Acta biochimica et biophysica Sinica最新文献

Chemoresistance remains a critical barrier to the efficacy of oxaliplatin in colon cancer treatment. While the deubiquitinating enzyme USP46 is implicated in multiple tumor progression pathways, its specific role in oxaliplatin resistance remains undetermined. Our analysis reveals that USP46 is significantly overexpressed in colon cancer tissues, with its elevated expression correlating with poor clinical outcomes in colon cancer patients. Silencing USP46 suppresses both the proliferation and metastatic potential of colon cancer cells while simultaneously enhancing cellular sensitivity to the DNA-damaging agent oxaliplatin. Mechanistically, overexpression of USP46 leads to upregulation of nuclear RAD51 expression and facilitates the assembly of RAD51 foci, thereby increasing homologous recombination repair (HRR) capacity and contributing to oxaliplatin resistance in colon cancer cells. MCM7 is identified as a bona fide substrate of USP46 by LC-MS/MS profiling. Subsequent experiments confirm that USP46 specifically removes K48-linked polyubiquitin chains from MCM7, thereby stabilizing its protein expression. Rescue assays validate that USP46 modulates RAD51 expression and HRR function in an MCM7-dependent manner. Collectively, our study uncovers a novel USP46-MCM7-RAD51 signaling cascade that confers oxaliplatin resistance in colon cancer via augmentation of HRR-dependent DNA repair, thereby establishing this axis as a promising therapeutic target for overcoming oxaliplatin resistance.

The relentless evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the emergence of immune-evasive variants underscore an urgent need for novel therapeutic strategies that are resilient to viral mutations. Targeting conserved host factors essential for viral entry represents a promising approach to overcome this challenge. Here, we report the development of a bifunctional therapeutic platform targeting the primary human receptor for SARS-CoV-2, angiotensin-converting enzyme 2 (ACE2). Using systematic evolution of ligands by exponential enrichment (SELEX), we isolate a high-affinity DNA aptamer, designated AA2, that binds to human ACE2 with a dissociation constant ( Kd) of 5.41 ± 1.23 nM. Molecular docking and competitive binding assays confirm that AA2 sterically hinders the interaction between the viral spike receptor-binding domain (RBD) and ACE2. Consequently, AA2 demonstrates potent neutralization of SARS-CoV-2 S pseudovirus entry into host cells. To achieve a synergistic antiviral effect, we engineer an aptamer-siRNA chimera (AsiC) by conjugating AA2 to a short interfering RNA (siRNA) targeting the GFP coding region of the pseudovirus genome. This AsiC construct significantly represses viral replication compared to aptamer or siRNA treatment alone, validating a dual mechanism of action that combines receptor blockade with targeted gene silencing. This study establishes a robust proof-of-concept for an ACE2-targeted AsiC, representing a new class of dual-function antiviral therapeutics with the potential to effectively combat current and future ACE2-dependent coronaviruses.

Transfer RNA (tRNA) acts not only as an indispensable adaptor in protein synthesis but also as a key contributor to tumorigenesis when its regulation is disrupted. This review systematically summarizes aberrant tRNA-related mechanisms in cancer, including altered tRNA expression profiles, abnormal post-transcriptional modifications, dysregulated aminoacylation, production of tRNA-derived small RNAs (tdRs), and defects in tRNA trafficking and translational fidelity. Notably, the metabolically abnormal tumor microenvironment actively shapes tRNA reprogramming to facilitate adaptive survival, while dysregulated tRNA elements, such as specific modifications and tdRs, further drive cancer stem cell properties and therapeutic resistance. Collectively, these alterations reprogram the oncoproteome and signaling networks, thereby promoting tumor cell proliferation, metastasis, immune evasion, and drug resistance. Targeting these mechanisms represents a promising strategy for developing novel cancer therapies. Potential approaches include the use of suppressor tRNAs to restore tumor suppressor gene function, the employment of tdRs to modulate oncogenic signaling pathways, or direct inhibition of enzymes involved in tRNA biogenesis. These strategies aim to remodel the dysfunctional tRNA network in cancer and offer new avenues for innovative treatments.

MgtE channels play crucial roles in Mg ^{2 +} homeostasis and are implicated in bacterial survival under antibiotic exposure. Previous structural and biophysical studies have focused predominantly on Thermus thermophilus MgtE, leaving the structural and mechanistic diversity of MgtE family proteins largely unexplored. In this study, via a genome mining approach, we identify diverse MgtE homologs, including a novel subclass termed the "mini-N type", which lacks the canonical cytoplasmic N and CBS domains but possesses a unique small N-like domain. Despite extensive expression screening, mini-N-type homologs cannot be stably purified. To address this issue, we design a series of de novo proteins and determine their crystal structures. A selected de novo protein is fused to a mini-N-type MgtE, enabling successful purification and preliminary cryo-EM imaging. Our findings demonstrate that de novo-designed protein fusions serve as powerful tools for stabilizing and purifying otherwise unstable membrane proteins, opening new avenues for structural and functional studies of otherwise inaccessible membrane proteins.

This study aims to investigate the role of macrophage PELI1 in sepsis-induced inflammation and coagulation dysfunction, focusing on its regulatory mechanism over the secretome through the JAK2/STAT3 signaling pathway. Analysis of a public single-cell RNA-seq dataset from septic patients reveals significant upregulation of PELI1 in CD14 ⁺ monocytes from non-survivors. To functionally validate this finding, a murine sepsis model is established using cecal ligation and puncture (CLP). Protein and gene expression levels in lung tissue and plasma are detected by RT-qPCR, western blotting, and ELISA, while lung injury and fibrin deposition are assessed by H&E staining and immunohistochemistry. For in vitro experiments, PELI1 expression is modulated in RAW264.7 macrophages using gene knockdown strategies. Our results confirm that PELI1 is significantly upregulated in septic mice and closely associates with severe inflammatory responses and coagulation dysfunction. Mechanistically, PELI1 knockout suppresses the activation of the JAK2/STAT3 signaling pathway, thereby reducing the production and secretion of key inflammatory cytokines and coagulation factors induced by lipopolysaccharide. Importantly, transfer of the secretome from bone marrow-derived macrophages (BMDM) of PELI1-knockout mice into wild-type septic mice is sufficient to alleviate sepsis pathology, which recapitulates the protective effect observed in genetic knockout. Our findings demonstrate that PELI1 mediates sepsis-induced tissue injury by regulating the secretome via the JAK2/STAT3 pathway, which identifies the PELI1-secretome axis as a potential therapeutic target for this life-threatening condition.

Osimertinib is the standard first-line treatment for patients with non-small cell lung cancer (NSCLC) harboring EGFR-sensitive mutations. However, drug resistance inevitably develops, highlighting the critical need for strategies to overcome this resistance and prolong therapeutic efficacy. Understanding the mechanisms underlying drug resistance is essential, and drug-resistant cell models serve as valuable tools for investigating acquired resistance. In this study, we establish an osimertinib resistance evolution model in vitro by continuous high-dose drug induction and identify cell lines exhibiting "permanent" resistance to osimertinib (osimertinib resistant, OR). Transcriptome sequencing (RNA-seq), gain- and loss-of-function assay, including lentiviral-mediated overexpression and RNAi knockdown, pharmacological inhibition, and protein degradation analysis reveal significant alterations in genes associated with epigenetic regulation, notably a marked upregulation of histone deacetylase 6 (HDAC6) in OR cells. Knockdown of HDAC6 or pharmacological inhibition of HDAC6 restores the sensitivity of OR cells to osimertinib, whereas overexpression of HDAC6 in sensitive cells reduces drug efficacy and accelerates the onset of resistance. Furthermore, we find that HDAC6 upregulation promotes EGFR degradation, thereby contributing to resistance. Collectively, our findings demonstrate the utility of drug resistance evolution models in identifying key resistance factors. HDAC6 plays a pivotal role in osimertinib resistance, and targeting HDAC6 may represent a novel therapeutic strategy to overcome resistance and enhance treatment efficacy.

Necrosis by sodium overload (NECSO) is a distinct cell death modality induced by the chemical regulator necrocide 1 (NC1), which targets the transient receptor potential melastatin 4 (TRPM4) channel to drive excessive sodium influx and potassium efflux. This unique necrosis is characterized by the exchange of monovalent ions, a restrained ATP supply, redox disorder and a final membrane rupture as main features. Real-time monitoring of metabolic and redox causality during the whole process in living cells has been technically challenging. To bridge this gap, we integrate an advanced toolset of genetically encoded fluorescent sensors to monitor monovalent ions, energy metabolites, and redox equivalents with high spatiotemporal resolution. By directing these sensors to specific subcellular compartments, we successfully capture the real-time choreography of potassium loss specifically induced by NC1 via TRPM4. Furthermore, we establish a precise detection paradigm for evaluating energy currency by integrating sensors for NADH and ATP that are capable of subcellular imaging. We observe general and rapid NADH accumulation along with an ATP shortage in the mitochondria and cytosol. A concomitant reduction in mitochondrial oxidative stress is observed. This study not only elucidates the metabolic progression of a peculiar type of necrosis but also establishes a robust methodological framework for applying genetically encoded sensors to broader physiological and toxicological research.