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A MFS-like plasma membrane transporter required for Leishmania virulence protects the parasites from iron toxicity.

ABSTRACT: Iron is essential for many cellular processes, but can generate highly toxic hydroxyl radicals in the presence of oxygen. Therefore, intracellular iron accumulation must be tightly regulated, by balancing uptake with storage or export. Iron uptake in Leishmania is mediated by the coordinated action of two plasma membrane proteins, the ferric iron reductase LFR1 and the ferrous iron transporter LIT1. However, how these parasites regulate their cytosolic iron concentration to prevent toxicity remains unknown. Here we characterize Leishmania Iron Regulator 1 (LIR1), an iron responsive protein with similarity to membrane transporters of the major facilitator superfamily (MFS) and plant nodulin-like proteins. LIR1 localizes on the plasma membrane of L. amazonensis promastigotes and intracellular amastigotes. After heterologous expression in Arabidopsis thaliana, LIR1 decreases the iron content of leaves and worsens the chlorotic phenotype of plants lacking the iron importer IRT1. Consistent with a role in iron efflux, LIR1 deficiency does not affect iron uptake by L. amazonensis but significantly increases the amount of iron retained intracellularly in the parasites. LIR1 null parasites are more sensitive to iron toxicity and have drastically impaired infectivity, phenotypes that are reversed by LIR1 complementation. We conclude that LIR1 functions as a plasma membrane iron exporter with a critical role in maintaining iron homeostasis and promoting infectivity in L. amazonensis.

SUBMITTER: Laranjeira-Silva MF

PROVIDER: S-EPMC6021107 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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A MFS-like plasma membrane transporter required for Leishmania virulence protects the parasites from iron toxicity.

Laranjeira-Silva Maria Fernanda MF Wang Wanpeng W Samuel Tamika K TK Maeda Fernando Y FY Michailowsky Vladimir V Hamza Iqbal I Liu Zhongchi Z Andrews Norma W NW

PLoS pathogens 20180615 6

Iron is essential for many cellular processes, but can generate highly toxic hydroxyl radicals in the presence of oxygen. Therefore, intracellular iron accumulation must be tightly regulated, by balancing uptake with storage or export. Iron uptake in Leishmania is mediated by the coordinated action of two plasma membrane proteins, the ferric iron reductase LFR1 and the ferrous iron transporter LIT1. However, how these parasites regulate their cytosolic iron concentration to prevent toxicity rema ...[more]

PMID: 29906288

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Project description:Mitochondria play essential biological functions including the synthesis and trafficking of porphyrins and iron/sulfur clusters (ISC), processes that in mammals involve the mitochondrial ATP-Binding Cassette (ABC) transporters ABCB6 and ABCB7, respectively. The mitochondrion of pathogenic protozoan parasites such as Leishmania is a promising goal for new therapeutic approaches. Leishmania infects human macrophages producing the neglected tropical disease known as leishmaniasis. Like most trypanosomatid parasites, Leishmania is auxotrophous for heme and must acquire porphyrins from the host.LmABCB3, a new Leishmania major protein with significant sequence similarity to human ABCB6/ABCB7, was identified and characterized using bioinformatic tools. Fluorescent microscopy was used to determine its cellular localization, and its level of expression was modulated by molecular genetic techniques. Intracellular in vitro assays were used to demonstrate its role in amastigotes replication, and an in vivo mouse model was used to analyze its role in virulence. Functional characterization of LmABCB3 was carried out in Leishmania promastigotes and Saccharomyces cerevisiae. Structural analysis of LmABCB3 was performed using molecular modeling software.LmABCB3 is an atypical ABC half-transporter that has a unique N-terminal extension not found in any other known ABC protein. This extension is required to target LmABCB3 to the mitochondrion and includes a potential metal-binding domain. We have shown that LmABCB3 interacts with porphyrins and is required for the mitochondrial synthesis of heme from a host precursor. We also present data supporting a role for LmABCB3 in the biogenesis of cytosolic ISC, essential cofactors for cell viability in all three kingdoms of life. LmABCB3 fully complemented the severe growth defect shown in yeast lacking ATM1, an orthologue of human ABCB7 involved in exporting from the mitochondria a gluthatione-containing compound required for the generation of cytosolic ISC. Indeed, docking analyzes performed with a LmABCB3 structural model using trypanothione, the main thiol in this parasite, as a ligand showed how both, LmABCB3 and yeast ATM1, contain a similar thiol-binding pocket. Additionally, we show solid evidence suggesting that LmABCB3 is an essential gene as dominant negative inhibition of LmABCB3 is lethal for the parasite. Moreover, the abrogation of only one allele of the gene did not impede promastigote growth in axenic culture but prevented the replication of intracellular amastigotes and the virulence of the parasites in a mouse model of cutaneous leishmaniasis.Altogether our results present the previously undescribed LmABCB3 as an unusual mitochondrial ABC transporter essential for Leishmania survival through its role in the generation of heme and cytosolic ISC. Hence, LmABCB3 could represent a novel target to combat leishmaniasis.

Dataset Information

A MFS-like plasma membrane transporter required for Leishmania virulence protects the parasites from iron toxicity.

Publications

A MFS-like plasma membrane transporter required for Leishmania virulence protects the parasites from iron toxicity.

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