title: The cysteine protease inhibitors EhICP1 and EhICP2 perform different tasks in the regulation of endogenous protease activity in trophozoites of Entamoeba histolytica.
abstract: Trophozoites of E. histolytica are equipped with two chagasin-like cysteine protease inhibitors, EhICP1 and EhICP2, also known as amoebiasin 1 and 2. Expression studies using E. invadens as model organism showed that corresponding mRNAs were detectable in both life stages of the parasite, cyst and trophozoite state. Unlike EhICP1 known to act in the cytosol, EhICP2 co-localized with cysteine protease EhCP-A1 in lysosome-like vesicles, as demonstrated by immunofluorescence microscopy. Silencing or overexpressing of the two inhibitors did not show any effect on morphology and viability of the trophozoites. Overexpression of the EhICPs, however, although dramatically dampening the proteolytic activity of cell extracts from the corresponding cell lines, did not influence expression rate or localization of the major amoebic cysteine proteases as well as phagocytosis and digestion of erythrocytes. Activity gels of cell extracts from strains overexpressing ehicp1 showed a drastically reduced activity of EhCP-A1 suggesting a high affinity of EhICP1 towards this protease. From these data, we propose that EhCP-A1 accidentally released into the cytosol is the main target of EhICP1, whereas EhICP2, beside its role in house-keeping processes, may control the proteolytic processing of other hydrolases or fulfils other tasks different from protease inhibition.
authors: Faculty of Biology, Department of Biochemistry, University of Osnabrueck, Barbarastr. 13, D-49069 Osnabrueck, Germany.
authors: Mirela
authors: M
authors: Šarić
authors: Henriette
authors: H
authors: Irmer
authors: Daniela
authors: D
authors: Eckert
authors: Ann-Katrein
authors: AK
authors: Bär
authors: Iris
authors: I
authors: Bruchhaus
authors: Henning
authors: H
authors: Scholze
mesh_terms: D000595:Amino Acid Sequence; D057056:Cysteine Proteases / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004748:Entamoeba histolytica / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D004749:Entamoebiasis / Q000469:parasitology*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008969:Molecular Sequence Data; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D053058:Trophozoites / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*
chemical_list: D015853:Cysteine Proteinase Inhibitors; D015800:Protozoan Proteins; D057056:Cysteine Proteases