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In the arms race between a pathogen and the host, the defense mechanisms of the host cell, including the ubiquitin system, are often counteracted by bacteria. Simkania negevensis (Sne), an obligate intracellular Chlamydia-like bacterium connected with respiratory diseases, possesses numerous deubiquitinases, but not much is known about its other ubiquitin-modifying enzymes. Sne infects a wide range of hosts, developing inside a tubular vacuole in close contact with the host endoplasmic reticulum (ER) and mitochondria. Our study describes an uncharacterized Sne ubiquitin E3 RING-ligase (SNE_A12920 or SneRING), which primarily generates K63- and K11-linked ubiquitin chains and preferentially interacts with UbcH5b and UBE2T E2 enzymes. SneRING is expressed upon infection of various human cell lines, as well as amoebae. We show that a portion of the expressed SneRING co-localizes with mitochondria and ER and that the SneRING interactome includes mitochondrial and ER proteins involved in organelle morphology and stress response. Our work offers an initial characterization of a bacterial RING ligase potentially involved in the host cell remodeling to accommodate the unique intracellular lifestyle of Sne. Author summaryUbiquitination is a protein modification system that regulates protein degradation, localization, or interactions. As such, ubiquitination has many important functions in cell signalling, and its dysregulation can lead to cancer and neurodegenerative diseases. Bacteria that live and develop inside human or other eukaryotic cells, such as Chlamydia, often modulate the ubiquitination system to ensure their own survival. Simkania negevensis is a Chlamydia-like bacterium connected to respiratory diseases in humans. We have discovered a novel enzyme expressed by these bacteria that can ubiquitinate other proteins and thus potentially modify host cell processes that would otherwise hinder infection. In this work, we explore the function of this enzyme and determine its possible cellular localization, as well as some of the proteins it interacts with. Our study provides new insights into how bacterial pathogens adapt to and manipulate host cells using one of the major cell function regulatory systems.

The human bone marrow (BM) microenvironment involves hematopoietic and non-hematopoietic cell subsets organized in a complex architecture. Tremendous efforts have been made to model it in order to analyze normal or pathological hematopoiesis and its stromal counterpart. Herein, we report an original, fully-human in vitro 3D model of the BM microenvironment dedicated to study interactions taking place between mesenchymal stromal cells (MSC) and hematopoietic stem and progenitor cells (HSPC) during the hematopoietic differentiation. This fully-human Artificial Marrow Organoid (AMO) model is highly efficient to recapitulate MSC support to myeloid differentiation and NK cell development from the immature CD34?+?HSPCs to the most terminally differentiated CD15?+?polymorphonuclear neutrophils, CD64?+?monocytes or NKG2A-KIR2D?+?CD57?+?NK subset. Lastly, our model is suitable for evaluating anti-leukemic NK cell function in presence of therapeutic agents. Overall, the AMO is a versatile, low cost and simple model able to recapitulate normal hematopoiesis and allowing more physiological drug testing by taking into account both immune and non-immune BM microenvironment interactions.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-07717-9.

The Mas-related G protein-coupled receptor (MRGPR) X2 is expressed on skin mast cells and can be stimulated by an unusually broad spectrum of ligands, including specific drugs and even endogenous peptides. MRGPRX2 activation can induce mast cell degranulation and consequently mediator release, leading to inflammatory and hypersensitivity reactions. In addition, MRGPRX2 mediates pain and itching sensations, leading to increased efforts to identify MRGPRX2 inhibitors, including plant-derived compounds. Components within oat extracts have been shown to mediate anti-inflammatory and itch-relieving properties, but a possible inhibitory effect on MRGPRX2 activation has not yet been investigated. We aimed to fill this gap and explored whether an oat kernel extract can modulate MRGPRX2 activation. For this purpose, we established a mast cell model with the human LAD2 cell line and used it to investigate the consequences of exposure to oat extract. While we did not observe any influence on cell viability, we analyzed the impact of oat extract on MRGPRX2-mediated mast cell activation and degranulation initiated by the three confirmed MRGPRX2 ligands c48/80, substance P, and cortistatin 14. Exposure to oat extract resulted in a significant reduction in mast cell degranulation for all three ligands, as assessed by the release of ¦Â-hexosaminidase, tryptase, cell surface expression of CD63 and CD107a, and phosphorylation of ERK. All results were confirmed with primary human mast cells. Thus, we demonstrated for the first time that oat extract leads to a significant reduction in MRGPRX2 activation, pointing to a previously unrecognized capacity of natural compounds to modulate this pathway.