Biology subjects

Huc-Brandt, S.

Publications and source records attributed to Huc-Brandt, S..

6 recordsLinked to original sources

bioRxiv2025

Verapamil limits inflammation by restoring VGCC-driven epithelial Ca2+ in models of cystic fibrosis

RationaleIn cystic fibrosis (CF), caused by mutations in the CFTR gene, excessive neutrophilic inflammation drives lung damage and premature mortality. Current anti-inflammatory therapies have limited efficacy, partly due to an incomplete understanding of the mechanisms underlying CF-associated inflammation. Increased epithelial Ca{superscript 2} signaling has been implicated, but how CFTR dysfunction perturbs the CFTR/Ca{superscript 2} axis to promote inflammation remains unclear. ObjectivesUsing Cftr-depleted zebrafish and human approaches, we sought to i) define how CFTR dysfunction alters epithelial Ca{superscript 2} signaling and promotes inflammation, and ii) assess whether Ca{superscript 2} channel antagonists can attenuate inflammatory damage in CF. Methods and ResultsWe generated a transgenic zebrafish line expressing the Ca{superscript 2} reporter GCaMP6 under an epithelial promoter to dynamically map epithelial Ca{superscript 2} activity in vivo. Cftr-depleted zebrafish exhibited exaggerated epithelial Ca{superscript 2} elevations following injury compared with wild-type animals. Genetic or pharmacological inhibition of L-type voltage-gated Ca{superscript 2} channels (VGCCs) normalized epithelial Ca{superscript 2} responses and reduced both oxidative stress and neutrophil recruitment. Among FDA-approved VGCCs antagonists tested, only verapamil promoted resolution of neutrophilic inflammation and improved tissue repair in CF zebrafish. Mechanistically, verapamil reduced aberrant epithelial Ca{superscript 2} fluxes, ROS generation and NF-{kappa}B activation. These effects were confirmed in the human CF epithelial cell CFBE41o-, where verapamil reduced Ca2+ and oxidative stress. ConclusionsThese findings establish dysregulated Ca{superscript 2} signaling via L-type VGCCs as a pathogenic driver of inflammation in CF and identify verapamil as a promising therapeutic candidate. By restoring Ca{superscript 2} and oxidative homeostasis, verapamil alleviates inflammatory damage, supporting its repurposing as a candidate anti-inflammatory therapy in CF.

immunology↗

bioRxiv2025

HIV-1 Tat favors the multiplication of Mycobacterium tuberculosis and toxoplasma by inhibiting clathrin-mediated endocytosis and autophagy

AbstractHIV-1 and Mycobacterium tuberculosis (Mtb) coinfections are a major public health problem but are not well characterized. HIV-1 Tat is secreted by infected cells, generating nanomolar concentrations of Tat in the sera of people living with HIV. Circulating Tat enters cells, binds to PI(4,5)P2 then undergoes palmitoylation, thereby becoming resident on this phosphoinositide. Here, we found that Tat favors the multiplication of Mtb in macrophages. Moreover, Tat renders zebrafish larvae more sensitive to mycobacterial infection. We found that Tat binding to PI(4,5)P2 and palmitoylation enable Tat to inhibit the recruitment of the AP-2 adaptor, thereby inhibiting clathrin-mediated endocytosis and in turn autophagy. This inhibition prevents the degradation of intracellular pathogens such as Mtb and opsonized Toxoplasma gondii, but also of lipid droplets, thereby facilitating the access of these pathogens to lipids. We thus identified a mechanism enabling HIV Tat to favor the multiplication of intracellular pathogens such as Mtb.

microbiology↗

bioRxiv2025

The Staphylococcus aureus prophage-encoded SSBP attenuates virulence and enhances IL-6-mediated macrophage clearance

Pathogens often manipulate host immune responses to promote infection. Here, we describe a novel mechanism by which a secreted prophage-encoded single-stranded DNA-binding protein (SSBP) attenuates Staphylococcus aureus virulence while enhancing host immune defenses. SSBP, encoded by the ROSA-like prophage in a colonizing, reduced-virulence strain of S. aureus (NSA1385), significantly increases bacterial susceptibility to macrophage-mediated killing in vitro and reduces pathogenicity in a zebrafish infection model. Treatment with purified recombinant SSBP decreases bacterial survival within macrophages and demonstrates therapeutic potential. Notably, SSBP activates macrophages via interleukin-6 (IL-6), a pro-inflammatory cytokine that promotes bacterial clearance and macrophage activation. These findings uncover an unexpected prophage-derived mechanism in a colonizing S. aureus strain that attenuates virulence while stimulating host immunity, offering promising avenues for anti-infective therapies and immunomodulatory strategies.

microbiology↗

bioRxiv2025

Achromobacter xylosoxidans modulates Pseudomonas aeruginosa virulence through a multi-target mechanism of competition

The colonization and persistence of Pseudomonas aeruginosa in chronically diseased lungs are driven by the production of various virulence factors. However, pulmonary infections in cystic fibrosis (CF) patients are predominantly polymicrobial. While Achromobacter xylosoxidans is an opportunistic pathogen in these patients, its impact on P. aeruginosa virulence during co-infection remains largely unknown. This study investigated the interaction between P. aeruginosa and two clonally related A. xylosoxidans strains, Ax 198 and Ax 200, co-isolated from a CF patient sputum. We found that the interaction between P. aeruginosa and co-isolated A. xylosoxidans was strain-dependent, with the Ax 200 strain significantly reducing P. aeruginosa virulence in a zebrafish model, providing the first in vivo evidence of interaction between these two species during co-infection. Proteomic analysis revealed that the P. aeruginosa proteome was differently impacted by the two A. xylosoxidans strains, with Ax 200 altering proteins involved in biofilm formation, swimming motility, iron acquisition, and secretion systems. These proteomic findings were further validated by phenotypic assays, which confirmed that A. xylosoxidans affected major P. aeruginosa virulence phenotypes, including biofilm formation, swimming motility, and siderophore production. Genetic analysis also confirmed that distinct regulatory mechanisms, including mechanisms involved in the iron cycle, may account for the strain-dependent interaction effects of A. xylosoxidans with P. aeruginosa. These findings reveal a novel multi-target competitive mechanism through which A. xylosoxidans significantly disrupts P. aeruginosa virulence. IMPORTANCEPseudomonas aeruginosa, a major human pathogen, is a leading cause of mortality in cystic fibrosis (CF) patients. Understanding its virulence mechanisms is critical for developing effective infection management strategies. Given the polymicrobial nature of CF infections, it is essential to investigate interspecies interactions that may influence bacterial virulence. While A. xylosoxidans is recognized as an opportunistic pathogen in CF, its impact on P. aeruginosa virulence during co-infection remains largely unexplored. Deciphering the molecular basis of P. aeruginosa virulence in polymicrobial settings could reveal novel and specific therapeutic targets to improve treatment strategies.

microbiology↗

bioRxiv2021

Investigating pathogenicity and virulence of Staphylococcus pettenkoferi: an emerging pathogen

Staphylococcus pettenkoferi is a coagulase-negative Staphylococcus identified in 2002 that has been implicated in human diseases as an opportunistic pathogenic bacterium. Its multiresistant character is becoming a major health problem, yet the pathogenicity of S. pettenkoferi is poorly characterized. In this study, pathogenicity of a S. pettenkoferi clinical isolate from diabetic foot osteomyelitis was compared to a Staphylococcus aureus strain in various in vitro and in vivo experiments. Growth kinetics were compared against S. aureus and bacteria survival was assessed in the RAW 264.7 murine macrophage cell line, the THP-1 human leukemia monocytic cell line and the HaCaT human keratinocyte cell line. Ex vivo analysis were performed in whole blood survival assays, and in vivo assays via the infection model of zebrafish embryos. Moreover, whole-genome analysis was performed. Our results showed that S. pettenkoferi was able to survive in human blood, human keratinocytes, murine macrophages, and human macrophages. S. pettenkoferi demonstrated its virulence by causing substantial embryo mortality in the zebrafish model. Genomic analysis revealed virulence factors such as biofilm- (e.g., icaABCD; rsbUVW) and regulator- (e.g., agr, mgrA, sarA, saeS) encoding genes well characterized in S. aureus. This study thus advances the knowledge of this under investigated pathogen and validates the zebrafish infection model for this bacterium.

microbiology↗

bioRxiv2019

The Coxiella burnetii secreted protein kinase CstK influences vacuole development and interacts with the GTPase-activating protein TBC1D5

Coxiella burnetii is the etiological agent of the emerging zoonosis Q fever. Crucial to the pathogenesis of this intracellular pathogen is the secretion of bacterial effectors into host cells by a Type 4b Secretion System (T4SS), to subvert host cell membrane trafficking, leading to the biogenesis of a parasitophorous vacuole allowing intracellular replication. The characterization of prokaryotic Serine/Threonine Protein Kinases (STPKs) in bacterial pathogens is emerging as an important strategy to better understand host-pathogen interactions. In this study, we investigated CstK (for Coxiella Ser/Thr kinase), a bacterial protein kinase identified in C. burnetii by in silico analysis. Here, we demonstrated that this putative protein kinase undergoes autophosphorylation on Ser, Thr, and Tyr residues, and phosphorylates a classical eukaryotic protein kinase substrate in vitro. This dual Ser/Thr and Tyr kinase activity is similarly observed for eukaryotic dual specificity Tyr phosphorylation-regulated kinase class. CstK is translocated during infections and localizes at Coxiella-containing vacuoles (CCVs). Moreover, a C. burnetii mutant strain overexpressing CstK displays a severe CCVs development phenotype, suggesting a finely tuned regulation by the bacterial kinase during infection. Protein-protein interaction studies identified the Rab7-GTPase activating protein (GAP) TBC1D5 as a candidate CstK-specific host target, suggesting a role for this eukaryotic GAP in Coxiella infections. Indeed, CstK colocalizes with TBC1D5 in non-infected cells, and TBC1D5 is recruited at CCVs during infection. Accordingly, depletion of TBC1D5 from infected cells significantly affects CCVs development. Our results indicate that CstK has a critical role during infection as a bacterial effector protein that interacts with host proteins to facilitate vacuole biogenesis and intracellular replication.

microbiology↗