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

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

Influence of inflammation on parasitism and area of experimental amoebic liver abscess: an immunohistochemical and morphometric study

The influence of inflammation on the number of trophozoites and on the murine amoebic liver abscess area following infection with Entamoeba histolytica and E. dispar was evaluated. Immunohistochemistry and digital morphometry were used to identify and quantify the trophozoites, neutrophils, macrophages, and lesions. Positive correlation was observed between the number of trophozoites and inflammatory cells. A significant decrease in parasitism and inflammation in groups treated with dexamethasone was observed. The scarceness or absence of trophozoites in the treated groups suggest the importance of the inflammatory response in the production of amoebic hepatic abscesses in spite of the inherent virulence of the parasite being decisive in the establishment of the lesion

IQGAP1 Interacts with Components of the Slit Diaphragm Complex in Podocytes and Is Involved in Podocyte Migration and Permeability In Vitro

IQGAP1 is a scaffold protein that interacts with proteins of the cytoskeleton and the intercellular adhesion complex. In podocytes, IQGAP1 is associated with nephrin in the glomerular slit diaphragm (SD) complex, but its role remains ill-defined. In this work, we investigated the interaction of IQGAP1 with the cytoskeleton and SD proteins in podocytes in culture, and its role in podocyte migration and permeability. Expression, localization, and interactions between IQGAP1 and SD or cytoskeletal proteins were determined in cultured human podocytes by Western blot (WB), immunocytolocalization (IC), immunoprecipitation (IP), and In situ Proximity Ligation assay (IsPL). Involvement of IQGAP1 in migration and permeability was also assessed. IQGAP1 expression in normal kidney biopsies was studied by immunohistochemistry. IQGAP1 expression by podocytes increased during their in vitro differentiation. IC, IP, and IsPL experiments showed colocalizations and/or interactions between IQGAP1 and SD proteins (nephrin, MAGI-1, CD2AP, NCK 1/2, podocin), podocalyxin, and cytoskeletal proteins (α-actinin-4). IQGAP1 silencing decreased podocyte migration and increased the permeability of a podocyte layer. Immunohistochemistry on normal human kidney confirmed IQGAP1 expression in podocytes and distal tubular epithelial cells and also showed an expression in glomerular parietal epithelial cells. In summary, our results suggest that IQGAP1, through its interaction with components of SD and cytoskeletal proteins, is involved in podocyte barrier properties

Glucose Starvation Boosts Entamoeba histolytica Virulence

The unicellular parasite, Entamoeba histolytica, is exposed to numerous adverse conditions, such as nutrient deprivation, during its life cycle stages in the human host. In the present study, we examined whether the parasite virulence could be influenced by glucose starvation (GS). The migratory behaviour of the parasite and its capability to kill mammalian cells and to lyse erythrocytes is strongly enhanced following GS. In order to gain insights into the mechanism underlying the GS boosting effects on virulence, we analyzed differences in protein expression levels in control and glucose-starved trophozoites, by quantitative proteomic analysis. We observed that upstream regulatory element 3-binding protein (URE3-BP), a transcription factor that modulates E.histolytica virulence, and the lysine-rich protein 1 (KRiP1) which is induced during liver abscess development, are upregulated by GS. We also analyzed E. histolytica membrane fractions and noticed that the Gal/GalNAc lectin light subunit LgL1 is up-regulated by GS. Surprisingly, amoebapore A (Ap-A) and cysteine proteinase A5 (CP-A5), two important E. histolytica virulence factors, were strongly down-regulated by GS. While the boosting effect of GS on E. histolytica virulence was conserved in strains silenced for Ap-A and CP-A5, it was lost in LgL1 and in KRiP1 down-regulated strains. These data emphasize the unexpected role of GS in the modulation of E.histolytica virulence and the involvement of KRiP1 and Lgl1 in this phenomenon

Nouveau modèle expérimental d’amibiase cæcale chez le rat

Le Raton a été utilisé comme modèle expérimental d’amibiase cæcale, en pratiquant l’implantation, sans effraction du cæcum, d’une suspension de trophozoites d'Entamaeba histolytica, souche gnotoxénique Rahman, de virulence élevée. L’atteinte de la paroi est objectivée par l’aspect macroscopique du cæcum, par la densité des trophozoites présents et par un examen anatomopathologique. Comme il existe une corrélation entre les paramètres macroscopiques et l’histologie, un indice de gravité est défini, qui prend en compte plusieurs critères macro- et microscopiques. Ce modèle permet donc de suivre les différentes phases de la cicatrisation et de la guérison des ratons et d’apprécier ainsi l’activité de substances antiamibiennes

Effets des levures

Un modèle original d’amibiase cæcale mis au point chez le raton a été utilisé pour étudier l’effet de la levure Saccharomyces boulardii sur le développement des lésions. Des ratons infectés par Entamoeba histolytica ont été traités par Saccharomyces boulardii ; chez les traités, le nombre de ratons malades est significativement moins élevé, la gravité de l’affection, appréciée par l’aspect macroscopique du cæcum et la présence d’amibes a été diminuée. Les lésions observées sont semblables à celles des animaux témoins, mais leur processus de cicatrisation est accéléré. Par ailleurs, Saccharomyces boulardii n’a pas d’action amœbicide in vitro