roles in many biological processes, including important functions in inflammation and cancer through regulating various signalling pathways. In regulating cell growth, TRIM8 exerts either a tumour suppressor action, playing a prominent role in regulating p53 tumour suppressor activity, or an oncogene function, through the positive regulation of the NF-κB pathway. The molecular mechanisms underlying this dual role in human cancer will be discussed in depth in this review, and it will highlight the challenge and importance of developing novel therapeutic strategies specifically aimed at blocking the pro-oncogenic arm of the TRIM8 signalling pathway without affecting its tumour suppressive effects.

The TRIMendous Role of TRIMs in Virus-Host Interactions

The innate antiviral response is integral in protecting the host against virus infection. Many proteins regulate these signaling pathways including ubiquitin enzymes. The ubiquitin-activating (E1), -conjugating (E2), and -ligating (E3) enzymes work together to link ubiquitin, a small protein, onto other ubiquitin molecules or target proteins to mediate various effector functions. The tripartite motif (TRIM) protein family is a group of E3 ligases implicated in the regulation of a variety of cellular functions including cell cycle progression, autophagy, and innate immunity. Many antiviral signaling pathways, including type-I interferon and NF-κB, are TRIM-regulated, thus influencing the course of infection. Additionally, several TRIMs directly restrict viral replication either through proteasome-mediated degradation of viral proteins or by interfering with different steps of the viral replication cycle. In addition, new studies suggest that TRIMs can exert their effector functions via the synthesis of unconventional polyubiquitin chains, including unanchored (non-covalently attached) polyubiquitin chains. TRIM-conferred viral inhibition has selected for viruses that encode direct and indirect TRIM antagonists. Furthermore, new evidence suggests that the same antagonists encoded by viruses may hijack TRIM proteins to directly promote virus replication. Here, we describe numerous virus–TRIM interactions and novel roles of TRIMs during virus infections.

TRIM proteins and diseases

Ubiquitination is one of the posttranslational modifications that regulates a number of intracellular events including signal transduction, protein quality control, transcription, cell cycle, apoptosis and development. The ubiquitin system functions as a garbage machine to degrade target proteins and as a regulator for several signalling pathways. Biochemical reaction of ubiquitination requires several enzymes including E1, E2 and E3, and E3 ubiquitin ligases play roles as receptors for recognizing target proteins. Most of the tripartite motif (TRIM) proteins are E3 ubiquitin ligases. Recent studies have shown that some TRIM proteins function as important regulators for a variety of diseases including cancer, inflammatory diseases, infectious diseases, neuropsychiatric disorders, chromosomal abnormalities and developmental diseases. In this review, we summarize the involvement of TRIM proteins in the aetiology of various diseases.

The E3 ligase tripartite motif 8 targets TAK1 to promote insulin resistance and steatohepatitis

Tripartite motif 8 (TRIM8), an E3 ligase ubiquitously expressed in various cells, is closely involved in innate immunity. However, its role in nonalcoholic steatohepatitis is largely unknown. Here, we report evidence that TRIM8 is a robust enhancer of steatohepatitis and its complications induced by a high-fat diet or a genetic deficiency (ob/ob). Using gain-of-function and loss-of-function approaches, we observed dramatic exacerbation of insulin resistance, hepatic steatosis, inflammation, and fibrosis by hepatocyte-specific TRIM8 overexpression, whereas deletion or down-regulation of TRIM8 in hepatocytes led to a completely opposite phenotype. Furthermore, investigations of the underlying mechanisms revealed that TRIM8 directly binds to and ubiquitinates transforming growth factor-beta-activated kinase 1, thus promoting its phosphorylation and the activation of downstream c-Jun N-terminal kinase/p38 and nuclear factor κB signaling. Importantly, the participation of TRIM8 in human nonalcoholic fatty liver disease and nonalcoholic steatohepatitis was verified on the basis of its dramatically increased expression in the livers of these patients, suggesting a promising development of TRIM8 disturbance for the treatment of nonalcoholic steatohepatitis-related metabolic disorders.

CONCLUSION

The E3 ligase TRIM8 is a potent regulator that exacerbates steatohepatitis and metabolic disorders dependent on its binding and ubiquitinating capacity on transforming growth factor-beta-activated kinase 1. (Hepatology 2017;65:1492-1511).

miR-182 promotes tumor growth and increases chemoresistance of human anaplastic thyroid cancer by targeting tripartite motif 8

Chemotherapy is one of the most effective forms of cancer treatment and has been used in the treatment of various malignant tumors. We have gained significant insight into the mechanisms of chemoresistance but the details of the molecular mechanisms remain unclear. In the present study, we found that tripartite motif 8 (TRIM8) expression was downregulated in anaplastic thyroid cancer (ATC) tissues and cell lines. This downregulation of TRIM8 was significantly correlated with the upregulation of miR-182 in human ATC tissues. Bioinformatic analysis and luciferase reporter assays identified TRIM8 as a direct target of miR-182 in ATC. A functional assay using an MTT assay and colony formation showed that miR-182 induced cellular growth by repressing TRIM8 expression. Additionally, overexpressed miR-182 contributed to the chemoresistance of ATC cells by the repression of TRIM8 expression. In conclusion, these results demonstrate that miR-182/TRIM8 may be a therapeutic target for the treatment of chemoresistant human thyroid papillary cancer.

Expression profiling of TRIM protein family in THP1-derived macrophages following TLR stimulation

Activated macrophages play an important role in many inflammatory diseases including septic shock and atherosclerosis. However, the molecular mechanisms limiting macrophage activation are not completely understood. Members of the tripartite motif (TRIM) family have recently emerged as important players in innate immunity and antivirus. Here, we systematically analyzed mRNA expressions of representative TRIM molecules in human THP1-derived macrophages activated by different toll-like receptor (TLR) ligands. Twenty-nine TRIM members were highly induced (>3 fold) by one or more TLR ligands, among which 19 of them belong to TRIM C-IV subgroup. Besides TRIM21, TRIM22 and TRIM38 were shown to be upregulated by TLR3 and TLR4 ligands as previous reported, we identified a novel group of TRIM genes (TRIM14, 15, 31, 34, 43, 48, 49, 51 and 61) that were significantly up-regulated by TLR3 and TLR4 ligands. In contrast, the expression of TRIM59 was down-regulated by TLR3 and TLR4 ligands in both human and mouse macrophages. The alternations of the TRIM proteins were confirmed by Western blot. Finally, overexpression of TRIM59 significantly suppressed LPS-induced macrophage activation, whereas siRNA-mediated knockdown of TRIM59 enhanced LPS-induced macrophage activation. Taken together, the study provided an insight into the TLR ligands-induced expressions of TRIM family in macrophages.

TRIM8 regulates stemness in glioblastoma through PIAS3-STAT3

Glioblastoma (GBM) is the most malignant form of primary brain tumor, and GBM stem-like cells (GSCs) contribute to the rapid growth, therapeutic resistance, and clinical recurrence of these fatal tumors. STAT3 signaling supports the maintenance and proliferation of GSCs, yet regulatory mechanisms are not completely understood. Here, we report that tri-partite motif-containing protein 8 (TRIM8) activates STAT3 signaling to maintain stemness and self-renewing capabilities of GSCs. TRIM8 (also known as 'glioblastoma-expressed ring finger protein') is expressed equally in GBM and normal brain tissues, despite its hemizygous deletion in the large majority of GBMs, and its expression is highly correlated with stem cell markers. Experimental knockdown of TRIM8 reduced GSC self-renewal and expression of SOX2, NESTIN, and p-STAT3, and promoted glial differentiation. Overexpression of TRIM8 led to higher expression of p-STAT3, c-MYC, SOX2, NESTIN, and CD133, and enhanced GSC self-renewal. We found that TRIM8 activates STAT3 by suppressing the expression of PIAS3, an inhibitor of STAT3, most likely through E3-mediated ubiquitination and proteasomal degradation. Interestingly, we also found that STAT3 activation upregulates TRIM8, providing a mechanism for normalized TRIM8 expression in the setting of hemizygous gene deletion. These data demonstrate that bidirectional TRIM8-STAT3 signaling regulates stemness in GSC.

Tripartite Motif 8 Contributes to Pathological Cardiac Hypertrophy Through Enhancing Transforming Growth Factor β–Activated Kinase 1–Dependent Signaling Pathways

Tripartite motif (TRIM) 8 functions as an E3 ubiquitin ligase, interacting with and ubiquitinating diverse substrates, and is implicated in various pathological processes. However, the function of TRIM8 in the heart remains largely uncharacterized. This study aims to explore the role of TRIM8 in the development of pathological cardiac hypertrophy. Mice and isolated neonatal rat cardiomyocytes overexpressing or lacking TRIM8 were examined in several experiments. The effect of aortic banding–induced cardiac hypertrophy was analyzed by echocardiographic, pathological and molecular analyses. Our results indicated that the TRIM8 overexpression in hearts exacerbated the cardiac hypertrophy triggered by aortic banding. In contrast, the development of pathological cardiac hypertrophy was profoundly blocked in TRIM8-deficient hearts. Mechanistically, our study suggests that TRIM8 may elicit cardiodetrimental effects by promoting the activation of transforming growth factor β–activated kinase 1 (TAK1)-p38/JNK signaling pathways. Similar results were observed in cultured neonatal rat cardiomyocytes treated with angiotensin II. The rescue experiments using the TAK1-specific inhibitor 5z-7-ox confirmed the requirement of TAK1 activation in TRIM8-mediated pathological cardiac hypertrophy. Furthermore, TRIM8 contributed to TAK1 activation by binding to and promoting TAK1 ubiquitination. In conclusion, our study demonstrates that TRIM8 plays a deleterious role in pressure overload–induced cardiac hypertrophy by accelerating the activation of TAK1-dependent signaling pathways.

Fish interferon-stimulated genes: The antiviral effectors

Type I interferons (IFN) are the cornerstone cytokine of innate antiviral immunity. In response to a viral infection, IFN signaling results in the expression of a diverse group of genes known as interferon-stimulated genes (ISGs). These ISGs are responsible for interfering with viral replication and infectivity, helping to limit viral infection within a cell. In mammals, many antiviral effector ISGs have been identified and the antiviral mechanisms are at least partially elucidated. In fish fewer ISGs have been identified and while there is evidence they limit viral infection, almost nothing is known of their respective antiviral mechanisms. This review discusses seven ISGs common to mammals and fish and three ISGs that are unique to fish. The lack of understanding regarding fish ISG's antiviral effector functions is highlighted and draws attention to the need for research in this aspect of aquatic innate immunity.

Regulation of T helper cell differentiation by E3 ubiquitin ligases and deubiquitinating enzymes

CD4 T cells are essential components of adaptive immunity and play a critical role in anti-pathogenic or anti-tumor responses as well as autoimmune and allergic diseases. Naive CD4 T cells differentiate into distinct subsets of T helper (Th) cells by various signals including TCR, costimulatory and cytokine signals. Accumulating evidence suggests that these signaling pathways are critically regulated by ubiquitination and deubiquitination, two reversible posttranslational modifications mediated by E3 ubiquitin ligases and deubiquitinating enzymes (DUBs), respectively. In this review, we briefly introduce the signaling pathways that control the differentiation of Th cells and then focused on the roles of E3s- and DUBs-mediated ubiquitin modification or demodification in regulating Th cell differentiation.