Leukocyte lipid bodies are specialized, inducible intracellular domains that function as signaling platforms in inflammatory mediator production and leukocyte activation. Although several groups are studying the protein content of adipocyte lipid droplets, there is few data on structural proteins of leukocyte lipid body. In order to improve the structural characterization of this organelle, we have been performed the analysis of the lipid body lipid moiety, by both HPTLC and mass spectrometry, and also the identificati9on of the protein moiety. Adipose-differentiation-related protein (ADRP) is known to be a structural protein found in lipid bodies of cells that typically accumulate lipids (adipocytes; ovary cells). Here we show, by both immuno-fluorescence and western blotting, that ADRP localizes specifically with lipid bodies in several inflammation-related leukocytes (macrophages, neutrophils and eosinophils) and leukocyte cell lineages. Moreover, resting leukocytes, specifically neutrophils, exhibited a preformed cytosolic ADRP pool that rapidly translocates to lipid bodies upon cell activation, as seen by western blotting of samples from cell fractionation by sucrose gradient.
Therefore, the recognition that ADRP localizes at leukocyte lipid bodies, and that the formation of lipid bodies are independent on new ADRP protein synthesis, will assist in identifying and understanding the functions of cytoplasmic lipid bodies.