Poster: 123 - Print

Inositol catabolism via myo-inositol oxygenase in Drosophila melanogaster

Authors

Abstract

myo-Inositol is a six-carbon ring sugar that is important for many cellular processes in eukaryotes and some bacteria. It plays a role as a precursor of the membrane component phosphatidylinositol, in signal transduction pathways, and as an osmoregulator in response to environmental stress. myo-Inositol oxygenase (MIOX) catalyzes the conversion of myo-inositol to glucuronic acid in the first committed step of eukaryotic inositol catabolism. In human diabetics inositol homeostasis is often disturbed through mechanisms that are largely unknown. Depletion of myo-inositol is associated with diabetic complications (e.g. nephropathies, retinopathies, and diabetic cataracts). MIOX has been shown to be expressed in the kidneys and the extra-renal tissues where these complications occur. MIOX has not been annotated in the model organism Drosophila melanogaster, but the protein encoded by the D. melanogaster CG6910 gene has 54.6% identity to the Mus musculus MIOX protein. CG6910 is also highly similar to MIOX genes in a number of other organisms. D. melanogaster has an inositol catabolic pathway because wild-type strains can grow on defined media with inositol as the only carbon source. Establishing that CG6910 encodes MIOX allows for studies on D. melanogaster to have cross-species relevance to humans. The knock-down expression of CG6910 was explored using RNAi gene silencing. The ubiquitous Act5C-GAL4 driver was introduced into two independent CG6910 RNAi strains of D. melanogaster. These constructs should yield two independent variants of ubiquitous knock-down expression of CG6910. To determine if the knock-down expression of CG6910 altered inositol catabolism, these D. melanogaster were grown on defined media with either sucrose or inositol. Similar to flies on defined media without any sugar as a carbon/energy source, flies with the CG6910 RNAi and with the Act5C-GAL4 driver did not survive more than five days on the inositol defined media. This indicates that CG6910 encodes MIOX. Preliminary experiments of Western blot analyses show a decrease in MIOX expression in CG6910 RNAi flies with the Act5C-GAL4 driver. Other initial experiments include a biochemical assay demonstrating MIOX activity in D. melanogaster. These studies may contribute to understanding the role of inositol catabolism in fruit fly development and diabetes.

Keywords

drosophila melanogaster, metabolism, rna interference