Bioinformatics and Functional Analysis of an Entamoeba histolytica Mannosyltransferase Necessary for Parasite Complement Resistance and Hepatical Infection

Christian Weber,Alok Bhattacharya,Rachid C Maroun,Marie-Christine Rigothier,Mickael Krzeminski,Christophe Ausseur,Divya Vats,Sabrina Marion,Nancy Guillén,Samantha Blazquez

doi:10.1371/journal.pntd.0000165

Abstract

The glycosylphosphatidylinositol (GPI) moiety is one of the ways by which many cell surface proteins, such as Gal/GalNAc lectin and proteophosphoglycans (PPGs) attach to the surface of Entamoeba histolytica, the agent of human amoebiasis. It is believed that these GPI-anchored molecules are involved in parasite adhesion to cells, mucus and the extracellular matrix. We identified an E. histolytica homolog of PIG-M, which is a mannosyltransferase required for synthesis of GPI. The sequence and structural analysis led to the conclusion that EhPIG-M1 is composed of one signal peptide and 11 transmembrane domains with two large intra luminal loops, one of which contains the DXD motif, involved in the enzymatic catalysis and conserved in most glycosyltransferases. Expressing a fragment of the EhPIG-M1 encoding gene in antisense orientation generated parasite lines diminished in EhPIG-M1 levels; these lines displayed reduced GPI production, were highly sensitive to complement and were dramatically inhibited for amoebic abscess formation. The data suggest a role for GPI surface anchored molecules in the survival of E. histolytica during pathogenesis.

Highlights

Glycosylphosphatidylinositol (GPI) is a glycolipid required for anchoring many cell surface proteins and glycoconjugates to the surface of a wide range of human parasites including Trypanosoma brucei, the agent of sleeping sickness, Leishmania the causative agent of leishmaniasis, Plasmodium falciparum the agent of malaria and Entamoeba histolytica responsible for amoebiasis [1]
The causative agent of the infectious disease, amoebiasis, is the parasite Entamoeba histolytica, which targets human intestine and liver. This parasite attaches to human cells and matrix components via factors at its surface such as the Gal/GalNAc lectin and proteophosphoglycans (PPGs)
A homolog of the PIG-M1 enzyme was shown to be present in E. histolytica (EhPIG-M1)

Summary

Introduction

Glycosylphosphatidylinositol (GPI) is a glycolipid required for anchoring many cell surface proteins and glycoconjugates to the surface of a wide range of human parasites including Trypanosoma brucei, the agent of sleeping sickness, Leishmania the causative agent of leishmaniasis, Plasmodium falciparum the agent of malaria and Entamoeba histolytica responsible for amoebiasis [1]. In the context of human infection by P. falciparum, it has been proposed that the secreted GPI of parasite origin functions as the dominant malarial toxin [3,4]. GPIs of T. cruzi have the same function [5] These data support the view that GPIs of the parasitic protozoa are dominant proinflammatory agents playing a role in the immunopathology of these parasitic infections. Amoeba trophozoites bind to colonic mucins and to epithelial cells through the Gal/GalNAc lectin, an immunodominant protein complex containing a GPIanchored subunit [6]. This lectin associates with another GPIanchored protein, the intermediate IgL sub-unit. The non-virulent E. histolytica strain Rahman synthesizes one class of PPGs containing short disaccharide side-chains [8] and no similar molecule was detected in the Mannosyltransferase from E. histolytica

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Discussion

Conclusion