A Potent Kalihinol Analogue Disrupts Apicoplast Function and Vesicular Trafficking in P. falciparum Malaria.

Here we report the discovery of MED6-189, a new analogue of the kalihinol family of isocyanoterpene (ICT) natural products. MED6-189 is effective against drug-sensitive and -resistant P. falciparum strains blocking both intraerythrocytic asexual replication and sexual differentiation. This compound was also effective against P. knowlesi and P. cynomolgi. In vivo efficacy studies using a humanized mouse model of malaria confirms strong efficacy of the compound in animals with no apparent hemolytic activity or apparent toxicity. Complementary chemical biology, molecular biology, genomics and cell biological analyses revealed that MED6-189 primarily targets the parasite apicoplast and acts by inhibiting lipid biogenesis and cellular trafficking. Genetic analyses in P. falciparum revealed that a mutation in PfSec13, which encodes a component of the parasite secretory machinery, reduced susceptibility to the drug. The high potency of MED6-189 in vitro and in vivo, its broad range of efficacy, excellent therapeutic profile, and unique mode of action make it an excellent addition to the antimalarial drug pipeline.

PfMORC protein regulates chromatin accessibility and transcriptional repression in the human malaria parasite, P. falciparum.

The environmental challenges the human malaria parasite, Plasmodium falciparum, faces during its progression into its various lifecycle stages warrant the use of effective and highly regulated access to chromatin for transcriptional regulation. Microrchidia (MORC) proteins have been implicated in DNA compaction and gene silencing across plant and animal kingdoms. Accumulating evidence has shed light into the role MORC protein plays as a transcriptional switch in apicomplexan parasites. In this study, using CRISPR/Cas9 genome editing tool along with complementary molecular and genomics approaches, we demonstrate that PfMORC not only modulates chromatin structure and heterochromatin formation throughout the parasite erythrocytic cycle, but is also essential to the parasite survival. Chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) experiments suggest that PfMORC binds to not only sub-telomeric regions and genes involved in antigenic variation but is also most likely a key modulator of stage transition. Protein knockdown experiments followed by chromatin conformation capture (Hi-C) studies indicate that downregulation of PfMORC induces the collapse of the parasite heterochromatin structure leading to its death. All together these findings confirm that PfMORC plays a crucial role in chromatin structure and gene regulation, validating this factor as a strong candidate for novel antimalarial strategies.

TLC of p-nitroanilines and their analogues with cyclodextrins in the mobile phase.

The addition of alpha-, beta-, gamma-, and hydroxypropyl-beta-cyclodextrins to aqueous mobile phases can be used to enhance the migration of p-nitroanilines and their analogues on thin-layer chromatography. Urea, which is used to solubilize the cyclodextrins in aqueous solutions, is also found to increase the migration of these compounds. The equilibrium binding constants for the solute-cyclodextrin complexes formed in the mobile phase are determined. The results obtained using either silica gel or polyamide plates are similar.

Thin-layer chromatography of laser dyes and dye analogs with cyclodextrins in the mobile phase.

The addition of beta-cyclodextrin and substituted hydroxyethyl and hydroxypropyl-beta-cyclodextrins to aqueous urea-containing mobile phases, can be used to enhance the migration of various laser dyes on thin layer chromatography. Selected laser dyes from the coumarin, rhodamine and bimane families were examined, as well as a number of dye analogs. Silica gel, polyamide and C18 reverse phase plates were utilized. Overall, the substituted hydroxypropyl-beta-cyclodextrins appeared to be the most effective for increasing dye migration.