Identification of functional FKB protein in Echinococcus granulosus: Its involvement in the protoscolicidal action of rapamycin derivates and in calcium homeostasis.

CUMINO A. C; LAMENZA P.; DENEGRI G. M.

INTERNATIONAL JOURNAL FOR PARASITOLOGY

Elsevier

Año: 2010 vol. 40 p. 651 - 661

0020-7519

FK506-binding proteins are cellular targets for polyketide macrolactones as rapamycin and its derivates, and they display a peptidylprolyl rotamase function that is believed to catalyze protein folding. These proteins are well-validated antiproliferative drug targets in certain pathogenic microorganisms, and their functions have been characterized in parasitic protozoa. However, much less is known in helminthes, and trials with rapalogs on cestoda have not yet been reported. Due to a growing need for new treatment options for human cystic echinococcosis, the in vitro efficacy of rapalogs in Echinococcus granulosus was investigated. We determined the effect of ramapycin, FK506, and everolimus against this cestode, demonstrating their protoscolicidal ability. Also, we observed synergic scolicidal actions during the combined therapy with rapalogs plus cyclosporine A, proposing dual administration of drugs to improve pharmacological effect in vivo. We have identified an Eg-fkb1 gene that encodes Eg-FKBP, an archetypal protein of the FKBP family, which includes all residues implicated in the binding of pharmacological ligands, in the enzymatic activity and in interactions with possible target proteins. Levels of Eg-fkb1 mRNA are overexpressed by acid but not rapalog treatment. We also described the presence of receptor-operated calcium channels in the larval stage, suggesting that exogenous ligands, may dissociate the interaction of Eg-FKBP with these intracellular channels, enhancing the activity of the Ca2+ release and interfering with their normal regulatory functions. As rapamycin sensitivity is the major criterion used to detect target of rapamycin kinase, we identified and analyzed in silico critical residues of putative homologs in Echinococcus genome. These preliminary results will let us continue subsequent studies that could reveal the precise intracellular functions of Eg-FKBP and may improve the outline for further identification of downstream target proteins, a promising target for chemotherapy of cystic echinococcosis.