EMBO Reports最新文献

Host defense against many Gram-positive bacteria and fungal pathogens is mainly provided by the Toll-dependent systemic immune response in Drosophila. While antimicrobial peptides active against these categories of pathogens contribute only modestly to protection, Bomanin peptides are major effectors of the Toll pathway. Remarkably, flies deleted for the 55C locus that contains ten Bomanin genes are as sensitive as Toll pathway mutant flies to these infections. Yet, the exact functions of single Bomanins in resistance or resilience to infections remain poorly characterized. Here, we have extensively studied the role of these Bomanin genes. BomT1 functions in resistance to Enterococcus faecalis while playing a role in resilience against Metarhizium robertsii infection, like BomS2. BomT1 and BomT2 can prevent the dissemination of Candida albicans throughout the host, even though they are not sufficient to confer protection to immunodeficient flies against this pathogen in survival experiments. Furthermore, BomT1 and BomBc1 mutants are sensitive to an Aspergillus fumigatus ribotoxin. We conclude that 55C Bomanins have defined albeit sometimes overlapping roles in the different facets of host defense against infections.

The potential role of small interfering RNAs (siRNAs) produced from double-stranded RNA in aging has not been fully addressed. The networks of genes regulated by siRNAs and their partner Argonaute proteins are best understood in C. elegans, a pioneering model of aging and small RNA studies. Here, we describe synergistic lifespan extension of insulin/IGF-1 signaling (IIS) mutant age-1(hx546) by rde-4 or alg-3; alg-4 deficiencies. By analyzing gene expression and siRNA populations in these IIS and RNAi mutants, we show here that redundant spermatogenesis-specific Argonautes ALG-3 and ALG-4 are capable of regulating IIS, potentially through direct control of the Major Sperm Protein (MSP) genes in the germline. MSPs and MSP domains of some mammalian proteins are secreted and directly inhibit the Eph receptor (EphR). In turn, EphR interacts with and destabilizes PTEN, a major negative regulator of IIS. We show that enhanced MSP expression correlates with EphR mislocalization and elevated PTEN levels in oocytes of alg-3/4(-) worms. At the same time, ALG-3/4 expression is regulated by IIS. Thus, we propose mutual regulation of IIS and ALG-3/4 through secreted ligands.

5'-Azacitidine (Aza) and 5-Aza-2'-deoxycytidine (Dac) are widely used demethylating drugs that directly integrate into nucleic acids. They are frequently used interchangeably, surprisingly as their selectivity is unique from the other, with no predictors of response or clinical biomarkers to indicate drug preference. Using these drugs to induce demethylation, we combine DRIPc-Seq, Immunostaining, RNA-Seq and Mass spectrometry to uncover unique cellular responses. Activation of p53, exclusively by Aza, sustains accumulation of R-loops in CpG islands of p53 target genes. This effect is abolished by the removal of p53, compounded by destabilisation of heterochromatin marks. Dac treatment induces global chromatin modification, sustaining DNA damage, which is heightened in the absence of p53. Rescue experiments reverse the changes observed in the epigenome, demonstrating a direct role for p53 in preserving H3K9me3 and H3K27me3. These insights further our knowledge of how cells recognize and respond to methylation changes and uncover novel roles for p53 in modulation of the epigenome. Further to this, we determine a first in kind biomarker in p53 status that may be relevant for clinical settings.

Muscle stem cells (MuSCs) are essential for skeletal muscle repair. Following injury, MuSCs reside in low oxygen environments until muscle fibers and vascularization are restablished. The dynamics of oxygen levels during the regenerative process and its impact on muscle repair has been underappreciated. We confirm that muscle repair is initiated in a low oxygen environment followed by gradual reoxygenation. Strikingly, when muscle reoxygenation is limited by keeping mice under systemic hypoxia, muscle repair is impaired and leads to the formation of hypotrophic myofibers. Sustained hypoxia decreases the ability of MuSCs to differentiate and fuse independently of HIF-1α or HIF-2α. Prolonged hypoxia specifically affects the circadian clock by increasing Rev-erbα expression in MuSCs. Using pharmacological tools, we demonstrate that Rev-ERBα negatively regulates myogenesis by reducing late myogenic cell fusion under prolonged hypoxia. Our results underscore the critical role of progressive muscle reoxygenation after transient hypoxia in coordinating proper myogenesis through Rev-ERBα.

Mild rupture of aged erythrocytes occurs in the spleen, resulting in hemoglobin (Hb) release, whereas pathological hemolysis characterizes several diseases. Hb detoxification is attributed to macrophages, but other routes of Hb clearance remain elusive. Here, we uncover that Hb uptake is chiefly executed by liver sinusoidal endothelial cells (LSECs) via macropinocytosis. Consistently, LSECs display proteomic signatures indicative of heme catabolism, ferritin iron storage, antioxidant defense, and macropinocytic capacity, alongside high iron content and expression of the iron exporter ferroportin. Erythrocyte/Hb transfusion assays demonstrate that splenic macrophages excel in erythrophagocytosis, while LSECs and Kupffer cells scavenge the spleen-borne hemolysis products Hb and erythrocyte membranes, respectively. High Hb doses result in transient hepatic iron retention, LSEC-specific induction of heme-catabolizing Hmox1, along with the iron-sensing Bmp6-hepcidin axis culminating in hypoferremia. Transcriptional induction of Bmp6 in LSECs is phenocopied by erythrocyte lysis upon phenylhydrazine and elicits a distinct transcriptional signature compared to iron. Collectively, we identify LSECs as key Hb scavengers, a function that establishes the spleen-to-liver axis for iron recycling and contributes to heme detoxification during hemolysis.

Effective visualization of 3D microscopy data is essential for communicating biological results. While scientific 3D rendering software is specifically designed for this purpose, it often lacks the flexibility found in non-scientific software like Blender, which is a free and open-source 3D graphics platform. However, loading microscopy data in Blender is not trivial. To bridge this gap, we introduce Microscopy Nodes, an extension for Blender that enables the seamless integration of large microscopy data. Microscopy Nodes provides efficient loading and visualization of up to 5D microscopy data from Tif and OME-Zarr files. Microscopy Nodes supports various visualization modes including volumetric, isosurface, and label-mask representations, and offers additional tools for slicing, annotation, and dynamic adjustments. By leveraging Blender's advanced rendering capabilities, users can create high-quality visualizations that accommodate both light and electron microscopy. Microscopy Nodes makes powerful, clear data visualization available to all researchers, regardless of their computational experience, and is available through the Blender extensions platform with comprehensive tutorials.

TRIM2 is a mammalian E3 ligase with particularly high expression in Purkinje neurons, where it contributes to neuronal development and homeostasis. The understanding of ubiquitin E3 ligase function hinges on thoroughly identifying their cellular targets, but the transient nature of signaling complexes leading to ubiquitination poses a significant challenge for detailed mechanistic studies. Here, we tailored a recently developed ubiquitin-specific proximity labeling tool to identify substrates of TRIM2 in cells. We show that TRIM2 targets proteins involved in the endolysosomal pathway. Specifically, we demonstrate using biochemical and structural studies, that TRIM2 ubiquitinates TMEM106B at lysine residues located in the cytosolic N-terminal region. Substrate recognition involves a direct interaction between TRIM2 and a newly identified zinc-coordination motif in TMEM106B that mediates homodimerization, is required for specific protein-protein interactions, and lysosomal size regulation. We found that in addition to catalysis, the tripartite motif is involved in substrate recruitment. Our study thus contributes a catalog of TRIM2 effectors and identifies a previously unrecognized regulatory region of TMEM106B crucial to its function.

Folliculogenesis is a process that requires accurate interpretation of female physiological cues and elaborate coordination between the growing oocyte and its surrounding follicle cells, each being capable of responding to external signals. Here, we investigate the role of insulin signaling in Drosophila follicle cells. Using a phase separation-based reporter system, we observe a surge of insulin receptor activity in follicle cells during vitellogenic stages, a surge that is disrupted by a maternal high-sucrose diet. Single-cell RNA-seq reveals a diet-sensitive subpopulation of stage-8 follicle cells, which exhibits a reduction in CrebA-mediated transcription of genes for yolk and vitelline membrane proteins. Our results suggest a critical role of CrebA in implementing the stage-specific effect of insulin signaling to boost the secretory capacity of follicle cells. Mechanistically, CrebA is directly repressed by nuclear FoxO that is subject to insulin control, a regulatory axis that we show is conserved in human granulosa cells. This study delineates a mechanism through which insulin and nutrient cues act on a developmental transition via modulating the biosynthetic and secretory functions of the ovary.

Astrocytes, the most abundant glial cell type in the central nervous system, have traditionally been viewed from the perspective of metabolic support, particularly supplying neurons with lactate via glycolysis. This view has focused heavily on glucose metabolism as the primary mode of sustaining neuronal function. However, recent research challenges this paradigm by positioning astrocytes as dynamic metabolic hubs that actively engage in lipid metabolism, especially mitochondrial fatty acid β-oxidation. Far from serving solely as an energy source, fatty acid ß-oxidation in astrocytes orchestrates reactive oxygen species-mediated signaling pathways that modulate neuron-glia communication and cognitive outcomes. This review integrates recent advances on astrocytic fatty acid ß-oxidation and ketogenesis, alongside other metabolic pathways converging on reactive oxygen species dynamics, including cholesterol metabolism and peroxisomal β-oxidation. In reframing astrocytic metabolism from energy provision to signaling, we propose new directions for understanding central nervous system function and dysfunction.