Insight into the Exoproteome of the Tissue-Derived Trypomastigote form of Trypanosoma cruzi.

Rayner M L Queiroz,Sébastien Charneau,Mara O Machado,Jaime M De Santana,Izabela M D Bastos,Peter Roepstorff,Carlos A O Ricart,Marcelo V De Sousa

doi:10.3389/fchem.2016.00042

Rayner M L Queiroz, Sébastien Charneau + Show 6 more

Open Access

https://doi.org/10.3389/fchem.2016.00042

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Abstract

The protozoan parasite Trypanosoma cruzi causes Chagas disease, one of the major neglected infectious diseases. It has the potential to infect any nucleated mammalian cell. The secreted/excreted protein repertoire released by T. cruzi trypomastigotes is crucial in host-pathogen interactions. In this study, mammalian tissue culture-derived trypomastigotes (Y strain) were used to characterize the exoproteome of the infective bloodstream life form. Proteins released into the serum-free culture medium after 3 h of incubation were harvested and digested with trypsin. NanoLC-MS/MS analysis resulted in the identification of 540 proteins, the largest set of released proteins identified to date in Trypanosoma spp. Bioinformatic analysis predicted most identified proteins as secreted, predominantly by non-classical pathways, and involved in host-cell infection. Some proteins possess predicted GPI-anchor signals, these being mostly trans-sialidases, mucin associated surface proteins and surface glycoproteins. Moreover, we enriched phosphopeptides and glycopeptides from tryptic digests. The majority of identified glycoproteins are trans-sialidases and surface glycoproteins involved in host-parasite interaction. Conversely, most identified phosphoproteins have no Gene Ontology classification. The existence of various proteins related to similar functions in the exoproteome likely reflects this parasite's enhanced mechanisms for adhesion, invasion, and internalization of different host-cell types, and escape from immune defenses.

Highlights

Adhesion and invasion are the first stages of interaction between an obligate intracellular pathogen and its host-cell that involve cell surface molecules and secreted molecules
Besides the classical secretory pathway (Schatz and Dobberstein, 1996), several functional proteins are released into the extracellular medium despite lacking any predicted signal peptides, thereby proving the existence of unconventional mechanisms of protein secretion in eukaryotes (Nickel and Rabouille, 2009)
The term secretome was first introduced in a bioinformatic survey of proteins secreted by Bacillus subtilis (Tjalsma et al, 2000)

Summary

Introduction

Adhesion and invasion are the first stages of interaction between an obligate intracellular pathogen and its host-cell that involve cell surface molecules and secreted molecules. Besides the classical secretory pathway (Schatz and Dobberstein, 1996), several functional proteins are released into the extracellular medium despite lacking any predicted signal peptides, thereby proving the existence of unconventional mechanisms of protein secretion in eukaryotes (Nickel and Rabouille, 2009). Nowadays the term secretome is used primarily to denote proteins secreted by cells into the extracellular region (Greenbaum et al, 2001). These released proteins are secreted proteins and proteins that arise from other export mechanisms. Only those proteins that are stable in the extracellular medium will remain in abundance. The best term to describe the protein content found in the extracellular proximity of a given biological system is the “exoproteome” (Armengaud et al, 2012)

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