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

Abstract

bEntamoeba 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.T he intestinal parasite Entamoeba histolytica is known to cause amoebic dysentery and liver abscess. E. histolytica enters the human host via contaminated food or water as an environmentally stable cyst. Excystation leads to the release of trophozoites in the small intestine, which colonize the bowel lumen. From here, the parasite can enter two non-mutually exclusive routes of infection, noninvasive or invasive disease (reviewed in reference 1). In the noninvasive mode, the trophozoite encysts and exits the host, whereas in the invasive mode, the parasite adheres to and destroys the colonic epithelium and enters the circulatory system. This results in extraintestinal infection, of which amoebic liver abscess (ALA) is the most common manifestation. Motility is a key virulence function that enables this parasite to cause extraintestinal infection (2).Motile amoebae display a polarized morphology with a pseudopod at the leading edge and a uroid (also referred to as a uropod in other eukaryotic cells) at the trailing edge. A key feature of a polarized cell is the differential distribution of proteins and lipids, including cell surface receptors, signaling molecules, and cytoskeletal elements. For example, the pseudopod of E. histolytica is enriched in F actin, myosin IB (3, 4), and signaling molecules like phosphatidylinositol-3,4,5-trisphosphate [PI(3,4,5)P 3 ] (5), while the uroid is enriched in myosin II and signaling molecules, including an important heterotrimeric adhesin, the galactose/N-acetylgalactosamine (Gal/GalNAc) lectin (6), F actin, and var...

A Genomewide Overexpression Screen Identifies Genes Involved in the Phosphatidylinositol 3-Kinase Pathway in the Human Protozoan Parasite Entamoeba histolytica

“…Lipid rafts are small cholesterol-and sphingolipid-rich membrane domains that regulate signaling, including PI3K signaling. In E. histolytica the PI3K substrate, PI(4,5)P 2 , is also enriched in rafts (47). Although it remains to be seen if PI(3,4,5)P 3 is localized to rafts in E. histolytica, the connection between SREHP and PI3K is strengthened by the fact that SREHP colocalizes with PI3K-based signaling lipids in rafts.…”

Intracellular traffic of the lysine and glutamic acid rich protein KERP1 reveals features of endomembrane organization inEntamoeba histolytica

“…histolytica is reinforced by the fact that the small GTPase Rac1 (EHI_181250) was found in one of the IP/LC‐MS/MS experiments. Also interestingly, E. histolytica PtdIns 4,5P 2 has been described to be associated with membrane lipid rafts and the heavy chain of the Gal/GalNAc surface lectin (Goldston et al ., ; Koushik et al ., ). In summary, our in vitro and in vivo data suggest the association between PiPs, Synaptojanin‐2 and KERP1, overall highlighting amoebic endocytosis features.…”

Interaction of pathogens with host cholesterol metabolism

“…For example, Entamoeba histolitica aquires host cholesterol to build its own lipid rafts required to attach to the intestinal wall [40] and for complex signalling regulating amoeba mobility [41]. …”