The heterogeneous nuclear ribonucleoprotein (hnRNP) glorund functions in the Drosophila fat body to regulate lipid storage and transport

Abstract

The availability of excess nutrients in Western diets has led to the overaccumulation of these nutrients as triglycerides, a condition known as obesity. The full complement of genes important for regulating triglyceride storage is not completely understood. Genome-wide RNAi screens in Drosophila cells have identified genes involved in mRNA splicing as important lipid storage regulators. Our lab has shown that a group of splicing factors called heterogeneous nuclear ribonucleoproteins (hnRNPs) regulate lipid metabolism in the fly fat body; however, the identities of all the hnRNPs that function to control triglyceride storage are not known. Here, we used the GAL4/UAS system to induce RNAi to the hnRNP glorund (glo) in the Drosophila fat body to assess whether this hnRNP has any metabolic functions. Decreasing glo levels resulted in less triglycerides being stored throughout the fly. Interestingly, decreasing fat body glo expression resulted in increased triglyceride storage in the fat body, but blunted triglyceride storage in non-fat body tissues, suggesting a defect in lipid transport. Consistent with this hypothesis, the expression of apolipophorin (apolpp), microsomal triglyceride transfer protein (mtp), and apolipoprotein lipid transfer particle (apoltp), apolipoprotein genes important for lipid transport through the fly hemolymph, was decreased in glo-RNAi flies, suggesting that glo regulates the transport of lipids from the fly fat body to surrounding tissues. Together, these results indicate that glorund plays a role in controlling lipid transport and storage and provide additional evidence of the link between gene expression and the regulation of lipid metabolism.