Background A homologue of the ecdysone receptor has previously been identified in human filarial parasites. As the ecdysone receptor is not found in vertebrates, it and the regulatory pathways it controls represent attractive potential chemotherapeutic targets.
Methodology/ Principal Findings Administration of 20-hydroxyecdysone to gerbils infected with B. malayi infective larvae disrupted their development to adult stage parasites. A stable mammalian cell line was created incorporating the B. malayi ecdysone receptor ligand-binding domain, its heterodimer partner and a secreted luciferase reporter in HEK293 cells. This was employed to screen a series of ecdysone agonist, identifying seven agonists active at sub-micromolar concentrations. A B. malayi ecdysone receptor ligand-binding domain was developed and used to study the ligand-receptor interactions of these agonists. An excellent correlation between the virtual screening results and the screening assay was observed. Based on both of these approaches, steroidal ecdysone agonists and the diacylhydrazine family of compounds were identified as a fruitful source of potential receptor agonists. In further confirmation of the modeling and screening results, Ponasterone A and Muristerone A, two compounds predicted to be strong ecdysone agonists stimulated expulsion of microfilaria and immature stages from adult parasites.
Conclusions The studies validate the potential of the B. malayi ecdysone receptor as a drug target and provide a means to rapidly evaluate compounds for development of a new class of drugs against the human filarial parasites.
Digital Object Identifier (DOI)
The research was supported by a grant from the National Institute of Allergy and Infectious Diseases, USA to TRU (project R21AI103302).
Mhashilkar, Amruta S.; Vankayala, Sai L.; Liu, Canhui; Kearns, Fiona; Mehrotra, Priyanka; Tzertzinis, George; Palli, Subba R.; Woodcock, H. Lee; and Unnasch, Thomas R., "Identification of Ecdysone Hormone Receptor Agonists as a Therapeutic Approach for Treating Filarial Infections" (2016). Entomology Faculty Publications. 120.
S1 Appendix. Homology modeling and virtual screening studies.
journal.pntd.0004772.s002.TIF (1469 kB)
S1 Fig. Strategy for production of a stable mammalian cell line for screening for agonists and antagonists of the BmaEcR.
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S2 Fig. Ramachandaran plot compiled of the phi-psi backbone dihedrals from the model after molecular dynamics simulations.
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S3 Fig. Superposition of Prime homology model (yellow) over I-Tasser homology model (blue).
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S4 Fig. MD simulation results.
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S5 Fig. Predicted structures of compounds docked in the active site of the BmaEcR LBD.
journal.pntd.0004772.s007.DOCX (80 kB)
S1 Table. Summary of RMSFs calculated from the MD simulation of for all residues within 3 Å of the 20-hydroxyecdysone binding site.
journal.pntd.0004772.s008.DOCX (80 kB)
S2 Table. Summary of XP energy decomposition analyses.
journal.pntd.0004772.s009.DOCX (129 kB)
S3 Table. Compounds identified by the in-silico virtual screening and their docking scores.
journal.pntd.0004772.s010.DOCX (35 kB)
S4 Table. Molting of L3 stage larvae when treated with 20-hydroxyecdysone.
journal.pntd.0004772.s011.DOCX (35 kB)
S5 Table. Comparison of the transient transfection assay when conducted with NIH3T3 and HEK293 cells.