Biology subjects

Rombouts, Y.

Publications and source records attributed to Rombouts, Y..

6 recordsLinked to original sources

bioRxiv2026

CysK2 couples copper sensing to metabolic and redox adaptation in Mycobacterium tuberculosis

Copper is increasingly recognized as a host-derived cue encountered by Mycobacterium tuberculosis and other microbes during infections, yet the magnitude, intracellular distribution, and physiological consequences of this exposure remain incompletely understood. Here, we combined high-resolution imaging, transcriptomic profiling, intracellular reporter assays, isotope tracing, and mouse infection models to define how M. tuberculosis responds to physiologically relevant copper levels during macrophage infection. NanoSIMS analysis showed that copper reaches intracellular bacilli and accumulates in discrete phosphorus-rich foci in bacteria. Exposure to physiological copper concentrations in vitro triggered a highly specific transcriptional response dominated by the copper-inducible CsoR and RicR regulons. The RicR-regulated gene cysK2 gene, encoding the S-sulfocysteine synthase CysK2, was one of the most strongly induced loci. In infected macrophages, cysK2 expression was modulated by extracellular copper availability, host copper transport pathways, and hypoxia. In vitro, an H37Rv cysK2-deficient mutant showed reduced amino acid biosynthesis in response to copper exposure. In vivo, the mutant was impaired in long-term persistence in mice and displayed a higher oxidation status. Together, these findings identify CysK2 as a copper-responsive metabolic effector that couples host-derived copper sensing to redox homeostasis and intracellular adaptation in M. tuberculosis. IMPORTANCESuccessful infection by Mycobacterium tuberculosis depends on its ability to detect and adapt to host-imposed changes in the phagosomal environment. Our work shows that copper contributes to this adaptation not simply by imposing toxicity, but by triggering a metabolic response that helps sustain bacterial fitness within host cells. We identify CysK2 as a key component of this response, linking copper sensing to sulfur metabolism, redox balance, and persistence during infection. These findings shift the view of copper from a purely antimicrobial factor to a host-derived environmental signal that remodels M. tuberculosis physiology, and they uncover a new mechanism by which the pathogen maintains intracellular survival.

microbiology↗

bioRxiv2026

ST8SIA4-mediated polysialylation is critical for CCR2-driven monocyte egress from the bone marrow

Polysialylation is a rare post-translational protein modification essential for brain development and synaptic plasticity, where it fine-tunes cell-cell and cell-matrix interactions to direct neuronal migration, neurite outgrowth and synaptogenesis. Although polysialic acid is also expressed on circulating leukocytes, its functions in the immune system remain largely unexplored. Guided by analysis of publicly available human genomic data showing that naturally occurring variants of ST8SIA4, which encodes one of the two enzymes that mediate polysialylation, associate with reduced circulating monocyte counts, we investigated the in vivo role of this enzyme in monocyte biology. Using St8sia4-deficient mice, we show that ST8SIA4-dependent polysialylation is essential for CCR2-mediated egress of inflammatory monocytes from the bone marrow at steady state and during Mycobacterium tuberculosis infection. We confirm NCAM1 as the principal polysialylated protein in inflammatory monocytes and demonstrate that Ncam1-deficient mice phenocopy the monocyte defects observed in St8sia4-deficient animals. Mechanistically, loss of ST8SIA4-dependent polysialylation impairs engagement and internalization of the CCR2 ligands CCL2 and CCL7, accompanied by disrupted CCR2 surface organization and extensive cytoskeletal remodeling. Together, these findings identify polysialylation as a previously unrecognized regulator of CCR2 function and monocyte mobilization, with broad implications for immune surveillance and inflammatory responses. Highlights- Human ST8SIA4 variants are associated with reduced blood monocyte and lymphocyte counts and increased risk of SLE. - St8sia4-/- mice exhibit monocytopenia with impaired CCR2-mediated egress of inflammatory monocytes from the bone marrow both at steady state and during Mycobacterium tuberculosis infection. - ST8SIA4 polysialylates NCAM1 (CD56) in inflammatory monocytes, and Ncam1-/- - mice phenocopy the monocytopenia observed in St8sia4-/- mice. - Loss of ST8SIA4 and polysialylation impairs CCR2-mediated binding and endocytosis of CCL2 and CCL7 by monocytes. - Polysialic acid itself does not function as a co-receptor for these chemokines, revealing a new paradigm for its role in immune cell trafficking. - Proper CCR2 surface distribution and function, as well as cytoskeletal organization in inflammatory monocytes, depend on ST8SIA4-mediated polysialylation.

immunology↗

bioRxiv2025

Identification of a unique TUBB3+ cell population in the tuberculosis granuloma

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a leading cause of mortality worldwide. Granulomas, hallmark structures of TB in the lungs and other infected tissues, are critical sites of host-pathogen interactions, yet their full cellular composition is not completely understood. Here, we identify a previously unrecognized {beta}3-tubulin (TUBB3)-positive cell population within TB granulomas in mice, guinea pigs, non-human primates, and TB patients. TUBB3 is a well-established pan-neuronal marker, yet these TUBB3+ cells are distinct from typical pulmonary resident cells and leukocytes. They exhibit a branched, elongated morphology, which is suggestive of neuron-like features. Intriguingly, their appearance is independent of adaptive immunity and is also observed in viral and fungal infections, but not in asthma. Our findings suggest the existence of a neuro-immune component within granulomas that may influence TB pathogenesis. Further investigation into the origin, function, and signaling pathways of these TUBB3+ cells is required to clarify their identity and potential role in host defense, which could reveal novel therapeutic targets for TB and other pulmonary infections.

immunology↗

bioRxiv2024

The human and mouse dendritic cell receptor DCIR binds to LRP1 N-glycans containing terminal galactoses, including the α-Gal antigen

The dendritic cell immunoreceptor (DCIR) is a C-type lectin receptor expressed by myeloid cells that plays a key immunoregulatory role in a wide range of diseases, from inflammation to cancer. However, the ligand(s) of DCIR remain(s) unknown, hampering our understanding of the exact function of this immune receptor. Here, we found that both human DCIR and mouse DCIR1 bind specifically to the low-density lipoprotein receptor-related protein 1 (LRP1), a heavily glycosylated receptor mediating the clearance of various molecules from the extracellular matrix and apoptotic cells. This interaction is mediated by galactose-terminated biantennary complex-type N-glycans, including those carrying the immunogenic -Gal epitope. Our study provides a deeper understanding of the role of DCIR in immune regulation and its potential impact on a range of immune disorders, highlighting its specificity in ligand recognition which is crucial for developing therapeutic strategies.

immunology↗

bioRxiv2021

Phospholipid peroxidation fuels ExoU phospholipase-dependent cell necrosis and supports Pseudomonas aeruginosa-driven pathology

Regulated cell necrosis supports immune and anti-infectious strategies of the body; however, dysregulation of these processes drives pathological organ damage. Pseudomonas aeruginosa expresses a phospholipase, ExoU that triggers pathological host cell necrosis through a poorly characterized pathway. Here, we investigated the molecular and cellular mechanisms of ExoU-mediated necrosis. We show that cellular peroxidised phospholipids enhance ExoU phospholipase activity, which drives necrosis of immune and non-immune cells. Conversely, both the endogenous lipid peroxidation regulator GPX4 and the pharmacological inhibition of lipid peroxidation delay ExoU-dependent cell necrosis and improve bacterial elimination in vitro and in vivo. Our findings also pertain to the ExoU-related phospholipase from the bacterial pathogen Burkholderia thailandensis, suggesting that exploitation of peroxidised phospholipids might be a conserved virulence mechanism among various microbial phospholipases. Overall, our results identify an original lipid peroxidation-based virulence mechanism as a strong contributor of microbial phospholipase-driven pathology.

immunology↗

bioRxiv2020

Colon-specific immune microenvironment regulates cancer progression versus rejection

BackgroundImmunotherapies have achieved clinical benefit in many types of cancer but remain limited to a subset of patients in colorectal cancer (CRC). Resistance to immunotherapy can be attributed in part to tissue-specific factors constraining antitumor immunity. Thus, a better understanding of how the colon microenvironment shapes the immune response to CRC is needed to identify mechanisms of resistance to immunotherapies and guide the development of novel therapeutics. MethodsIn an orthotopic mouse model of MC38-CRC, tumor progression was monitored by bioluminescence imaging and the immune signatures were assessed at a transcriptional level using NanoString and at a cellular level by flow cytometry. ResultsDespite initial tumor growth in all mice, only 25 to 35% of mice developed a progressive lethal CRC while the remaining animals spontaneously rejected their solid tumor. No tumor rejection was observed in the absence of adaptive immunity, nor when MC38 cells were injected in non-orthotopic locations, subcutaneously or into the liver. We observed that progressive CRC tumors exhibited a protumor immune response, characterized by a regulatory T-lymphocyte pattern, discernible shortly post-tumor implantation, as well as suppressive myeloid cells. In contrast, tumor-rejecting mice presented an early inflammatory response and an antitumor microenvironment enriched in CD8+ T cells. ConclusionsTaken together, our data demonstrate the role of the colon microenvironment in regulating the balance between anti or protumor immune responses. While emphasizing the relevance of the CRC orthotopic model, they set the basis for exploring the impact of the identified signatures in colon cancer response to immunotherapy.

cancer biology↗