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A hallmark of muscle atrophy is the excessive degradation of myofibrillar proteins primarily by the ubiquitin proteasome system. In mice, during the rapid muscle atrophy induced by fasting, the desmin cytoskeleton and the attached Z-band–bound thin filaments are degraded after ubiquitination by the ubiquitin ligase tripartite motif-containing protein 32 (Trim32). To study the order of events leading to myofibril destruction, we investigated the slower atrophy induced by denervation (disuse). We show that myofibril breakdown is a two-phase process involving the initial disassembly of desmin filaments by Trim32, which leads to the later myofibril breakdown by enzymes, whose expression is increased by the paired box 4 (PAX4) transcription factor. After denervation of mouse tibialis anterior muscles, phosphorylation and Trim32-dependent ubiquitination of desmin filaments increased rapidly and stimulated their gradual depolymerization (unlike their rapid degradation during fasting). Trim32 down-regulation attenuated the loss of desmin and myofibrillar proteins and reduced atrophy. Although myofibrils and desmin filaments were intact at 7 d after denervation, inducing the dissociation of desmin filaments caused an accumulation of ubiquitinated proteins and rapid destruction of myofibrils. The myofibril breakdown normally observed at 14 d after denervation required not only dissociation of desmin filaments, but also gene induction by PAX4. Down-regulation of PAX4 or its target gene encoding the p97/VCP ATPase reduced myofibril disassembly and degradation on denervation or fasting. Thus, during atrophy, the initial loss of desmin is critical for the subsequent myofibril destruction, and over time, myofibrillar proteins become more susceptible to PAX4-induced enzymes that promote proteolysis.

The CST (CTC1‐STN1‐TEN1) complex, a single‐stranded DNA (ssDNA) binding complex, is essential for telomere maintenance and genome stability. Depletion of either CTC1 or STN1 results in cellular senescence, while mutations in these components are associated with severe hereditary disorders. In this study, we demonstrate that the direct STN1‐CTC1 interaction stabilizes CTC1 by preventing its degradation via TRIM32 mediated ubiquitination. Functional assays indicate that TRIM32 and the CTC1/STN1 complex exert opposing effects on cellular proliferation. Additionally, transcriptomic analysis of large‐scale RNA sequencing data from the Genotype‐Tissue Expression (GTEx) reveals inverse expression patterns of TRIM32 and CTC1/STN1 during somatic cell aging. Structural modeling using AlphaFold3 predicts that the TRIM32‐CTC1 interaction occurs at the OB‐G domain of CTC1, with the binding interface positioned near the STN1‐interacting region, termed the “cleft” motif. Mechanistically, STN1 likely associates with the OB‐G domain of CTC1, competing with TRIM32 for binding sites and thereby interfering with TRIM32‐mediated ubiquitination of CTC1. Collectively, our findings identify STN1 as a critical regulator of CST complex integrity and cellular aging by safeguarding CTC1 from TRIM32‐driven ubiquitin‐proteasome degradation. STN1 safeguards CTC1 from TRIM32‐mediated ubiquitin‐proteasome degradation, thereby preserving CST complex integrity and its roles in telomere maintenance, DNA replication, and DNA damage repair.

Background Bone metastasis is a principal cause of mortality in patients with prostate cancer (PCa). Increasing evidence indicates that high expression of stromal interaction molecule 1 (STIM1)-mediated store-operated calcium entry (SOCE) significantly activates the calcium (Ca 2+ ) signaling pathway and is involved in multiple steps of bone metastasis in PCa. However, the regulatory mechanism and target therapy of STIM1 is poorly defined. Methods Liquid chromatography-mass spectrometry analysis was performed to identify tetraspanin 18 (TSPAN18) as a binding protein of STIM1. Co-IP assay was carried out to explore the mechanism by which TSPAN18 inhibits STIM1 degradation. The biological function of TSPAN18 in bone metastasis of PCa was further investigated in vitro and in vivo models. Result We identified that STIM1 directly interacted with TSPAN18, and TSPAN18 competitively inhibited E3 ligase tripartite motif containing 32 (TRIM32)-mediated STIM1 ubiquitination and degradation, leading to increasing STIM1 protein stability. Furthermore, TSPAN18 significantly stimulated Ca 2+ influx in an STIM1-dependent manner, and then markedly accelerated PCa cells migration and invasion in vitro and bone metastasis in vivo. Clinically, overexpression of TSPAN18 was positively associated with STIM1 protein expression, bone metastasis and poor prognosis in PCa. Conclusion Taken together, this work discovers a novel STIM1 regulative mechanism that TSPAN18 protects STIM1 from TRIM32-mediated ubiquitination, and enhances bone metastasis of PCa by activating the STIM1-Ca 2+ signaling axis, suggesting that TSPAN18 may be an attractive therapeutic target for blocking bone metastasis in PCa.

Ferroptosis, characterized by iron-dependent phospholipid peroxidation, is recognized as one of the cell death pathways activated following spinal cord injury (SCI). However, the precise regulatory mechanisms governing this process remain poorly understood. Here, this study identified TRIM32, an E3 ubiquitin ligase, as a key enhancer of neuronal ferroptosis. TRIM32 promoted neuronal ferroptosis by accelerating the degradation of GPX4, which is an essential inhibitor of ferroptosis. Conditional deletion of in neurons markedly inhibited neuronal ferroptosis and promoted neuronal survival, eventually improving mouse locomotor functional recovery after SCI. However, overexpression of showed aggravated neuronal loss and poor behavioral function, which could be attenuated by ferroptosis inhibitor Liproxstatin-1. Mechanistically, TRIM32 interacted with GPX4, promoted K63-linked ubiquitination modification of GPX4 at K107, thus enhanced p62-dependent autophagic degradation of GPX4. Moreover, ROS-ATM-Chk2 signaling pathway phosphorylates TRIM32 at S55, further contributing to GPX4 ubiquitination and degradation and subsequent neuronal ferroptosis after SCI, suggesting a positive feedback loop between ROS and TRIM32. Clinically, lipid peroxidation was significantly promoted in patients with SCI. These findings reveal that TRIM32 functions as a neuronal ferroptosis enhancer which is detrimental to neuronal survival and locomotor functional recovery in mice after SCI by promoting K63-linked ubiquitination and subsequent p62-dependent autophagic degradation of GPX4, suggesting a promising therapeutic target for SCI.

The tripartite motif (TRIM) family comprises more than 70 members involved in the regulation of many cellular pathways. TRIM32 acts as an E3 ubiquitin ligase and has been reported to participate in many human cancers. Here, we aimed to investigate the role of TRIM32 in gastric cancer (GC) and the clinical implications. High expression of TRIM32 was observed in GC tissues and cell lines, and was significantly associated with poor prognosis. Knockdown TRIM32 expression remarkably suppressed the proliferation, migration, and invasion of GC cells in vitro and tumour growth in vivo, whereas overexpression of TRIM32 yielded the opposite results. Western blotting and quantitative reverse‐transcription PCR (qRT‐PCR) analyses revealed that up‐regulation of TRIM32 significantly enhanced expression of β‐catenin protein and of its downstream targets TCF1, cyclin D1, Axin2 and MMP7 mRNAs. Moreover, we found that the mechanism behind the TRIM32‐promoted GC progression was related to the β‐catenin signalling pathway. Collectively, these data suggest that TRIM32 promotes GC cell proliferation, migration, and invasion by activating the β‐catenin signalling pathway.

Spinal cord injury (SCI) is a disabling disease associated with microglial activation. Tripartite motif containing 32 (TRIM32) is an E3 ubiquitin ligase that plays a role in SCI. This study aimed to explore the role of TRIM32 in SCI and its potential mechanisms. We established an SCI mouse model to assess the function of TRIM32 using quantitative real-time polymerase chain reaction (qPCR), and hematoxylin and eosin staining. Additionally, a lipopolysaccharides (LPS)-induced cell injury model was generated to explore the impact of TRIM32 on pyroptosis using qPCR, propidium iodide staining, and western blotting. The ubiquitylation of NEK7 was analyzed using western blotting, co-immunoprecipitation, and immunofluorescence staining. The results showed that TRIM32 expression was increased in SCI mice and LPS-induced BV-2 cells. Overexpression of TRIM32 ameliorated SCI in mice and suppressed pyroptosis in LPS-treated BV-2 cells. Additionally, the E3 ligase TRIM32 promoted the ubiquitylation of NEK7 at the K64 site, leading to the downregulation of NEK7 levels. Inhibiting NEK7 ubiquitylation reversed the suppression of pyroptosis by TRIM32. In conclusion, TRIM32 inhibits microglia pyroptosis by facilitating the ubiquitylation of NEK7 at the K64 site, thereby alleviating the progression of SCI. The findings suggest that TRIM32 has the potential to be a therapeutic target of SCI.

Background The tumor microenvironment (TME) in gastric cancer (GC) exhibits immunosuppressive features that facilitate tumor advancement and obstruct the effectiveness of immunotherapy. The role of tripartite motif 32 (TRIM32) in the TME has not been extensively studied. Methods GC mouse model was utilized along with flow cytometry analysis, transwell assays, and immunohistochemistry to investigate the impact of TRIM32 on tumor progression and macrophage. To uncover the mechanisms by which TRIM32 operates within the GC microenvironment, various molecular and biochemical methods were utilized, including RNA-sequencing, western blotting, quantitative reverse transcription-polymerase chain reaction, coimmunoprecipitation, and immunofluorescence. Results TRIM32 originating from tumors was found to be linked to poor prognosis and notably associated with tumor-associated macrophages (TAMs) in. In vitro experiments revealed that TRIM32 induced TAMs recruitment and M2-like polarization. Mechanismly, TRIM32 interacted with Phosphodiesterase 9 A (PDE9A) and activated the downstream phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) signaling pathway. Additionally, the reprogramming of TAMs by TRIM32 diminished the resistance to anti-PD-1 treatment in GC models. Conclusion TRIM32/PDE9A axis promotes immune evasion in tumors and hinders the effectiveness of anti-PD-1 treatment by inducing TAMs recruitment and M2-like polarization in GC. This research provides insight into the role of TRIM32 in modulating tumor immunity and suggests that TRIM32 could be a promising target to overcoming resistance to anti-PD-1 therapy in GC.

Background Exploiting cancer metabolism during nutrient availability holds immense potential for the clinical and therapeutic benefits of hepatocellular carcinoma (HCC) patients. Dietary methionine is a metabolic dependence of cancer development, but how the signal transduction integrates methionine status to achieve the physiological demand of cancer cells remains unknown. Methods Low or high levels of dietary methionine was fed to mouse models with patient-derived xenograft or diethyl-nitrosamine induced liver cancer. RNA sequence and metabolomics were performed to reveal the profound effect of methionine restriction on gene expression and metabolite changes. Immunostaining, sphere formation assays, in vivo tumourigenicity, migration and self-renewal ability were conducted to demonstrate the efficacy of methionine restriction and sorafenib. Results We discovered that mTORC1-c-Myc-SIRT4 axis was abnormally regulated in a methionine-dependent manner and affected the HCC progression. c-Myc rewires methionine metabolism through TRIM32 mediated degradation of SIRT4, which regulates MAT2A activity by ADP-ribosylation on amino acid residue glutamic acid 111. MAT2A is a key enzyme to generate S-adenosylmethionine (SAM). Loss of SIRT4 activates MAT2A, thereby increasing SAM level and dynamically regulating gene expression, which triggers the high proliferation rate of tumour cells. SIRT4 exerts its tumour suppressive function with targeted therapy (sorafenib) by affecting methionine, redox and nucleotide metabolism. Conclusions These findings establish a novel characterization of the signaling transduction and the metabolic consequences of dietary methionine restriction in malignant liver tissue of mice. mTORC1, c-Myc, SIRT4 and ADP ribosylation site of MAT2A are promising clinical and therapeutic targets for the HCC treatment.

TRIM32 protein represents a crucial member of TRIM family that is highly expressed in numerous human cancers, and is associated with a poor prognosis. However, the mechanism of TRIM32 in colorectal cancer (CRC) is unclear. The expression of TRIM32 and its prognostic value in CRC were analyzed using The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database. Real-time quantitative PCR, immunohistochemistry (IHC), and cell proliferation assays were used to explore the effects of down-regulation of TRIM32 expression on the proliferation, migration, and apoptosis of cultured CRC cells (HCT116 and SW480 cells) and in xenogeneic tumorigenic animals. Bioinformatics analysis showed that TRIM32 is up-regulated in many types of cancers, and exhibits significant prognostic value in CRC. Western blotting results showed that after knocking down TRIM32, the expression level of IκBα increased, and the expression levels of TRIM32, p-p65, Bcl-2, and IKKβ decreased. The inhibitory effect of TRIM32 on CRC in vivo was evaluated by measuring tumor volume and weight, Hematoxylin and eosin (H&E) staining, and Ki67 IHC staining in heterotopic tumor-forming mice with CRC. Down-regulation of TRIM32 can inhibit the activation of the NF-κB signaling pathway and the occurrence of CRC. Our research provides a new insight into the pathogenesis of CRC, and a therapeutic target for the treatment of CRC.