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Functional Characterization of an Interferon Gamma Receptor-Like Protein on Entamoeba histolytica.

ABSTRACT: Entamoeba histolytica is an anaerobic parasitic protozoan and the causative agent of amoebiasis. E. histolytica expresses proteins that are structurally homologous to human proteins and uses them as virulence factors. We have previously shown that E. histolytica binds exogenous interferon gamma (IFN-?) on its surface, and in this study, we explored whether exogenous IFN-? could modulate parasite virulence. We identified an IFN-? receptor-like protein on the surface of E. histolytica trophozoites by using anti-IFN-? receptor 1 (IFN-?R1) antibody and performing immunofluorescence, Western blot, protein sequencing, and in silico analyses. Coupling of human IFN-? to the IFN-? receptor-like protein on live E. histolytica trophozoites significantly upregulated the expression of E. histolytica cysteine protease A1 (EhCP-A1), EhCP-A2, EhCP-A4, EhCP-A5, amebapore A (APA), cyclooxygenase 1 (Cox-1), Gal-lectin (Hgl), and peroxiredoxin (Prx) in a time-dependent fashion. IFN-? signaling via the IFN-? receptor-like protein enhanced E. histolytica's erythrophagocytosis of human red blood cells, which was abrogated by the STAT1 inhibitor fludarabine. Exogenous IFN-? enhanced chemotaxis of E. histolytica, its killing of Caco-2 colonic and Hep G2 liver cells, and amebic liver abscess formation in hamsters. These results demonstrate that E. histolytica expresses a surface IFN-? receptor-like protein that is functional and may play a role in disease pathogenesis and/or immune evasion.

SUBMITTER: Pulido-Ortega J

PROVIDER: S-EPMC6803330 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Functional Characterization of an Interferon Gamma Receptor-Like Protein on Entamoeba histolytica.

Pulido-Ortega Julieta J Talamás-Rohana Patricia P Muñoz-Ortega Martín Humberto MH Aldaba-Muruato Liseth Rubí LR Martínez-Hernández Sandra Luz SL Campos-Esparza María Del Rosario MDR Cervantes-García Daniel D Leon-Coria Aralia A Moreau France F Chadee Kris K Ventura-Juárez Javier J

Infection and immunity 20191018 11

Entamoeba histolytica is an anaerobic parasitic protozoan and the causative agent of amoebiasis. E. histolytica expresses proteins that are structurally homologous to human proteins and uses them as virulence factors. We have previously shown that E. histolytica binds exogenous interferon gamma (IFN-γ) on its surface, and in this study, we explored whether exogenous IFN-γ could modulate parasite virulence. We identified an IFN-γ receptor-like protein on the surface of E. ...[more]

PMID: 31427448

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Project description:BACKGROUND: The polyamines putrescine, spermidine, and spermine are organic cations that are required for cell growth and differentiation. Ornithine decarboxylase (ODC), the first and rate-limiting enzyme in the polyamine biosynthetic pathway, is a highly regulated enzyme. METHODOLOGY AND RESULTS: To use this enzyme as a potential drug target, the gene encoding putative ornithine decarboxylase (ODC)-like sequence was cloned from Entamoeba histolytica, a protozoan parasite causing amoebiasis. DNA sequence analysis revealed an open reading frame (ORF) of approximately 1,242 bp encoding a putative protein of 413 amino acids with a calculated molecular mass of 46 kDa and a predicted isoelectric point of 5.61. The E. histolytica putative ODC-like sequence has 33% sequence identity with human ODC and 36% identity with the Datura stramonium ODC. The ORF is a single-copy gene located on a 1.9-Mb chromosome. The recombinant putative ODC protein (48 kDa) from E. histolytica was heterologously expressed in Escherichia coli. Antiserum against recombinant putative ODC protein detected a band of anticipated size approximately 46 kDa in E. histolytica whole-cell lysate. Difluoromethylornithine (DFMO), an enzyme-activated irreversible inhibitor of ODC, had no effect on the recombinant putative ODC from E. histolytica. Comparative modeling of the three-dimensional structure of E. histolytica putative ODC shows that the putative binding site for DFMO is disrupted by the substitution of three amino acids-aspartate-332, aspartate-361, and tyrosine-323-by histidine-296, phenylalanine-305, and asparagine-334, through which this inhibitor interacts with the protein. Amino acid changes in the pocket of the E. histolytica enzyme resulted in low substrate specificity for ornithine. It is possible that the enzyme has evolved a novel substrate specificity. CONCLUSION: To our knowledge this is the first report on the molecular characterization of putative ODC-like sequence from E. histolytica. Computer modeling revealed that three of the critical residues required for binding of DFMO to the ODC enzyme are substituted in E. histolytica, resulting in the likely loss of interactions between the enzyme and DFMO.

Dataset Information

Functional Characterization of an Interferon Gamma Receptor-Like Protein on Entamoeba histolytica.

Publications

Functional Characterization of an Interferon Gamma Receptor-Like Protein on Entamoeba histolytica.

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