Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2025046
The cGAS-STING signaling pathway serves as a pivotal surveillance mechanism for cytosolic double-stranded DNA (dsDNA) detection in mammalian systems. While STING-mediated type I interferon production is crucial for host defense, sustained activation of this pathway contributes to autoimmune pathologies, including systemic lupus erythematosus (SLE). Maintaining immune homeostasis requires precise regulation of STING activity to prevent hyperactivation. Our study identifies TRIM21 as a novel positive regulator of cGAS-STING signaling in SLE pathogenesis. Our results demonstrate that TRIM21 overexpression stabilizes STING by suppressing autophagic degradation, whereas TRIM21 depletion accelerates this clearance process. Mechanistically, TRIM21 catalyzes the K63-linked polyubiquitylation of the selective autophagy receptor p62/SQSTM1, disrupting its interaction with STING. This post-translational modification prevents the sequestration of STING into autophagosomes, thereby stabilizing the adaptor protein and amplifying downstream type I interferon responses. Our findings reveal a previously unrecognized regulatory circuit in which TRIM21 orchestrates cross-talk between ubiquitin signaling and autophagy to control STING turnover. The TRIM21-p62 axis represents a potential therapeutic target for attenuating pathological interferon production in STING-dependent autoimmune disorders. This work advances our understanding of immune regulation by demonstrating how E3 ligase-mediated ubiquitin modifications modulate cargo recognition in selective autophagy pathways. The identified mechanism provides new insights into the molecular interplay between protein ubiquitylation and autophagic degradation in maintaining the innate immune balance, offering novel perspectives for developing targeted therapies against interferonopathies associated with cGAS-STING hyperactivity.
Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2025019
Cancer cells evade immune detection through checkpoint molecules like PD-L1 and PD-L2 which suppress T-cell activation. While PD-L1 is well-studied, the role of PD-L2 remains unclear. Pyruvate kinase M2 (PKM2), a metabolic enzyme, influences immune checkpoint regulation, but its role in PD-L1 and PD-L2 modulation is not well defined. Here, we investigate the role of pyruvate kinase M2 (PKM2) in modulating the immune checkpoint molecules PD-L1 and PD-L2 via GATA3 in cancer cells, with insights from both human and mouse models. We find that PKM2 enhances PD-L1 expression while inhibiting PD-L2, a dual regulatory mechanism that facilitates immune evasion. Knockdown and overexpression experiments revealed GATA3 as a key mediator. PKM2 knockout reduced GATA3 level, leading to decreased PD-L1 and increased PD-L2 expression. Chromatin immunoprecipitation (ChIP)-qPCR demonstrates that GATA3 functions as a direct transcription factor capable of binding to the promoters of PD-L1 and PD-L2. In silico analyses of 81 esophageal squamous cell carcinoma (ESCC) cases from the TCGA database demonstrate that PKM2 mRNA is unrelated to PD-L1 and PD-L2 expression but is negatively correlated with CD8+ T-cell infiltration in ESCC. To further validate these findings, we establish a xenograft model using immune-competent C57/BL6N mice, where knockdown of PKM2 results in significant downregulation of both PD-L1 and PD-L2 expression. Collectively, these findings underscore the divergent roles of PKM2 in regulating immune checkpoint expression in human and mouse cancer models and suggest that targeting the PKM2-GATA3 axis could enhance cancer immunotherapy by fine-tuning PD-L1 and PD-L2 levels.
Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2024162
Hepatic fibrosis (HF) is an abnormal reparative response of the liver to chronic injury and is histologically reversible. In recent years, increasing interest has been given to changes in m6A in liver disease. In this study, we explore the role of the m6A-modified reading protein YTHDF2 in HF and its regulatory mechanism. The HF mouse model is generated through CCl4 injection, and the cell model is via TGF-β stimulation. The liver tissues are subjected to hematoxylin-eosin, Masson, and α-SMA immunohistochemical staining. Reactive oxygen species (ROS) and iron levels are examined via relevant kits. Quantitative real-time PCR, immunofluorescence staining, and western blot analysis were conducted to measure the YTHDF2 and ACSL4 levels. RNA immunoprecipitation, methylated RNA immunoprecipitation, RNA pull-down, and polysome fractionation were performed to understand the regulatory mechanism by which YTHDF2 affects ACSL4. The results show that YTHDF2 is highly expressed after HF induction, and the inhibition of YTHDF2 reduces fibrosis as well as ROS and iron levels. In vitro, overexpression of YTHDF2 increases hepatic stellate cell activation, as well as ROS and iron levels, and this effect is blocked by the silencing of ACSL4. YTHDF2 acts as a regulator of ACSL4 expression and is involved in m6A modification. In addition, in vivo experiments indicate that overexpression of ACSL4 reverses the attenuating effect of YTHDF2 interference on HFs. Therefore, YTHDF2 mediates the expression of the ferroptosis marker protein ACSL4 in an m6A-dependent manner, thereby affecting HF.
Stem Cell Research & Therapy•2026•DOI: 10.1186/s13287-026-04919-4
Lung cancer remains the leading cause of cancer mortality worldwide, with non-small cell lung cancer (NSCLC) accounting for approximately 85% of diagnoses. Lung cancer stem-like cells (LCSCs) drive metastasis, recurrence, and therapeutic failure, yet effective targeting strategies remain elusive. Oxysterol-binding protein-like 2 (OSBPL2/ORP2) is a lipid transport protein that localizes to lipid droplets (LDs) and regulates cholesterol homeostasis, but its role in lung cancer stemness has not been defined. Here, we demonstrate that OSBPL2 reduces cellular cholesterol content, as quantified by HPLC-MS, and inhibits lipid droplet accumulation in lung cancer cells. OSBPL2-mediated lipid transportation significantly suppressed tumor sphere formation, stemness marker expression (ALDH1A1, CD133, Nanog), and in vivo tumorigenesis and metastasis. In peritoneal carcinomatosis models using BALB/c mice (n=10 per group) injected with L-Osbpl2 or L-Vector transduced LLC cells (5×10^6 cells/100µL), OSBPL2 overexpression reduced metastatic tumor burden. Clinical specimen analysis revealed that OSBPL2 represses LCSC marker expression and its level negatively correlates with tumor stage progression and lymph node metastasis. These findings establish OSBPL2 as a critical regulator of lung cancer stemness through lipid metabolic reprogramming, offering a potential therapeutic target for aggressive NSCLC.
Chinese Journal of Tissue Engineering Research•2026•DOI: 10.12307/2026.21207
BACKGROUND: Hypoxia preconditioning can increase extracellular vesicles, growth factors, anti-inflammatory and immunosuppressive factors in the parasecretory secretions of mesenchymal stem cells. Exosomes derived from human amniotic mesenchymal stem cells preconditioned with hypoxia are expected to play a better therapeutic role in tissue damage repair. OBJECTIVE: To observe the repair effect of exosomes from human amniotic mesenchymal stem cells preconditioned with hypoxia on radiation-induced submandibular gland epithelial cell damage. METHODS: The passage 3 human amniotic mesenchymal stem cells were divided into two groups: hypoxia and normoxia. They were pretreated with hypoxia (1% O2 by volume) and normoxia (20% O2 by volume) for 48 hours, respectively. Then, normoxic and hypoxic human amniotic mesenchymal stem cell exosomes were extracted from the culture supernatant of human amniotic mesenchymal stem cells by modified ultrahigh-speed centrifugation. The submandibular gland epithelial cells of SD newborn rats were divided into blank control group, radiation control group, normoxia-treated group, and hypoxia-treated group. The submandibular gland epithelial cells were treated with 5 Gy radiation to construct a radiation-induced injury model. The normoxia-treated and hypoxia-treated groups were co-cultured with normoxic or hypoxic exosomes for 3 days. CCK-8 assay was used to detect the proliferation activity of rat submandibular gland epithelial cells; ELISA was used to measure the content of α-amylase in the supernatant; RT-qPCR was used to detect the expression of aquaporin 5 mRNA. RESULTS AND CONCLUSION: The cell proliferation activity in the radiation control group was significantly lower than that in the blank control group (P < 0.05). The cell proliferation activity in the normoxia-treated and hypoxia-treated groups on days 2 and 3 was significantly higher than that in the radiation control group (P < 0.05). The cell proliferation activity in the hypoxia-treated group on day 1 was higher than that in the normoxia-treated group, and showed an increasing trend on days 2 and 3, but there was no statistical difference compared with the normoxia-treated group (P > 0.05). The α-amylase content in the radiation control group was significantly lower than that in the blank control group (P < 0.05). The α-amylase content in the normoxia-treated and hypoxia-treated groups was significantly higher than that in the radiation control group (P < 0.05). Compared with the normoxia-treated group, the α-amylase content in the hypoxia-treated group showed an increasing trend, but there was no statistical difference (P > 0.05). The expression of aquaporin 5 mRNA in the radiation control group was significantly lower than that in the blank control group (P < 0.05). The expression of aquaporin 5 mRNA in the normoxia-treated and hypoxia-treated groups was significantly higher than that in the radiation control group (P < 0.05). The expression of aquaporin 5 mRNA in the hypoxia-treated group was slightly higher than that in the normoxia-treated group, but there was no statistical difference (P > 0.05). The results indicate that both normoxic and hypoxic preconditioned human amniotic mesenchymal stem cell exosomes have a repair effect on radiation-induced submandibular gland epithelial cell damage, but hypoxic exosomes have no obvious advantage.
Stem Cell Research & Therapy•2026•DOI: 10.1186/s13287-026-04919-4
Lung cancer is the first leading cause of cancer death worldwide. Oxysterol-binding protein-like 2 (OSBPL2) is a lipid transport protein regulating cholesterol homeostasis. Here, we clarified the previously unreported role of OSBPL2 in lung cancer stemness properties. We observed that OSBPL2 reduced cholesterol content by HPLC-MS. It inhibited the accumulation of lipid droplets (LDs) in lung cancer. OSBPL2-mediated lipid transportation significantly suppressed tumor sphere formation, stemness markers expression and in vivo tumorigenesis and tumor metastasis. In clinical specimens, we also demonstrated that OSBPL2 repressed the expression of Lung cancer stem-like cells (LCSCs) markers-ALDH1A1, CD133 and Nanog. The level of OSBPL2 was negatively correlated with malignant of lung cancer, such as tumor stage progression and lymph node metastasis. Taken together, these findings illustrated that OSBPL2-mediated lipid transportation inhibited the stemness and aggressiveness of lung cancer cells. OSBPL2 was a potential therapeutic target to develop novel cancer-preventive compound.
Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2025019
Cancer cells evade immune detection through checkpoint molecules PD-L1 and PD-L2, which suppress T-cell activation. While PD-L1 is well-studied, the role of PD-L2 remains unclear. Pyruvate kinase M2 (PKM2), a metabolic enzyme, influences immune checkpoint regulation, but its role in PD-L1 and PD-L2 modulation is not well defined. Here, we investigate the role of PKM2 in modulating PD-L1 and PD-L2 via GATA3 in cancer cells, with insights from both human and mouse models. We find that PKM2 enhances PD-L1 expression while inhibiting PD-L2, a dual regulatory mechanism that facilitates immune evasion. Knockdown and overexpression experiments revealed GATA3 as a key mediator. PKM2 knockout reduced GATA3 level, leading to decreased PD-L1 and increased PD-L2 expression. Chromatin immunoprecipitation (ChIP)-qPCR demonstrates that GATA3 functions as a direct transcription factor capable of binding to the promoters of PD-L1 and PD-L2. In silico analyses of 81 esophageal squamous cell carcinoma (ESCC) cases from the TCGA database demonstrate that PKM2 mRNA is unrelated to PD-L1 and PD-L2 expression but is negatively correlated with CD8+ T-cell infiltration in ESCC. To further validate these findings, we establish a xenograft model using immune-competent C57/BL6N mice, where knockdown of PKM2 results in significant downregulation of both PD-L1 and PD-L2 expression. Collectively, these findings underscore the divergent roles of PKM2 in regulating immune checkpoint expression in human and mouse cancer models and suggest that targeting the PKM2-GATA3 axis could enhance cancer immunotherapy by fine-tuning PD-L1 and PD-L2 levels.