Functional Analysis of Glutamine Synthetase in Drosophila melanogaster Semper Cells

Abstract

Record ID: 234

Program Affiliation: Capstone

Presentation Type: Poster

Abstract: Glutamine Synthetase is an important protein used in metabolizing nitrogen, a natural product of protein metabolism, and also is important in glia for the metabolic support of adjacent neurons.  Enhanced expression of Glutamine Synthetase also has been noted in glial support cells of both arthropod and vertebrate eyes. Here we used the Semper Cells (a type of eye glia) in Drosophila melanogaster to test the role of Glutamine Synthetase in these support cells. Two lines of flies were reared, a control line, and a line in which Glutamine Synthetase was knocked down specifically in Semper cells. These lines were then metabolically stressed with the use of a high-protein diet that would result in a relatively high nitrogen load and a high need for Glutamine Synthetase. To test if this treatment results in deficiencies pertaining to eye function, two lines of flies, and two types of food for each line were evaluated electrophysiologically. Specifically, electroretinography was used to test the ability of photoreceptors to respond to increasing intensities of light, a metabolically costly process. In contrast to our expectations,  test flies showed no significant reduction in photoreceptor responses. This outcome could suggest that in the fly eye, the surrounding pigment cells, which also have a heightened expression of Glutamine Synthetase, may be able to compensate for the increased energy demand or that other redundant energy sources are available.  Overall, this study still showed useful insight into our understanding of the roles that specific support cells play in invertebrate eyes.