Glutamine synthetase expression and stress tolerance in Drosophila melanogaster

Abstract

This thesis explores glutamine synthetase in Drosophila melanogaster. L-glutamine, more than other amino acids, is strictly required for cell survival. Like many complex organisms, D. melanogaster has two forms of the enzyme glutamine synthetase (GS): GS1, located in the mitochondria, and GS2, located in the cytosol. Interestingly, how these two isozymes partition GS function is unknown. I validated a sample preparation protocol to separate the mitochondria and cytosol from Drosophila samples, and assay solutions for the measurement of GS transferase and GS biosynthetic activity. I created knockdowns of GS1 and GS2 and subjected these to heat shock and paraquat-induced stress. The GS1 and GS2 knockdowns displayed differences in their response to both stressors, indicating a potential functional differentiation of the two isozymes in stress tolerance. This project is a step in the use of Drosophila to explore the GS network and how glutamine modulates cell survival.