title: Human hololactoferrin: endocytosis and use as an iron source by the parasite Entamoeba histolytica.
abstract: Entamoeba histolytica is an enteric protozoan that exclusively infects human beings. This parasite requires iron for its metabolic functions. Lactoferrin is a mammalian glycoprotein that chelates extracellular iron on mucosal surfaces, including the surface of the large intestine, where E. histolytica initiates infection. This work examined the interaction in vitro of E. histolytica trophozoites with human hololactoferrin (iron-saturated lactoferrin). A minimum concentration of 50 microM Fe from hololactoferrin supported growth of the amoeba. Amoebic binding sites for hololactoferrin were different from those for human apolactoferrin, holotransferrin and haemoglobin. One amoebic hololactoferrrin-binding polypeptide of 90 kDa was found, which was not observed after treatment of trophozoites with trypsin. Hololactoferrin-binding-protein levels increased in amoebas starved of iron, or grown in hololactoferrin. Internalization of hololactoferrin was inhibited by filipin. Endocytosed hololactoferrin colocalized with an anti-chick embryo caveolin mAb in amoebic vesicles, and lactoferrin was further detected in acidic vesicles; amoebic caveolin of 22 kDa was detected by Western blotting using this antibody. Cysteine proteases from amoebic extracts were able to cleave hololactoferrin. Together, these data indicate that E. histolytica trophozoites bind to hololactoferrin through specific membrane lactoferrin-binding proteins. This ferric protein might be internalized via caveolae-like microdomains, then used as an iron source, and degraded.
authors.affiliation: Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México, D F 07000, Mexico.
authors.forename: Nidia
authors.initials: N
authors.lastname: León-Sicairos
authors.affiliation: Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México, D F 07000, Mexico.
authors.forename: Magda
authors.initials: M
authors.lastname: Reyes-López
authors.affiliation: Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México, D F 07000, Mexico.
authors.forename: Adrián
authors.initials: A
authors.lastname: Canizalez-Román
authors.affiliation: Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México, D F 07000, Mexico.
authors.forename: Rosa María
authors.initials: RM
authors.lastname: Bermúdez-Cruz
authors.affiliation: Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México, D F 07000, Mexico.
authors.forename: Jesús
authors.initials: J
authors.lastname: Serrano-Luna
authors.affiliation: Departamento de Patología Experimental, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México, D F 07000, Mexico.
authors.forename: Rossana
authors.initials: R
authors.lastname: Arroyo
authors.affiliation: Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. 14-740, México, D F 07000, Mexico.
authors.forename: Mireya
authors.initials: M
authors.lastname: de la Garza
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000913:Antibodies, Protozoan / Q000276:immunology*; D004705:Endocytosis / Q000502:physiology*; D004748:Entamoeba histolytica / Q000254:growth & development / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins; D007781:Lactoferrin / Q000378:metabolism*; D033863:Transferrin-Binding Proteins
chemical_list: D000911:Antibodies, Monoclonal; D000913:Antibodies, Protozoan; D033862:Iron-Binding Proteins; D033863:Transferrin-Binding Proteins; C492629:hololactoferrin, human; D007501:Iron; D007781:Lactoferrin