Eukaryotic Ribosomal Expansion Segments as Antimicrobial Targets

Area of Science:

• Molecular Biology
• Biochemistry
• Drug Discovery

Background:

• Eukaryotic ribosomes possess unique rRNA expansion segments (ESs) absent in prokaryotes, offering potential for targeted therapies.
• Expansion segment 7 (ES7) is a large, variable region in eukaryotic ribosomes, with species-specific structures and functions.
• ES7 of the pathogenic fungus Candida albicans (ES7_CA) is proposed as a potential drug target due to its unique characteristics.

Purpose of the Study:

• To investigate the potential of ES7_CA as a therapeutic target against Candida albicans.
• To develop and validate a method for screening drug candidates against ES7_CA.
• To evaluate the efficacy and safety of identified drug candidates.

Main Methods:

• Reversible folding of isolated ES7_CA was demonstrated.
• A fluorescence displacement assay using F-neo was developed to measure binding affinities to ES7_CA and human ES7 (ES7_HS).
• A library of peptidic aminosugar conjugates (PAs) was screened for ES7_CA affinity, and minimum inhibitory concentrations (MICs) were determined for top candidates.

Main Results:

• ES7_CA folds reversibly to a native-like state.
• F-neo exhibits high affinity for ES7_CA (K_d = 2.5 × 10^-9 M) but low affinity for ES7_HS (K_d > 7 μM).
• Selected PAs with high ES7_CA affinity demonstrated low MIC values against C. albicans and showed no cytotoxicity in HEK293T cells.

Conclusions:

• ES7_CA is a viable and specific drug target for antifungal development.
• High-affinity PAs targeting ES7_CA are effective against C. albicans and safe for human cells.
• Ribosomal expansion segments represent a promising class of targets for novel chemotherapeutics against eukaryotic pathogens.