Affecting one out of every three Americans, nonalcoholic fatty liver disease (NAFLD) can be seen as a harmful threat to society. NAFLD is the enlargement of lipid droplets within liver cells and in extreme cases this can cause cirrhosis and even death. Lipid droplets are a key component in the energy of a cell. The lipid droplet is composed of a phospholipid monolayer with triglycerides and cholesterol esters making up the actual internal components of the lipid droplet. Coating the phospholipid monolayer is a multitude of proteins with a wide range of functions. These functions include aiding in the metabolism of the lipid droplets to the movement and localization of the lipid droplets within the cell. To examine how these lipid droplet proteins are regulated under physiological conditions, mice were fasted for four hours and then injected with glucagon for ten minutes. Afterwards, the liver cells were harvested and the lipid droplets were isolated. Phosphorylated proteins were enriched and then identified by use of LC/MS and database analysis. Two proteins that are of primary interest are Perilipin-2 (Plin-2) and Ras-related protein Rab-18 (Rab-18). Under normal conditions, Plin-2 localizes around the lipid droplets and has been shown to prevent lipolysis. Rab-18 is involved with the regulation of vesicle transportation around the cell. To determine the role of phosphorylation in the activity of Plin-2 and Rab-18, we will mutate the phosphorylated serine residues so as to either “mock” (aspartic acid) or prevent (alanine) the phosphorylation. We plan to determine by fluorescence microscopy if phosphorylation of these proteins is essential in their localization to the lipid droplet, in their interaction with other proteins, and in determining the size or amount of lipid droplets.<br/>

Role of phosphorylation in lipid droplet protein activity

253rd National Meeting (2017)

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