A study on Manduca sexta perilipin 2: cloning, developmental expression and characterization of the recombinant protein

Abstract

Animals accumulate excess energy as triglycerides (TG) in cytosolic organelles, the lipid droplets (LD), in which the lipid core is surrounded by phospholipids and a dynamic coat of proteins. The perilipins (PLIN) are a distinctive group of LD proteins involved in TG storage. PLIN 1‐2 occur in insects. PLIN2 is required for normal storage of TG in the fruit fly. To expand our knowledge on the function of PLIN2 in insects, we have cloned M. sexta PLIN2 and profiled the mRNA and protein levels in several TG‐storing tissues. PLIN2 was predominantly expressed in ovary where its abundance followed an inverse relationship with the content of TG. In the fat body PLIN2 was more abundant in the lipid‐mobilizing tissue of adult animals than in the lipid‐storing tissue of larval insects. In the larval fat body, PLIN2 increased at the beginning of the development when the tissue is storing lipids but declined at the end of the period when TG storage peaks. However, an increase of fat body PLIN2 that correlated with TG synthesis was observed during the re‐feeding of starved larval insects in which fat body lipids were depleted by starvation. In the midgut, PLIN2 expression correlated with TG synthesis. PLIN2 was exclusively localized to LDs. PLIN2 was a soluble protein with a folded conformation that binds to phospholipids. In agreement with the intracellular localization, lipid‐bound PLIN2 showed higher stability than the lipid‐free form. Our study suggests that MsPLIN2 is not critical for LD stability. PLIN2 seems to be required for the early deposition of lipids presumably stored in new LD. In this context, the high abundance of PLIN2 in the lipid mobilizing fat body suggests an involvement of PLIN2 in TG re‐synthesis.