Biology subjects

Morschhaeuser, J.

Publications and source records attributed to Morschhaeuser, J..

3 recordsLinked to original sources

bioRxiv2025

Glucose Metabolism Controls Oxidative Burst and Lipid Mediator Production in Neutrophils upon Microbial Challenge

Neutrophils are frontline responders against bacterial and fungal pathogens, requiring rapid energy and biosynthetic precursors to mount effective antimicrobial responses. To meet these demands, they primarily rely on aerobic glycolysis, making glucose uptake essential. Murine and human neutrophils express the glucose transporters GLUT1 and GLUT3; however, their specific roles in neutrophil immunobiology have not yet been fully elucidated. Here, we show that neutrophilic immune responses to Candida albicans and Staphylococcus aureus critically depend on GLUT1/3-dependent glucose uptake and glycolysis. Combined deletion of GLUT1 and GLUT3 almost completely abolished glucose uptake and aerobic glycolysis in murine neutrophils, yet did not impair granulopoiesis, indicating that homeostatic neutrophil development is largely independent of extracellular glucose. By contrast, during microbial challenge, loss of GLUT1/3 severely compromised NADPH-dependent ROS production, oxidative burst and cyclooxygenase-derived lipid mediator (LM) biosynthesis, demonstrating that glucose uptake via GLUT1/3 controls inflammatory effector functions of neutrophils. Moreover, genetic and pharmacologic inhibition of GLUT1/3-mediated glucose utilization reprograms neutrophil metabolism and LM biosynthesis toward an immunomodulatory phenotype. These findings identify a conserved nutrient-sensing metabolic checkpoint that governs neutrophil reprogramming and highlight novel opportunities for therapeutic immunomodulation.

immunology↗

bioRxiv2025

Relative contributions of the ERG11VF125AL and MRR1AN647T mutations to fluconazole resistance in Clade III Candidozyma (Candida) auris clinical isolates

ObjectivesCandidozyma (Candida) auris is an emerging fungal pathogen of global concern that often exhibits multi-drug resistance. Over 90% of isolates are resistant to fluconazole. Of the six described clades of C. auris, Clade III has been found to be nearly universally fluconazole resistant and almost every Clade III isolate described carries a mutation in the gene encoding the fluconazole target sterol demethylase (ERG11) leading to a VF125AL substitution and a mutation leading to a N647T substitution in the gene encoding Mrr1a, a transcriptional regulator of the Mdr1 transporter. Both mutations have been shown to contribute to fluconazole resistance in C. auris. MethodsIn the present study we introduced the Clade III MRR1A mutation into a Clade I background using CRISPR-Cas9 gene editing. In two Clade III clinical isolates we corrected the native MRR1A and ERG11 mutations to their wild-type sequences as well as disrupted MDR1. Triazole susceptibilities and MDR1 gene expression were measured in all strains. ResultsIntroduction of the N647T substitution in a Clade I background confers a modest reduction in fluconazole and voriconazole susceptibility. Similarly, correction of MRR1A or disruption of MDR1 in each Clade III background resulted in a one-dilution decrease in fluconazole and voriconazole MIC while the ERG11 correction resulted in a three-dilution decrease in fluconazole and voriconazole MIC. ConclusionsOur findings show that while the MRR1A mutation makes a modest contribution, the ERG11 mutation is responsible for most of the fluconazole resistance observed in Clade III isolates. We also show that while these mutations likewise affect voriconazole susceptibility, they have no effect on susceptibility to itraconazole, isavuconazole, or posaconazole suggesting the potential therapeutic utility of these antifungals for infections due to Clade III isolates of C. auris.

microbiology↗

bioRxiv2020

The zinc cluster transcription factor Rha1 is a positive filamentation regulator in Candida albicans

Zinc cluster transcription factors are essential fungal specific regulators of gene expression. In the dimorphic pathogen Candida albicans, they control processes ranging from metabolism and stress adaptation to mating, virulence, and antifungal resistance. Here, we have identified the gene CaORF19.1604 as encoding a zinc cluster transcription factor that acts as a regulator of filament development. Hyperactivation of CaORF19.1604, which we have named RHA1 for Regulator of Hyphal Activity, leads to a wrinkled colony morphology under non-hyphal growth conditions, to pseudohyphal growth and filament formation, to invasiveness and enhanced biofilm formation. Cells with activated Rha1 are sensitive to cell wall modifying agents such as Congo red and the echinocandin drug caspofungin but show normal sensitivity to fluconazole. RNA-sequencing-based transcriptional profiling of the activated Rha1 strain reveals the up-regulation of genes for core filamentation and cell-wall-adhesion-related proteins such as Als1, Als3, Ece1, and Hwp1. Upregulation is also seen for the genes for the hyphal-inducing transcription factors Brg1 and Ume6 and genes encoding several enzymes involved in arginine metabolism, while downregulation is seen for the hyphal repressor Nrg1. The deletion of BRG1 blocks the filamentation caused by activated Rha1, while null mutants of UME6 result in a partial block. Deletion of RHA1 can partially reduce healthy hyphal development triggered by environmental conditions such as Spider medium or serum at 37{degrees}C. In contrast to the limited effect of either single mutant, the double rha1 ume6 deletion strain is totally defective in both serum and Spider medium stimulated hyphal development. While the loss of Brg1 function blocks serum-stimulated hyphal development, this block can be significantly bypassed by Rha1 hyperactivity, and the combination of Rha1 hyperactivity and serum addition can generate significant polarization in even brg1 ume6 double mutants. Our results thus suggest that in response to external signals, Rha1 functions to facilitate the switch from an Nrg1 controlled yeast state to a Brg1/Ume6 regulated hyphal state. Author SummaryCandida albicans is the predominant human fungal pathogen, generating a mortality rate of 40% in systemically infected patients. The ability of Candida albicans to change its morphology is a determinant of its tissue penetration and invasion in response to variant host-related stimuli. The regulatory mechanism for filamentation includes a complex network of transcription factors that play roles in regulating hyphae associated genes. We identify here a new regulator of filamentation from the zinc cluster transcription factor family. We present evidence suggesting that this transcription factor assists the Nrg1/Brg1 switch regulating hyphal development.

microbiology↗