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. 2012 Oct 8:5:224.
doi: 10.1186/1756-3305-5-224.

A Toll/IL-1R/resistance domain-containing thioredoxin regulates phagocytosis in Entamoeba histolytica

Ismael Mancilla-Herrera  1 , Alfonso Méndez-Tenorio, Isabel Wong-Baeza, Alexis P Jiménez-Uribe, Marcela Alcántara-Hernández, Ramon Ocadiz-Ruiz, Mario A Moreno-Eutimio, Lourdes A Arriaga-Pizano, Constantino López-Macías, Jorge González-y-Merchand, Armando Isibasi
Affiliations

A Toll/IL-1R/resistance domain-containing thioredoxin regulates phagocytosis in Entamoeba histolytica

Ismael Mancilla-Herrera et al. Parasit Vectors. .

Abstract

Background: Entamoeba histolytica is a protozoan parasite that infects humans and causes amebiasis affecting developing countries. Phagocytosis of epithelial cells, erythrocytes, leucocytes, and commensal microbiota bacteria is a major pathogenic mechanism used by this parasite. A Toll/IL-1R/Resistance (TIR) domain-containing protein is required in phagocytosis in the social ameba Dictyostelium discoideum, an ameba closely related to Entamoeba histolytica in phylogeny. In insects and vertebrates, TIR domain-containing proteins regulate phagocytic and cell activation. Therefore, we investigated whether E. histolytica expresses TIR domain-containing molecules that may be involved in the phagocytosis of erythrocytes and bacteria.

Methods: Using in silico analysis we explored in Entamoeba histolytica databases for TIR domain containing sequences. After silencing TIR domain containing sequences in trophozoites by siRNA we evaluated phagocytosis of erythrocytes and bacteria.

Results: We identified an E. histolytica thioredoxin containing a TIR-like domain. The secondary and tertiary structure of this sequence exhibited structural similarity to TIR domain family. Thioredoxin transcripts silenced in E. histolytica trophozoites decreased erythrocytes and E. coli phagocytosis.

Conclusion: TIR domain-containing thioredoxin of E. histolytica could be an important element in erythrocytes and bacteria phagocytosis.

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Figures

Figure 1
Figure 1
Sequence alignment of TIR domains from several species. Representative sequences are show from: Homo sapiens (IL-1R, TLR2, and MyD88_[Hs]), Drosophila melanogaster (Toll4_[Dm]), Arabidopsis thaliana (TAO1_[At]) as well as the sequences from Entamoeba invadens (EIN_134280_[Ei]) and Entamoeba histolytica (thioredoxin_[Eh]). Colors correspond to secondary structure derived from 3D structures for representative TIR domains, Psipred predictions for EIN_134280_[Ei] and the 3D modeled structure for Thioredoxin_[Eh]: helixes are colored in red and sheets in yellow. The three highly conserved regions previously described in TIR domains [14] are highlighted as boxes 1 to 3. I-Tasser secondary structure assignments are shown at the bottom (H= helix, S= sheet).
Figure 2
Figure 2
Comparison of structures of IL1R from Homo sapiens and Thioredoxin from E. histolytica . TIR domain of human interleukin-1 receptor (PDB: 1T3GA) is show in left model. Tertiary structure of TIR domain-containing thioredoxin was calculated by I-Tasser and show in right model. Structure superimposition is show in the center. (Calculated by Chimera).
Figure 3
Figure 3
Thioredoxin silencing in E. histolytica reduce the Erythrocytes and E. coli phagocytosis. Entamoeba histolytica trophozoites were preincubated in the presence or absence of 50, 100 or 250 μg of PATMK and thioredoxin siRNA during 15 h. a) representative RT-PCR bands of PAMTK and thioredoxin amplified products of silencing and non-silencing trophozoites. b) Densitometric analysis RT-PCR products normalized to PATMK/Actin or Thioredoxin/Actin density of non-silenced trophozoites. c) Erythrophagocytosis of siRNA PATMK and thioredoxin silenced trophozoites. d) GFP-labeled E. coli phagocytosis of siRNA PATMK or thioredoxin silenced trophozoites (MIF: Median Intensity Fluorescence). Results were analyzed using Repeated-measures one-way ANOVA and Bonferroni test. Significance was set at P < 0.05.
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