Biology subjects

Niedergang, F.

Publications and source records attributed to Niedergang, F..

9 recordsLinked to original sources

bioRxiv2026

Human rhinovirus 16 impairs macrophage cytokine secretion by disrupting NF-κB nuclear translocation and intracellular cytokine trafficking

Human rhinovirus (HRV) infections are a major cause of acute exacerbations in chronic obstructive pulmonary disease (COPD), often promoting secondary bacterial infections by dysregulating macrophage function. Although HRV16 has previously been shown to impair macrophage cytokine secretion, the underlying molecular mechanisms remain poorly understood. To address this, we examined the effects of HRV16 on primary human monocyte-derived macrophages, subsequently challenged with lipopolysaccharide (LPS) to mimic secondary bacterial infection. HRV16 significantly reduced IL-10 and IL-1{beta} expression at both the mRNA and protein levels. In contrast, IL-6 transcription was increased despite markedly reduced cytokine secretion. Immunofluorescence analysis revealed enhanced colocalization of IL-6 with the Golgi apparatus following HRV16 infection, consistent with intracellular retention and defective trafficking. These findings reveal that HRV16 disrupts cytokine secretion through distinct transcriptional and post-transcriptional mechanisms. To investigate the basis of transcriptional dysregulation, we performed quantitative histone post-translational modification profiling by mass spectrometry, which identified multiple HRV16-induced epigenetic alterations. Notably, a decrease in the active epigenetic mark H2AZK4Ac was observed. Chromatin immunoprecipitation demonstrated unchanged H2AZK4Ac occupancy at the IL-10 and IL-1{beta} promoters but increased enrichment at the IL-6 promoter, consistent with its selective transcriptional upregulation. HRV16 infection also induced sustained phosphorylation of NF-{kappa}B p65 that was accompanied by impaired nuclear translocation, suggesting defective activation of NF-{kappa}B-dependent transcription. Together, these results demonstrate that HRV16 inhibits cytokine secretion through disruption of NF-{kappa}B signalling and defective intracellular cytokine trafficking and identify associated alterations in the macrophage epigenetic landscape. These findings provide new mechanistic insight into rhinovirus-mediated dysregulation of macrophage inflammatory responses and its potential contribution to impaired antibacterial immunity during COPD exacerbations.

microbiology↗

bioRxiv2026

The lysosomal glutamine transporter SLC38A7/SNAT7 modulates SAMHD1 antiviral activity and promotes HIV-1 production in human macrophages

HIV-1 (Human Immunodeficiency Virus type 1) infects macrophages, which resist to the cytopathic effects of the virus and are considered as viral reservoirs. However, the cellular factors involved in viral production by human macrophages have not been fully identified. In this study, we focused on the amino acid transporter SNAT7 (small neutral amino-acid transporter 7), member of the SLC38 solute carrier family, which is the main lysosomal transporter of glutamine from the lysosome to the cytoplasm. Its expression was increased by HIV-1 infection. We revealed that the absence of SNAT7 inhibited viral production not only at the level of protein synthesis, but also early at the level of reverse transcription, without affecting global RNA or protein synthesis in the cells. The reduction in HIV expression upon SNAT7 depletion correlated with a reduction in the levels of an inactive form of the SAMHD1 (SAM domain- and HD domain-containing protein) restriction factor and was rescued following SAMHD1 degradation. Lastly, supplementation of the extracellular medium with glutamine in the absence of SNAT7 partially restored viral production. Together, our data reveal that glutamine extracted from lysosomes is involved in the early stages of the HIV-1 cycle and that the SNAT7 glutamine transporter acts as a dependency factor for HIV-1 in human macrophages.

microbiology↗

bioRxiv2025

Targeted fluorescent lipid microparticles for quantitative measurement of phagosomal pH

Phagosomal acidification plays a pivotal role in pathogen destruction and immune signaling, yet tools capable of reporting these biochemical changes with spatial and mechanistic precision remain scarce. A modular biosensing strategy is presented in which BODIPY-derived hydrophilic fluorophores are conjugated to phospholipids and incorporated at the surface of targeted lipid microparticles. These soft and biomimetic particles combine receptor-specific uptake with ratiometric fluorescence readouts, enabled by pairing pH-responsive dyes at the interface with a pH-invariant reference probe in the core. Following Fc{gamma} receptor-mediated internalization by macrophages, the particles deliver real-time insight into the onset and progression of phagosomal acidification. This versatile platform provides a direct means to couple defined surface recognition events to intracellular pH measurements, offering new opportunities to unravel how particle identity and ligand presentation modulate phagosomal physiology.

biophysics↗

bioRxiv2025

The unique lipopolysaccharide composition of Salmonella Typhimurium ST313 dampens pyroptosis and inflammasome activation and suppresses host cell death

In humans, non-typhoidal Salmonella (NTS) serovars, such as Salmonella enterica Typhimurium cause self-limiting gastroenteritis. However, invasive non-typhoidal Salmonella (iNTS) isolates ST313 have emerged in sub-Saharan Africa that cause a severe bacteremia in immunocompromised individuals including HIV-positive adults. Despite a decade of studies comparing ST313 to the classical diarrheal S. Typhimurium ST19 pathovariant, the molecular basis of the differences of pathogenesis between these bacteria remains unclear. Here we used primary human macrophages infected with the invasive S. Typhimurium ST313 D23580 isolate and the reference ST19 4/74 isolate as an in vitro model of infection. Transcriptomic profiling revealed that primary human macrophages infected with ST313 bacteria had distinct patterns of host cell death and inflammation responses compared to ST19-infected cells. Specifically, infection with ST313 isolate induced significantly less pyroptotic cell death which was associated with minimal processing of Gasdermin-D. We discovered that S. Typhimurium ST313 stimulated reduced IL-1{beta} release and a low-level activation of the upstream inflammasome signaling cascade with reduced Caspase-4 and Caspase-1 cleavage. To investigate the molecular basis of this phenotype we purified lipopolysaccharide (LPS) species from ST313 to identify physical properties and structures that were distinct from ST19 LPS. The ST313-derived LPS was less pro- inflammatory than LPS from ST19, mirroring the low inflammatory phenotype of the live bacteria. Together, our data reveal that the unique LPS of ST313 is responsible for the reduced level of pyroptosis in human macrophages. This phenotype is consistent with the intracellular persistence and dissemination of these pathogenic bacteria. AUTHOR SUMMARYNon-typhoidal Salmonella (NTS) is a foodborne microbial pathogen that causes a self- limiting gastroenteritis in humans. However, in recent decades invasive non-typhoidal Salmonella (iNTS) isolates have emerged in sub-Saharan Africa, and are currently causing severe bloodstream infections responsible for about 66,000 deaths each year, largely in immunocompromised individuals. To investigate differences in pathogenicity between iNTS and NTS strains, we studied the infection of primary human macrophage with an iNTS ST313 isolate from Malawi in comparison to a gastroenteritis-associated ST19 reference strain. Primary macrophages play a key role in clearing Salmonella infections by recognizing bacterial components such as lipopolysaccharide (LPS). LPS induces immune responses including activation of cytokine release, inflammation and host cell death for effective bacterial elimination. Our study revealed that the iNTS isolate survived better in human primary macrophages than the NTS strain due to reduced inflammatory cell death, weakened inflammasome activation and lower cytokine release. We suggest that the distinct LPS structure is responsible for these dampened immune responses which aid the spread and persistence of S. Typhimurium ST313 in the human host.

microbiology↗

bioRxiv2025

HIV-1 and Chlamydia trachomatis restrict their respective growth but promote their survival in co-infected human macrophages

HIV-1 and Chlamydia trachomatis (CT) are two significant sexually transmitted pathogens that frequently co-infect individuals. However, the mechanisms by which these two obligate intracellular pathogens interact at the cellular level remain elusive, particularly in tissue macrophages, where persistent infections can occur. In this study, we demonstrate that CT generates inclusions in macrophages of murine and human origins. We also show that both HIV-1 and CT reciprocally restrict the growth and replication of each other within co-infected human macrophages, irrespective of whether the viral or bacterial infection is established first. Notably, the co-infection resulted in improved survival of the macrophage hosts, as the inflammatory cell death pathways induced by CT were prevented by the virus. Collectively, these findings demonstrate that HIV-1 and CT collaborate to persist in human macrophages. IMPORTANCEWhile HIV-1 and Chlamydia trachomatis (CT) infections are associated at the epidemiological level, very little is known at the cellular and molecular level on co-infections by these two intracellular pathogens. The significance of our research is in dissecting the impact of one pathogen on replication and production of infectious progeny by the other. For this, we studied human macrophages, which are targeted by both HIV-1 and CT and could play an important role in their intracellular persistence. This work reveals the close interplay between these two pathogens that benefit from each other to survive in human macrophages. Consequently, we emphasize the need to address these cells as a unique target during the co-infections.

microbiology↗

bioRxiv2021

IL4I1 binds to TMPRSS13 and competes with SARS-Cov2 Spike

The secreted enzyme interleukin four-induced gene 1 (IL4I1) is involved in the negative control of the adaptive immune response. IL4I1 expression in human cancer is frequent and correlates with poor survival and resistance to immunotherapy. Nevertheless, its mechanism of action remains partially unknown. Here, we identified transmembrane serine protease 13 (TMPRSS13) as an immune cell-expressed surface protein that binds IL4I1. TMPRSS13 is a paralog of TMPRSS2, whose protease activity participates in the cleavage of SARS-Cov2 Spike protein and facilitates virus induced-membrane fusion. We show that TMPRSS13 is expressed by human lymphocytes, monocytes and monocyte-derived macrophages, can cleave the Spike protein and allow Sars-Cov2 Spike pseudotyped virus entry into cells. We identify regions of homology between IL4I1 and Spike and demonstrate competition between the two proteins for TMPRSS13 binding. These findings may be relevant for both interfering with SARS-Cov2 infection and limiting IL4I1-dependent immunosuppressive activity in cancer. One-Sentence SummaryThrough binding to its newly identified receptor TMPRSS13, the enzyme IL4I1 interferes with SARS-Cov2 Spike cleavage thereby blocking viral entry into host cells.

immunology↗

bioRxiv2021

Dynamin-2 controls complement receptor 3- mediated phagocytosis completion and closure

Phagocytosis is the mechanism of the internalization of large particles, microorganisms and cellular debris. The complement pathway represents one of the first mechanisms of defense against infection and the complement receptor 3 (CR3), which is highly expressed on macrophages, is a major receptor for many pathogens and debris. Key to dissecting the mechanisms by which CR3-mediated phagocytosis occurs, is understanding how the complex actin binding protein machinery and associated regulators interact with actin during phagocytosis, from triggering of receptor, through to phagosome formation and closure. However, how CR3-mediated phagosome completion and closure are orchestrated is not known. Here, we reveal that dynamin-2 is recruited concomitantly with polymerised actin at the site of the nascent phagosomes and accumulates until membrane scission. Inhibition of dynamin activity leads to stalled phagocytic cups and a decrease in the amount of F-actin at the site of phagocytosis. Acute inhibition of dynamin activity in living phagocytosing cells established that dynamin-2 plays a critical role in the effective scission of the CR3-phagosome from the plasma membrane. Thus, dynamin-2 has two distinct roles in CR3-mediated phagocytosis, in the assembly of the F-actin phagocytic cup and during phagosome scission.

cell biology↗

bioRxiv2020

LPS induces GFAT2 expression to promote O-GlcNAcylation and attenuate inflammation in macrophages

O-GlcNAc glycosylation is a reversible post-translational modification that regulates the activity of intracellular proteins according to glucose availability and its metabolism through the hexosamine biosynthesis pathway (HBP). This modification has been involved in the regulation of various immune cell types, including macrophages. However, little is known concerning the mechanisms that regulate protein O-GlcNAcylation level in these cells. In the present work, we demonstrate that LPS treatment induces a marked increase in protein O-GlcNAcylation in RAW264.7 cells, bone-marrow-derived and peritoneal mouse macrophages, as well as human monocyte-derived macrophages. Targeted deletion of OGT in macrophages resulted in an increased effect of LPS on NOS2 expression and cytokine production, suggesting that O-GlcNAcylation may restrain inflammatory processes induced by TLR4 activation. The effect of LPS on protein O-GlcNAcylation in macrophages was associated with an increased expression and activity of glutamine fructose 6-phosphate amido-transferase (GFAT), the enzyme that catalyzes the rate-limiting step of the HBP. More specifically, we observed that LPS rapidly and potently stimulated GFAT2 isoform mRNA and protein expression. Genetic or pharmacological inhibition of FoxO1 impaired LPS effect on GFAT2 expression, suggesting a FoxO1-dependent mechanism. We conclude that GFAT2 should be considered as a new TLR4-inducible gene involved in regulation of protein O-GlcNAcylation, that permits to limit exacerbated inflammation upon macrophage activation.

biochemistry↗

bioRxiv2018

Differential screening identifies molecules specifically inhibiting CCR5 transport to the cell surface and HIV infection

Proteins destined to the cell surface are conveyed through membrane-bound compartments using the secretory pathway. Multiple secretory routes exist in cells, which paves the way to the development of inhibitory molecules able to specifically perturb the transport of a chosen cargo. We used differential high-content screening of chemical libraries to identify molecules reducing the secretion of CCR5, the major co-receptor for HIV-1 entry. Three molecules strongly affected the anterograde transport of CCR5, without inhibiting the transport of the related G protein-coupled receptors CCR1 and CXCR4. These three molecules perturb the transport of endogenous CCR5 and decrease the entry of HIV in human primary target cells. Two molecules were found to share the same mode of action, inhibiting palmitoylation of CCR5. Our results demonstrate that secretory routes can be specifically targeted which allows to envisage novel strategies to provoke the intracellular retention or rerouting of secretory proteins involved in disease development.

cell biology↗