The Roles of Ras in Controlling Cell Fate – A Yeast Model of Oncogenic Potential

The dynamic nature and diverse functionality of intracellular lipid droplets is associated with many cellular processes and signalling pathways, that collectively coordinate the maintenance of cellular health, adaptability, and survival. Lipid droplet regulation is intrinsically linked to the state of lipid metabolism within the intracellular environment, being essential in ensuring lipid levels in the cytosol are appropriately maintained, to prevent states of lipid starvation or lipotoxicity. The regulatory mediators of lipid droplet biogenesis and maintenance are poorly defined, alongside the full extent of interactions that are shared between lipid droplets and other organelles of the cell. The aims of this study were to investigate the link between the mitochondria and lipid droplets, specifically identifying how lipid droplet regulation was affected by the induction of mitochondrial dysfunction - by the loss of Cytochrome c oxidase (COX) function. The role of Ras2 and Yno1 signalling were also identified as points of interest to elicit the signalling pathways associated with lipid droplet regulation. Through the visualisation of cells using fluorescent microscopy and the additional analysis of the neutral lipid content of cells using flow cytometry, the levels of intracellular lipid droplets were assessed. Findings in this study suggest that mitochondrial dysfunction, induced by the loss of COX function, leads to lipid droplet dysregulation. Furthermore, Ras2 signalling appears to be essential in this regulation, promoting the increase in lipid droplets following exposure to the appropriate stimuli. Interestingly, the NADPH oxidase Yno1 also appears to have a role in the regulation of lipid droplets, while also interacting with Ras2 - thus suggesting that multiple layers of regulation, involving both Yno1 and Ras2 signalling, exist to appropriately regulate levels of intracellular lipid droplet. Detailing these intracellular signalling pathways that regulate lipid droplets is key in understanding the depth of functionality associated with lipid droplets in S. cerevisiae. Developing this understanding may help us to understand the pathophysiology of diseases associated with both mitochondrial dysfunction and lipid droplet dysregulation as well as providing new avenues to explore for the treatment of such condition.