Characterization of manganese transport mediated by the iron transporter LIR1 in Leishmania

Abstract

Leishmaniasis is a group of infectious diseases caused by protozoa of the genus Leishmania, which occur frequently in vulnerable populations and with difficult access to health services. These microorganisms have a digenetic life cycle and during the amastigote phase are obligate intracellular parasites that reside in the parasitophorous vacuoles (phagolysosomes) of macrophages. In this environment they face diverse stress situations, among them the restricted availability of iron, an important cofactor of essential Leishmania enzymes. One of these enzymes, the iron dependent superoxide dismutase (FeSOD) provides protection from free radicals produced during host immune response. Thus, it is essential to understand the mechanisms of iron absorption, storage and regulation through membrane transporters. Among already identified iron transporters, LIR1 (Leishmania Iron Regulator 1) was characterized as a MFS-like transporter (Major Facilitator Superfamily), sharing similarity with nodulin-like proteins, which are involved in the regulation of intracellular iron concentration in plants. It has been shown that LIR1 functions as an iron exporter, playing an important role in iron homeostasis while preventing toxicity, because high concentrations of transition metals as iron can lead to generation of reactive oxidative species (ROS). Furthermore, some results obtained during the characterization of LIR1 indicate that this transporter also participates in the regulation of intracellular concentration of other transition metals, such as manganese, which is the cofactor of arginase. Arginase is a metalloenzyme that converts L-arginine into urea and ornithine, a precursor of polyamines essential for parasite replication. In addition to its replication role, arginase also plays a significant role in the modulation of arginine availability to the inducible nitric oxide synthase (iNOS) pathway, responsible for the synthesis of nitric oxide, the main effector molecule generated by macrophages against invading microorganisms. Our hypothesis is that LIR1 participates in the regulation of intracellular levels of manganese, modulating the expression and activity of arginase and, consequently, parasite growth and infectivity. Therefore, the aim of this project is to evaluate the effect of manganese supplementation in the replication of LIR1 knockout parasites and determine the modulation of expression and enzymatic activity of arginase in LIR1 knockout parasites. The demonstration of LIR1's role in the regulation of manganese intracellular levels may expand the importance of this transporter in Leishmania, strengthening its potential as a chemotherapeutic target.