XI International Meeting on Paracoccidioidomycosis

XI International Meeting on Paracoccidioidomycosis

Resume:1-1

Poster (Painel)

1-1	REDUCTIVE UPTAKE AND IRON SOURCE PREFERENCE IN Paracoccidioides brasiliensis
Authors:	Elisa Flávia Luiz Cardoso Bailão (UFG - Universidade Federal de Goiás) ; Mirelle Garcia Silva (UFG - Universidade Federal de Goiás) ; Kelly Pacheco de Castro (UFG - Universidade Federal de Goiás) ; Alexandre Melo Bailão (UFG - Universidade Federal de Goiás) ; Célia Maria de Almeida Soares (UFG - Universidade Federal de Goiás)

Abstract

Although iron is required by a range of microbial pathogens, most environmental sources contain insoluble ferric iron, which can be reduced to ferrous iron by ferric reductases in the plasma membrane. The ferrous iron, then, can be either transported directly into the cell or be reoxidated to Fe+3 and be simultaneously internalized. Low-affinity systems of iron uptake are activated when iron is abundant, whereas high-affinity systems are important under iron-limiting conditions. On the other hand, excessive iron is toxic, since iron reacts with oxygen causing the formation of free radicals. So the iron homeostasis is an essential function that is generally tightly regulated in microorganisms. The goal of this study is the understanding of iron homeostasis in Paracoccidioides brasiliensis, a human pathogenic fungus. We have done a homology based searching in P. brasiliensis structural genome databank for possible genes involved in the homeostasis maintenance. After, it was investigated the expression of ferric reductases (fre3, fre7, frp1 and ggt1), ferroxidases (lac1, lac3 and lacIV), a low-affinity permease (zrt2), a high-affinity permease (zrt1), a vacuolar Fe2+ transporter (ccc1), an inner mitochondrial membrane carrier protein (mrs4), a mitochondrial matrix iron chaperone (yfh1), in the presence or absence of iron at different times by reverse transcription real-time PCR. Expression of recombinant proteins and immunocytochemistry had also been employed. The relative expression of iron metabolism related genes investigated suggests that P. brasiliensis has a refined mechanism to reduce ferric iron and to maintain the normal intracellular iron levels. Moreover, extracellular ferric reductase activity was identified by standardizing a qualitative solid-phase ferric reductase assay for this fungus. Furthermore P. brasiliensis can grow in the presence of hemoglobin as iron source. A cell surface protein, member of putative hemoglobin-receptor gene family, was induced in the presence of hemoglobin and had been characterized as a GPI anchored protein. The results indicated that iron is likely to be an important factor to growth, survival and virulence of this fungus, that presumably can utilizes iron sources within the host.

Keyword: ferric reductases, hemoglobin, iron homeostasis

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