Abstract
Fluoroquinolones (FQs) are widely prescribed broad-spectrum antibiotics, with newer generations capable of crossing the blood brain barrier (BBB). Previous studies have reported the actin-destabilizing effects of FQs, suggesting their potential for drug repurposing. Actin-associated neuropathies are characterised by the formation of persistent, F-actin aggregates in neurons, which impair critical cellular functions. Therefore, identifying small molecules that can disrupt these actin filaments and aggregates can provide a promising therapeutic strategy. This research aims to map the direct interaction between FQs and F-actin to identify the structural basis for actin disruption. We demonstrated that FQs irreversibly disrupt F-actin filaments in a concentration-dependent manner using scattering-based assay. Electron microscopy and gel filtration confirmed generation-dependent disruption activity. In particular, Gen3 and Gen4 FQs reduced actin aggregates in more than 60% yeast cells. FQ treatment altered the thermal stability of F-actin at both 1:30 and 1:50 molar ratios with minor secondary structural changes. To explore the molecular insights of FQs interaction with F-actin, saturation transfer difference-NMR combined with complementary molecular dynamics simulations revealed the importance of the fluorinated quinolone core, which is common to all FQs. These studies highlight the involvement of an amino group at R5, and bulky piperazine, azabicyclo rings at the R7 position in driving F-actin disruption. We would like to propose that rational modifications at R5 and R7 positions can enhance both actin-disrupting potency and BBB permeability, thereby providing a basis for developing FQs derived therapeutics against actin-related neurodegenerative disorders.
Data availability
The data used to support the findings of this study are available from the corresponding author upon request.
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Acknowledgements
We thank Dr. Debasis Das from the Department of Biological Sciences, TIFR, Mumbai, for granting us access to the ultracentrifugation facility. We also acknowledge the support of Dr. Sri Rama Koti Ainavarapu from the Department of Chemical Sciences, TIFR, Mumbai, for providing access to the Bio-Rad NGC chromatography system. We are grateful to Ms. Siddhi A. Redkar for her assistance with TEM image acquisition at the Electron Microscopy Facility, ACTREC. We also thank Mr. Sudipta Goswami at Bruker, Bangalore, for his technical assistance with the STD NMR experiments.
Funding
This work was funded and supported by the Department of Atomic Energy. The MD simulations were performed using high-performance computing time allocated by the UK High-End Computing Consortium for Biomolecular Simulation (HECBioSim; http://hecbiosim.ac.uk), supported by the EPSRC under grant EP/X035603/1. R.G. is supported by UGC-CSIR NET JRF PhD fellowship no. 786/ (CSIR-UGC NET DEC. 2018). T.R.S. is supported by IIT Guwahati through her fellowship.
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R.G. conceptualised the study, designed and conducted all in vitro experiments, performed data analysis and visualisation, and contributed to the writing, reviewing, and editing of the manuscript. H.N. performed all in silico experiments, carried out data analysis and visualisation, and contributed to the writing and reviewing of the manuscript. T.R.S. performed the yeast cell assays and analysed the corresponding data. S.N. supervised the yeast cell assays and contributed to data analysis. P.P.G. provided guidance for the in silico experiments. S.C.D. supervised the in silico experiments and computational analyses, managed computational resources, and contributed to the writing, reviewing, and editing of the manuscript. R.M.M. helped with data interpretation and discussion. A.K. conceptualised the study, provided overall supervision, managed the project and resources, conducted data analysis, and contributed to the writing, reviewing, and editing of the manuscript. All authors reviewed and approved the final manuscript drafts.
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Gupta, R.J., Nair, H., Sarhadi, T.R. et al. R5 and R7 positions on fluoroquinolone scaffolds drive F-actin filament disruption. Sci Rep (2026). https://doi.org/10.1038/s41598-026-36089-x
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DOI: https://doi.org/10.1038/s41598-026-36089-x
