Biology subjects

Inaoka, D. K.

Publications and source records attributed to Inaoka, D. K..

6 recordsLinked to original sources

bioRxiv2026

Structural insights and mechanistic inhibition of Plasmodium falciparum dihydroorotate dehydrogenase by newly identified chemotypes

Resistance to frontline antimalarial drugs continues to threaten malaria control, highlighting the need for new chemotypes. Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) catalyzes a key step in de novo pyrimidine biosynthesis and remains a validated antimalarial target. Although the PfDHODH inhibitor DSM265 advanced to clinical development, resistance-associated mutations highlight the need for structurally distinct inhibitors. Here, we report the discovery and structural characterization of PfDHODH inhibitors identified through target-based high-throughput screening of 432,592 compounds. Primary hits were evaluated by dose-response assays against asexual blood-stage parasites, mammalian mitochondrial toxicity assays, and HepG2 cytotoxicity profiling, yielding 348 hits. Seven representative compounds were prioritized based on efficacy against PfDHODH and orthologs from P. vivax and P. berghei, and their X-ray co-crystal structures revealed distinct binding modes within the active site. Ferulenol exhibited sub-micromolar inhibition of recombinant PfDHODH (rPfDHODH) and rPvDHODH, together with potent blood-stage activity, with its prenylated tail contributing additional hydrophobic interactions. Compound 2 showed the highest potency across the tested DHODH enzymes but reduced selectivity for PfDHODH, potentially due to its distinct binding orientation and furylmethyl substituent. Comparative structural analyses with DSM265 identified binding-site features that may guide the design of next-generation PfDHODH inhibitors with improved potency and selectivity.

microbiology↗

bioRxiv2025

Plasmodium falciparum diacylglycerol acyltransferase maintains phospholipid homeostasis to regulate sexual differentiation, ER stress, and cytoadhesion

Plasmodium falciparum is the causative agent of human malaria, a life-threating infectious disease that imposes a major global health burden. Lipid metabolism is indispensable for this parasites replication and survival, yet most of the molecular components and mechanisms involved remain poorly understood. In eukaryotes, lipid droplets (LDs) serve as dynamic organelles that store neutral lipids (NLs), buffer lipotoxic stress, and regulate signaling pathways, with their biogenesis controlled by diacylglycerol o-acyltransferases (DGATs). Although P. falciparum encodes a putative DGAT (PF3D7_0322300), its role in the parasite life cycle has not been elucidated. We generated conditional PfDGAT-knockout parasites to investigate the enzymes functional significance. PfDGAT deficiency led to parasite death, accompanied by reduced LD formation, elevated phospholipid levels, and induction of ER stress. Moreover, PfDGAT deletion altered protein trafficking, resulting in the decreased cytoadherence of parasite-infected erythrocytes to human brain microvascular endothelial cells, and suppressed parasite sexual differentiation. Thus, PfDGAT deletion affected multiple aspects of the parasites life cycle, highlighting its critical role in parasite survival and pathogenesis. Our findings provide new insights into parasite lipid homeostasis and highlight DGAT as a potential target of antimalarial intervention.

microbiology↗

bioRxiv2025

Efficient identification of antimalarials with novel mechanism of action via multi-sample transcriptomic profiling

Malaria poses a significant health burden to endemic countries, necessitating the development of new antimalarials with novel mechanisms of action to combat emerging drug resistance. However, target identification methods for antimalarial compounds selected through phenotypic screening are currently limited, which has been a major obstacle in the field of antimalarial drug discovery. Here, we aim to address this need using perturbation transcriptomics to efficiently select antimalarial compounds targeting new pathways or molecules. The method involves comparing the transcriptomic changes by drug perturbation in the asexual blood stage of the malaria parasite Plasmodium falciparum. Using this method, we identified several compounds that exhibited distinct transcriptomic profiling from a diverse set of antimalarials with known modes of action, indicating their potential to target different pathways. In addition, we successfully identified a novel histone deacetylase inhibitor using this approach and chemogenetically validated its target through in vitro evolution. These results highlight the effectiveness of this platform in accelerating antimalarial drug discovery.

microbiology↗

bioRxiv2024

Accelerating antimalarial drug discovery with a new high-throughput screen for fast-killing compounds

The urgent need for rapidly acting compounds in the development of antimalarial drugs underscores the significance of such compounds in overcoming resistance issues and improving patient adherence to antimalarial treatments. The present study introduces a high-throughput screening (HTS) approach using 1536-well plates, employing Plasmodium falciparum lactate dehydrogenase (PfLDH) combined with nitroreductase (NTR) and fluorescent probes to evaluate inhibition of the growth of the asexual blood stage of malaria parasites. This method was adapted to efficiently measure the parasite reduction ratio (PRR) in a 384-well plate format, streamlining the traditionally time-consuming screening process. By successfully screening numerous compounds, this approach identified fast-killing hits early in the screening process, addressing challenges associated with artemisinin-based combination therapies. The high-throughput PRR method is expected to be of value in continuously monitoring fast-killing properties during structure-activity relationship studies, expediting the identification and development of novel, rapidly acting antimalarial drugs within phenotypic drug discovery campaigns.

microbiology↗

bioRxiv2024

Glycolytic enzymes form membrane-less condensates in the malaria parasite Plasmodium falciparum by sensing glucose levels

Recent studies have shown that liquid-liquid phase separation (LLPS) in cells can regulate essential cellular events, including metabolic processes. Glycolytic bodies (G-bodies) are biomolecular condensates formed through the LLPS of glycolytic enzymes, and they accelerate glycolysis to overcome hypoxic stress in several organisms. Although the asexual blood stage (ABS) of the human malaria parasite Plasmodium falciparum highly depends on glycolysis for energy production, there have been no reports of the formation of such G-bodies throughout the parasites lifecycle. Using fluorescence tagging and live imaging, we found that G-body-like condensates containing phosphofructokinase 9 (PFK9) and phosphoglycerate kinase (PGK) were formed in the parasite cells after long-term culture under conditions of low glucose. These G-body-like structures appeared stable, but membrane staining and osmotic stress experiments suggested that the observed condensates were not associated with lipid membrane. Further microscopic observations and mathematical analyses of high signal-to-noise ratio images indicated that small condensates were formed transiently first, and these then gradually grew and stabilized in the cytosol. These results suggested that the formation of glycolytic enzyme condensates may be an important cellular response for adapting to blood sugar level oscillations in the host and maintaining the parasites multiplication in the ABS. Significance statementGlycolytic bodies (G-bodies), which are biomolecular condensates formed through the liquid-liquid phase separation of glycolytic enzymes, can accelerate glycolysis to produce energy and overcome hypoxic stress. The parasites that cause malaria depend on glycolysis for energy production, but there have been no reports that these parasites form G-bodies. We demonstrated that membrane-less G-body-like structures formed in media containing low levels of glucose. Small condensates appeared first and over time, the condensates became larger and more stable. The formation of glycolytic enzyme condensates may be important for the malaria parasite to adapt to fluctuating blood sugar levels in the host. These results further our understanding of the cellular mechanisms for the survival of malaria parasites.

cell biology↗

bioRxiv2020

5-amino levulinic acid inhibits SARS-CoV-2 infection in vitro

The current COVID-19 pandemic requires urgent development of effective therapeutics. 5-amino levulinic acid (5-ALA) is a naturally synthesized amino acid and has been used for multiple purposes including as an anticancer therapy and as a dietary supplement due to its high bioavailability. In this study, we demonstrated that 5-ALA treatment potently inhibited infection of SARS-CoV-2, a causative agent of COVID-19. The antiviral effects could be detected in both human and non-human cells, without significant cytotoxicity. Therefore, 5-ALA is a candidate as an oral antiviral drug for COVID-19.

microbiology↗