Targeting prolyl-tRNA synthetase via a series of ATP-mimetics to accelerate drug discovery against toxoplasmosis

Dual-mode recognition of tRNAPro isoacceptors by Toxoplasma gondii Prolyl-tRNA synthetase

Prolyl-tRNA synthetases (ProRSs) exhibit diverse domain architectures and motifs, evolving into prokaryotic (P-type) and eukaryotic/archaeal (E-type) variants. Both types exhibit high specificity for the recognition and aminoacylation of their cognate tRNAs. Interestingly, the parasitic eukaryote Toxoplasma gondii encodes a single E-type ProRS (TgProRS) but utilizes two distinct tRNAPro isoacceptors: a cytosolic E-type (with C72/C73) and an apicoplast P-type (with G72/A73). Our study demonstrates that TgProRS, despite being classified as an E-type enzyme, efficiently charges both tRNAPro isoacceptors and functionally compensates for yeast cytoplasmic and mitochondrial ProRS activities. Notably, while C72/C73 are dispensable for cytosolic tRNAPro charging, G72/A73 are crucial for apicoplast tRNAPro aminoacylation. Furthermore, Mutations in the motif 2 loop selectively affect E- or P-type tRNAPro recognition. While TgProRS exhibits similar susceptibility to azetidine (a proline mimic) when charging both tRNAPro types, cytosolic tRNAPro charging is five times more sensitive to inhibition by halofuginone (a Pro-A76 mimic) compared to apicoplast tRNAPro charging. These findings underscore TgProRS's dual functionality, showcasing its remarkable evolutionary adaptability and providing valuable insights for developing more selective therapeutic agents.

Structure-Based Virtual Screening of Potential Inhibitors Targeting the Prolyl-tRNA Synthetase (PRS) in Eimeria tenella: Insights from Molecular Docking, ADMET Studies, and Molecular Dynamics Simulations

Avian coccidiosis, caused by protozoan parasites of the genus Eimeria, poses a major threat to the poultry industry worldwide, leading to severe economic losses through reduced growth rates, poor feed efficiency, and increased mortality. Although the conventional management of this disease has relied on anticoccidial drugs, the overwhelming use of these agents has led to the rapid emergence and spread of drug-resistant Eimeria isolates, highlighting the urgent need for novel therapeutic approaches. This study employed computational approaches to identify novel inhibitors targeting Eimeria tenella prolyl-tRNA synthetase (EtPRS). Based on the virtual screening of a library of 3045 natural compounds, 42 high-confidence inhibitors were identified. Three compounds, including Chelidonine, Bicuculline, and Guggulsterone, demonstrated strong and selective binding to EtPRS through stable interactions within the active site. ADMET predictions revealed favorable safety profiles, while molecular dynamic simulations confirmed binding stability. Overall, this research established a solid framework for the development of effective anticoccidial agents targeting PRS, contributing to the advancement of therapeutic strategies for combating parasitic infections in the poultry industry.

ATP mimetics targeting prolyl-tRNA synthetases as a new avenue for antimalarial drug development

The prolyl-tRNA synthetase (PRS) is an essential enzyme for protein translation and a validated target against malaria parasite. We describe five ATP mimetics (L95, L96, L97, L35, and L36) against PRS, exhibiting enhanced thermal stabilities in co-operativity with L-proline. L35 displays the highest thermal stability akin to halofuginone, an established inhibitor of Plasmodium falciparum PRS. Four compounds exhibit nanomolar inhibitory potency against PRS. L35 exhibits the highest potency of ∼1.6 nM against asexual-blood-stage (ABS) and ∼100-fold (effective concentration [EC50]) selectivity for the parasite. The macromolecular structures of PfPRS with L95 and L97 in complex with L-pro reveal their binding modes and catalytic site malleability. Arg401 of PfPRS oscillates between two rotameric configurations when in complex with L95, whereas it is locked in one of the configurations due to the larger size of L97. Harnessing such specific and selective chemical features holds significant promise for designing potential inhibitors and expediting drug development efforts.

Evodiamine inhibits EPRS expression to regulate glutamate metabolism and proliferation of oral squamous cell carcinoma cells

The effects of evodiamine (EVO) on oral squamous cell carcinoma (OSCC) are not yet understood. Based on our earlier findings, we hypothesized that evodiamine may affect OSCC cell proliferation and glutamate metabolism by modulating the expression of EPRS (glutamyl-prolyl-tRNA synthetase 1). From GEPIA, we obtained EPRS expression data in patients with OSCC as well as survival prognosis data. An animal model using Cal27 cells in BALB/c nude mice was established. The expression of EPRS was assessed by immunofluorescence, Western blotting, and quantitative PCR. Glutamate measurements were performed to evaluate the impact of evodiamine on glutamate metabolism of Cal27 and SAS tumor cells. transient transfection techniques were used to knock down and modulate EPRS in these cells. EPRS is expressed at higher levels in OSCC than in normal tissues, and it predicts poor prognosis in patients. In a nude mouse xenograft model, evodiamine inhibited tumor growth and the expression of EPRS. Evodiamine impacted cell proliferation, glutamine metabolism, and EPRS expression on Cal27 and SAS cell lines. In EPRS knockdown cell lines, both cell proliferation and glutamine metabolism are suppressed. EPRS's overexpression partially restores evodiamine's inhibitory effects on cell proliferation and glutamine metabolism. This study provides crucial experimental evidence supporting the potential therapeutic application of evodiamine in treating OSCC. Evodiamine exhibits promising anti-tumor effects by targeting EPRS to regulate glutamate metabolism.