Cryptococcus neoformans is a major comorbidity of HIV infection and transplantation with high mortality rates due to the toxicity and limited availability and efficacy of existing antifungal agents. As an environmental saprophyte, cryptococcal pathogenesis requires adaptation to the environment of the human host. Our work has led us to the scientific premise that stress adaptation in C. neoformans requires two sequential post- transcriptional events. First, the accelerated degradation mRNAs encoding metabolically expensive processes such as the translational machinery, and second, the translation of stress response mRNAs via cap- independent translation mechanisms on recycled ribosomes. This premise implicates the ribosome as a sensor of cellular stress through translation quality control mechanisms.
The aims i n this proposal will investigate co- translational quality control as a trigger for accelerated mRNA degradation in response to temperature sturess (Aim1) and will investigate cap-independent translation mechanisms (Aims 2) in stress adaptation.
Aim 2 will focus on two CNBP orthologues expressed in C. neoformans that we hypothesize to regulate translation via internal ribosome entry sites (IRES) in response to temperature and oxidative stress. Finally, we will assess the contributing role of ribosome-associated quality control in starvation stress responsive translation and define the contributions of each quality control pathway in the response of C. neoformans to compound stressors (Aim 3). These studies will be the first investigation of translation in C. neoformans, and include the first application of ribosome profiling in this pathogen. Translation is known to be pharmacologically targetable but conservation in eukaryotes is thought to be a hindrance. Only through molecular investigation of translation regulation can fungal-specific aspects of the process be identified for future investigation as drug targets.
Cryptococcus neoformans will kill over 600,000 people this year, the majority of which will be co-infected with HIV and live in under-resourced areas. In this proposal we will investigate the mechanism of stress adaptation in C. neoformans through the lens of the ribosome ? the protein synthesis machinery. Protein synthesis is a common target of antimicrobials; investigating the ribosome as a stress sensor in this pathogen may identify specific targets for future drug development.
