Sesamin targets ClpP which attenuates virulence of S. aureus and protects mice from fatal pneumonia induced by MRSA.

Aims: The aim of this study was to identify sesamin as a Casein hydrolase P (ClpP) inhibitor and to determine whether it could attenuate the virulence of methicillin-resistant Staphylococcus aureus (MRSA).

Methods and results: Through fluorescence resonance energy transfer (FRET) screening, a natural compound sesamin demonstrated a significant inhibitory effect on ClpP enzyme activity with an IC50 of 20.62 μg/mL. Sesamin suppressed the expression of virulence factors of MRSA such as α-hemolysin (Hla) and Panton-Valentine leucocidin (PVL) by protein immunoblotting. Thermal shift assay (TSA) and cellular thermal shift assay (CETSA) showed that sesamin could bind to ClpP and enhance the thermal stability of ClpP. Furthermore, the binding affinity between sesamin and ClpP was determined by surface plasmon resonance (SPR) with a KD value of 7.18 × 10-6 M. Molecular docking, dynamics simulations and point mutation analysis confirmed the stability of the sesamin-ClpP complex with a -10.184 kcal/mol total binding energy and identified PHE-174 in ClpP as a key binding site. In mice pneumonia model, sesamin combined vancomycin treatment markedly reduced the pathogenicity of MRSA-infected mice, offering protection against fatal lung infections.

Conclusions: Overall, these findings validate sesamin as a promising compound that targets ClpP, reducing virulence factor expression, that holds potential as a hit compound against MRSA infections.