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Theses Doctoral

Cellular Fatty Acid Toxicity: Extrapolating Yeast Screens into Mammalian Models

Ruggles, Kelly Valentine

Fatty acid deposition in non-adipose tissue leads to a cellular dysfunction known as lipotoxicity. Neutral lipid synthesis is known to protect against lipotoxicity but many additional pathways are likely to be integral in this process. In order to identify pathways protective against lipid induced cell death, we performed a genome-wide unsaturated fatty acid (UFA) sensitivity screen in yeast. Of the ~5,500 gene mutants tested, we identified 156 which resulted in sensitivity to growth on media containing palmitoleate. These genes identified many cellular processes, including vesicular trafficking, lipid metabolism and vacuolar protein sorting. Deletion of three members of the GET complex, a complex essential for tail anchored protein insertion into the ER, caused vulnerability to fatty acids. We went on to assess the role of GET3 in cellular lipid metabolism and found that ablation of GET3 results in a defect in vacuolar hydrolysis and a reduction in lipid droplet number; pathways which we hypothesize to be integrally related. Furthermore, a major goal of this study was to find mammalian genes playing an integral role in pathways of lipoprotection. Of the 156 gene deletions found to confer fatty acid sensitivity in yeast, 68 have been conserved in mammals. We demonstrate that two of these mammalian orthologs, ARV1and ASNA1, are vulnerable to fatty acid treatment upon knockdown in the MIN6 pancreatic beta-cell line. These mammalian genes, which were identified through the fatty acid sensitivity screen in yeast, are involved in lipid induced cellular dysfunction in pancreatic beta-cells and, in the case of ARV1, hepatocytes. Therefore, these genes likely play a role in the progression of the lipotoxic diseases; type 2 diabetes and nonalcoholic fatty liver disease.

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Academic Units
Nutritional and Metabolic Biology
Thesis Advisors
Sturley, Stephen L.
Degree
Ph.D., Columbia University
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