Cell Discovery最新文献

DNA unwinding and primer synthesis are fundamental processes in genome replication. The human herpes simplex virus type 1 (HSV-1) helicase-primase forms a unique heterotrimeric primosome that is essential for viral DNA unwinding and primer synthesis and represents an ideal drug target. However, its molecular mechanism remains poorly understood. Here we report the cryo-electron microscopic structure of the primosome in complex with single-stranded DNA, ADP and Mg²⁺ to 3.47 Å resolution, which reveals that the primosome forms an unprecedented architecture in a fully open DNA binding groove between the helicase domains 1A and 2A-2B and that the primase subunit UL52 interacts extensively with the helicase subunit UL5 and accessory protein subunit UL8. Integrating mutagenesis, biochemical assays, structural analysis and 3D variability display analysis, we have identified the active sites of the ATPase, helicase and primase and critical interfaces between UL52, UL5 and UL8. Our work suggests that the primosome unwinds and translocates DNA via bidirectional rotation, and proposes a mechanistic model for DNA-dependent ATPase activation and alternating activity between helicase and primase. Herpesviridae family viruses pose significant threats to human health worldwide, and this trimeric assembly of primosomes is conserved. Our work provides a framework for understanding replication mechanisms across related viruses and for the rational design of broad-spectrum antivirals.

In cancer, extrachromosomal DNA (ecDNA) contributes to tumor heterogeneity and is associated with poor prognosis, but studies on patient-derived ecDNA are relatively limited at single-cell resolution. Here, we introduce scCirclehunter, a framework designed to identify ecDNA from scATAC-seq data and assign ecDNA to specific cell populations. Leveraging scCirclehunter and available glioblastoma (GBM) datasets, we uncover the inter-cellular heterogeneity of ecDNA-carrying cells across GBM patients and trace the trajectories of malignant cells within a single patient that harbors multiple ecDNAs. By integrating scRNA-seq data, we use ecNR2E1 as an example to demonstrate that ecDNA drives tumor progression in GBM through several mechanisms. Additionally, our findings suggest a potential link between ecDNA and increased mitochondrial transfer frequency. Overall, scCirclehunter provides a novel framework for analyzing patient-specific ecDNAs with single-cell precision, offering insights into the role of ecDNA-carrying cells in driving GBM heterogeneity.

Protease-activated receptor 2 (PAR2) is a transmembrane receptor that is irreversibly activated by proteolytic cleavage of its N-terminus via extracellular proteases, resulting in the release of the tethered ligand (TL), which binds to and activates the receptor. PAR2 plays a pivotal role in the inflammatory response and pain sensation and is a promising drug target for treating arthritis, asthma, and neuronal pain. Here, we present the cryo-electron microscopy structures of active PAR2 complexed with miniG_s/q and miniG₁₃. Combining functional assays with structural analysis, our study revealed that TL forms a parallel β-sheet with the extracellular loop 2 of PAR2 to engage the receptor. The binding of TL triggers a conformational rearrangement in the transmembrane core, releasing the inhibitory ion lock and allowing receptor activation. Furthermore, we provide structural insights into the engagement of G_q and G₁₃ with PAR2, highlighting that a hydrophobic interaction mediated by the last methionine residue of Gα₁₃ is crucial for G₁₃ coupling selectivity. In combination with molecular dynamics simulations and mutagenesis, we identified the I39^TL3/D62^N-term interaction at the pocket side of the receptor as a key determinant of G₁₃ signaling. Disrupting this interaction significantly inhibits G₁₃ signaling while preserving G_q activity, enabling us to design a biased peptide ligand that selectively activates G_q signaling. The information revealed in this study provides a framework for understanding PAR2 signaling and offers a rational basis for the design of biased PAR2 ligands.

Myopia is a leading cause of visual impairment, with its prevalence rising rapidly worldwide. Our prior investigations suggest that cross-organ communication, involving the eye, brain, and gut, may play a role in myopia. However, the extent of this cross-organ communication in myopia remains unclear. To elucidate the underlying mechanisms, this study generates a comprehensive pan-tissue transcriptome profile of myopic mice covering eye, brain, blood, bone marrow, spleen, thymus, intestines, liver, kidney, lung, and adrenal gland using single-cell RNA sequencing (scRNA-seq). Widespread immunologic alterations in myopia are identified, characterized by a significant increase in macrophage abundance and macrophage-mediated cell communications across multiple tissues. Notably, these macrophages exhibit a cross-tissue proinflammatory phenotype, which is marked by significant activation of the hypoxia pathway, with upregulation of key markers, including Car1, HIF-1α, and reactive oxygen species, a pattern also observed in the blood of myopic patients. Further analysis suggested that hypoxia stress likely regulates the energy metabolism of proinflammatory macrophages. Inhibition of the hypoxia pathway suppressed the proinflammatory phenotype of macrophages and their hypoxia-related gene expression in myopic mice, reducing the degree of myopia. More importantly, analysis of a large cohort of 114,661 patients reveals 16 extraocular diseases with a myopia-biased prevalence. Our findings underscore the link between myopia and extraocular diseases and suggest that proinflammatory macrophages may potentially serve as the shared mechanism across organs.

Immunochemotherapy has shown promising outcomes in treating small-cell lung cancer. To explore whether surgery after immunochemotherapy benefits patients with stage I‒III small-cell lung cancer, we conducted a phase II trial (NCT04539977). Eligible patients received four cycles of anti-PD-L1 antibody (TQB2450) therapy and chemotherapy, followed by surgery or radiotherapy and one-year maintenance immunotherapy (TQB2450). Forty patients were enrolled between December 2020 and January 2023. Thirty-eight (95.0%) patients had stage III disease. We found that the objective response rate, as the primary endpoint of this study, was 92.5% (95% CI: 83.9%‒100%) in the intention-to-treat population. At a median follow-up of 25.8 months, the median event-free survival (EFS) was 16.2 months. The median overall survival (OS) was not reached. The major pathological response and pathological complete response rate of operative patients (n = 21) were 61.9% and 42.9%, respectively. The 24-month EFS and 24-month OS of operative patients were 61.9% and 85.7%, respectively. All patients with N1 disease (n = 9) underwent surgery, with the 24-month EFS of 66.7% and 24-month OS of 88.9%. The most common TQB2450-specific adverse event was rash of grade 1‒2 (12.5%). We further explored the biomarker of immunochemotherapy and molecular changes during immunochemotherapy through bulk-RNA sequencing and whole-exome sequencing. We demonstrated that PRSS8 was a potential biomarker for poor effectiveness of immunochemotherapy. In conclusion, surgery after neoadjuvant immunochemotherapy is feasible for treating patients with stage I‒III small-cell lung cancer.

Exocrine and endocrine disorders and insufficiency are two major harmful pathological processes in chronic pancreatitis (CP) and can lead to steatorrhea and diabetes. However, there is a lack of reliable clinical classification schemes for evaluating the severity of exocrine and endocrine disorders in CP, and the underlying mechanisms are also unclear. In particular, exosome-based liquid biopsy and classification in CP are lacking. Here, we performed transcriptome sequencing on plasma exosomes from CP patients with different degrees of CP severity. Additionally, we analyzed single-cell sequencing data from pancreatic lesions in CP patients to interpret the classification, and an external cohort was established to verify the classification. Ultimately, we established and preliminarily verified a 3-stage classification system to predict steatorrhea and diabetes onset in CP patients based on the expression of 12 miRNAs in plasma exosomes. A publicly-available online tool implementing this classification system was also developed. Further analysis, in combination with single-cell sequencing data from CP mice, identified exosome-derived miR-24-3p and neutrophil S100A8 as pivotal factors in CP progression. Mechanistically, our findings suggest that downregulated exosome-derived miR-24-3p in CP may lead to the upregulation of its target gene, S100A8, in neutrophils, thus promoting CP-related exocrine and endocrine disorders by activating the fibrotic phenotype of pancreatic stellate cells and inducing inflammation in macrophages, leading to the apoptosis of pancreatic β cells. Together, our work provides a novel exosome-based 3-stage classification system for CP and highlights the role of exosomal miR-24-3p and S100A8 in fibrosis and pancreatic β-cell apoptosis.