Biology subjects

Ventura, M. N.

Publications and source records attributed to Ventura, M. N..

2 recordsLinked to original sources

bioRxiv2026

Stress-responsive roles of the C. neoformans human-like eIF3 complex

Eukaryotic translation initiation factor 3 (eIF3) is a complex of proteins that plays a pleiotropic role in translation regulation across eukaryotes, but the composition of eIF3 complexes varies with retention and loss of subunit genes across evolution. The model yeast Saccharomyces cerevisiae encodes six eIF3 subunits whereas mammals encode thirteen subunits. The basidiomycete fungus and opportunistic fungal pathogen, Cryptococcus neoformans, encodes a mammalian complement of eIF3 subunits. In this report, we investigated the contribution of the non-essential eIF3 subunit genes to cryptococcal stress tolerance. We found that mutants in the four nonessential subunits, eIF3d, eIF3e, eIF3k and eIF3l all exhibit sensitivity to mitochondrial perturbation, and that mutants in eIF3d and eIF3e exhibit opposite susceptibilities to the antifungal drug fluconazole and the hypoxia mimetic cobalt chloride. Loss of eIF3d resulted in reduced eIF2 phosphorylation in response to stress, but the mutant was still able to repress translation to the same extent as the wild type and was defective in induction of integrated stress response regulon. Despite producing higher levels of urease and melanin, the eIF3d deletion mutant was avirulent in Galleria mellonella larvae. Together our data demonstrates the importance of C. neoformans eIF3 in stress adaptation and pathogenesis. ImportanceCryptococcus neoformans is an opportunistic fungal pathogen that causes cryptococcal meningoencephalitis in immunocompromised individuals leading to [~]120,000 deaths worldwide annually. When C. neoformans is exposed to host-relevant stressors, such as oxidative stress and thermal stress, it reprograms the translating pool of mRNAs to favor stress adaptation. Eukaryotic translation initiation factor 3 is a multi-subunit complex with roles in stress-responsive translation across eukaryotes yet is unexplored in C. neoformans. We found that C. neoformans encodes orthologues of all thirteen mammalian eIF3 subunits. Mutational analysis of non-essential subunits implicated eIF3 in responses to mitochondrial stress and antifungal susceptibility in C. neoformans, and demonstrates a role for eIF3d in the induction of the integrated stress response as well as in Cryptococcal pathogenesis. Further work will investigate the specific mRNAs that are regulated by eIF3 in response to host-relevant stressors in C. neoformans.

microbiology↗

bioRxiv2024

Gcn2 rescues reprogramming in the absence of Hog1/p38 signaling in C. neoformans during thermal stress.

The fungus Cryptococcus neoformans is an opportunistic pathogen of people that reprograms its translatome to facilitate adaptation and virulence within the host. We studied the role of Hog1/p38 in reprogramming translation during thermal stress adaptation, and found that this pathway acts on translation via crosstalk with the Gcn2 pathway, a well-studied regulator of general translation control. Using a combination of molecular assays and phenotypic analysis, we show that increased output from the Gcn2 pathway in a Hog1 deletion mutant is associated with rescue of thermal stress adaptation at both molecular and phenotypic scales. We characterize known outputs of the Hog1 pathway during thermal stress as either Gcn2-dependent or Gcn2-independent, and demonstrate that Hog1 activation regulates the Gcn2 pathway even in the absence of thermal stress. Finally, we implicate this phenomenon in another Hog1-regulated process, morphogenesis, and recapitulate Hog1-Gcn2 crosstalk in the distantly related fungal pathogen, Candida albicans. Our results point to an important link between the stress response machinery and translation control, and clarify the etiology of phenotypes associated with Hog1 deletion. More broadly, this study highlights complex interplay between core conserved signal transduction pathways and the utility of molecular assays to better understand how these pathways are connected. ImportanceCryptococcus neoformans is an opportunistic pathogen of people that causes deadly cryptococcal meningitis, which is is responsible for an estimated 19% of AIDS-related mortality. When left untreated, cryptococcal meningitis is uniformly fatal, and in patients receiving the most effective antifungal regimens, mortality remains high. Thus, there is a critical need to identify additional targets that play a role in adaptation to the human host and virulence. This study explores the role of the stress response kinases Hog1 and Gcn2 in thermoadaptation, which is pre-requisite for virulence. Our results show that compensatory signaling occurs via the Gcn2 pathway when Hog1 is deleted, and that disruption of both pathways increases sensitivity to thermal stress. Importantly, our study highlights the insufficiency of using single gene deletion mutants to study gene function, since many phenotypes associated with Hog1 deletion were driven by Gcn2 signaling in this background, rather than loss of direct Hog1 activity.

microbiology↗