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BioMed Research International
Volume 2015, Article ID 416712, 8 pages
Research Article

Iron-Binding Protein Degradation by Cysteine Proteases of Naegleria fowleri

1Department of Infectomics and Molecular Pathogenesis, Center for Research and Advanced Studies of the National Polytechnic Institute, Avenida IPN 2508, 07360 Mexico City, Mexico
2Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute, Avenida IPN 2508, 07360 Mexico City, Mexico
3Faculty of Professional Studies, Autonomous University of Mexico, Campus Cuautitlán, Km 2.5 Carretera Cuautitlán-Teoloyucan, 54714 Cuautitlán Izcalli, Mexico

Received 22 September 2014; Revised 17 December 2014; Accepted 19 December 2014

Academic Editor: Mehdi Chenik

Copyright © 2015 Moisés Martínez-Castillo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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.