Investigating the Role of Lipid Droplets in Stress Response Regulation in S. cerevisiae

Lipid droplets are spherical lipid storage vesicles that sequester fatty acids as the "neutral lipids" in a manner that is non-toxic to the cell. Creation of the primary neutral lipid within a lipid droplet's core, triacylglycerol (TAG) is controlled by Dga1 and Lro1, with sterol ester (SE) formation being controlled by Are1 and Are2. This work reveals that disruption of the actin cytoskeleton, or exposure to a variety of stresses that trigger cell wall integrity (CWI) signalling, promotes formation of lipid droplets. We propose that formation of lipid droplets is an important step within CWI signalling, as deletion of DGA1 and LRO1, a disruption of TAG synthesis, prevent pathway activation. I show that constitutive activation of CWI signalling leads to a lipid droplet dependent increase in necrosis, suggesting a mechanism by which cells that cannot adapt to stress may be removed from the population. Unpublished work from our lab has established the presence of the mitochondrial outer membrane protein, porin, as a necessary component of the CWI pathway. This data outlines a novel mechanism through which mitochondria and lipid droplets facilitate CWI signalling and cell fate decisions in yeast.