Cell Death & Disease最新文献

Caspase-2 is a unique and conserved cysteine protease that is involved in several cellular processes, including different forms of cell death, maintenance of genomic stability, and the response to reactive oxygen species. Despite advances in caspase-2 research in recent years, the mechanisms underlying its activation remain largely unclear. Although caspase-2 is activated in the PIDDosome complex, its processing could occur even in the absence of PIDD1 and/or RAIDD, suggesting the existence of an alternative platform for caspase-2 activation. Here, we show that caspase-2 undergoes ubiquitination and interacts with scaffolding protein p62/sequestosome-1 (SQSTM1) under normal conditions and in response to DNA damage. p62 promotes proteasomal but not autophagic caspase-2 degradation as well as its dimerization and activation that triggers the caspase cascade and, subsequently, cell death. Inhibition of p62 expression attenuates cisplatin-induced caspase-2 processing and apoptosis. Notably, the ZZ domain of p62 is critical for caspase-2 binding, whereas the UBA domain is seemingly required to stabilize the p62-caspase-2 complex. Thus, we have uncovered the dual role of p62 in regulating caspase-2 activity: it can foster the degradation of caspase-2 in the proteasome or facilitate its activation by acting as a scaffold platform.

Unraveling the molecular nature of skin aging and keratinocyte senescence represents a challenging research project in epithelial biology. In this regard, depletion of p63, a p53 family transcription factor prominently expressed in human and mouse epidermis, accelerates both aging and the onset of senescence markers in vivo animal models as well as in ex vivo keratinocytes. Nonetheless, the biochemical link between p63 action and senescence phenotype remains largely unexplored. In the present study, through ultrahigh performance liquid chromatography-tandem mass spectroscopy (UPLC-MS/MS) and gas chromatography/mass spectrometry (GC/MS) metabolomic analysis, we uncover interesting pathways linking replicative senescence to metabolic alterations during p63 silencing in human keratinocytes. Integration of our metabolomic profiling data with targeted transcriptomic investigation empowered us to demonstrate that absence of p63 and senescence share similar modulation profiles of oxidative stress markers, pentose phosphate pathway metabolites and lyso-glycerophospholipids, the latter due to enhanced phospholipases gene expression profile often under p63 direct/indirect gene control. Additional biochemical features identified in deranged keratinocytes include a relevant increase in lipids production, glucose and pyruvate levels as confirmed by upregulation of gene expression of key lipid synthesis and glycolytic enzymes, which, together with improved vitamins uptake, characterize senescence phenotype. Silencing of p63 in keratinocytes instead, translates into a blunted flux of metabolites through both glycolysis and the Krebs cycle, likely due to a p63-dependent reduction of hexokinase 2 and citrate synthase gene expression. Our findings highlight the potential role of p63 in counteracting keratinocyte senescence also through fine regulation of metabolite levels and relevant biochemical pathways. We believe that our research might contribute significantly to the discovery of new implications of p63 in keratinocyte senescence and related diseases.

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.

The PI3K/Akt pathway is overexpressed in nearly 50% of hepatocellular carcinomas and inhibits apoptosis by promoting the expression of antiapoptotic genes. Serine protease inhibitors have been shown to induce apoptosis in hepatoma cells by downregulating SPINK13 in the PI3K/Akt pathway. In this study, SPINK13 was expressed in lentiviral vectors. Changes in signaling pathway adapter proteins, apoptosis regulatory proteins, cell cycle regulatory proteins, and the biological behavior of hepatocellular carcinoma were observed in cell and nude mouse xenograft models. The underlying mechanism of endogenous SPINK13-induced apoptosis in hepatocellular carcinoma cells was explored via transcriptomics. As a result, endogenous SPINK13 might inhibit the activity of Furin protease, downregulate the Notch1/Hes1 pathway in a binding manner, activate the direct effector PTEN, inhibit Akt phosphorylation, inactivate the downstream PI3K/Akt pathway, and ultimately lead to mitochondrial apoptosis and cell cycle arrest in hepatoma cells. Therefore, the Notch1/Hes1/PTEN pathway may act upstream of SPINK13 to downregulate the PI3K/Akt signaling pathway. Our study helps elucidate the underlying mechanism of SPINK13 in anti-hepatocellular carcinoma and lays a theoretical foundation for the development of novel therapeutic serine protease inhibitors.

Angiogenesis is well known to play a critical role in breast cancer. We previously reported that TNFAIP2 activates Rac1 to promote triple-negative breast cancer (TNBC) cell proliferation, migration, and chemoresistance. However, the potential contribution of TNFAIP2 to tumor angiogenesis remains unknown. In this study, we demonstrated that TNFAIP2 promotes TNBC angiogenesis by activating the Rac1-ERK-AP1-HIF1α signaling axis. Under hypoxia, TNFAIP2 activates Rac1 and ERK sequentially. Following that, ERK activates the AP-1 (c-Jun/Fra1) transcription factor. By employing chromatin immunoprecipitation and luciferase reporter assays, we showed that AP-1 directly interacts with the HIF1α gene promoter, thereby enhancing its transcription. The combined application of ERK inhibitors, U0126 or trametinib, with the VEGFR inhibitor Apatinib, additively suppresses angiogenesis and tumor growth of HCC1806 in nude mice. These findings provide new therapeutic strategies for TNBC.

In the context of acute brain injuries, where zinc neurotoxicity and oxidative stress are acknowledged contributors to neuronal damage, we investigated the pivotal role of lysosomes as a potential protective mechanism. Our research commenced with an exploration of epidermal growth factor (EGF) and its impact on lysosomal dynamics, particularly its neuroprotective potential against zinc-induced cytotoxicity. Using primary mouse cerebrocortical cultures, we observed the rapid induction of EGFR endocytosis triggered by EGF, resulting in a transient increase in lysosomal vesicles. Furthermore, EGF stimulated lysosomal biogenesis, evident through elevated expression of lysosomal-associated membrane protein 1 (LAMP-1) and the induction and activation of prominent lysosomal proteases, particularly cathepsin B (CTSB). This process of EGFR endocytosis was found to promote lysosomal augmentation, thus conferring protection against zinc-induced lysosomal membrane permeabilization (LMP) and subsequent neuronal death. Notably, the neuroprotective effects and lysosomal enhancement induced by EGF were almost completely reversed by the inhibition of clathrin-mediated and caveolin-mediated endocytosis pathways, along with the disruption of retrograde trafficking. Furthermore, tyrosine kinase inhibition of EGFR nullified EGFR endocytosis, resulting in the abrogation of EGF-induced lysosomal upregulation and neuroprotection. An intriguing aspect of our study is the successful replication of EGF's neuroprotective effects through the overexpression of LAMP-1, which significantly reduced zinc-induced LMP and cell death, demonstrated in both primary mouse cerebrocortical neuronal cultures and human embryonic kidney (HEK) cells. Our research extended beyond zinc-induced neurotoxicity, as we observed EGF's protective effects against other oxidative stressors linked to intracellular zinc release, including hydrogen peroxide (H₂O₂) and 1-methyl-4-phenylpyridinium ion (MPP⁺). Collectively, our findings unveil the intricate interplay between EGF-triggered EGFR endocytosis, lysosomal upregulation, an increase in the regulatory capacity for zinc homeostasis, and the subsequent alleviation of zinc-induced neurotoxicity. These results present promising avenues for therapeutic interventions to enhance neuroprotection by targeting lysosomal augmentation.

Autophagy has both protective and pathogenetic effects on injury caused by cerebral ischemia/reperfusion (I/R). Our previous research has indicated that stimulator of interferon genes (STING) could orchestrate microglia polarization following middle cerebral artery occlusion. However, it remains largely unexplored whether STING balances microglial polarization by regulating autophagy in brain I/R injury. Here, STING was observed to show an up-regulation in the microglia from mice subjected to experimental ischemic stroke. Strikingly, the deletion of STING led to the significant skewness of microglia activated by ischemia from a pro- to anti-inflammatory state and substantially alleviated ischemia-induced infarction and neuronal injury. In addition, STING-null mice can restore long-term neurobehavioral function. Then, the crosstalk between neuroinflammation and microglia autophagy was analyzed. The differential activity of autophagy in wild-type and STING-knockout (KO) mice or primary microglia was largely reversed when STING was restored in microglia. Irritating autophagy by rapamycin skewed the anti‑inflammatory state induced by STING-KO to a pro‑inflammatory state in microglia. Furthermore, microtubule-associated protein light-chain-3 (LC3) was identified as the key factor in the STING regulation of autophagy by glutathione-S-transferase (GST) pull-down analysis. Mechanically, STING can directly interact with LC3 through the STING transmembrane domain (1-139aa). Herein, current data determine the pivotal role of autophagy, specifically via LC3 protein, in the regulation of microglial phenotypic transformation by STING. These findings may provide a possible treatment target for delaying the progression of ischemic stroke.

In a retrospective analysis of clinical data from 587 DLBCL (diffuse large B-cell lymphoma) patients in China, 13.8% of cases were associated with HBV (hepatitis B virus) infection, leading to distinct clinical features and poorer prognosis. Moreover, HBV infection has a more pronounced impact on the survival of the GCB (germinal center B-cell-like) type DLBCL patients compared to the ABC (activated B-cell-like) type. In this study, we found that the expression of LncRNA MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) was downregulated in the HBV-infected GCB-type DLBCL patients, and the HBV core protein (HBX) directly inhibited the MALAT1 expression in DLBCL cells. Notably, the overexpression of HBX could attenuate the Erastin-induced ferroptosis in the GCB-type DLBCLs, while MALAT1 re-expression restored sensitivity in the HBX-overexpressing DLBCLs in vitro and in vivo. Mechanistically, MALAT1 competitively hindered SFPQ (splicing factor proline and glutamine-rich) from effectively splicing the pre-mRNA of SLC7A11 (solute carrier family 7 member 11), due to a shared TTGGTCT motif, which impeded the SLC7A11 pre-mRNA maturation and hence diminished its negative regulation on ferroptosis. Together, our study identified HBX's role in inhibiting MALAT1 expression, promoting SFPQ-mediated splicing of SLC7A11 pre-mRNA, and reducing the GCB-type DLBCL sensitivity to Erastin-induced ferroptosis. Combined with the recent studies that ferroptosis may be involved in the occurrence and development of DLBCL, these findings explain our clinical data analysis that DLBCL patients with low expression of MALAT1 have poorer prognosis and shorter overall survival, and provide a valuable therapeutic target for the HBV-infected GCB-type DLBCL patients.

SNF2L encodes an ISWI chromatin remodeling factor that promotes gene transcription and is consistently elevated in cancers. Previous studies have shown that inhibiting SNF2L expression in cancer cells leads to significant growth suppression, DNA damage, and cell death. However, the underlying mechanisms remain poorly understood. In this study, we demonstrated that cancer cells lacking SNF2L show significantly decreased glutathione (GSH) levels, leading to elevated reactive oxygen species (ROS) and increased oxidative stress. SNF2L deficiency also heightened the sensitivity of cancer cells to APR-246, a drug that depletes GSH and induces oxidative stress, consequently decreasing cell viability and increasing ROS levels, regardless of p53 status. Mechanistically, we found that NRF2 recruits SNF2L to the SLC7A11 promoter, leading to increased chromatin accessibility and facilitating SLC7A11 transcription. This results in decreased cystine uptake and impaired GSH biosynthesis. These findings suggest that targeting the SNF2L/SLC7A11 axis could enhance the effectiveness of APR-246 by depleting GSH and increasing ROS level in cancer cells, highlighting SNF2L as a promising therapeutic target.

The linear ubiquitin chain assembly complex (LUBAC) plays crucial roles in NF-κB signaling and protection against cell death by generating linear ubiquitin chains. Its accessory subunits, HOIL-1L and SHARPIN, regulate LUBAC function by binding to ubiquitin chains via their Npl4 zinc finger (NZF) domains. However, the synergistic effects of the two NZF domains on LUBAC function remain unclear. Here, we demonstrate that the ubiquitin-binding activity of the two NZF domains cooperatively regulates LUBAC functions. Simultaneous loss of the ubiquitin-binding activity of the NZF domains profoundly impaired both NF-κB activation and cell death protection functions. HOIL-1L NZF robustly binds to linear ubiquitin chains, whereas SHARPIN NZF binds to Lys(K)63-linked ubiquitin chains in addition to linear chains. Binding of both NZF domains to linear ubiquitin chains regulated NF-κB signaling, whereas SHARPIN NZF predominantly regulated the cell death protection function independently of the ubiquitin chain type, K63-linked or linear ubiquitin. However, concomitant loss of linear ubiquitin binding by HOIL-1L NZF drastically impaired cell death protection. A screen of compounds capable of inhibiting binding between HOIL-1L NZF and linear ubiquitin chains identified a small compound that inhibited SHARPIN NZF as well as HOIL-1L NZF binding to linear ubiquitin chains, supporting the synergistic effect of the two NZF domains on cell death protection and suggesting a potential therapeutic strategy for targeting increased LUBAC activity in diseases such as cancer.