title: A membrane-bound eIF2 alpha kinase located in endosomes is regulated by heme and controls differentiation and ROS levels in Trypanosoma cruzi.
abstract: Translation initiation has been described as a key step for the control of growth and differentiation of several protozoan parasites in response to environmental changes. This occurs by the activation of protein kinases that phosphorylate the alpha subunit of the translation initiation factor 2 (eIF2α), which decreases translation, and in higher eukaryotes favors the expression of stress remedial response genes. However, very little is known about the signals that activate eIF2α kinases in protozoan parasites. Here, we characterized an eIF2α kinase of Trypanosoma cruzi (TcK2), the agent of Chagas' disease, as a transmembrane protein located in organelles that accumulate nutrients in proliferating parasite forms. We found that heme binds specifically to the catalytic domain of the kinase, inhibiting its activity. In the absence of heme, TcK2 is activated, arresting cell growth and inducing differentiation of proliferative into infective and non-proliferative forms. Parasites lacking TcK2 lose this differentiation capacity and heme is not stored in reserve organelles, remaining in the cytosol. TcK2 null cells display growth deficiencies, accumulating hydrogen peroxide that drives the generation of reactive oxygen species. The augmented level of hydrogen peroxide occurs as a consequence of increased superoxide dismutase activity and decreased peroxide activity. These phenotypes could be reverted by the re-expression of the wild type but not of a TcK2 dead mutant. These findings indicate that heme is a key factor for the growth control and differentiation through regulation of an unusual type of eIF2α kinase in T. cruzi.
authors: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil.
authors: Leonardo
authors: L
authors: da Silva Augusto
authors: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil.
authors: Nilmar Silvio
authors: NS
authors: Moretti
authors: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil.
authors: Thiago Cesar Prata
authors: TC
authors: Ramos
authors: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil.
authors: Teresa Cristina Leandro
authors: TC
authors: de Jesus
authors: Department of Pathology, New York University School of Medicine, New York, New York, United States of America.
authors: Min
authors: M
authors: Zhang
authors: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil.
authors: Beatriz A
authors: BA
authors: Castilho
authors: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, São Paulo, Brazil.
authors: Sergio
authors: S
authors: Schenkman
mesh_terms: D011992:Endosomes / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006418:Heme / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D017382:Reactive Oxygen Species / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000201:enzymology*; D019892:eIF-2 Kinase / Q000378:metabolism*
chemical_list: D017382:Reactive Oxygen Species; D006418:Heme; D019892:eIF-2 Kinase