Screening for small molecule modulators of Hsp70 chaperone activity using protein aggregation suppression assays: inhibition of the plasmodial chaperone PfHsp70-1

Abstract

Plasmodium falciparum heat shock protein 70 (PfHsp70-1) is thought to play an essential role in parasite survival and virulence in the human host, making it a potential antimalarial drug target. A malate dehydrogenase based aggregation suppression assay was adapted for the screening of small molecule modulators of Hsp70. A number of small molecules of natural (marine prenylated alkaloids and terrestrial plant naphthoquinones) and related synthetic origin were screened for their effects on the protein aggregation suppression activity of purified recombinant PfHsp70-1. Five compounds (malonganenone A-C, lapachol and bromo-β-lapachona) were found to inhibit the chaperone activity of PfHsp70-1 in a concentration dependent manner, with lapachol preferentially inhibiting PfHsp70-1 compared to another control Hsp70. Using growth inhibition assays on P. falciparum infected erythrocytes, all of the compounds, except for malonganenone B, were found to inhibit parasite growth with IC(50) values in the low micromolar range. Overall, this study has identified two novel classes of small molecule inhibitors of PfHsp70-1, one representing a new class of antiplasmodial compounds (malonganenones). In addition to demonstrating the validity of PfHsp70-1 as a possible drug target, the compounds reported in this study will be potentially useful as molecular probes for fundamental studies on Hsp70 chaperone function.

Investigating the Chaperone Properties of a Novel Heat Shock Protein, Hsp70.c, fromTrypanosoma brucei

“…Demonstration of the holdase-function, by suppressing protein aggregation, is used to display chaperone activity [48, 49]. MDH aggregation suppression assays are often performed in the absence of ATP [50, 51]. The addition of ATP decreases the affinity of an Hsp70 protein for MDH, resulting in its release and subsequent re-aggregation [52].…”

Hsp40 Co-chaperones as Drug Targets: Towards the Development of Specific Inhibitors

“…For these reasons, targeting members of the PfHsp40 family and the interaction between them and PfHsp70s seem applicable [124]. However, while a few classes of compounds able to modulate PfHsp70-1 and PfHsp70-x chaperone activities and affect parasite growth in vitro have been identified [176][177][178], there are no known inhibitors of PfHsp40s. Nevertheless, in a study in which two small molecule modulators of Hsp70s belonging to the pyrimidinone class (MAL3-39 and DMT2264) (Fig.…”

Heat Shock Proteins in Mycobacterium tuberculosis: Involvement in Survival and Virulence of the Pathogen

“…Hsf1 is thought to play a fundamental role in thermal homeostasis, adjusting the levels of essential chaperones to changes in growth temperature (Brown et al, 2010). In Plasmodium falciparum heat shock protein 70 is thought to play an essential role in parasite survival and virulence inside the host; Hsp70 is also being tried as a target for designing potential anti-malarial drugs (Cockburn et al, 2010). Histoplasma capsulatum is the causative agent of histoplasmosis in humans.…”