The TRIM proteins in cancer: from expression to emerging regulatory mechanisms

New clinical evidence suggests that dysregulation of the ubiquitin-mediated destruction of tumor suppressors or oncogene products is probably engaged in the etiology of leukemia and carcinoma. The superfamily of tripartite motif (TRIM)-containing protein family is among the biggest recognized single protein RING finger E3 ubiquitin ligases that are considered vital carcinogenesis regulators, which is not shocking since TRIM proteins are engaged in various biological processes, including cell growth, development, and differentiation; hence, TRIM proteins’ alterations may influence apoptosis, cell proliferation, and transcriptional regulation. In this review article, the various mechanisms through which TRIM proteins exert their role in the most prevalent malignancies including lung, prostate, colorectal, liver, breast, brain cancer, and leukemia are summarized.

TRIMs: Generalists Regulating the NLRP3 Inflammasome Signaling Pathway.

Inflammation is a double-edged sword. The moderate inflammatory response is a fundamental defense mechanism produced by the body's resistance to dangerous stimuli and a repair process of the body itself. Increasing studies have confirmed that the overactivation of the inflammasome is involved in the occurrence and development of inflammatory diseases. Strictly controlling the overactivation of the inflammasome and preventing excessive inflammatory response have always been the research focus on inflammatory diseases. However, the endogenous regulatory mechanism of inflammasome is not completely clear. The tripartite motif (TRIM) protein is one of the members of E3 ligases in the process of ubiquitination. The universality and importance of the functions of TRIM members are recognized, including the regulation of inflammatory response. This article will focus on research on the relationship between TRIMs and NLRP3 Inflammasome, which may help us make some references for future related research and the discovery of treatment methods.

The TRIM proteins in cancer: from expression to emerging regulatory mechanisms.

New clinical evidence suggests that dysregulation of the ubiquitin-mediated destruction of tumor suppressors or oncogene products is probably engaged in the etiology of leukemia and carcinoma. The superfamily of tripartite motif (TRIM)-containing protein family is among the biggest recognized single protein RING finger E3 ubiquitin ligases that are considered vital carcinogenesis regulators, which is not shocking since TRIM proteins are engaged in various biological processes, including cell growth, development, and differentiation; hence, TRIM proteins' alterations may influence apoptosis, cell proliferation, and transcriptional regulation. In this review article, the various mechanisms through which TRIM proteins exert their role in the most prevalent malignancies including lung, prostate, colorectal, liver, breast, brain cancer, and leukemia are summarized.

TRIM59 promotes osteosarcoma progression via activation of STAT3.

Osteosarcoma (OS) is a common, highly malignant bone tumor. Tripartite motif-containing protein 59 (TRIM59) has been identified as a potential oncogenic protein involved in the initiation and progression of various human carcinomas. Nonetheless, the possible roles and molecular mechanisms of action of TRIM59 in OS remain unclear. In this study, we found that TRIM59 expression levels were frequently upregulated in OS tissues and cell lines. TRIM59 knockdown significantly suppressed the proliferation, migration, and invasion of OS cells and promoted OS cell apoptosis, whereas TRIM59 overexpression had the opposite effects. In vivo experiments demonstrated that TRIM59 knockdown suppressed OS tumor growth and metastasis in vivo. Furthermore, we found that TRIM59 directly interacted with phospho-STAT3 in OS cells. The downregulation of STAT3 levels attenuated TRIM59-induced cell proliferation and invasion. Taken together, our results indicate that TRIM59 promoted OS progression via STAT3 activation. Therefore, our study may provide a novel therapeutic target for OS.

Biochemical strategies of E3 ubiquitin ligases target viruses in critical diseases.

Viruses are known to cause various diseases in human and also infect other species such as animal plants, fungi, and bacteria. Replication of viruses depends upon their interaction with hosts. Human cells are prone to such unwanted viral infections. Disintegration and reconstitution require host machinery and various macromolecules like DNA, RNA, and proteins are invaded by viral particles. E3 ubiquitin ligases are known for their specific function, that is, recognition of their respective substrates for intracellular degradation. Still, we do not understand how ubiquitin proteasome system-based enzymes E3 ubiquitin ligases do their functional interaction with different viruses. Whether E3 ubiquitin ligases help in the elimination of viral components or viruses utilize their molecular capabilities in their intracellular propagation is not clear. The first time our current article comprehends fundamental concepts and new insights on the different viruses and their interaction with various E3 Ubiquitin Ligases. In this review, we highlight the molecular pathomechanism of viruses linked with E3 Ubiquitin Ligases dependent mechanisms. An enhanced understanding of E3 Ubiquitin Ligase-mediated removal of viral proteins may open new therapeutic strategies against viral infections.

Tripartite motif 16 ameliorates nonalcoholic steatohepatitis by promoting the degradation of phospho-TAK1.

Nonalcoholic steatohepatitis (NASH)-related hepatocellular carcinoma and liver disorders have become the leading causes for the need of liver transplantation in developed countries. Lipotoxicity plays a central role in NASH progression by causing endoplasmic reticulum stress and disrupting protein homeostasis. To identify key molecules that mitigate the detrimental consequences of lipotoxicity, we performed integrative multiomics analysis and identified the E3 ligase tripartite motif 16 (TRIM16) as a candidate molecule. In particular, we found that lipid accumulation and inflammation in a mouse NASH model is mitigated by TRIM16 overexpression but aggravated by its depletion. Multiomics analysis showed that TRIM16 suppressed NASH progression by attenuating the activation of the mitogen-activated protein kinase (MAPK) signaling pathway; specifically, by preferentially interacting with phospho-TAK1 to promote its degradation. Together, these results identify TRIM16 as a promising therapeutic target for the treatment of NASH.

Tripartite Motif 22 (TRIM22) protein restricts herpes simplex virus 1 by epigenetic silencing of viral immediate-early genes.

Intrinsic resistance is a crucial line of defense against virus infections, and members of the Tripartite Ring Interaction Motif (TRIM) family of proteins are major players in this system, such as cytoplasmic TRIM5α or nuclear promyelocytic leukemia (PML/TRIM19) protein. Previous reports on the antiviral function of another TRIM protein, TRIM22, emphasized its innate immune role as a Type I and Type II interferon-stimulated gene against RNA viruses. This study shows that TRIM22 has an additional intrinsic role against DNA viruses. Here, we report that TRIM22 is a novel restriction factor of HSV-1 and limits ICP0-null virus replication by increasing histone occupancy and heterochromatin, thereby reducing immediate-early viral gene expression. The corresponding wild-type equivalent of the virus evades the TRIM22-specific restriction by a mechanism independent of ICP0-mediated degradation. We also demonstrate that TRIM22 inhibits other DNA viruses, including representative members of the ß- and γ- herpesviruses. Allelic variants in TRIM22 showed different degrees of anti-herpesviral activity; thus, TRIM22 genetic variability may contribute to the varying susceptibility to HSV-1 infection in humans. Collectively, these results argue that TRIM22 is a novel restriction factor and expand the list of restriction factors functioning in the infected cell nucleus to counter DNA virus infection.

The role of TRIM family proteins in autophagy, pyroptosis, and diabetes mellitus.

The ubiquitin-proteasome system, which is one of the systems for cell protein homeostasis and degradation, happens through the ordered and coordinated action of three types of enzymes, E1 ubiquitin-activating enzyme, E2 ubiquitin-carrier enzyme, E3 ubiquitin-protein ligase. Tripartite motif-containing (TRIM) family proteins are the richest subfamily of really interesting new gene E3 ubiquitin ligases, which play a critical role not only in many biological processes, including proliferation, apoptosis, pyroptosis, innate immunity, and autophagy, but also many diseases like cancer, diabetes mellitus, and neurodegenerative disease. Increasing evidence suggests that TRIM family proteins play a vital role in modulating autophagy, pyroptosis, and diabetes mellitus. The aim of this review is to discuss the role of TRIM proteins in the regulation of autophagy, pyroptosis, diabetes mellitus, and diabetic complications.

LncRNA NEAT1 acts as a key regulator of cell apoptosis and inflammatory response by the miR-944/TRIM37 axis in acute lung injury.

Acute lung injury (ALI), a common complication of sepsis, is characterized by the impairment and injury of pulmonary function. The nuclear factor kappa-B (NF-κB) pathway is activated in ALI. Tripartite motif-containing 37 (TRIM37) can activate the NF-κB pathway and is closely associated with inflammation. The purpose of our study is to reveal the role of TRIM37 in ALI. The present study revealed that TRIM37 presented high levels in lung tissues of ALI mice, and knockdown of TRIM37 alleviated lipopolysaccharide (LPS)-induced lung injury, inflammatory response, and cell apoptosis in vivo. In addition, knockdown of TRIM37 inhibited the inflammatory response, and cell apoptosis of LPS-treated WI-38 cells. Mechanistically, miR-944 was identified to bind with and negatively regulate TRIM37. Furthermore, NEAT1 was indicated to act as a competitive endogenous RNA to promote TRIM37 expression by sequestering miR-944. Detailly, NEAT1 bound with miR-944, negatively modulated miR-944 expression, and positively modulated TRIM37 expression. The rescue assays suggested that overexpression of TRIM37 rescued the influence of NEAT1 knockdown on cell apoptosis and inflammatory response. Overall, NEAT1 facilitated cell apoptosis and inflammatory response of WI-38 cells by the miR-944/TRIM37 axis in sepsis-induced ALI, implying that NEAT1 may provide a novel insight for the treatment of sepsis-induced ALI.

The TRIM9/TRIM67 neuronal interactome reveals novel activators of morphogenesis.

TRIM9 and TRIM67 are neuronally enriched E3 ubiquitin ligases essential for appropriate morphogenesis of cortical and hippocampal neurons and fidelitous responses to the axon guidance cue netrin-1. Deletion of murine Trim9 or Trim67 results in neuroanatomical defects and striking behavioral deficits, particularly in spatial learning and memory. TRIM9 and TRIM67 interact with cytoskeletal and exocytic proteins, but the full interactome is not known. Here we performed the unbiased proximity-dependent biotin identification (BioID) approach to define TRIM9 and TRIM67 protein-protein proximity network in developing cortical neurons and identified putative neuronal TRIM interaction partners. Candidates included cytoskeletal regulators, cytosolic protein transporters, exocytosis and endocytosis regulators, and proteins necessary for synaptic regulation. A subset of high-priority candidates was validated, including Myo16, Coro1A, MAP1B, ExoC1, GRIP1, PRG-1, and KIF1A. For a subset of validated candidates, we utilized total internal reflection fluorescence microscopy to demonstrate dynamic colocalization with TRIM proteins at the axonal periphery, including at the tips of filopodia. Further analysis demonstrated that the RNA interference-based knockdown of the unconventional myosin Myo16 in cortical neurons altered growth cone filopodia density and axonal branching patterns in a TRIM9- and netrin-1-dependent manner. Future analysis of other validated candidates will likely identify novel proteins and mechanisms by which TRIM9 and TRIM67 regulate neuronal form and function. [Media: see text].

Tripartite Motif Containing 52 Positively Regulates NF-κB Signaling by Promoting IκBα Ubiquitination in Lipopolysaccharide-Treated Microglial Cell Activation.

BACKGROUND Microglial cell activation is the first response to spinal cord injury (SCI). The purpose of the study was to investigate the role and mechanism of tripartite motif containing 52 (TRIM52) in microglial cell activation and the inflammatory response. MATERIAL AND METHODS The cerebral cortex was isolated in rats, and primary microglial cells were subsequently incubated for 7 to 9 days and activated by lipopolysaccharide (LPS). TRIM52 overexpression and interference lentivirus were constructed, and primary microglial cells were transfected. Cytokine levels of interleukin-1ß and tumor necrosis factor-a were detected using enzyme-linked immunosorbent assay kits. TRIM52 mRNA expression and protein levels were examined by real-time polymerase chain reaction and nuclear factor-kappa B (NF-kappaB) and inhibitory kappa B-alpha (IkappaBalpha) protein expression were examined by western blot. The interaction between TRIM52 and IkappaBalpha was analyzed by co-immunoprecipitation (Co-IP) detection. Microglial marker Iba-1 and microglial cell activation marker OX-42 were detected by immunofluorescent staining. RESULTS Primary rat microglial cells were successfully isolated and activated by LPS. The expression levels of cytokines and TRIM52 and nuclear accumulation of NF-kappaB in microglial cells all increased in a dose-dependent manner with LPS. Cytokine and nuclear NF-kappaB levels decreased after TRIM52 knockdown, while the opposite expression pattern was found in microglial cells transfected with TRIM52 gene overexpression lentivirus. Co-IP revealed the association between TRIM52 and IkappaBalpha, and overexpressed TRIM52 promoted the ubiquitination of IkappaBalpha and significantly reduced its protein expression. CONCLUSIONS TRIM52 activated the NF-kappaB signaling pathway by promoting IkappaBalpha ubiquitination, thereby regulating LPS-induced microglial cell activation and the inflammatory response.

A non-canonical role for the autophagy machinery in anti-retroviral signaling mediated by TRIM5α.

TRIM5α is a key cross-species barrier to retroviral infection, with certain TRIM5 alleles conferring increased risk of HIV-1 infection in humans. TRIM5α is best known as a species-specific restriction factor that directly inhibits the viral life cycle. Additionally, it is also a pattern-recognition receptor (PRR) that activates inflammatory signaling. How TRIM5α carries out its multi-faceted actions in antiviral defense remains incompletely understood. Here, we show that proteins required for autophagy, a cellular self-digestion pathway, play an important role in TRIM5α's function as a PRR. Genetic depletion of proteins involved in all stages of the autophagy pathway prevented TRIM5α-driven expression of NF-κB and AP1 responsive genes. One of these genes is the preeminent antiviral cytokine interferon ß (IFN-ß), whose TRIM5-dependent expression was lost in cells lacking the autophagy proteins ATG7, BECN1, and ULK1. Moreover, we found that the ability of TRIM5α to stimulate IFN-ß expression in response to recognition of a TRIM5α-restricted HIV-1 capsid mutant (P90A) was abrogated in cells lacking autophagy factors. Stimulation of human macrophage-like cells with the P90A virus protected them against subsequent infection with an otherwise resistant wild type HIV-1 in a manner requiring TRIM5α, BECN1, and ULK1. Mechanistically, TRIM5α was attenuated in its ability to activate the kinase TAK1 in autophagy deficient cells, and both BECN1 and ATG7 contributed to the assembly of TRIM5α-TAK1 complexes. These data demonstrate a non-canonical role for the autophagy machinery in assembling antiviral signaling complexes and in establishing a TRIM5α-dependent antiviral state.

TRIM32 regulates mitochondrial mediated ROS levels and sensitizes the oxidative stress induced cell death.

Emerging evidence suggests that ubiquitin mediated post translational modification is a critical regulatory process involved in diverse cellular pathways including cell death. During ubiquitination, E3 ligases recognize target proteins and determine the topology of ubiquitin chains. Recruitment of E3 ligases to targets proteins under stress conditions including oxidative stress and their implication in cell death have not been systemically explored. In the present study, we characterized the role of TRIM32 as an E3 ligase in regulation of oxidative stress induced cell death. TRIM32 is ubiquitously expressed in cell lines of different origin and form cytoplasmic speckle like structures that transiently interact with mitochondria under oxidative stress conditions. The ectopic expression of TRIM32 sensitizes cell death induced by oxidative stress whereas TRIM32 knockdown shows a protective effect. The turnover of TRIM32 is enhanced during oxidative stress and its expression induces ROS generation, loss of mitochondrial transmembrane potential and decrease in complex-I activity. The pro-apoptotic effect was rescued by pan-caspase inhibitor or antioxidant treatment. E3 ligase activity of TRIM32 is essential for oxidative stress induced apoptotic cell death. Furthermore, TRIM32 decreases X-linked inhibitor of apoptosis (XIAP) level and overexpression of XIAP rescued cells from TRIM32 mediated oxidative stress and cell death. Overall, the results of this study provide the first evidence supporting the role of TRIM32 in regulating oxidative stress induced cell death, which has implications in numerous pathological conditions including cancer and neurodegeneration.

TRIM31 inhibits NLRP3 inflammasome and pyroptosis of retinal pigment epithelial cells through ubiquitination of NLRP3.

NOD-like receptor protein 3 (NLRP3) is associated with age-related macular degeneration (AMD). Retinal pigment epithelial (RPE) cells serve as the immune defense of macula, and their dysfunction causes clinically relevant changes in AMD. In the present study, oxidized low-density lipoprotein (ox-LDL) activated the NLRP3 inflammasome in human RPE cell line ARPE-19. Our data showed that the expression of NLRP3, interleukin-1ß (IL-1ß), and caspase-1 and the release of IL-1ß in ARPE-19 cells were substantially increased by ox-LDL, whereas the addition of NLRP3 inhibitor INF39 dose-dependently reversed the effect of ox-LDL. Overexpression of tripartite motif-containing protein 31 (TRIM31) also suppressed the effect of ox-LDL in ARPE-19 cells. TRIM31 knockdown had similar effects with ox-LDL but INF39 could block the effect of TRIM31 knockdown. Moreover, TRIM31 could interact with NLRP3 in ARPE-19 cells. Overexpression of TRIM31 increased NLRP3 ubiquitination. In conclusion, the results propose that TRIM31 could enhance NLRP3 ubiquitination, therefore inhibiting NLRP3 inflammasome and pyroptosis in human RPE cells.

TRIM59 Protects Mice From Sepsis by Regulating Inflammation and Phagocytosis in Macrophages.

Sepsis is associated with bacterial invasion and inflammation and has a high mortality rate. Previous studies have demonstrated that tripartite motif 59 (TRIM59) was involved in NF-κB signaling and could promote phagocytosis of macrophages, but the role of TRIM59 in sepsis is still unknown. In our study, we found that TRIM59 was downregulated in lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMDMs). In the cecal ligation and puncture (CLP) sepsis mice model, the mortality of Trim59flox/floxLyz-Cre (Trim59-cKO) mice was higher, the immune cell infiltration and damage of liver and lung were more severe, and bacteria burden was increased. We also found that TRIM59 altered the production of pro-inflammation cytokines, as well as macrophage phagocytosis ability. Further analysis indicated that NF-κB signal pathway and Fcγ receptors might be involved in these regulations. Our study demonstrated for the first time that TRIM59 protects mice from sepsis by regulating inflammation and phagocytosis in macrophages.

E3 ubiquitin ligase TRIM7 negatively regulates NF-kappa B signaling pathway by degrading p65 in lung cancer.

The gene trim7 encodes at least four isoforms Glycogenin-interacting protein 1 (GNIP1), GNIP2, GNIP3 and Tripartite motif containing 7 (TRIM7). GNIP1, the longest isoform, has been reported acting as an oncogene. However, it is very interesting that TRIM7, the shortest isoform, only 15 amino acids different from GNIP1 in C-terminal, acts in a completely different way from that of GNIP1 in our present study. TRIM7 expression was decreased in tumor compared with adjacent normal tissues, and the level of TRIM7 was negatively correlated with clinical stage of 94 patients with lung cancer. In vitro, TRIM7 dramatically inhibited the proliferation and migration of tumor cells, and promoted cell apoptosis. Further study showed that TRIM7 interacted with p65 via its C-terminal which is different from GNIP1. The interaction between TRIM7 and p65 promoted the ubiquitination of p65 and finally accelerated the degradation of p65 via 26S proteasome. In vivo, the tumor volume and weight were decreased by TRIM7 stable expression. Meanwhile, Ki67 was down-regulated, thyroid transcription factor 1 (TTF-1) and Caspase 3 were up-regulated in TRIM7 overexpression group in xenograft model. It is very impressive that TRIM7t (a truncated TRIM7 without C-terminal sequence that different with GNIP1) had little effect on the tumor growth in vivo. These findings highlight a curious mechanism for negative regulation of NF-kappa B signaling pathway by TRIM7 and demonstrate that TRIM7 would be a potential therapeutic target for lung cancer.

The E3 ubiquitin ligase TRIM7 suppressed hepatocellular carcinoma progression by directly targeting Src protein.

Aberrant Src kinase activity is known to be involved in a variety of human malignancies, whereas the regulatory mechanism of Src has not been completely clarified. Here, we demonstrated that tripartite motif containing 7 (TRIM7) directly interacted with Src, induced Lys48-linked polyubiquitination of Src and reduced the abundance of Src protein in hepatocellular carcinoma (HCC) cells. We further identified TRIM7 as a tumor suppressor in HCC cells through its negative modulation of the Src-mTORC1-S6K1 axis in vivo and in vitro in several HCC models. Moreover, we verified the dysregulated expression of TRIM7 in clinical liver cancer tissues and its negative correlation with Src protein in clinical HCC specimens. Overall, we demonstrated that TRIM7 suppressed HCC progression through its direct negative regulation of Src and modulation of the Src-mTORC1-S6K1 axis; thus, we provided a novel insight into the development of HCC and defined a promising therapeutic strategy for cancers with overactive Src by modulating TRIM7.

A pair of E3 ubiquitin ligases compete to regulate filopodial dynamics and axon guidance.

Appropriate axon guidance is necessary to form accurate neuronal connections. Axon guidance cues that stimulate cytoskeletal reorganization within the growth cone direct axon navigation. Filopodia at the growth cone periphery have long been considered sensors for axon guidance cues, yet how they respond to extracellular cues remains ill defined. Our previous work found that the filopodial actin polymerase VASP and consequently filopodial stability are negatively regulated via nondegradative TRIM9-dependent ubiquitination. Appropriate VASP ubiquitination and deubiquitination are required for axon turning in response to the guidance cue netrin-1. Here we show that the TRIM9-related protein TRIM67 outcompetes TRIM9 for interacting with VASP and antagonizes TRIM9-dependent VASP ubiquitination. The surprising antagonistic roles of two closely related E3 ubiquitin ligases are required for netrin-1-dependent filopodial responses, axon turning and branching, and fiber tract formation. We suggest a novel model in which coordinated regulation of VASP ubiquitination by a pair of interfering ligases is a critical element of VASP dynamics, filopodial stability, and axon guidance.

The mRNA repressor TRIM71 cooperates with Nonsense-Mediated Decay factors to destabilize the mRNA of CDKN1A/p21.

Nonsense-mediated decay (NMD) plays a fundamental role in the degradation of premature termination codon (PTC)-containing transcripts, but also regulates the expression of functional transcripts lacking PTCs, although such 'non-canonical' functions remain ill-defined and require the identification of factors targeting specific mRNAs to the NMD machinery. Our work identifies the stem cell-specific mRNA repressor protein TRIM71 as one of these factors. TRIM71 plays an essential role in embryonic development and is linked to carcinogenesis. For instance, TRIM71 has been correlated with advanced stages and poor prognosis in hepatocellular carcinoma. Our data shows that TRIM71 represses the mRNA of the cell cycle inhibitor and tumor suppressor CDKN1A/p21 and promotes the proliferation of HepG2 tumor cells. CDKN1A specific recognition involves the direct interaction of TRIM71 NHL domain with a structural RNA stem-loop motif within the CDKN1A 3'UTR. Importantly, CDKN1A repression occurs independently of miRNA-mediated silencing. Instead, the NMD factors SMG1, UPF1 and SMG7 assist TRIM71-mediated degradation of CDKN1A mRNA, among other targets. Our data sheds light on TRIM71-mediated target recognition and repression mechanisms and uncovers a role for this stem cell-specific factor and oncogene in non-canonical NMD, revealing the existence of a novel mRNA surveillance mechanism which we have termed the TRIM71/NMD axis.