The SR proteins SF2 and RBP1 regulate triglyceride storage in the fat body of Drosophila

In Western societies where food is abundant, these excess nutrients are stored as fats mainly in adipose tissue. Fats are stored in structures known as lipid droplets, and a genome-wide screen performed in Drosophila cells has identified several genes that are important for the formation of these droplets. One group of genes found during this screen included those that regulate mRNA splicing. Previous work from our lab has identified some splicing factors that play a role in regulating fat storage; however, the full complement of splicing proteins that regulate lipid metabolism is still unknown. In this study, the levels of a number of serine-arginine (SR) domain containing splicing factors (RSF1, RBP1, RBP1-like, SF2 and Srp-54) were decreased using RNAi in the adult fat body to assess their role in the control of Drosophila metabolism. Decreasing SF2 and RBP1 showed increased triglycerides, while inducing RNAi towards RSF1, RBP1-Like and Srp-54 had no effect on triglycerides. Interestingly, the increased triglyceride phenotype in the SF2-RNAi flies was due to an increase in the amount of fat stored per cell while the RBP1-RNAi flies have more fat cells. In addition, the splicing of the β-oxidation enzyme, CPT1, was altered in the SF2-RNAi flies potentially promoting the increased triglycerides in these animals. Together, this study identifies novel splicing factors responsible for the regulation of lipid storage in the Drosophila fat body and contributes to our understanding of the mechanisms, which influence the regulation of fat storage in adipose-like cells.