Localization of Phosphatidylinositol 4,5-Bisphosphate to Lipid Rafts and Uroids in the Human Protozoan Parasite Entamoeba histolytica

Abstract

ABSTRACT Entamoeba histolytica is an intestinal protozoan parasite and is the causative agent of amoebiasis. During invasive infection, highly motile amoebae destroy the colonic epithelium, enter the blood circulation, and disseminate to other organs such as liver, causing liver abscess. Motility is a key factor in E. histolytica pathogenesis, and this process relies on a dynamic actomyosin cytoskeleton. In other systems, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P 2 ] is known to regulate a wide variety of cellular functions, including signal transduction, actin remodeling, and cell motility. Little is known about the role of PI(4,5)P 2 in E. histolytica pathogenicity. In this study, we demonstrate that PI(4,5)P 2 is localized to cholesterol-rich microdomains, lipid rafts, and the actin-rich fractions of the E. histolytica membrane. Microscopy revealed that the trailing edge of polarized trophozoites, uroids, are highly enriched in lipid rafts and their constituent lipid, PI(4,5)P 2 . Polarization and enrichment of uroids and rafts with PI(4,5)P 2 were enhanced upon treatment of E. histolytica cells with cholesterol. Exposure to cholesterol also increased intracellular calcium, which is a downstream effector of PI(4,5)P 2 , with a concomitant increase in motility. Together, our data suggest that in E. histolytica , PI(4,5)P 2 may signal from lipid rafts and cholesterol may play a role in triggering PI(4,5)P 2 -mediated signaling to enhance the motility of this pathogen.