title: Tryparedoxin peroxidases protect African trypanosomes from iron-induced damages of distinct cellular membranes
creator: Schaffroth, Corinna
description: In African trypanosomes, detoxification of lipid hydroperoxides is achieved by three virtually identical non-selenium glutathione peroxidase (Px)-type enzymes which obtain their reducing equivalents from the unique trypanothione/tryparedoxin system. Previous knockout studies in bloodstream Trypanosoma brucei revealed that the two cytosolic Px I and II are essential in contrast to the mitochondrial Px III. Parasites lacking Px I and II are fully viable in the presence of Trolox, but show severe lipid peroxidation and lysis when the vitamin E analog is removed from the medium. Here, I showed that the underlying mechanism is an iron-induced damage of the lysosome. Live cell imaging and immunofluorescence analysis of px I-II knockout cells displayed the progressive loss of different lysosomal signals upon withdrawal of Trolox. In addition, staining of the lysosomal membrane protein p67 was lost prior to the MitoTracker Red signal in accordance with lysosomal disintegration preceding damage of the mitochondrion. Lysis of the px I-II knockout cells was accelerated by supplementing the medium with iron and transferrin whereas it was slowed down in the presence of apo-transferrin and the iron chelator deferoxamine. These data demonstrated that the lethal phenotype was linked to the high-efficiency endocytic iron acquisition of bloodstream trypanosomes. In contrast, generation and phenotypic analyses of procyclic cells lacking either the cytosolic, the mitochondrial or all three enzymes revealed that in the insect form, the cytosolic or the mitochondrial peroxidase is sufficient for cell viability and proliferation whereas the knockout of the whole px locus resulted in cells that require the presence of Trolox. The phenotype was also linked to the iron metabolism of the parasite. Deferoxamine in the medium protected the cells from lysis but starch-coupled deferoxamine − residing in the endosomal/lysosomal compartments − displayed almost no protection. Immunofluorescence microscopy with MitoTracker and antibodies against the glycosomal aldolase and the lysosomal p67 revealed that mitochondrial damage precedes that of the other organelles. Indeed, in procyclic parasites, the mitochondrion seems to be the primary site of intracellular oxidative injury. The distinct mechanisms for the acquisition and metabolism of iron can explain the different phenotypes observed upon deletion of the Px-type enzymes in the infective and insect stage of T. brucei.
date: 2022
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/32188/1/Doktorarbeit%2010032015.pdf
identifier: DOI:10.11588/heidok.00032188
identifier: urn:nbn:de:bsz:16-heidok-321884
identifier:   Schaffroth, Corinna  (2022) Tryparedoxin peroxidases protect African trypanosomes from iron-induced damages of distinct cellular membranes.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/32188/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng