title: Iron-Binding Protein Degradation by Cysteine Proteases of Naegleria fowleri.
abstract: Naegleria fowleri causes acute and fulminant primary amoebic meningoencephalitis. This microorganism invades its host by penetrating the olfactory mucosa and then traveling up the mesaxonal spaces and crossing the cribriform plate; finally, the trophozoites invade the olfactory bulbs. During its invasion, the protozoan obtains nutrients such as proteins, lipids, carbohydrates, and cationic ions (e.g., iron, calcium, and sodium) from the host. However, the mechanism by which these ions are obtained, particularly iron, is poorly understood. In the present study, we evaluated the ability of N. fowleri to degrade iron-binding proteins, including hololactoferrin, transferrin, ferritin, and hemoglobin. Zymography assays were performed for each substrate under physiological conditions (pH 7 at 37°C) employing conditioned medium (CM) and total crude extracts (TCEs) of N. fowleri. Different degradation patterns with CM were observed for hololactoferrin, transferrin, and hemoglobin; however, CM did not cause ferritin degradation. In contrast, the TCEs degraded only hololactoferrin and transferrin. Inhibition assays revealed that cysteine proteases were involved in this process. Based on these results, we suggest that CM and TCEs of N. fowleri degrade iron-binding proteins by employing cysteine proteases, which enables the parasite to obtain iron to survive while invading the central nervous system.
authors.affiliation: Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies of the National Polytechnic Institute, Avenida IPN 2508, 07360 Mexico City, Mexico.
authors.forename: Moisés
authors.identifier: 0000-0001-9569-0064
authors.initials: M
authors.lastname: Martínez-Castillo
authors.affiliation: Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, Avenida IPN 2508, 07360 Mexico City, Mexico ; Faculty of Professional Studies, Autonomous University of Mexico, Campus Cuautitlán, Km 2.5 Carretera Cuautitlán-Teoloyucan, 54714 Cuautitlán Izcalli, Mexico.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Ramírez-Rico
authors.affiliation: Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, Avenida IPN 2508, 07360 Mexico City, Mexico.
authors.forename: Jesús
authors.initials: J
authors.lastname: Serrano-Luna
authors.affiliation: Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies of the National Polytechnic Institute, Avenida IPN 2508, 07360 Mexico City, Mexico.
authors.forename: Mineko
authors.initials: M
authors.lastname: Shibayama
mesh_terms: D000818:Animals; D020808:Central Nervous System Protozoal Infections / Q000378:metabolism* / Q000469:parasitology / Q000473:pathology; D057056:Cysteine Proteases / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins / Q000378:metabolism; D007781:Lactoferrin / Q000378:metabolism; D016848:Naegleria fowleri / Q000201:enzymology / Q000472:pathogenicity; D009830:Olfactory Bulb / Q000378:metabolism / Q000473:pathology; D059748:Proteolysis; D014168:Transferrin / Q000378:metabolism; D053058:Trophozoites / Q000378:metabolism
chemical_list: D033862:Iron-Binding Proteins; D014168:Transferrin; C492629:hololactoferrin, human; D007501:Iron; D057056:Cysteine Proteases; D007781:Lactoferrin