Phosphatidylinositide 3-kinase (PI3K) is a key enzyme implicated in intracellular signaling of diverse cellular responses including receptor-mediated responses and neutrophil activation. Several PI3K subunits have been cloned and shown to be localized to plasma membrane receptors, the cytosol, or intracellular vesicles or caveolae. We report the localization of PI3K to a distinct intracellular site, cytoplasmic lipid bodies, in leukocytes. In U937 monocyte cells, PI3K p85 regulatory and p110β catalytic subunits were localized to lipid bodies by immunocytochemistry and/or immunoblotting and enzyme assays of subcellular fractions. In RAW murine macrophages, p55, p85, and p85β PI3K subunits were present at isolated lipid bodies. PI3K p85 was also shown to colocalize and, by co-immunoprecipitation, to be physically associated with phosphorylated Lyn kinase in lipid bodies induced to form in human polymorphonuclear leukocytes. These findings, therefore, indicate a novel site for PI3K compartmentalization and suggest that PI3K-mediated signaling is active within cytoplasmic lipid bodies in leukocytes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.