Characterization of Insect Lipid Storage Droplet Protein I

Abstract

Insects use stored fat as energy during flight, stress, and reproduction. These lipid stores need to be mobilized in order to provide energy for essential functions. Recent development in the study of lipolysis has revealed that it is mainly controlled by substrate (lipid droplet) activation. The substrate activation is mediated via protein kinase A phosphorylation of lipid droplet associated proteins on the surface of lipid droplets as well as TG-lipase in the cytosol. Analysis of the phosphorylation state of LD-associated protein showed that in vivo stimulation of lipolysis promotes a rapid phosphorylation of a 42-44 kDa protein. This protein was identified by mass spectrometry as Lipid storage droplet protein-1 (Lsdp-1). Phosphorylation of Lsdp-1 correlates with augmented TG-lipase activity suggesting that Lsdp-1 is one of the prominent contributors of lipolysis. The purpose of this study was to investigate further the hypothesis that Lsdp-1 is involved in activation of lipolysis. The specific aims were: 1) Purification of Lsdp-1 from the fat body of adult M. sexta; 2) Determining the role of Lsdp-1 in TG-lipase activity using Lsdp-1 purified from M.sexta; 3) Determining the role of Lsdp-1 in TG-lipase activity using D. melanogester recombinant protein (dLsdp-1); 4) Investigate the protein expression levels of Lsdp-1 in different developmental stages and tissues of M. sexta.