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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.

Changes in the immune microenvironment are frequent in cancers occurring in adult patients, yet our understanding of the pediatric cancer immune microenvironment and its clinical relevance is limited. We investigate the immune microenvironment in pediatric T cell acute lymphoblastic leukemia (T-ALL), using single-cell CITE-seq and immune repertoire analyses. We identify a T-ALL subgroup characterized by a remodeled immune microenvironment, which is associated with adverse clinical outcome in minimal residual disease low patients. This adverse immune landscape is dominated by the presence of a population of non-malignant CD4-CD8-TCR¦Á¦Â T cells that interact with CXCL16 expressing non-classical monocytes. Leukemia cell intrinsic transcriptional rewiring in these patients is associated with activation of Rap1 signaling. Inhibiting Rap1 signaling results in increased sensitivity to the BCL2/BCL-XL inhibitor navitoclax. Our study provides insights into the immune microenvironment of pediatric hematologic malignancies, forming the basis for identifying potential (immuno) therapeutic targets and risk stratification for treatment. Understanding of the immune microenvironment in pediatric acute T cell lymphoblastic leukemia is limited. By analyzing single-cell transcriptome, surface protein expression and immune repertoire data, the authors here identify non-malignant CD4-CD8- TCR¦Á¦Â T cells that are present in a subset of patients with Rap1 signaling in leukemia cells and are associated with adverse clinical outcome in patients with low minimal residual disease.

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.