Redistribution of Parasite and Host Cell Membrane Components during Toxoplasma gondii Invasion.

Abstract

Keywords: Toxoplasma go«d///parasite-host cell interaction/parasitophorous vacuole/fluorescence microscopy ABSTRACT. The initial association of tachyzoites of Toxoplasma gondii with a host cell induces an endocytic process which leads to the formation of a vacuole known as the parasitophorous vacuole (PV). Weanalyzed the parasite-host cell interaction process using either parasites or host cells whose membranewas previously labeled with probes specific for proteins, sialoglycoconjugates and lipids, and then allowed to interact for periods varying from 5 minutes to 24 hours. The fate of the fluorscents probes was followed by con focal laser scanning microscopy. In host cells previously labeled with PKH26, FITC-Thiosemicarbazide or DTAF, which label membraneproteins, siloglycoconjugates and lipids, respectively, a uniform labeling of the cell surface was observed before interaction.When allowed to interact with T. gondii, labeling for PKH26and DTAF, but not for FITC-Thiosemicarbazide, was observed initially at the region of contact between the two cells and subsequently on the membrane lining the PV and the intravacuolar parasites. These observations show that some, but not all, membranecomponents contribute to the formation of the PVmembrane. Previously labeled parasites attach to the host cell surface but lose the fluorescent probes during the invasion process so that no labeled parasites were seen within the PV. These observations point to the existence of a dynamic process of membraneassociated components of the parasite and host cell during the interaction process.

A Conserved Subtilisin-like Protein TgSUB1 in Microneme Organelles of Toxoplasma gondii

“…Cleavage of host or parasite proteins may then allow their attachment as ligands mediating invasion. Although the membrane of the parasitophorous vacuole appears to be primarily derived from the host cell (40), few host cell proteins are present in the nascent vacuole (41). Proteolytic cleavage at or near the host cell membrane may allow the parasite to exclude host cell proteins from its vacuolar membrane.…”

Survival of intracellular pathogens within macrophages

“…It arises from a mechanism of entry that does not involve the specific receptors required for phagocytosis (Morisaki etal. 1995, Dobrowolski andSibley 1996), and it excludes host plasma membrane-associated proteins (de Carvahlo andde Souza 1989, Pacheco-Soares andDe Souza 1998). This exclusion may account for the fusion incapacity of the vacuole which apparently lacks the molecular machinery required for fusion.…”

Internalization of components of the host cell plasma membrane during infection by Trypanosoma cruzi

“…In the case of T. gondii both proteins and lipids are internalized during formation of the PV (Pacheco-Soares & De Souza 1998, Lingenlbach & Joiner 1998). Both probes described have been used to label the surface before interaction and to follow their fate during formation of the PV containing Plasmodium and Toxoplasma (Ward et al 1993, Pacheco-Soares & De Souza 1998, Lingelbach & Joiner 1998. Our observations showed an initial concentration of the labeled probes at the site of parasite attachment and their subsequent incorporation, together with the parasites, concentrating in the membrane lining the PV.…”