In silico identification of modulators of J domain protein-Hsp70 interactions in Plasmodium falciparum: a drug repurposing strategy against malaria

Abstract

Plasmodium falciparum is a unicellular, intracellular protozoan parasite, and the causative agent of malaria in humans, a deadly vector borne infectious disease. A key phase of malaria pathology, is the invasion of human erythrocytes, resulting in drastic remodeling by exported parasite proteins, including molecular chaperones and co-chaperones. The survival of the parasite within the human host is mediated by P. falciparum heat shock protein 70s (PfHsp70s) and J domain proteins (PfJDPs), functioning as chaperones-co-chaperones partnerships. Two complexes have been shown to be important for survival and pathology of the malaria parasite: PfHsp70-x-PFE0055c (exported); and PfHsp70-2-PfSec63 (endoplasmic reticulum). Virtual screening was conducted on the drug repurposing library, the Pandemic Response Box, to identify small-molecules that could specifically disrupt these chaperone complexes. Five top ranked compounds possessing preferential binding affinity for the malarial chaperone system compared to the human system, were identified; three top PfHsp70-PfJDP binders, MBX 1641, zoliflodacin and itraconazole; and two top J domain binders, ezetimibe and a benzo-diazepinone. These compounds were validated by repeat molecular dockings and molecular dynamics simulation, resulting in all the compounds, except for MBX 1461, being confirmed to bind preferentially to the malarial chaperone system. A detailed contact analysis of the PfHsp70-PfJDP binders identified two different types of modulators, those that potentially inhibit complex formation (MBX 1461), and those that potentially stabilize the complex (zoliflodacin and itraconazole). These data suggested that zoliflodacin and itraconazole are potential novel modulators specific to the malarial system. A detailed contact analysis of the J domain binders (ezetimibe and the benzo-diazepinone), revealed that they bound with not only greater affinity but also a better pose to the malarial J domain compared to that of the human system. These data suggested that ezetimibe and the benzo-diazepinone are potential specific inhibitors of the malarial chaperone system. Both itraconazole and ezetimibe are FDA-approved drugs, possess anti-malarial activity and have recently been repurposed for the treatment of cancer. This is the first time that such drug-like compounds have been identified as potential modulators of PfHsp70-PfJDP complexes, and they represent novel candidates for validation and development into anti-malarial drugs.

Plasmodium falciparum heat shock proteins as antimalarial drug targets: An update

“… 36 , 53 , 60 , 61 , 62 , 63 Furthermore, molecular docking studies have compared PfHSP70–PfHSP40 complexes to their human HSP70–HSP40 equivalents, and used these complexes to screen drug repurposing small molecule libraries to identify compounds with preferential binding to the malarial over the human system. 64 As expected, the J domain–NBD interfaces of PfHSP70-x–PFE0055c and human HSP70 (HSPA1A)-DNAJA1 both involved multiple topologically equivalent hydrogen bond interactions between highly conserved positively charged J domain helix II residues and NBD negatively charged residues ( Figure 2 ). 64 However, the interfaces were not identical, reflecting differences in the nature and number of contacts, with the malarial J domain–NBD interface containing a greater number of hydrogen bonds and an electrostatic energy of interaction that suggested a higher binding affinity.…”

“… 64 As expected, the J domain–NBD interfaces of PfHSP70-x–PFE0055c and human HSP70 (HSPA1A)-DNAJA1 both involved multiple topologically equivalent hydrogen bond interactions between highly conserved positively charged J domain helix II residues and NBD negatively charged residues ( Figure 2 ). 64 However, the interfaces were not identical, reflecting differences in the nature and number of contacts, with the malarial J domain–NBD interface containing a greater number of hydrogen bonds and an electrostatic energy of interaction that suggested a higher binding affinity. 64 Virtual screening studies identified five drug-like compounds that were potential preferential modulators of the malarial system: three binding at the interface of the PfHSP70–PfHSP40 complex (MBX 1641, PfHSP70-x–PFE0055c; and zoliflodacin and itraconazole, PfHSP70-2-PfSec63); and two binding to the J domain of the PfHSP40s (ezetimibe and a benzodiazepinone, PFE0055c J domain).…”

“… 64 However, the interfaces were not identical, reflecting differences in the nature and number of contacts, with the malarial J domain–NBD interface containing a greater number of hydrogen bonds and an electrostatic energy of interaction that suggested a higher binding affinity. 64 Virtual screening studies identified five drug-like compounds that were potential preferential modulators of the malarial system: three binding at the interface of the PfHSP70–PfHSP40 complex (MBX 1641, PfHSP70-x–PFE0055c; and zoliflodacin and itraconazole, PfHSP70-2-PfSec63); and two binding to the J domain of the PfHSP40s (ezetimibe and a benzodiazepinone, PFE0055c J domain). Interestingly, itraconazole and ezetimibe have both been approved by the Food and Drug Administration (FDA, USA), and shown to inhibit the growth of the malaria parasite.…”

“…Interestingly, itraconazole and ezetimibe have both been approved by the Food and Drug Administration (FDA, USA), and shown to inhibit the growth of the malaria parasite. 64 However, further experimental biophysical, biochemical, and medicinal chemistry efforts on these candidate compounds are required to validate their potential as specific modulators of the PfHSP70–PfHSP40 system, as well as their potential for development into antimalarial drugs.

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“… 69 As already alluded to, virtual screening studies identified two drug-like compounds that were potential preferential modulators of PfHSP70-2-PfSec63 over human GRP78-Sec63 (zoliflodacin and itraconazole). 64 Building on these recent findings, further experimental studies are required to validate and develop these novel compounds into derivatives with proven specificity for the malarial chaperones and potential candidate antimalarial drugs.…”