Can a proteomics strategy be used to identify the anti-malarial activity of chloroquine?

Role of Quinone Reductase 2 in the Antimalarial Properties of Indolone-Type Derivatives

Indolone-N-oxides have antiplasmodial properties against Plasmodium falciparum at the erythrocytic stage, with IC₅₀ values in the nanomolar range. The mechanism of action of indolone derivatives involves the production of free radicals, which follows their bioreduction by an unknown mechanism. In this study, we hypothesized that human quinone reductase 2 (hQR2), known to act as a flavin redox switch upon binding to the broadly used antimalarial chloroquine, could be involved in the activity of the redox-active indolone derivatives. Therefore, we investigated the role of hQR2 in the reduction of indolone derivatives. We analyzed the interaction between hQR2 and several indolone-type derivatives by examining enzymatic kinetics, the substrate/protein complex structure with X-ray diffraction analysis, and the production of free radicals with electron paramagnetic resonance. The reduction of each compound in cells overexpressing hQR2 was compared to its reduction in naïve cells. This process could be inhibited by the specific hQR2 inhibitor, S29434. These results confirmed that the anti-malarial activity of indolone-type derivatives was linked to their ability to serve as hQR2 substrates and not as hQR2 inhibitors as reported for chloroquine, leading to the possibility that substrate of hQR2 could be considered as a new avenue for the design of new antimalarial compounds.

Proteomics Evidence for the Activity of the Putative Antibacterial Plant Alkaloid (-)-Roemerine: Mainstreaming Omics-Guided Drug Discovery

Discovery of new antibacterials with novel mechanisms is important to counteract the ingenious resistance mechanisms of bacteria. In this connection, omics-guided drug discovery offers a rigorous method in the quest of new antibacterials. (-)-Roemerine is a plant alkaloid that has been reported to possess putative antibacterial activity against Escherichia coli, Bacillus subtilis, and Salmonella typhimurium. The aim of the present study was to characterize the activity of (-)-roemerine in Escherichia coli TB1 using proteomics tools. With (-)-roemerine treatment, we found limited permeability through the outer membrane and repression of transport proteins involved in carbohydrate metabolism, resulting in poor carbon source availability. The shortfall of intracellular carbon sources in turn led to impaired cell growth. The reduction in the abundance of proteins related to translational machinery, amino acid biosynthesis, and metabolism was accompanied by a nutrient-limited state. The latter finding could suggest a metabolic shutdown in E. coli cells. High osmolarity was clearly not one of the reasons of bacterial death by (-)-roemerine. These observations collectively attest to the promise of plant omics and profiling of putative drug candidates using proteomics tools. Omics-guided drug discovery deserves greater attention in mainstream pharmacology so as to better understand the plants' medicinal potentials.

Excretory/secretory proteome of the adult stage of Echinostoma caproni

The excretory/secretory proteome of Echinostoma caproni (Trematoda: Echinostomatidae) adults collected from experimentally infected mice was investigated using a proteomic approach. We performed a shot-gun liquid chromatography/tandem mass spectrometry for the separation and identification of tryptic peptides from the excretory/secretory products of E. caproni adult worms. Database search was performed using MASCOT search engine (Matrix-Science) and ProteinPilot software v2.0 (Applied Biosystems). A total of 39 parasite proteins were accurately identified. Strikingly, metabolic enzymes, and particularly glycolytic enzymes, constituted the largest protein family in the excretory/secretory proteome of E. caproni adult worms. Moreover, representative proteins involved in parasite structure, response against stress, chaperones, calcium-binding, and signal transduction were also identified. This work extends our knowledge of host-parasite relationships in the E. caproni-rodent model that is extensively used to analyze the factors determining the intestinal helminth rejection. Consequently, information on many proteins may be useful to better understand the molecular basis that determines the survival of this parasite in the definitive host.