Date Published: September 23, 2015
Publisher: Public Library of Science
Author(s): Andre Azevedo Reis Teixeira, Veronica de Cássia Sardinha de Vasconcelos, Walter Colli, Maria Júlia Manso Alves, Ricardo José Giordano, Barbara A Burleigh. http://doi.org/10.1371/journal.pntd.0004099
Abstract: BackgroundChagas’ disease, caused by the protozoan parasite Trypanosoma cruzi, is a disease that affects millions of people most of them living in South and Central Americas. There are few treatment options for individuals with Chagas’ disease making it important to understand the molecular details of parasite infection, so novel therapeutic alternatives may be developed for these patients. Here, we investigate the interaction between host cell intermediate filament proteins and the T. cruzi gp85 glycoprotein superfamily with hundreds of members that have long been implicated in parasite cell invasion.Methodology/Principal FindingsAn in silico analysis was utilized to identify peptide motifs shared by the gp85 T. cruzi proteins and, using phage display, these selected peptide motifs were screened for their ability to bind to cells. One peptide, named TS9, showed significant cell binding capacity and was selected for further studies. Affinity chromatography, phage display and invasion assays revealed that peptide TS9 binds to cytokeratins and vimentin, and prevents T. cruzi cell infection. Interestingly, peptide TS9 and a previously identified binding site for intermediate filament proteins are disposed in an antiparallel β-sheet fold, present in a conserved laminin-G-like domain shared by all members of the family. Moreover, peptide TS9 overlaps with an immunodominant T cell epitope.Conclusions/SignificanceTaken together, the present study reinforces previous results from our group implicating the gp85 superfamily of glycoproteins and the intermediate filament proteins cytokeratin and vimentin in the parasite infection process. It also suggests an important role in parasite biology for the conserved laminin-G-like domain, present in all members of this large family of cell surface proteins.
Partial Text: Chagas’ disease, also known as American trypanosomiasis, is a tropical and neglected disease caused by the parasite Trypanosoma cruzi. The disease affects 7 to 8 million people worldwide most of them living in South and Central American countries, accordingly to recent assessments from the World Health Organization, (http://www.who.int/mediacentre/factsheets/fs340/en/). However, migration has spread the disease to all countries in the Americas and several European and Western Pacific countries. In endemic areas, the parasite is transmitted to humans primarily by triatomine insect vectors (kissing bug) while in non-endemic countries, transmission is restricted by contact with contaminated blood or tissues, such as blood transfusions and organ transplants . Chagas’ disease can be a life-threatening and debilitating illness to those that develop cardiomyopathy or one of the digestive forms of the disease making it a significant burden for health care and society at large .
Proteins belonging to the group II of the gp85/TS family have long been implicated in adhesion to cells and extracellular matrix components but the structural details of such interactions are still largely unknown. One of the difficulties to unveil the structural details of such interactions is the large number of proteins contained in these multigene families; having hundreds of individual members, it is often challenging to associate an individual member to its ligand. Besides, the characterization of each member separately is not practical. This task is particularly challenging in the case of T. cruzi where genetic tools like RNAi cannot be used . Here we took a systematic approach to identify conserved peptide motifs shared by multiple members of the family and analyze them using bacteriophage and functional assays. This approach proved successful and led to the identification of the peptide TS9, a novel motif involved in parasite cell adhesion and invasion. Noteworthy is the fact that the identification of peptide TS9 further confirms previous results from our group and reinforces the knowledge that cytokeratins are an important ligands for T. cruzi adhesion and invasion [10,16,21]. It also highlights the importance in parasite biology of the LamG domain contained in all gp85/TS family members.