The Ubiquitin E3 Ligase TRIM21 Promotes Hepatocarcinogenesis by Suppressing the p62-Keap1-Nrf2 Antioxidant Pathway

AP5Z1 affects hepatocellular carcinoma growth and autophagy by regulating PTEN ubiquitination and modulating the PI3K/Akt/mTOR pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide, with high incidence and mortality rates, and the number of cases is expected to increase by 2030. Understanding the molecular mechanisms of HCC and identifying new therapeutic targets and biomarkers for HCC are crucial.

METHODS

In this study, we examined adaptor-related protein complex 5 subunit ζ1 (AP5Z1) expression in liver cancer and nearby noncancerous tissues to explore its effects on HCC cell growth, death, and autophagy. The functional and molecular mechanisms of AP5Z1 were studied using clinical sample analysis, Western blot (WB), immunohistochemistry (IHC), quantitative reverse-transcription polymerase chain reaction (qRT‒PCR), coimmunoprecipitation (Co-IP), cell proliferation assays, flow cytometry (FCM), autophagy assays, electron microscopy, mass spectrometry (MS), transcriptome analysis, and animal model experiments.

RESULTS

AP5Z1 expression was notably higher in HCC tissues than in normal tissues and was linked to a poor prognosis. The results of both in vitro and in vivo studies revealed that AP5Z1 promoted HCC cell growth and reduced apoptosis. In addition, AP5Z1 regulates cellular autophagy by ubiquitinating the phosphatase and tensin homolog (PTEN) protein and modulating the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway.

CONCLUSIONS

AP5Z1 influences autophagy and apoptosis in HCC cells by interacting with PTEN to modulate the PI3K/Akt/mTOR pathway. This gene might promote PTEN ubiquitination and degradation by recruiting tripartite motif-containing protein 21 (TRIM21), making it a potential biomarker for diagnosing and predicting the outcome of HCC as well as a target for new treatment strategies.

Phospho-TRIM21 orchestrates RPA2 ubiquitination switch to promote homologous recombination and tumor radio/chemo-resistance

RPA2, a key component of the RPA complex, is essential for single-stranded DNA (ssDNA) binding and DNA repair. However, the regulation of RPA2-ssDNA interaction and the recruitment of repair proteins following DNA damage remain incompletely understood. Our study uncovers a novel mechanism by which phosphorylated TRIM21 (Phospho-TRIM21) regulates RPA2 ubiquitination, thereby modulating homologous recombination and tumor radio/chemo-resistance. In the absence of DNA damage, TRIM21 mediates K63-linked ubiquitination of RPA2, countering K6-linked ubiquitination. Upon DNA damage, ubiquitination-modified RPA2 binds ssDNA, stabilizing the DNA structure and facilitating ATRIP/ATR recruitment. ATR subsequently phosphorylates TRIM21 at Ser41, leading to the dissociation of the TRIM21-RPA2 complex and a shift in RPA2 ubiquitination from K63 to K6 linkage. This shift maintains RPA2 ubiquitination homeostasis and stabilizes the RPA2-ATRIP complex, which is crucial for efficient homologous recombination (HR) repair and enhanced tumor radio/chemo-resistance. We also demonstrate that TRIM21 is frequently upregulated in cancers, and its depletion sensitizes cancer cells to radio/chemotherapy, suggesting its potential as a therapeutic target. This study provides novel insights into TRIM21's role in the DNA damage response and its implications for cancer treatment.

Conjugated Lithocholic Acid Activates Hepatic TGR5 to Promote Lipotoxicity and MASLD-MASH Transition by Disrupting Carnitine Biosynthesis

Conjugated lithocholic acid (LCA) plays a critical role in the development of metabolic dysfunction-associated steatotic liver disease (MASLD). In this process, hepatocyte inflammation-caused upregulation of its receptor, Takeda G protein-coupled receptor 5 (TGR5) is a crucial factor. Serum bile acid profiling shows an increase in conjugated LCA, which correlates with disease severity. Depletion of Gpbar1 in hepatocytes significantly protects against the progression from MASLD to metabolic dysfunction-associated steatohepatitis (MASH) that is related to conjugated LCA. In vivo and in vitro experiments indicate that TGR5 activation in hepatocytes promotes lipotoxicity-induced cell death and inflammation by suppressing de novo carnitine biosynthesis. Mechanistically, TGR5 binding to CD36 facilitates E3 ubiquitin ligase TRIM21 recruitment, leading to the degradation of BBOX1, a crucial enzyme in de novo carnitine biosynthesis. Targeting TGR5 therapeutically can restore carnitine biosynthesis, which may offer a potent strategy to prevent or reverse the transition from MASLD to MASH.

TRIM21-mediated ubiquitination and phosphorylation of ERK1/2 promotes cell proliferation and drug resistance in pituitary adenomas

BACKGROUND

Pituitary adenomas (PAs) are common intracranial tumors and the TRIM family plays a crucial role in cell proliferation and therapeutic resistance of tumors. However, the role of the TRIM family in PAs is not well recognized.

METHODS

CRISPR screening explored the role of the TRIM family in cell proliferation and drug resistance in PAs. In vitro and in vivo experiments were performed to evaluate the effects of Tripartite Motif Containing 21 (TRIM21). RNA-sequencing, mass spectrometry, immunoprecipitation, and ubiquitination experiments were performed to explore the molecular mechanism. NanoBiT assays were used to screen the drugs reducing TRIM21 expression.

RESULTS

CRISPR-Cas9 screens identified that TRIM21 facilitated cell proliferation and drug resistance in PAs. Mechanistically, TRIM21 interacted with ERK1/2 through PRY-SPRY domain, leading to ERK1/2 K27-linked ubiquitination. The ERK1/2 ubiquitination promotes the interaction between ERK1/2 and MEK1/2, thereby facilitating the phosphorylation of ERK1/2. However, an excess presence of TRIM21 suppressed the phosphorylation of ERK1/2 and cell proliferation via activating ERK1/2 negative feedback pathways. Importantly, TRIM21 was upregulated in dopamine-resistant prolactinomas and cabergoline-resistant MMQ cells. Furthermore, drug screening identified that Fimepinostat and Quisinostat, can reduce the protein levels of TRIM21, inhibit tumor progression, and increase drug sensitivity.

CONCLUSIONS

TRIM21 may represent a therapeutic target for tumors, and inhibiting TRIM21 could be a potential strategy for tumor treatment.

Targeting the TRIM21-PD-1 axis potentiates immune checkpoint blockade and CAR-T cell therapy

Dysregulation of T cells is a major limitation for the clinical success of T cell-based cancer immunotherapies, such as immune checkpoint blockade and chimeric antigen receptor (CAR)-T cell therapy. Understanding the underlying mechanisms for regulating T cell functions can facilitate designing therapeutic strategies to improve immunotherapies. Here, we report that TRIM21 impairs CD8+ T cell activation and anti-tumor immunity. Mechanistically, TRIM21 catalyzes the K63-linked ubiquitination on programmed cell death-1 (PD-1) at K233, leading to stabilization of PD-1 through antagonizing its K48-linked ubiquitination and degradation. Thus, Trim21 knockout (KO) significantly decreases PD-1 expression and enhances the activation of cytotoxic CD8+ T cells, which sensitizes tumors to anti-CTLA-4 immunotherapy. Notably, Trim21 KO anti-CD19 CAR-T cells exhibit improved anti-tumor efficacy. These results reveal the molecular mechanism by which TRIM21-mediated K63-linked ubiquitination on PD-1 restrains the activation of CD8+ T cells, highlighting that targeting the TRIM21-PD-1 axis as a potential therapeutic strategy to potentiate cancer immunotherapy.

TRIM21 Promotes Endothelial Cell Activation via Accelerating SOCS3 Ubiquitination Degradation in Atherosclerosis

Activated endothelial cells play an important role in the beginning of atherosclerotic disease by secreting various proteins and inflammatory cytokines. Ubiquitination is one of the most common post-translational changes in cells. However, the role and mechanisms of ubiquitination in endothelial cell activation remain poorly understood. In this study, we identified TRIM21 as an E3 ubiquitin ligase with increased expression in atherosclerotic disease and activated endothelial cells. Knockdown of TRIM21 resulted in reduced secretion of inflammatory factors and attenuated the pyroptosis of endothelial cells, inhibiting the progression of atherosclerosis. Mechanistically, TRIM21 could bind and ubiquitinate SOCS3, thereby enhancing NLRP3-mediated pyroptosis. Taken together, we found that endothelial TRIM21 activated the JAK/STAT3 pathway by degrading SOCS3, which in turn promoted NLRP3-mediated pyroptosis and aggravated atherosclerosis, revealing that TRIM21 may be a promising treatment target for the medical management of atherosclerosis.

Micropeptide hSPAR regulates glutamine levels and suppresses mammary tumor growth via a TRIM21-P27KIP1-mTOR axis

mTOR plays a pivotal role in cancer growth control upon amino acid response. Recently, CDK inhibitor P27KIP1 has been reported as a noncanonical inhibitor of mTOR signaling in MEFs, via unclear mechanisms. Here, we find that P27KIP1 degradation via E3 ligase TRIM21 is inhibited by human micropeptide hSPAR through its C-terminus (hSPAR-C), causing P27KIP1's cytoplasmic accumulation in breast cancer cells. Furthermore, hSPAR/hSPAR-C also serves as an inhibitor of glutamine transporter SLC38A2 expression and thereby decreases the cellular glutamine levels specifically in cancer cells. The resultant glutamine deprivation sequentially triggers translocation of cytoplasmic P27KIP1 to lysosomes, where P27KIP1 disrupts the Ragulator complex and suppresses mTORC1 assembly. Administration of hSPAR or hSPAR-C significantly impedes breast cancer cell proliferation and tumor growth in xenograft models. These findings define hSPAR as an intrinsic control factor for cellular glutamine levels and as a novel tumor suppressor inhibiting mTORC1 assembly.

TRIM21 modulates stability of pro-survival non-coding RNA vtRNA1-1 in human hepatocellular carcinoma cells

Recent studies expanded our knowledge of diverse pro-survival functions of short non-coding vault RNAs. One of the human vault RNA paralogs, vtRNA1-1, modulates several intracellular processes, including proliferation, apoptosis, autophagy, and drug resistance in various types of human cancer cells. However, protein interaction partners and mechanisms by which vtRNA1-1 levels are controlled within the cells remained elusive. Here, we describe a regulatory process for vtRNA1-1 stabilization mediated by the newly identified interacting proteins, TRIM21 and TRIM25, in human hepatocellular carcinoma (HCC) cells. Depleting TRIM21 or TRIM25 reduced the stability of vtRNA1-1 both in vivo and in vitro. We also identified the responsible sequence of vtRNA1-1 for the stability regulation by TRIM21 and TRIM25 and revealed another critical factor for vtRNA1-1 stability, an NSUN2-mediated methylation at C69 of vtRNA1-1. Consequently, our findings demonstrated that the TRIM proteins govern the stability of vtRNA1-1 depending on its methylation status in HCC cells. Since vtRNA1-1 is crucial for pro-survival characteristics in HCC cells, insight into vtRNA1-1 protein binding partners and the regulation of its stability can impact the development of new anticancer strategies.

The Mechanism of TRIM21 Inhibiting the Invasion and Migration of ccRCC by Stabilizing ASS1

Clear cell renal cell carcinoma (ccRCC) is characterized by its aggressive invasion and metastasis, presenting significant clinical challenges. Gaining insights into the molecular mechanisms underlying its progression is crucial for the development of effective therapeutic strategies. Addressing a critical knowledge gap in understanding ccRCC tumorigenesis, this study aims to elucidate the expression patterns of TRIM21 in ccRCC, unravel its impact on ccRCC patient prognosis, and investigate the regulatory role of TRIM21 in ASS1 expression and urea cycle dysregulation within the context of ccRCC. The results demonstrate that TRIM21 is downregulated in ccRCC, and low expression of TRIM21 predicts an unfavorable prognosis for ccRCC patients. Furthermore, the upregulation of TRIM21 can inhibit the migration and invasion of ccRCC cells by regulating the ubiquitination modification of ASS1. This not only expands the functional role of TRIM21 in ccRCC tumorigenesis but also demonstrates its ability to reverse urea cycle dysregulation through stabilizing ASS1 expression. Specifically, abnormal downregulation of TRIM21 in ccRCC reduces K63 ubiquitination modification of ASS1, leading to decreased stability of the ASS1 protein, aggravated urea cycle dysregulation, and facilitated migration and invasion of ccRCC cells. Additionally, reduction in ASS1 reverses the depressed migration and invasion caused by overexpression of TRIM21 in ccRCC cells. In summary, our findings contribute to a deeper understanding of the functional role played by TRIM21 in ccRCC progression, pinpoint a unique and novel regulatory mechanism involving ectopic downregulation-mediated ASS1 ubiquitination modification and urea cycle dysfunction during ccRCC progression, and provide fresh insights for further investigation into the pathogenesis and metabolic reprogramming associated with ccRCC.

TRIM21 Promotes Tumor Growth and Gemcitabine Resistance in Pancreatic Cancer by Inhibiting EPHX1-Mediated Arachidonic Acid Metabolism

Pancreatic cancer (PC) progresses rapidly, and gemcitabine-based chemotherapy has brought only limited efficacy. Identifying key drivers and therapeutic targets holds significant clinical value. In this study, through comprehensive analysis of multiple PC databases, this work identifies TRIM21 as a promising driver mediator. This work further performs loss- and gain-of-function assays for TRIM21, revealing that TRIM21 knockout inhibits tumor proliferation and gemcitabine resistance both in vitro and vivo. Lipidomics reveal that silencing TRIM21 reduce the arachidonic acid production, and inhibit ferroptosis. Mechanically, through proteomics, ubiquitomics, and liquid chromatography-tandem mass spectrometry analysis, the key metabolic enzyme of arachidonic acid -EPHX1 is identified as a downstream substrate of TRIM21. TRIM21 interacts with EPHX1 through its SPRY domain and promotes ubiquitin-mediated degradation of EPHX1 via K33- and K48-linked ubiquitination at the K105 site. Given the targeting potential, this work screens Bezafibrate to block the interaction between TRIM21 and EPHX1 and validates its sensitizing effect. In summary, TRIM21 promotes tumour growth and gemcitabine resistance in PC by inhibiting EPHX1-mediated arachidonic acid metabolism. This provides a novel and promising target for clinical treatment of PC.

TRIM21-mediated PRMT1 degradation attenuates colorectal cancer malignant progression

Tripartite motif-containing 21 (TRIM21) plays a crucial role in antiviral responses and autoimmune diseases. While the impact of TRIM21 on cancer has been studied in various tumors, its role in colorectal cancer (CRC) remains unclear. In this study, we found that TRIM21 expression is reduced in primary CRC tissues. Low levels of TRIM21 in CRC are associated with unfavorable clinicopathological characteristics and shorter survival. Furthermore, we demonstrate that TRIM21 suppresses the proliferation, tumorigenesis, migration, and metastasis of CRC cells by promoting the ubiquitination-mediated degradation of PRMT1. These findings suggest that TRIM21 holds potential as a valuable predictive biomarker for assessing the prognosis of CRC patients.

TRIM21-mediated ubiquitination of SQSTM1/p62 abolishes its Ser403 phosphorylation and enhances palmitic acid cytotoxicity

Long-chain free fatty acids (FFAs) accumulation and oxidative toxicity is a major cause for several pathological conditions. The mechanisms underlying FFA cytotoxicity remain elusive. Here we show that palmitic acid (PA), the most abundant FFA in the circulation, induces S403 phosphorylation of SQSTM1/p62 (sequestosome 1) and its aggregation, which sequesters KEAP1 and activates the non-canonical SQSTM1-KEAP1-NFE2L2 antioxidant pathway. The PA-induced SQSTM1 S403 phosphorylation and aggregation are dependent on SQSTM1 K7-D69 hydrogen bond formation and dimerization in the Phox and Bem1 (PB1) domain, which facilitates the recruitment of TBK1 that phosphorylates SQSTM1 S403. The ubiquitin E3 ligase TRIM21 ubiquitinates SQSTM1 at the K7 residue and abolishes the PB1 dimerization, S403 phosphorylation, and SQSTM1 aggregation. TRIM21 is oxidized at C92, C111, and C114 to form disulfide bonds that lead to its oligomerization and decreased E3 activity. Mutagenizing the three C residues to S (3CS) abolishes TRIM21 oligomerization and increases its E3 activity. TRIM21 ablation leads to decreased SQSTM1 K7 ubiquitination, hence elevated SQSTM1 S403 phosphorylation and aggregation, which confers protection against PA-induced oxidative stress and cytotoxicity. Therefore, TRIM21 is a negative regulator of SQSTM1 phosphorylation, aggregation, and the antioxidant sequestration function. TRIM21 is oxidized to reduce its E3 activity that helps enhance the SQSTM1-KEAP1-NFE2L2 antioxidant pathway. Inhibition of TRIM21 May be a viable strategy to protect tissues from lipotoxicity resulting from long-chain FFAs.Abbreviations: ER: endoplasmic reticulum; FFA: free fatty acid; HMOX1/HO-1: heme oxygenase 1; IB: immunoblotting; IF: immunofluorescence; IP: immunoprecipitation; KEAP1: kelch like ECH associated protein 1; MASH: metabolic dysfunction-associated steatohepatitis; MEF: mouse embryonic fibroblast; NFE2L2/Nrf2: NFE2 like BZIP transcription factor 2; PA: palmitic acid; PB1: Phox and Bem 1; ROS: reactive oxygen species; SLD: steatotic liver disease; SQSTM1: sequestosome 1; TBK1: TANK-binding kinase 1; TRIM21: tripartite motif containing 21.

Fangchinoline suppresses hepatocellular carcinoma by regulating ROS accumulation via the TRIM7/Nrf2 signaling pathway

BACKGROUND

Dysregulation of redox homeostasis is associated with developing hepatocellular carcinoma (HCC). Oxidative stress (OS) is distinguished by the accumulation of ROS, which plays a variety of roles in cancer pathology. Fangchinoline (FAN), a bis-benzylisoquinoline alkaloid, has anti-cancer pharmacological activity. However, the regulatory mechanism of FAN on OS and whether it can inhibit HCC by mediating OS are still unclear.

HYPOTHESIS/PURPOSE

This paper aims to explore the effectiveness of FAN in preventing HCC via regulating OS and identify the underlying molecular mechanisms.

METHODS

We used the primary HCC mouse model and hepatoma cell line to explore the suppressive effect of FAN on hepatocarcinogenesis. To study the role of ROS in the anti-hepatocarcinoma effect of FAN in cell model and mouse model. The mechanism of FAN-induced nuclear factor erythroid 2-related factor 2 (Nrf2) pathway activation was studied through various techniques, including generation of Nrf2 and tripartite motif containing 7 (TRIM7) gene overexpressing or knockdown cell model, co-immunoprecipitation, immunohistochemistry and subcutaneous tumor xenograft models constructed by the stable TRIM7-overexpression HLE cells, etc. RESULTS: We showed that FAN significantly inhibited cell proliferation and hepatocarcinogenesis in HCC cells and primary HCC mouse model. The FAN-induced mitochondrial dysfunction promoted ROS accumulation, and using N-Acetylcysteine to clear ROS reversed the anti-HCC effects of FAN. We observed that FAN is capable of activating the Nrf2 pathway. This effect was thought to be due to the fact that, in response to the FAN-induced OS, the cancer cells created a feedback loop to stable Nrf2 via depressing the K48-linkage ubiquitination of it, which was caused by reduced binding of kelch-like ECH-associated protein 1 (Keap1) and Nrf2 and elevated TRIM7 expression. Indeed, overexpression of TRIM7 suppressed the anti-hepatocarcinoma effect of FAN.

CONCLUSION

The study determines the anti-liver cancer effect of FAN and first describes the positive regulatory effect of TRIM7 on Nrf2 signaling. We reveal that TRIM7/Nrf2 signaling served as a target of FAN-induced ROS accumulation in HCC, which helps to clarify the mechanism of action of FAN against HCC and provides a theoretical basis for FAN as an anti-cancer drug.

MDM4 inhibits ferroptosis in p53 mutant colon cancer via regulating TRIM21/GPX4 expression

MDM4 is one of the major regulators of p53. The biological effect of MDM4 on tumor is controversial, its role and molecular mechanism in colon cancer progression and prognosis are still unclear. In this study, we identify that MDM4 is significantly overexpressed in human colon cancer and high MDM4 expression was associated with poor prognosis of colon cancer with mutant p53. MDM4 inhibits the ubiquitination of the ferroptosis marker protein GPX4 at K167 and K191 by upregulating the protein expression level of the E3 ubiquitin ligase TRIM21, which promotes the polyubiquitination of GPX4 transfer from K48- to K63- linked ubiquitination. Thereby, MDM4 enhances the stability of GPX4 protein, inhibiting ferroptosis, increasing the resistance of colon cancer patients to chemotherapy, and promoting colon cancer progression. These findings elucidate the ferroptosis inhibition effect of MDM4 via regulating TRIM21/GPX4 on p53-mutated colon cancer and provide a potential therapeutic strategy for colon cancer therapy.

Erythropoietin regulates energy metabolism through EPO-EpoR-RUNX1 axis

Erythropoietin (EPO) plays a key role in energy metabolism, with EPO receptor (EpoR) expression in white adipose tissue (WAT) mediating its metabolic activity. Here, we show that male mice lacking EpoR in adipose tissue exhibit increased fat mass and susceptibility to diet-induced obesity. Our findings indicate that EpoR is present in WAT, brown adipose tissue, and skeletal muscle. Elevated EPO in male mice improves glucose tolerance and insulin sensitivity while reducing expression of lipogenic-associated genes in WAT, which is linked to an increase in transcription factor RUNX1 that directly inhibits lipogenic genes expression. EPO treatment in wild-type male mice decreases fat mass and lipogenic gene expression and increase in RUNX1 protein in adipose tissue which is not observed in adipose tissue EpoR ablation mice. EPO treatment decreases WAT ubiquitin ligase FBXW7 expression and increases RUNX1 stability, providing evidence that EPO regulates energy metabolism in male mice through the EPO-EpoR-RUNX1 axis.

Dual role of Nrf2 signaling in hepatocellular carcinoma: promoting development, immune evasion, and therapeutic challenges

Hepatocellular carcinoma (HCC) is the predominant form of liver cancer and ranks as the third leading cause of cancer-related mortality globally. The liver performs a wide range of tasks and is the primary organ responsible for metabolizing harmful substances and foreign compounds. Oxidative stress has a crucial role in growth and improvement of hepatocellular carcinoma (HCC). Nuclear factor erythroid 2 (1)-related factor 2 (Nrf2) is an element that regulates transcription located in the cytoplasm. It controls the balance of redox reactions by stimulating the expression of many genes that depend on antioxidant response elements. Nrf2 has contrasting functions in the normal, healthy liver and HCC. In the normal liver, Nrf2 provides advantageous benefits, while in HCC it promotes harmful effects that support the growth and survival of HCC. Continuous activation of Nrf2 has been detected in HCC and promotes its advancement and aggressiveness. In addition, Activation of Nrf2 may lead to immune evasion, weakening the immune cells' ability to attack tumors and thereby promoting tumor development. Furthermore, chemoresistance in HCC, which is considered a form of stress response to chemotherapy medications, significantly impedes the effectiveness of HCC treatment. Stress management is typically accomplished by activating specific signal pathways and chemical variables. One important element in the creation of chemoresistance in HCC is nuclear factor-E2-related factor 2 (Nrf2). Nrf2 is a transcription factor that regulates the activation and production of a group of genes that encode proteins responsible for protecting cells from damage. This occurs through the Nrf2/ARE pathway, which is a crucial mechanism for combating oxidative stress within cells.

SERPINH1 modulates apoptosis by inhibiting P62 ubiquitination degradation to promote bone metastasis of prostate cancer

Prostate cancer (PCa) is one of the most prevalent urogenital malignancies. Bone metastasis from PCa reduces patient survival rates significantly. There currently exists no effective treatment for bone metastatic PCa, and the underlying mechanisms remain unclear. This study performed transcriptomic screening on PCa bone metastasis specimens and intersection analysis in public databases and identified SERPINH1 as a potential target for treatment. SERPINH1 was found to be upregulated in PCa bone metastases and with poor prognosis, high Gleason score, and advanced metastatic status. SERPINH1 induced PCa cells' bone metastasis in vivo, promoted their proliferation, and mitigated apoptosis. Mechanistically, SERPINH1 bound to P62, reducing TRIM21-mediated K63-linked ubiquitination degradation of P62 and promoting proliferation and resistance to apoptosis of PCa. This study suggests the regulation of ubiquitination degradation of P62 by SERPINH1 that promotes PCa bone metastasis and can be considered as a potential target for treatment of bone metastatic PCa.

Targeting the regulation of iron homeostasis as a potential therapeutic strategy for nonalcoholic fatty liver disease

With aging and the increasing incidence of obesity, nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. NAFLD mainly includes simple hepatic steatosis, nonalcoholic steatohepatitis (NASH), liver fibrosis and hepatocellular carcinoma (HCC). An imbalance in hepatic iron homeostasis is usually associated with the progression of NAFLD and induces iron overload, reactive oxygen species (ROS) production, and lipid peroxide accumulation, which leads to ferroptosis. Ferroptosis is a unique type of programmed cell death (PCD) that is characterized by iron dependence, ROS production and lipid peroxidation. The ferroptosis inhibition systems involved in NAFLD include the solute carrier family 7 member 11 (SLC7A11)/glutathione (GSH)/glutathione peroxidase 4 (GPX4) and ferroptosis suppressor protein 1 (FSP1)/coenzyme Q10 (CoQ10)/nicotinamide adenine dinucleotide phosphate (NADPH) regulatory axes. The main promotion system involved is the acyl-CoA synthetase long-chain family (ACSL4)/arachidonic lipoxygenase 15 (ALOX15) axis. In recent years, an increasing number of studies have focused on the multiple roles of iron homeostasis imbalance and ferroptosis in the progression of NAFLD. This review highlights the latest studies about iron homeostasis imbalance- and ferroptosis-associated NAFLD, mainly including the physiology and pathophysiology of hepatic iron metabolism, hepatic iron homeostasis imbalance during the development of NAFLD, and key regulatory molecules and roles of hepatic ferroptosis in NAFLD. This review aims to provide innovative therapeutic strategies for NAFLD.

TRIM21-mediated ubiquitylation of TAT suppresses liver metastasis in gallbladder cancer

Liver metastasis is common in patients with gallbladder cancer (GBC), imposing a significant challenge in clinical management and serving as a poor prognostic indicator. However, the mechanisms underlying liver metastasis remain largely unknown. Here, we report a crucial role of tyrosine aminotransferase (TAT) in liver metastasis of GBC. TAT is frequently up-regulated in GBC tissues. Increased TAT expression is associated with frequent liver metastasis and poor prognosis of GBC patients. Overexpression of TAT promotes GBC cell migration and invasion in vitro, as well as liver metastasis in vivo. TAT knockdown has the opposite effects. Intriguingly, TAT promotes liver metastasis of GBC by potentiating cardiolipin-dependent mitophagy. Mechanistically, TAT directly binds to cardiolipin and leads to cardiolipin externalization and subsequent mitophagy. Moreover, TRIM21 (Tripartite Motif Containing 21), an E3 ubiquitin ligase, interacts with TAT. The histine residues 336 and 338 at TRIM21 are essential for this binding. TRIM21 preferentially adds the lysine 63 (K63)-linked ubiquitin chains on TAT principally at K136. TRIM21-mediated TAT ubiquitination impairs its dimerization and mitochondrial location, subsequently inhibiting tumor invasion and migration of GBC cells. Therefore, our study identifies TAT as a novel driver of GBC liver metastasis, emphasizing its potential as a therapeutic target.

Trim21 deficiency in mice increases HCC carcinogenesis in a NASH context and is associated with immune checkpoint upregulation

The global pandemic of metabolic diseases has increased the incidence of hepatocellular carcinoma (HCC) in the context of non-alcoholic steatohepatitis (NASH). The downregulation of the E3 ubiquitin ligase TRIM21 has been linked to poor prognosis in different cancers including HCC. In order to investigate the role of TRIM21 in liver cancer progression on NASH, Trim21+/+ and Trim21-/- male mice were injected with streptozotocin at the neonatal stage. The hypoinsulinemic mice were then fed with a high-fat high-cholesterol diet (HFHCD) for 4, 8 or 12 weeks. All mice developed NASH which systematically resulted in HCC progression. Interestingly, compared to the Trim21+/+ control mice, liver damage was worsened in Trim21-/- mice, with more HCC nodules found after 12 weeks on HFHCD. Immune population analysis in the spleen and liver revealed a higher proportion of CD4+PD-1+ and CD8+PD-1+ T cells in Trim21-/- mice. The liver and HCC tumors of Trim21-/- mice also exhibited an increase in the number of PD-L1+ and CD68+ PD-L1+ cells. Thus, TRIM21 limits the emergence of HCC nodules in mice with NASH by potentially restricting the expression of PD-1 in lymphocytes and PD-L1 in tumors.

TRIM21 is critical in regulating hepatocellular carcinoma growth and response to therapy by altering the MST1/YAP pathway

Liver cancer is the sixth most common cancer and the third leading cause of cancer-related death globally. Despite efforts being made in last two decades in cancer diagnosis and treatment, the 5-year survival rate of liver cancer remains extremely low. TRIM21 participates in cancer metabolism, glycolysis, immunity, chemosensitivity and metastasis by targeting various substrates for ubiquitination. TRIM21 serves as a prognosis marker for human hepatocellular carcinoma (HCC), but the mechanism by which TRIM21 regulates HCC tumorigenesis and progression remains elusive. In this study, we demonstrated that TRIM21 protein levels were elevated in human HCC. Elevated TRIM21 expression was associated with HCC progression and poor survival. Knockdown of TRIM21 in HCC cell lines significantly impaired cell growth and metastasis and enhanced sorafenib-induced toxicity. Mechanistically, we found that knockdown of TRIM21 resulted in cytosolic translocation and inactivation of YAP. At the molecular level, we further identified that TRIM21 interacted and induced ubiquitination of MST1, which resulted in MST1 degradation and YAP activation. Knockdown of MST1 or overexpression of YAP reversed TRIM21 knockdown-induced impairment of HCC growth and chemosensitivity. Taken together, the current study demonstrates a novel mechanism that regulates the Hippo pathway and reveals TRM21 as a critical factor that promotes growth and chemoresistance in human HCC.

TRIM21 silencing inhibits the apoptosis and expedites the osteogenic differentiation of dexamethasone‑induced MC3T3‑E1 cells by activating the Keap1/Nrf2 pathway

Steroid-induced osteonecrosis of the femoral head (ONFH) is a serious complication caused by long-term or excessive use of glucocorticoids. The present study aimed to ascertain the effects of tripartite motif-containing protein 21 (TRIM21) on the process of steroid-induced ONFH and its hidden action mechanism. TRIM21 expression in dexamethasone (Dex)-treated mouse MC3T3-E1 preosteoblast cells was examined using reverse transcription-quantitative PCR and western blotting. The Cell Counting Kit-8 (CCK-8) method and lactate dehydrogenase release assay were used to respectively measure cell viability and injury. Flow cytometry analysis was used to assay cell apoptosis. Caspase 3 activity was evaluated using a specific assay, while alkaline phosphatase and Alizarin red S staining were used to evaluate osteogenesis. 2,7-dichloro-dihydrofluorescein diacetate fluorescence probe was used to estimate reactive oxygen species generation. Specific assay kits were used to appraise oxidative stress levels. In addition, the expression of apoptosis-, osteogenic differentiation- and Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling-associated proteins was assessed using western blotting. In Nrf2 inhibitor (ML385)-pretreated MC3T3-E1 cells exposed to Dex, cell apoptosis, osteogenesis and oxidative stress were detected again as aforementioned. Results revealed that TRIM21 expression was raised in Dex-induced MC3T3-E1 cells and TRIM21 deletion improved the viability and osteogenic differentiation, whereas it hampered the oxidative stress and apoptosis in MC3T3-E1 cells with Dex induction. In addition, silencing of TRIM21 activated Keap1/Nrf2 signaling. Moreover, ML385 partially abrogated the effects of TRIM21 depletion on the oxidative stress, apoptosis and osteogenic differentiation in MC3T3-E1 cells exposed to Dex. In conclusion, TRIM21 silencing might activate Keap1/Nrf2 signaling to protect against steroid-induced ONFH.

TRIM21 Promotes Oxidative Stress and Ferroptosis through the SQSTM1-NRF2-KEAP1 Axis to Increase the Titers of H5N1 Highly Pathogenic Avian Influenza Virus

Tripartite motif-containing protein 21 (TRIM21) is involved in signal transduction and antiviral responses through the ubiquitination of protein targets. TRIM21 was reported to be related to the imbalance of host cell homeostasis caused by viral infection. Our studies indicated that H5N1 highly pathogenic avian influenza virus (HPAIV) infection up-regulated TRIM21 expression in A549 cells. Western blot and qPCR results showed that knockdown of TRIM21 alleviated oxidative stress and ferroptosis induced by H5N1 HPAIV and promoted the activation of antioxidant pathways. Co-IP results showed that TRIM21 promoted oxidative stress and ferroptosis by regulating the SQSTM1-NRF2-KEAP1 axis by increasing SQSTM1 K63-linked polyubiquitination under the condition of HPAIV infection. In addition, TRIM21 attenuated the inhibitory effect of antioxidant NAC on HPAIV titers and enhanced the promoting effect of ferroptosis agonist Erastin on HPAIV titers. Our findings provide new insight into the role of TRIM21 in oxidative stress and ferroptosis induced by viral infection.

TRIM21/USP15 balances ACSL4 stability and the imatinib resistance of gastrointestinal stromal tumors

BACKGROUND

Imatinib has become an exceptionally effective targeted drug for treating gastrointestinal stromal tumors (GISTs). Despite its efficacy, the resistance to imatinib is common in GIST patients, posing a significant challenge to the effective treatment.

METHODS

The expression profiling of TRIM21, USP15, and ACSL4 in GIST patients was evaluated using Western blot and immunohistochemistry. To silence gene expression, shRNA was utilized. Biological function of TRIM21, USP15, and ACSL4 was examined through various methods, including resistance index calculation, colony formation, shRNA interference, and xenograft mouse model. The molecular mechanism of TRIM21 and USP15 in GIST was determined by conducting Western blot, co-immunoprecipitation, and quantitative real-time PCR (qPCR) analyses.

RESULTS

Here we demonstrated that downregulation of ACSL4 is associated with imatinib (IM) resistance in GIST. Moreover, clinical data showed that higher levels of ACSL4 expression are positively correlated with favorable clinical outcomes. Mechanistic investigations further indicated that the reduced expression of ACSL4 in GIST is attributed to excessive protein degradation mediated by the E3 ligase TRIM21 and the deubiquitinase USP15.

CONCLUSION

These findings demonstrate that the TRIM21 and USP15 control ACSL4 stability to maintain the IM sensitive/resistant status of GIST.

The role of ferroptosis in cardio-oncology

With the rapid development of new generations of antitumor therapies, the average survival time of cancer patients is expected to be continuously prolonged. However, these therapies often lead to cardiotoxicity, resulting in a growing number of tumor survivors with cardiovascular disease. Therefore, a new interdisciplinary subspecialty called "cardio-oncology" has emerged, aiming to detect and treat cardiovascular diseases associated with tumors and antitumor therapies. Recent studies have highlighted the role of ferroptosis in both cardiovascular and neoplastic diseases. The balance between intracellular oxidative stress and antioxidant defense is crucial in regulating ferroptosis. Tumor cells can evade ferroptosis by upregulating multiple antioxidant defense pathways, while many antitumor therapies rely on downregulating antioxidant defense and promoting ferroptosis in cancer cells. Unfortunately, these ferroptosis-inducing antitumor therapies often lack tissue specificity and can also cause injury to the heart, resulting in ferroptosis-induced cardiotoxicity. A range of cardioprotective agents exert cardioprotective effects by inhibiting ferroptosis. However, these cardioprotective agents might diminish the efficacy of antitumor treatment due to their antiferroptotic effects. Most current research on ferroptosis only focuses on either tumor treatment or heart protection but rarely considers both in concert. Therefore, further research is needed to study how to protect the heart during antitumor therapies by regulating ferroptosis. In this review, we summarized the role of ferroptosis in the treatment of neoplastic diseases and cardiovascular diseases and also attempted to propose further research directions for ferroptosis in the field of cardio-oncology.

LANCL1, a cell surface protein, promotes liver tumor initiation through FAM49B-Rac1 axis to suppress oxidative stress

BACKGROUND AND AIMS

HCC is an aggressive cancer with a poor clinical outcome. Understanding the mechanisms that drive tumor initiation is important for improving treatment strategy. This study aimed to identify functional cell membrane proteins that promote HCC tumor initiation.

APPROACH AND RESULTS

Tailor-made siRNA library screening was performed for all membrane protein-encoding genes that are upregulated in human HCC (n = 134), with sphere formation as a surrogate readout for tumor initiation. Upon confirmation of membranous localization by immunofluorescence and tumor initiation ability by limiting dilution assay in vivo, LanC-like protein-1 (LANCL1) was selected for further characterization. LANCL1 suppressed intracellular reactive oxygen species (ROS) and promoted tumorigenicity both in vitro and in vivo. Mechanistically, with mass spectrometry, FAM49B was identified as a downstream binding partner of LANCL1. LANCL1 stabilized FAM49B by blocking the interaction of FAM49B with the specific E3 ubiquitin ligase TRIM21, thus protecting FAM49B from ubiquitin-proteasome degradation. The LANCL1-FAM49B axis suppressed the Rac1-NADPH oxidase-driven ROS production, but this suppression of ROS was independent of the glutathione transferase function of LANCL1. Clinically, HCCs with high co-expression of LANCL1 and FAM49B were associated with more advanced tumor stage, poorer overall survival, and disease-free survival. In addition, anti-LANCL1 antibodies targeting the extracellular N-terminal domain were able to suppress the self-renewal ability, as demonstrated by the sphere formation ability of HCC cells.

CONCLUSIONS

Our data showed that LANCL1 is a cell surface protein and a key contributor to HCC initiation. Targeting the LANCL1-FAM49B-Rac1-NADPH oxidase-ROS signaling axis may be a promising therapeutic strategy for HCC.

The Role of TRIM Proteins in Vascular Disease

There are more than 80 different tripartite motifs (TRIM) proteins within the E3 ubiquitin ligase subfamily, including proteins that regulate intracellular signaling, apoptosis, autophagy, proliferation, inflammation, and immunity through the ubiquitination of target proteins. Studies conducted in recent years have unraveled the importance of TRIM proteins in the pathophysiology of vascular diseases. In this review, we describe the effects of TRIM proteins on vascular endothelial cells, smooth muscle cells, heart, and lungs. In particular, we discuss the potential mechanisms by which TRIMs regulate diseases and shed light on the potential therapeutic applications of TRIMs.

Hepatocyte Deubiquitinating Enzyme OTUD5 Deficiency is a Key Aggravator for Metabolic Dysfunction-Associated Steatohepatitis by Disturbing Mitochondrial Homeostasis

BACKGROUND & AIMS

Metabolic dysfunction-associated steatohepatitis (MASH) is a common chronic liver disease worldwide. No effective pharmacologic therapies for MASH have been developed; to develop such promising drugs, the underlying mechanisms regulating MASH need to be elucidated. Here, we aimed to determine the role of ovarian tumor domain-containing protein 5 (OTUD5) in MASH progression and identify a specific mechanism.

METHODS

The expression levels of OTUD subfamily under palmitic acid/oleic acid (PAOA) stimulation were screened. OTUD5 expression was assessed in human liver tissues without steatosis, those with simple steatosis, and those with MASH. MASH models were developed in hepatocyte-specific Otud5-knockout mice that were fed high-fat high-cholesterol and high-fat high-cholesterol plus high-fructose/sucrose diet for 16 weeks.

RESULTS

The expression of OTUD5 was down-regulated in fatty liver and was negatively related to the progression of MASH. Lipid accumulation and inflammation were exacerbated by Otud5 knockdown but attenuated by Otud5 overexpression under PAOA treatment. Hepatocyte-specific Otud5 deletion markedly exacerbated steatosis, inflammation, and fibrosis in the livers of 2 MASH mouse models. We identified voltage-dependent anion channel 2 (VDAC2) as an OTUD5-interacting partner; OTUD5 cleaved the K48-linked polyubiquitin chains from VDAC2, and it inhibited subsequent proteasomal degradation. The anabolic effects of OTUD5 knockdown on PAOA-induced lipid accumulation were effectively reversed by VDAC2 overexpression in primary hepatocytes. Metabolomic results revealed that VDAC2 is required for OTUD5-mediated protection against hepatic steatosis by maintaining mitochondrial function.

CONCLUSIONS

OTUD5 may ameliorate MASH progression via VDAC2-maintained mitochondrial homeostasis. Targeting OTUD5 may be a viable MASH-treatment strategy.

The interconnected roles of TRIM21/Ro52 in systemic lupus erythematosus, primary Sjögren's syndrome, cancers, and cancer metabolism

Protein tripartite motif-containing 21 (TRIM21/Ro52), an E3 ubiquitin ligase, is an essential regulator of innate immunity, and its dysregulation is closely associated with the development of autoimmune diseases, predominantly systemic lupus erythematosus (SLE) and primary Sjögren's syndrome (pSS). TRIM21 /Ro52 also features anti-cancer and carcinogenic functions according to different malignancies. The interconnected role of TRIM21/Ro52 in regulating autoimmunity and cell metabolism in autoimmune diseases and malignancies is implicated. In this review, we summarize current findings on how TRIM21/Ro52 affects inflammation and tumorigenesis, and investigate the relationship between TRIM21/Ro52 expression and the formation of lymphoma and breast cancer in SLE and pSS populations.

TRIM21 of Micropterus salmoides exerts antiviral roles against largemouth bass ulcer syndrome virus

Tripartite motif 21 (TRIM21), a member of the TRIM family, plays an important role in apoptosis, autophagy and ubiquitination in human, and has been proven to play antiviral roles in different organisms. In this study, the TRIM21 gene of Micropterus salmoides (MsTRIM21) was cloned, and it encoded 376 amino acids, which showed 89.3% similarity with Micropterus dolomieu and 38.3% with homo sapiens. Bioinformatics analysis revealed MsTRIM21 contained four domains: C4HC3-type RING-variant (RINGv), coiled coil, PRY and SPRY. The high expression level of MsTRIM21 could be detected in liver, stomach and muscle of healthy Micropterus salmoides, and it was significantly upregulated in head kidney, muscle, gill and brain and significantly down-regulated in the stomach of Micropterus salmoides infected with largemouth bass ulcer syndrome virus (LBUSV). The overexpression of MsTRIM21 could significantly inhibit the viral replication in vitro, evidenced by the reduction of CPE severity and the downregulation of the viral gene transcription. In addition, the overexpression of MsTRIM21 could significantly increase the expression level of interferon regulatory factor (IRF) 3, IRF7, myxovirus resistance 1 (Mx1), interferon stimulated gene 15 (ISG15), double-stranded RNA-activated protein kinase (PKR) and tumor necrosis factor α (TNF-α) in vitro, indicating the enhancement of innate immune response and inflammatory response, which may directly affect the replication of LBUSV. Thus, these results provide new lights on the roles of fish TRIM21 in innate immune response against iridovirus.

Deciphering roles of TRIMs as promising targets in hepatocellular carcinoma: current advances and future directions

Tripartite motif (TRIM) family is assigned to RING-finger-containing ligases harboring the largest number of proteins in E3 ubiquitin ligating enzymes. E3 ubiquitin ligases target the specific substrate for proteasomal degradation via the ubiquitin-proteasome system (UPS), which seems to be a more effective and direct strategy for tumor therapy. Recent advances have demonstrated that TRIM genes associate with the occurrence and progression of hepatocellular carcinoma (HCC). TRIMs trigger or inhibit multiple biological activities like proliferation, apoptosis, metastasis, ferroptosis and autophagy in HCC dependent on its highly conserved yet diverse structures. Remarkably, autophagy is another proteolytic pathway for intracellular protein degradation and TRIM proteins may help to delineate the interaction between the two proteolytic systems. In depth research on the precise molecular mechanisms of TRIM family will allow for targeting TRIM in HCC treatment. We also highlight several potential directions warranted further development associated with TRIM family to provide bright insight into its translational values in hepatocellular carcinoma.

TRIM21-Promoted FSP1 Plasma Membrane Translocation Confers Ferroptosis Resistance in Human Cancers

Ferroptosis, an iron-dependent form of regulated cell death driven by excessive accumulation of lipid peroxides, has become a promising strategy in cancer treatment. Cancer cells exploit antioxidant proteins, including Ferroptosis Suppressor Protein 1 (FSP1), to prevent ferroptosis. In this study, it is found that the E3 ubiquitin ligase TRIM21 bound to FSP1 and mediated its ubiquitination on K322 and K366 residues via K63 linkage, which is essential for its membrane translocation and ferroptosis suppression ability. It is further verified the protective role of the TRIM21-FSP1 axis in RSL3-induced ferroptosis in cancer cells and a subcutaneous tumor model. Moreover, TRIM21 is highly expressed in multiple gastrointestinal (GI) tumors, and its expression is further stimulated upon ferroptosis induction in cancer cells and the KPC mouse model. In summary, This study identifies TRIM21 as a negative regulator of ferroptosis through K63 ubiquitination of FSP1, which can serve as a therapeutic target to enhance the chemosensitivity of tumors based on ferroptosis induction.

SQSTM1/p62 and Hepatic Mallory-Denk Body Formation in Alcohol-Associated Liver Disease

Sequestosome 1 (SQSTM1/p62; hereafter p62) is an autophagy receptor protein for selective autophagy primarily due to its direct interaction with the microtubule light chain 3 protein that specifically localizes on autophagosome membranes. As a result, impaired autophagy leads to the accumulation of p62. p62 is also a common component of many human liver disease-related cellular inclusion bodies, such as Mallory-Denk bodies, intracytoplasmic hyaline bodies, α1-antitrypsin aggregates, as well as p62 bodies and condensates. p62 also acts as an intracellular signaling hub, and it involves multiple signaling pathways, including nuclear factor erythroid 2-related factor 2, NF-κB, and the mechanistic target of rapamycin, which are critical for oxidative stress, inflammation, cell survival, metabolism, and liver tumorigenesis. This review discusses the recent insights of p62 in protein quality control, including the role of p62 in the formation and degradation of p62 stress granules and protein aggregates as well as regulation of multiple signaling pathways in the pathogenesis of alcohol-associated liver disease.

E3 ubiquitin ligase TRIM21 targets TIF1γ to regulate β-catenin signaling in glioblastoma

Background: Elucidation of the mechanism of ubiquitation has led to novel ways to treat glioblastoma (GBM). A tripartite motif (TRIM) protein mediates a reversible, stringent ubiquitation which is closely related to glioma malignancy. This study intends to screen the most vital and abnormal regulating component of the tripartite motif protein and to explore its underlying mechanisms. Methods: TRIM21 is identified as an important oncogene that accelerates the progression of glioma cell through database in a multidimensional way and this is confirmed in human samples and cells. Tandem Mass Tags (TMT) and MS analysis are performed to discover the substrates of TRIM21.The underlying mechanisms are further investigated by CO-IP, luciferase reporter assays and gain and loss of function assays. In vivo treatment with siRNA is applied to evaluate the therapeutic significance of TRIM21. Result: We screened a panel of TRIM proteins and identified TRIM21, a E3 ubiquitin-protein ligase and autoantigen, as well as a prognostic biomarker for GBM. Functionally, high expression of wild-type TRIM21 accelerates tumor progression in vitro and in vivo, whereas TRIM21 mutants, including one with a critical RING-finger deletion, do not. Mechanistically, TRIM21 stimulates K63-linked ubiquitination and subcellular translocation of active β-catenin from the cytoplasm to the nucleus. Moreover, TRIM21 forms a complex with the β-catenin upstream regulator, TIF1γ, in the nucleus and accelerated its degradation by inducing K48-linked ubiquitination at K5 site, consequently increasing further nuclear β-catenin presence. Endogenous TRIM21 levels are found to be inversely correlated with TIF1γ but positively correlated with β-catenin in glioma tissue microarray experiments. Furthermore, direct injection of TRIM21 small interfering RNA (siRNA) into U87 cell-derived tumors (in vivo treatment with siRNA) is proved to inhibit tumor growth in nude mice. Conclusion: This work suggests that TRIM21/TIF1γ/β-catenin axis is involved in the progression of human GBM. TRIM21 is a promising therapeutic and prognostic biomarker for glioma with hyperactive β-catenin.

FBXW10-S6K1 promotes ANXA2 polyubiquitination and KRAS activation to drive hepatocellular carcinoma development in males

The incidence rate of human hepatocellular carcinoma (HCC) is approximately three times higher in males than in females. A better understanding of the mechanisms underlying HCC development in males could lead to more effective therapies for HCC. Our previous study found that FBXW10 played a critical role in promoting HCC development in male mice and patients, but the mechanism remains unknown. Here, we found that FBXW10 promoted K63-linked ANXA2 polyubiquitination and activation in HCC tissues from males, and this process was required for S6K1-mediated phosphorylation. Activated ANXA2 further translocated from the cytoplasm to the cell membrane to bind KRAS and then activated the MEK/ERK pathway, leading to HCC proliferation and lung metastasis. Interfering with ANXA2 significantly blocked FBXW10-driven HCC growth and lung metastasis in vitro and in vivo. Notably, membrane ANXA2 was upregulated and positively correlated with FBXW10 expression in male HCC patients. These findings offer new insights into the regulation and function of FBXW10 signaling in HCC tumorigenesis and metastasis and suggest that the FBXW10-S6K1-ANXA2-KRAS-ERK axis may serve as a potential biomarker and therapeutic target in male HCC patients with high FBXW10 expression.

TRIM21 deficiency protects against atrial inflammation and remodeling post myocardial infarction by attenuating oxidative stress

Atrial remodeling is a major contributor to the onset of atrial fibrillation (AF) after myocardial infarction (MI). Tripartite motif-containing protein 21 (TRIM21), an E3 ubiquitin protein ligase, is associated with pathological cardiac remodeling and dysfunction. However, the role of TRIM21 in postmyocardial infarction atrial remodeling and subsequent AF remains unclear. This study investigated the role of TRIM21 in post myocardial infarction atrial remodeling using TRIM21 knockout mice and explored the underlying mechanisms by overexpressing TRIM21 in HL-1 atrial myocytes using a lentiviral vector. The expression of TRIM21 in the left atrium of the mouse MI model was significantly elevated. TRIM21 deficiency alleviated MI-induced atrial oxidative damage, Cx43 downregulation, atrial fibrosis and enlargement, and abnormalities in electrocardiogram parameters (prolongation of the P-wave and PR interval). TRIM21 overexpression in atrial myocyte HL-1 cells further enhanced oxidative damage and Cx43 downregulation, whereas these effects were reversed by the reactive oxygen species scavenger N-acetylcysteine. The findings suggest that TRIM21 likely induces Nox2 expression mechanistically by activating the NF-κB pathway, which in turn leads to myocardial oxidative damage, inflammation, and atrial remodeling.

Characteristic of molecular subtypes based on PANoptosis-related genes and experimental verification of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a type of liver cancer that originates from liver cells. It is one of the most common types of liver cancer and a leading cause of cancer-related death worldwide. Early detection and treatment can improve the HCC prognosis. Therefore, it is necessary to further improve HCC markers and risk stratification. PANoptosome is a cytoplasmic polymer protein complex that regulates a proinflammatory programmed cell death pathway called "PANoptosis". The role of PANoptosis in HCC remains unclear. In this study, the molecular changes of PANoptosis related genes (PAN-RGs) in HCC were systematically evaluated. We characterized the heterogeneity of HCC by using consensus clustering to identify two distinct subtypes. The two subtypes showed different survival rate, biological function, chemotherapy drug sensitivity and immune microenvironment. After identification of PAN-RG differential expression genes (DEGs), a prognostic model was established by Cox regression analysis using minimum absolute contraction and selection operator (LASSO), and its prognostic value was verified by Cox regression analysis, Kaplan-Meier curve and receiver operating characteristic (ROC) curve. Our own specimens were also used to further validate the prognostic significance and possible clinical value of the selected targets. Subsequently, we conducted a preliminary discussion on the reasons for the influence of the model on the prognosis through TME analysis, drug resistance analysis, TMB analysis and other studies. This study provides a new idea for individualized and precise treatment of HCC.

NEDD4L inhibits migration, invasion, cisplatin resistance and promotes apoptosis of bladder cancer cells by inactivating the p62/Keap1/Nrf2 pathway

PURPOSE

This study identified the function of neural precursor cell expressed developmentally down-regulated 4-like (NEDD4L) on bladder cancer (BLCA).

METHODS

NEDD4L expression in BLCA patients was scrutinized. The function of NEDD4L on the viability, apoptosis, migration and invasion of BLCA cells was evaluated by cell counting kit-8, flow cytometry and Transwell assays. The effect of NEDD4L on the cisplatin (DDP) resistance of the DDP-resistant BLCA cells was explored. The influence of NEDD4L on the p62/Keap1/Nrf2 pathway activity in BLCA cells was tested by Western blot. Rescue experiments were implemented to verify whether NEDD4L regulated BLCA cell malignant behavior by mediating the Keap1/Nrf2 pathway activity via p62. The effect of NEDD4L on the growth and the p62/Keap1/Nrf2 pathway activity in vivo was researched in xenograft tumor nude mice models.

RESULTS

The down-regulated NEDD4L in BLCA patients was associated with unfavorable survival. NEDD4L suppressed the viability (inhibition rate 57.1%/49.0%), migration (inhibition rate 49.7%/77.1%), invasion (inhibition rate 50.6%/75.7%), promoted the apoptosis of T24/5637 cells (promotion rate 243.8%/201.9%), reduced IC 50 of DDP-resistant T24/5637 cells from 132.2/101.8 to 57.81/59.71 μM, respectively, and inactivated the p62/Keap1/Nrf2 pathway in T24/5637 cells. p62 up-regulation partially abrogated the inhibition of NEDD4L on the Keap1/Nrf2 pathway activity, the malignant behavior of BLCA cells, and the DDP resistance of DDP-resistant BLCA cells. NEDD4L overexpression inhibited the tumor growth and the p62/Keap1/Nrf2 pathway activity in vivo in BLCA.

CONCLUSION

NEDD4L inhibits the progression of BLCA by inactivating the p62/Keap1/Nrf2 pathway. It may be an effective target for BLCA treatment.

The Multi-Faceted Consequences of NRF2 Activation throughout Carcinogenesis

The oxidative balance of a cell is maintained by the Kelch-like ECH-associated protein 1 (KEAP1)/nuclear factor erythroid 2-related factor 2 (NRF2) pathway. This cytoprotective pathway detoxifies reactive oxygen species and xenobiotics. The role of the KEAP1/NRF2 pathway as pro-tumorigenic or anti-tumorigenic throughout stages of carcinogenesis (including initiation, promotion, progression, and metastasis) is complex. This mini review focuses on key studies describing how the KEAP1/NRF2 pathway affects cancer at different phases. The data compiled suggest that the roles of KEAP1/NRF2 in cancer are highly dependent on context; specifically, the model used (carcinogen-induced vs genetic), the tumor type, and the stage of cancer. Moreover, emerging data suggests that KEAP1/NRF2 is also important for regulating the tumor microenvironment and how its effects are amplified either by epigenetics or in response to co-occurring mutations. Further elucidation of the complexity of this pathway is needed in order to develop novel pharmacological tools and drugs to improve patient outcomes.

The ubiquitin ligase TRIM21 regulates mutant p53 accumulation and gain of function in cancer

The tumor suppressor TP53 is the most frequently mutated gene in human cancers. Mutant p53 (mutp53) proteins often accumulate to very high levels in human cancers to promote cancer progression through the gain-of-function (GOF) mechanism. Currently, the mechanism underlying mutp53 accumulation and GOF is incompletely understood. Here, we identified TRIM21 as a critical E3 ubiquitin ligase of mutp53 by screening for specific mutp53-interacting proteins. TRIM21 directly interacted with mutp53 but not WT p53, resulting in ubiquitination and degradation of mutp53 to suppress mutp53 GOF in tumorigenesis. TRIM21 deficiency in cancer cells promoted mutp53 accumulation and GOF in tumorigenesis. Compared with p53R172H knockin mice, which displayed mutp53 accumulation specifically in tumors but not normal tissues, TRIM21 deletion in p53R172H knockin mice resulted in mutp53 accumulation in normal tissues, an earlier tumor onset, and a shortened life span of mice. Furthermore, TRIM21 was frequently downregulated in some human cancers, including colorectal and breast cancers, and low TRIM21 expression was associated with poor prognosis in patients with cancers carrying mutp53. Our results revealed a critical mechanism underlying mutp53 accumulation in cancers and also uncovered an important tumor-suppressive function of TRIM21 and its mechanism in cancers carrying mutp53.

TRIM21 Expression as a Prognostic Biomarker for Progression-Free Survival in HNSCC

Patients with head and neck squamous cell carcinoma (HNSCC) continue to have a rather poor prognosis. Treatment-related comorbidities have negative impacts on their quality of life. TRIM21 is a cytosolic E3 ubiquitin ligase that was initially described as an autoantigen in autoimmune diseases and later associated with the intracellular antiviral response. Here, we investigated the role of TRIM21 as a biomarker candidate for HNSCC in predicting tumor progression and patient survival. We analyzed TRIM21 expression and its association with clinical-pathological parameters in our HNSCC cohort using immunohistochemistry. Our HNSCC cohort included samples from 419 patients consisting of primary tumors (n = 337), lymph node metastases (n = 156), recurrent tumors (n = 54) and distant metastases (n = 16). We found that cytoplasmic TRIM21 expression was associated with the infiltration of immune cells into primary tumors. In addition, TRIM21 expression was significantly higher in primary tumors than in lymph node metastases, and increased TRIM21 expression was correlated with shorter progression-free survival in HNSCC patients. These results suggest that TRIM21 could be a new biomarker for progression-free survival.

Ginsenoside Rb1 Improves Post-Cardiac Arrest Myocardial Stunning and Cerebral Outcomes by Regulating the Keap1/Nrf2 Pathway

The prognosis of cardiac arrest (CA) is dismal despite the ongoing progress in cardiopulmonary resuscitation (CPR). ginsenoside Rb1 (Gn-Rb1) has been verified to be cardioprotective in cardiac remodeling and cardiac ischemia/reperfusion (I/R) injury, but its role is less known in CA. After 15 min of potassium chloride-induced CA, male C57BL/6 mice were resuscitated. Gn-Rb1 was blindly randomized to mice after 20 s of CPR. We assessed the cardiac systolic function before CA and 3 h after CPR. Mortality rates, neurological outcome, mitochondrial homeostasis, and the levels of oxidative stress were evaluated. We found that Gn-Rb1 improved the long-term survival during the post-resuscitation period but did not affect the ROSC rate. Further mechanistic investigations revealed that Gn-Rb1 ameliorated CA/CPR-induced mitochondrial destabilization and oxidative stress, partially via the activation of Keap1/Nrf2 axis. Gn-Rb1 improved the neurological outcome after resuscitation partially by balancing the oxidative stress and suppressing apoptosis. In sum, Gn-Rb1 protects against post-CA myocardial stunning and cerebral outcomes via the induction of the Nrf2 signaling pathway, which may offer a new insight into therapeutic strategies for CA.

Loss of SQSTM1/p62 Induces Obesity and Exacerbates Alcohol-Induced Liver Injury in Aged Mice

BACKGROUND

Alcohol-associated liver disease (ALD) is a worldwide health problem, of which the effective treatment is still lacking. Both detrimental and protective roles of adipose tissue have been implicated in ALD. Although alcohol increases adipose tissue lipolysis to promote alcohol-induced liver injury, alcohol also activates brown adipose tissue (BAT) thermogenesis as an adaptive response in protecting against alcohol-induced liver injury. Moreover, aging and obesity are also risk factors for ALD. In the present study, we investigated the effects of autophagy receptor protein SQSTM1/p62 on adipose tissue and obesity in alcohol-induced liver injury in both young and aged mice.

METHODS

Young and aged whole-body SQSTM1/p62 knockout (KO) and their age-matched wild-type (WT) mice were subjected to chronic plus binge (Gao-binge) alcohol feeding. Blood, adipose and liver tissues were collected for biochemical and histologic analysis.

RESULTS

Aged but not young SQSTM1/p62 KO mice had significantly increased body weight and fat mass compared with the matched WT mice. Gao-binge alcohol feeding induced white adipose atrophy and decreased levels of SQSTM1/p62 levels in adipose tissue in aged WT mice. SQSTM1/p62 KO aged mice were resistant to Gao-binge alcohol-induced white adipose atrophy. Alcohol feeding increased the expression of thermogenic genes in WT mouse BAT, which was significantly blunted in SQSTM1/p62 KO aged mice. Alcohol-fed aged SQSTM1/p62 KO mice showed significantly higher levels of serum alanine aminotransferase, hepatic triglyceride, and inflammation compared with young and aged WT mice fed with alcohol. Alcohol-fed SQSTM1/p62 KO mice also increased secretion of proinflammatory and angiogenic adipokines that may promote alcohol-induced liver injury.

CONCLUSIONS

Loss of SQSTM1/p62 in aged mice leads to obesity and impairs alcohol-induced BAT adaptation, resulting in exacerbated alcohol-induced liver injury in mice.

The intricate interplay between HIFs, ROS, and the ubiquitin system in the tumor hypoxic microenvironment

Alterations in protein ubiquitination and hypoxia-inducible factor (HIF) signaling both contribute to tumorigenesis and tumor progression. Ubiquitination is a dynamic process that is coordinately regulated by E3 ligases and deubiquitinases (DUBs), which have emerged as attractive therapeutic targets. HIF expression and transcriptional activity are usually increased in tumors, leading to poor clinical outcomes. Reactive oxygen species (ROS) are upregulated in tumors and have multiple effects on HIF signaling and the ubiquitin system. A growing body of evidence has shown that multiple E3 ligases and UBDs function synergistically to control the expression and activity of HIF, thereby allowing cancer cells to cope with the hypoxic microenvironment. Conversely, several E3 ligases and DUBs are regulated by hypoxia and/or HIF signaling. Hypoxia also induces ROS production, which in turn modulates the stability or activity of HIF, E3 ligases, and DUBs. Understanding the complex networks between E3 ligase, DUBs, ROS, and HIF will provide insights into the fundamental mechanism of the cellular response to hypoxia and help identify novel molecular targets for cancer treatment. We review the current knowledge on the comprehensive relationship between E3 ligase, DUBs, ROS, and HIF signaling, with a particular focus on the use of E3 ligase or DUB inhibitors in cancer.

CLEC-1 is a death sensor that limits antigen cross-presentation by dendritic cells and represents a target for cancer immunotherapy

Tumors exploit numerous immune checkpoints, including those deployed by myeloid cells to curtail antitumor immunity. Here, we show that the C-type lectin receptor CLEC-1 expressed by myeloid cells senses dead cells killed by programmed necrosis. Moreover, we identified Tripartite Motif Containing 21 (TRIM21) as an endogenous ligand overexpressed in various cancers. We observed that the combination of CLEC-1 blockade with chemotherapy prolonged mouse survival in tumor models. Loss of CLEC-1 reduced the accumulation of immunosuppressive myeloid cells in tumors and invigorated the activation state of dendritic cells (DCs), thereby increasing T cell responses. Mechanistically, we found that the absence of CLEC-1 increased the cross-presentation of dead cell-associated antigens by conventional type-1 DCs. We identified antihuman CLEC-1 antagonist antibodies able to enhance antitumor immunity in CLEC-1 humanized mice. Together, our results demonstrate that CLEC-1 acts as an immune checkpoint in myeloid cells and support CLEC-1 as a novel target for cancer immunotherapy.

Ginsenoside Rc Modulates SIRT6-NRF2 Interaction to Alleviate Alcoholic Liver Disease

Alcoholic liver disease (ALD) is a serious worldwide health problem. Ginsenoside Rc is a major active ingredient isolated from Panax ginseng, whose pharmacological effects counteract oxidative stress, inflammation, and lipid accumulation. However, it is still unclear whether ginsenoside Rc might exert beneficial effects on alcohol-induced liver injury. To this aim, mice primary hepatocytes (MPHs) were challenged with alcohol to test ginsenoside Rc's effects on their intracellular alcohol metabolism. C57BL/6J mice or SIRT6alb-/- mice were chronically fed a diet with added alcohol or given a single gavage of alcohol with or without ginsenoside Rc. Analyses of alcohol metabolism, oxidative stress, inflammation, lipid metabolism, and RNaseq expression were conducted to explore potential targets exploited by ginsenoside Rc to protect against ALD. Our results showed that ginsenoside Rc attenuated alcohol-induced liver injury by regulating oxidative stress, inflammation, and lipid accumulation both in vivo and in vitro. Ginsenoside Rc did increase the deacetylase activity of SIRT6, thereby lowering acetylated NRF2 levels, which elevated NRF2's stability, and subsequently exerting an antioxidant effect. In keeping with this, the hepatic knockout of SIRT6 almost abolished the hepatoprotective effects of ginsenoside Rc against ALD. Therefore, our results suggest that ginsenoside Rc attenuated hepatocytes' damage and oxidative stress in ALD by up-regulating the SIRT6/NRF2 pathway. Hence, ginsenoside Rc may be a promising drug to treat or relieve ALD.

Cytosolic TGM2 promotes malignant progression in gastric cancer by suppressing the TRIM21-mediated ubiquitination/degradation of STAT1 in a GTP binding-dependent modality

BACKGROUND

Previous studies have revealed the critical role of transglutaminase 2 (TGM2) as a potential therapeutic target in cancers, but the oncogenic roles and underlying mechanisms of TGM2 in gastric cancer (GC) are not fully understood. In this study, we examined the role and potential mechanism of TGM2 in GC.

METHODS

Western blotting, immunohistochemistry, CCK8, colony formation and transwell assays were used to measure TGM2 expression in the GC cells and tissues and to examine the in vitro role of TGM2 in GC. Xenograft and in vivo metastasis experiments were performed to examine the in vivo role of TGM2 in GC. Gene set enrichment analysis, quantitative PCR and western blotting were conducted to screen for potential TGM2 targets involved in GC. Gain/loss-of-function and rescue experiments were conducted to detect the biological roles of STAT1 in GC cells in the context of TGM2. Co-immunoprecipitation, mass spectrometry, quantitative PCR and western blotting were conducted to identify STAT1-interacting proteins and elucidate their regulatory mechanisms. Mutations in TGM2 and two molecules (ZM39923 and A23187) were used to identify the enzymatic activity of TGM2 involved in the malignant progression of GC and elucidate the underlying mechanism.

RESULTS

In this study, we demonstrated elevated TGM2 expression in the GC tissues, which closely related to pathological grade, and predicted poor survival in patients with GC. TGM2 overexpression or knockdown promoted (and inhibited) cell proliferation, migration, and invasion, which were reversed by STAT1 knockdown or overexpression. Further studies showed that TGM2 promoted GC progression by inhibiting STAT1 ubiquitination/degradation. Then, tripartite motif-containing protein 21 (TRIM21) was identified as a ubiquitin E3 ligase of STAT1 in GC. TGM2 maintained STAT1 stability by facilitating the dissociation of TRIM21 and STAT1 with GTP-binding enzymatic activity. A23187 abolished the role of TGM2 in STAT1 and reversed the pro-tumor role of TGM2 in vitro and in vivo.

CONCLUSIONS

This study revealed a critical role and regulatory mechanism of TGM2 on STAT1 in GC and highlighted the potential of TGM2 as a therapeutic target, which elucidates the development of medicine or strategies by regulating the GTP-binding activity of TGM2 in GC.

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.

STING pathway contributes to the prognosis of hepatocellular carcinoma and identification of prognostic gene signatures correlated to tumor microenvironment

Background

Hepatocellular carcinoma (HCC) is one of the most malignant solid tumors worldwide. Recent evidence shows that the stimulator of interferon genes (STING) pathway is essential for anti-tumor immunity via inducing the production of downstream inflammatory cytokines. However, its impact on the prognosis and tumor microenvironment of HCC was still limited known.

Methods

We obtained gene expression profiles of HCC from GEO, TCGA, and ICGC databases, and immune-related genes (IRGs) from the ImmPort database. Multivariate Cox regression was performed to identify independent prognostic factors. Nomogram was established to predict survival probability for individual patients. Kaplan–Meier curve was used to evaluate the survival difference. Afterward, ESTIMATE, TISCH, and TIMER databases were combined to assess the immune cell infiltration. Furthermore, the qPCR, western blotting, and immunohistochemistry were done to evaluate gene expression, and in vitro cell models were built to determine cell migratory ability.

Results

We found that gene markers of NLRC3, STING1, TBK1, TRIM21, and XRCC6 within STING pathway were independent prognostic factors in HCC patients. Underlying the finding, a predictive nomogram was constructed in TCGA-training cohort and further validated in TCGA-all and ICGC datasets, showing credible performance. Experimentally, up-regulated TBK1 promotes the ability of HCC cell migration. Next, the survival-related immune-related co-expressed gene signatures (IRCGS) (VAV1, RHOA, and ZC3HAV1) were determined in HCC cohorts and their expression was verified in human HCC cells and clinical samples. Furthermore, survival-related IRCGS was associated with the infiltration of various immune cell subtypes in HCC, the transcriptional expression of prominent immune checkpoints, and immunotherapeutic response.

Conclusion

Collectively, we constructed a novel prognostic nomogram model for predicting the survival probability of individual HCC patients. Moreover, an immune-related prognostic gene signature was determined. Both might function as potential therapeutic targets for HCC treatment in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02734-4.

The roles of E3 ligases in Hepatocellular carcinoma

Hepatocarcinogenesis is a complex multistep biological process involving genetic and epigenetic alterations that are accompanied by activation of oncoproteins and inactivation of tumor suppressors, which in turn results in Hepatocellular carcinoma (HCC), one of the common tumors with high morbidity and mortality worldwide. The ubiquitin-proteasome system (UPS) is the key to protein degradation and regulation of physiological and pathological processes, and E3 ligases are key enzymes in the UPS that contain a variety of subfamily proteins involved in the regulation of some common signal pathways in HCC. There is growing evidence that many structural or functional dysfunctions of E3 are engaged in the development and progression of HCC. Herein, we review recent research advances in HCC-associated E3 ligases, describe their structure, classification, functional roles, and discuss some mechanisms of the abnormal activation or inactivation of the HCC-associated signal pathway due to the binding of E3 to known substrates. In addition, given the success of proteasome inhibitors in the treatment of malignant cancers, we characterize the current knowledge and future prospects for targeted therapies against aberrant E3 in HCC.