Biology subjects

Mouyna, I.

Publications and source records attributed to Mouyna, I..

3 recordsLinked to original sources

bioRxiv2025

Kre6-Dependent β-1,6-glucan Biosynthesis Only Occurs in the Conidium of Aspergillus fumigatus

The structural role of {beta}-1,6-glucan has remained under-investigated in filamentous fungi compared to other fungal cell wall polymers, and previous studies have shown that the cell wall of the mycelium of A. fumigatus did not contain {beta}-1,6-glucans. In contrast, the current solid-state NMR investigations showed that the conidial cell wall contained a low amount of {beta}-1,6-glucan. ssNMR comparisons of the A. fumigatus and C. albicans {beta}-1,6-glucans showed they are structurally similar. Deletion of the KRE6 gene which is the only KRE gene in the A. fumigatus genome resulted in a mutant depleted of {beta}-1,6-glucan which has a growth phenotype similar to the parental strain. Even though it is not an essential polymer in A. fumigatus, {beta}-1,6-glucan play a role in cell wall organization since the kre6{Delta} mutant showed a higher sensitivity to Congo-red and Calcofluor white which are known to be general cell wall inhibitors. It is also another example of the significant structural differences seen between conidium and mycelium of filamentous fungi.

biochemistry↗

bioRxiv2023

Tur1 regulates alternative TSS usage in Cryptococcus

Alternative transcription start site (TSS) usage regulation has been identified as a major means of gene expression regulation in metazoans. However, in fungi, its impact remains elusive as its study has thus far been restricted to model yeasts. Here, we first re-analysed TSS-seq data to define genuine TSS clusters in two species of pathogenic Cryptococcus. We identified two types of TSS clusters associated with specific DNA sequence motifs. Our analysis also revealed that alternative TSS usage regulation in response to environmental cues is widespread in Cryptococcus, altering gene expression and protein targeting. Importantly, we performed a forward genetic screen to identify a unique transcription factor (TF) named Tur1, which regulates alternative TSS (altTSS) usage genome-wide when cells switch from exponential phase to stationary phase. ChiP-Seq and DamID-Seq analyses suggest that at some loci the role of Tur1 might be direct. Tur1 has been previously shown to be essential for virulence in C. neoformans. We demonstrated here that a tur1{Delta} mutant strain is more sensitive to superoxide stress and phagocytosed more efficiently by macrophages than the wild-type (WT) strain.

molecular biology↗

bioRxiv2023

Extracellular vesicles production regulates fluconazole resistance in Cryptococcus neoformans

Resistance to fluconazole (FLC), the most widely used antifungal drug, is typically achieved by altering the azole drug target and/or drug efflux pumps. Recent reports have suggested a link between vesicular trafficking and antifungal resistance. Here, we identified novel Cryptococcus neoformans regulators of extracellular vesicle (EV) biogenesis that impact FLC resistance. In particular, the transcription factor Hap2 does not affect the expression of the drug target or efflux pumps, yet it impacts the cellular sterol profile. Subinhibitory FLC concentrations also downregulate EV production. Moreover, in vitro spontaneous FLC-resistant colonies showed altered EV production, and the acquisition of FLC resistance was associated with decreased EV production in clinical isolates. Finally, the reversion of FLC resistance was associated with increased EV production. These data suggest a model in which fungal cells can regulate EV production in place of regulating the drug target gene expression as a first line of defense against antifungal assault in this fungal pathogen. IMPORTANCEExtracellular vesicles (EVs) are membrane-enveloped particles that are released by cells into the extracellular space. Fungal EVs can mediate community interactions and biofilm formation but thier functions remain poorly understood. Here, we report the identification of the first regulators of EV production in the major fungal pathogen Cryptococcus neoformans. Surprisingly, we uncover a novel role of EVs in modulating antifungal drug resistance. Disruption of EV production was associated with altered lipid composition and changes in fluconazole susceptibility. Spontaneous azole-resistant mutants were deficient in EV production, while loss of resistance restored initial EV production levels. These findings were recapitulated in C. neoformans clinical isolates, indicating that azole resistance and EV production are coregulated in diverse strains. Our study reveals a new mechanism of drug resistance in which cells adapt to azole stress by modulating EV production.

microbiology↗