Examining the Effect Metal Toxicity has on Vacuole Inheritance and Structure in Saccharomyces cerevisiae
Austin Irungu
Department of Biology
Faculty Supervisor: Mark Chan
Saccharomyces cerevisiae is a well-established model organism for studying eukaryotic cell biology due to its conservation of organelle dynamics. The vacuole, a membrane-bound organelle, is crucial for maintaining cellular homeostasis, metal detoxification, and shares homology with the mammalian lysosome in degrading cellular waste. Our research investigates how toxic metals, including lithium, magnesium, copper, and iron, affect vacuole function and structure. We discovered that lithium inhibits the inheritance of vacuoles from mother cells to daughter buds. Under lithium-free conditions, GSK3 phosphorylates Yck3, which subsequently phosphorylates Vps41, promoting proper vacuole inheritance. We tested this putative pathway by taking knockout strains of genes, and testing whether lithium continued to exert an effect on inheritance. Deletion of Yck3 caused higher inheritance defects, while deletion of Vps41 reduced defects, and introduction of a Vps41-phosphomimic plasmid into vps41Δ cells further lowered defects. To determine whether Vps41 phosphorylation alone could restore inheritance without Yck3, we transformed yck3Δ cells with the phosphomimic plasmid and quantified inheritance defects via microscopy. These experiments revealed inheritance was not restored, suggesting inheritance is regulated in a more complex, non-linear manner. By clarifying the molecular mechanisms of vacuole inheritance, this work expands our understanding of organelle dynamics in eukaryotic cells under stress conditions.