A new ATP-binding cassette protein is involved in intracellular haem trafficking in Leishmania.
The characterization of LABCG5, a new intracellular ATP-binding cassette protein in Leishmania donovani, is described. Unlike other ABCG half-transporters, LABCG5 is not involved in either drug resistance or phospholipid efflux. However, we provide evidence suggesting that this protein is involved in intracellular haem trafficking. Thus, downregulation of LABCG5 function produced upon overexpression of an inactive version of the protein caused a dramatic growth arrest unless a haemin supplement was added or the mutated gene was eliminated. Supplementation with haemoglobin, an upstream metabolite normally sufficient to meet parasite haem requirements, was unable to rescue the growth defect phenotype. Haemoglobin endocytosis was not hampered in dominant-negative parasites and neither was haem uptake, a process that we show here to be dependent on a specific transporter. In contrast, LABCG5 function was required for the correct intracellular trafficking of haemoglobin-bound porphyrins to the mitochondria, not affecting the routing of free haem. Finally, LABCG5 binds haem through hydrophobic and electrostatic interactions. Altogether, these data suggest that LABCG5 is involved in the salvage of the haem released after the breakdown of internalized haemoglobin. As Leishmania is auxotrophic for haem, the pharmacological targeting of this route could represent a novel approach to control fatal visceral leishmaniasis.
Instituto de Parasitología y Biomedicina 'López-Neyra', CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento s/n, 18100 Armilla, Granada, Spain.
Jenny
J
Campos-Salinas
María
M
Cabello-Donayre
Raquel
R
García-Hernández
Ignacio
I
Pérez-Victoria
Santiago
S
Castanys
Francisco
F
Gamarro
José M
JM
Pérez-Victoria
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002460:Cell Line; D006418:Heme / Q000378:metabolism*; D006801:Humans; D007893:Leishmania donovani / Q000235:genetics / Q000378:metabolism*; D007898:Leishmaniasis, Visceral / Q000378:metabolism / Q000469:parasitology*; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D015800:Protozoan Proteins; D006418:Heme