Drosophila melanogaster harbor the machinery to mediate an insulin-responsive sugar uptake response. Georgeta Crivat^1*, Vladimir Lizunov², Caroline Li¹, Karin Stenkula³, Joshua Ziammerberg², Samuel Cushman², Leslie Pick¹. 1) Entomology, University of Maryland, College Park, MD; 2) Laboratory of Cellular and Molecular Biophysics, Program on Physical Biology, Eunice Kennedy Schriver National Institute of Child Health and Human Development, and the Experimental Diabetes, Metabolism, and Nutrition Section, Diabetes, Endocrinology, and; 3) Department of Experimental Medical Science, Lund University BMC F10, SE-221 84 Lund, Sweden.

   Although insulin-signaling pathways are shared between mammals and insects, the extent to which this reflects conserved physiology is unclear. The Drosophila insulin receptor is structurally similar to the mammalian insulin receptor and was shown to auto-phosphorylate in response to mammalian insulin in cell culture. Here, we asked whether flies harbor the machinery to mediate an insulin-responsive sugar uptake response similar to mammals, by generating transgenic Drosophila expressing the human insulin-responsive sugar transporter GLUT4. We generated transgenic flies that carry UAS-HA-GLUT4-GFP: an HA tag inserted in the first exofacial loop of GLUT4 to monitor translocation of GLUT4 at the cell surface, and GFP at the C-terminus to monitor expression and trafficking. The GAL4/UAS system was used to express HA-GLUT4-GFP in the fat body. We used TIRF microscopy to examine the subcellular localization and trafficking of HA-GLUT4-GFP in living Drosophila fat body cells. We found that fat from transgenic animals expressing human GLUT4 responded to mammalian insulin with an increased rate of GLUT4 trafficking and translocation to the plasma membrane. This is, to our knowledge, the first study utilizing TIRFM to study insulin-mediated responses in the living cells of an insect and the first to show that insects harbor the machinery to mount a hormone-mediated sugar uptake response. Future studies will identify the endogenous Drosophila sugar transporter(s) that mediate this response.