Heat shock protein 90 inhibitors repurposed against Entamoeba histolytica

Abstract

Hsp90 is an essential chaperone responsible for trafficking a vast array of client proteins, which are substrates that Hsp90 regulates in eukaryotic cells under stress conditions. The ATP-binding N-terminal domain of Hsp90 (also known as a GHKL type ATPase domain) can serve as a specific drug target, because sufficient structural diversity in the ATP-binding pocket of Hsp90 allows for ortholog selectivity of Hsp90 inhibitors. The primary objective of this study is to identify inhibitors specific for the ATP-binding domain of Entamoeba histolytica Hsp90 (EhHsp90). An additional aim, using a combination of site-directed mutagenesis and a protein in vitro assay, is to show that the antiparasitic activity of Hsp90 inhibitors is dependent on specific residues within the ATP-binding domain. Here, we tested the activity of 43 inhibitors of Hsp90 that we previously identified using a high-throughput screen. Of the 43 compounds tested, 19 competed for binding of the EhHsp90 ATP-binding domain. Five out of the 19 EhHsp90 protein hits demonstrated activity against E. histolytica in vitro culture: rifabutin, rutilantin, cetylpyridinium chloride, pararosaniline pamoate and gentian violet. These five top E. histolytica Hsp90 inhibitors showed 30–100% inhibition of E. histolytica in culture in the micromolar range. These data suggest that E. histolytica-specific Hsp90 inhibitors are possible to identify and provide important lead compounds for the development of novel antiamebic drugs.

Heat Shock Protein 90 (Hsp90) as a Molecular Target for the Development of Novel Drugs Against the Dermatophyte Trichophyton rubrum

“…Thus, functional inhibitors of the Hsp90 that act on its ATPase-coupled conformation ( Siligardi et al, 2002 ; Lotz et al, 2003 ) disassemble the molecular complex of Hsp90 with co-chaperones and target proteins, thereby abrogating drug resistance and increasing the efficacy of traditional antifungal drugs ( Veri and Cowen, 2014 ). Although Hsp90 is conserved among eukaryotes, it presents some conformational differences in fungi, especially in regions such as the ATP binding and the MDs that could be selectively targeted by the chemical inhibitors ( Wider et al, 2009 ; Shahinas et al, 2015 ). Alternatively, it is possible to interfere with the Hsp90 targets or functional regulators, thus expanding the possibility to find clearer discrepancies between the pathogen and the host ( Veri and Cowen, 2014 ).…”

Drug Screening for Discovery of Broad-spectrum Agents for Soil-transmitted Nematodes

“…The four drugs selected were econazole nitrate, sulconazole nitrate, pararosaniline hydrochloride, and cetylpyridinium chloride. In prior repurposing screens, the first two drugs were found to have potent inhibitory activities against a cytochrome P450 (CYP-450) in a parasitic flatworm 46 whereas the latter two were found to be effective against an amoeboid parasite by targeting its Heat Shock Protein 90 (HSP-90) 47 . Both of these are believed to play critical roles in both parasite viability and the process of parasitism 48–50 .…”

“…HSP-90 is an evolutionary conserved chaperon protein essential in all eukaryotes, that is responsible for maintaining organisms in homoeostasis and may act as a guard for client proteins against host insults 73 . Pararosaniline and cetylpyridinium were previously reported to have inhibitory activities against parasite HSP-90s and to interrupt the development and growth of protozoan parasites, including Entamoeba histolytica 47 and Plasmodium falciparum 74 . Pararosaniline was also years ago subjected to a field study for the anthelmintic activity against schistosomiasis 75–77 .…”

Heat Shock Protein 90 Inhibitor Effects on Pancreatic Cancer Cell Cultures

“…Furthermore, rifabutin is best known as an antimycobacterial antibiotic used to treat tuberculosis. Although it interferes with Hsp90, it is also known to inhibit bacterial nucleic acid biosynthesis 31,32 and, because of its structural complexity, could have other molecular targets as well.…”