Selective targeting of Plasmodium falciparum Hsp90 disrupts the 26S proteasome.

The molecular chaperone heat shock protein 90 (Hsp90) has an essential but largely undefined role in maintaining proteostasis in Plasmodium falciparum, the most lethal malaria parasite. Herein, we identify BX-2819 and XL888 as potent P. falciparum (Pf)Hsp90 inhibitors.

and associate with host Arfs during infection.

Unlabelled: The apicomplexans and are intracellular parasites that reside within a host-derived compartment termed the parasitophorous vacuole (PV). During infection, the parasites must acquire critical host resources and transport them across their PV for development. However, the mechanism by which host resources are trafficked to and across the PV remains uncertain.

Characterization of 2,4-Dianilinopyrimidines Against Five Kinases PfARK1, PfARK3, PfNEK3, PfPK9, and PfPKB.

kinases are increasingly recognized as potential novel antiplasmodial targets for the treatment of malaria, but only a small subset of these kinases have had structure-activity relationship (SAR) campaigns reported. Herein we report the discovery of CZC-54252 () as an inhibitor of five kinases PfARK1, PfARK3, PfNEK3, PfPK9, and PfPKB. 39 analogues were evaluated against all five kinases to establish SAR at three regions of the kinase active site.

Exploring the Chain Release Mechanism from an Atypical Apicomplexan Polyketide Synthase.

Polyketide synthases (PKSs) are megaenzymes that form chemically diverse polyketides and are found within the genomes of nearly all classes of life. We recently discovered the type I PKS from the apicomplexan parasite , PKS2, which contains a unique putative chain release mechanism that includes ketosynthase (KS) and thioester reductase (TR) domains. Our bioinformatic analysis of the thioester reductase of PKS2, TR, suggests differences compared to other systems and hints at a possibly conserved release mechanism within the apicomplexan subclass Coccidia.

Synthesis and activity of β-carboline antimalarials targeting the Plasmodium falciparum heat shock 90 protein.

A collection of β-carbolines based on the natural product harmine, a compound known to target the heat shock 90 protein of Plasmodium falciparum, was synthesized and tested for antimalarial activity and potential toxicity. Several of these novel compounds display promising bioactivity, providing a new potential therapeutic with a mode of action that differs versus any currently available clinical treatment.

Labeling strategies to track protozoan parasite proteome dynamics.

Intracellular protozoan parasites are responsible for wide-spread infectious diseases. These unicellular pathogens have complex, multi-host life cycles, which present challenges for investigating their basic biology and for discovering vulnerabilities that could be exploited for disease control. Throughout development, parasite proteomes are dynamic and support stage-specific functions, but detection of these proteins is often technically challenging and complicated by the abundance of host proteins.

Examination of Secondary Metabolite Biosynthesis in Apicomplexa.

Natural product discovery has traditionally relied on the isolation of small molecules from producing species, but genome-sequencing technology and advances in molecular biology techniques have expanded efforts to a wider array of organisms. Protists represent an underexplored kingdom for specialized metabolite searches despite bioinformatic analysis that suggests they harbor distinct biologically active small molecules. Specifically, pathogenic apicomplexan parasites, responsible for billions of global infections, have been found to possess multiple biosynthetic gene clusters, which hints at their capacity to produce polyketide metabolites.

Characterization of Unexpected Self-Acylation Activity of Acyl Carrier Proteins in a Modular Type I Apicomplexan Polyketide Synthase.

Natural products play critical roles as antibiotics, anticancer therapeutics, and biofuels. Polyketides are a distinct natural product class of structurally diverse secondary metabolites that are synthesized by polyketide synthases (PKSs). The biosynthetic gene clusters that encode PKSs have been found across nearly all realms of life, but those from eukaryotic organisms are relatively understudied.

Discovery of potent Plasmodium falciparum protein kinase 6 (PfPK6) inhibitors with a type II inhibitor pharmacophore.

Malaria is a devastating disease that causes significant global morbidity and mortality. The rise of drug resistance against artemisinin-based combination therapy demonstrates the necessity to develop alternative antimalarials with novel mechanisms of action. We report the discovery of Ki8751 as an inhibitor of essential kinase PfPK6.

Identification of Novel 2,4,5-Trisubstituted Pyrimidines as Potent Dual Inhibitors of Plasmodial GSK3/PK6 with Activity against Blood Stage Parasites In Vitro.

Essential plasmodial kinases GSK3 and PK6 are considered novel drug targets to combat rising resistance to traditional antimalarial therapy. Herein, we report the discovery of as a dual GSK3/PK6 inhibitor active against blood stage 3D7 parasites. To establish structure-activity relationships for PK6 and GSK3, 52 analogues were synthesized and assessed for the inhibition of GSK3 and PK6, with potent inhibitors further assessed for activity against blood and liver stage parasites.

Cut it out! A CRISPR-Cas9 screen identifies host regulators of the Plasmodium liver stage.

In this issue of Cell Chemical Biology, Vijayan and colleagues identify host factors integral for Plasmodium liver-stage infection using a whole-genome CRISPR-Cas9 knockout screen. Their efforts reveal that liver-stage parasites redistribute host microtubules to the parasite membrane in a process dependent on the host Golgi.

Elucidating the path to Plasmodium prolyl-tRNA synthetase inhibitors that overcome halofuginone resistance.

The development of next-generation antimalarials that are efficacious against the human liver and asexual blood stages is recognized as one of the world's most pressing public health challenges. In recent years, aminoacyl-tRNA synthetases, including prolyl-tRNA synthetase, have emerged as attractive targets for malaria chemotherapy. We describe the development of a single-step biochemical assay for Plasmodium and human prolyl-tRNA synthetases that overcomes critical limitations of existing technologies and enables quantitative inhibitor profiling with high sensitivity and flexibility.

Random Forest Model Predictions Afford Dual-Stage Antimalarial Agents.

The need for novel antimalarials is apparent given the continuing disease burden worldwide, despite significant drug discovery advances from the bench to the bedside. In particular, small-molecule agents with potent efficacy against both the liver and blood stages of parasite infection are critical for clinical settings as they would simultaneously prevent and treat malaria with a reduced selection pressure for resistance. While experimental screens for such dual-stage inhibitors have been conducted, the time and cost of these efforts limit their scope.

A single amino acid residue controls acyltransferase activity in a polyketide synthase from .

Type I polyketide synthases (PKSs) are multidomain, multimodule enzymes capable of producing complex polyketide metabolites. These modules contain an acyltransferase (AT) domain, which selects acyl-CoA substrates to be incorporated into the metabolite scaffold. Herein, we reveal the sequences of three AT domains from a polyketide synthase (PKS2) from the apicomplexan parasite .

Erratum: A single amino acid residue controls acyltransferase activity in a polyketide synthase from .

[This corrects the article DOI: 10.1016/j.isci.

Plasmodium's fight for survival: escaping elimination while acquiring nutrients.

Plasmodium parasites extensively alter their host hepatocyte to evade host detection and support an unprecedented replication rate. Host cell manipulation includes association with the host early and late endomembrane systems, where Plasmodium accesses nutrients while suppressing cellular immune processes. Early endomembrane organelles provide an opportunity to sequester an abundance of lipids and proteins, but the association with late endomembrane organelles also risks autophagy-mediated elimination.

Characterization of the Tubovesicular Network in Liver Stage Hypnozoites and Schizonts.

is a genus of apicomplexan parasites which replicate in the liver before causing malaria. can also persist in the liver as dormant hypnozoites and cause clinical relapse upon activation, but the molecular mechanisms leading to activation have yet to be discovered. In this study, we use high-resolution microscopy to characterize temporal changes of the liver stage tubovesicular network (TVN), a parasitophorous vacuole membrane (PVM)-derived network within the host cytosol.

Chemoproteomics for Plasmodium Parasite Drug Target Discovery.

Emerging Plasmodium parasite drug resistance is threatening progress towards malaria control and elimination. While recent efforts in cell-based, high-throughput drug screening have produced first-in-class drugs with promising activities against different Plasmodium life cycle stages, most of these antimalarial agents have elusive mechanisms of action. Though challenging to address, target identification can provide valuable information to facilitate lead optimization and preclinical drug prioritization.

Activation of GPR37 in macrophages confers protection against infection-induced sepsis and pain-like behaviour in mice.

GPR37 was discovered more than two decades ago, but its biological functions remain poorly understood. Here we report a protective role of GPR37 in multiple models of infection and sepsis. Mice lacking Gpr37 exhibited increased death and/or hypothermia following challenge by lipopolysaccharide (LPS), Listeria bacteria, and the mouse malaria parasite Plasmodium berghei.

A Systematic Analysis of Mosquito-Microbiome Biosynthetic Gene Clusters Reveals Antimalarial Siderophores that Reduce Mosquito Reproduction Capacity.

Advances in infectious disease control strategies through genetic manipulation of insect microbiomes have heightened interest in microbially produced small molecules within mosquitoes. Herein, 33 mosquito-associated bacterial genomes were mined and over 700 putative biosynthetic gene clusters (BGCs) were identified, 135 of which belong to known classes of BGCs. After an in-depth analysis of the 135 BGCs, iron-binding siderophores were chosen for further investigation due to their high abundance and well-characterized bioactivities.

Plasmodium vivax Liver and Blood Stages Recruit the Druggable Host Membrane Channel Aquaporin-3.

Plasmodium vivax infects hepatocytes to form schizonts that cause blood infection, or dormant hypnozoites that can persist for months in the liver before leading to relapsing blood infections. The molecular processes that drive P. vivax schizont and hypnozoite survival remain largely unknown, but they likely involve a rich network of host-pathogen interactions, including those occurring at the host-parasite interface, the parasitophorous vacuole membrane (PVM).

chaperonin TRiC/CCT identified as a target of the antihistamine clemastine using parallel chemoproteomic strategy.

The antihistamine clemastine inhibits multiple stages of the parasite that causes malaria, but the molecular targets responsible for its parasite inhibition were unknown. Here, we applied parallel chemoproteomic platforms to discover the mechanism of action of clemastine and identify that clemastine binds to the TCP-1 ring complex or chaperonin containing TCP-1 (TRiC/CCT), an essential heterooligomeric complex required for de novo cytoskeletal protein folding. Clemastine destabilized all eight TRiC subunits based on thermal proteome profiling (TPP).

It's about Time: Insights into the Modes of Action of Antimalarials.

In this issue of Cell Chemical Biology, Murithi et al. (2020) integrate stage-specific phenotypic screening and metabolomics to uncover modes of action of antimalarials. This work highlights compounds with potent activity against all asexual blood stages, as well as compounds with unique stage specificity and metabolic profiles.

Tafenoquine: A Step toward Malaria Elimination.

There is a pressing need for compounds with broad-spectrum activity against malaria parasites at various life cycle stages to achieve malaria elimination. However, this goal cannot be accomplished without targeting the tenacious dormant liver-stage hypnozoite that causes multiple relapses after the first episode of illness. In the search for the magic bullet to radically cure malaria, tafenoquine outperformed other candidate drugs and was approved by the U.

Linking Genes to Molecules in Eukaryotic Sources: An Endeavor to Expand Our Biosynthetic Repertoire.

The discovery of natural products continues to interest chemists and biologists for their utility in medicine as well as facilitating our understanding of signaling, pathogenesis, and evolution. Despite an attenuation in the discovery rate of new molecules, the current genomics and transcriptomics revolution has illuminated the untapped biosynthetic potential of many diverse organisms. Today, natural product discovery can be driven by biosynthetic gene cluster (BGC) analysis, which is capable of predicting enzymes that catalyze novel reactions and organisms that synthesize new chemical structures.