From binding to breakdown: biophysical and molecular insights into fluoroquinolone induced F-actin perturbation

Neurodegenerative disorders involving actin dysregulation demand safer yet potent actin-disrupting compounds. Previous studies have reported the actin-destabilizing effects of fluoroquinolones (FQs), suggesting their potential for repurposing. FQs are widely prescribed broad-spectrum antibiotics known for their efficacy against bacterial infections. The newer generation FQs are also known to effectively cross the Blood Brain Barrier (BBB). In this study, we demonstrate that FQs irreversibly disrupts F-actin filaments in a concentration-dependent manner using scattering based assay. Electron microscopy and gel filtration confirms generation-dependent disruption activity. In particular, Gen3 and Gen4 FQs reduces actin aggregates in more than 60% yeast cells. FQ treatment alters the thermal stability of F-actin at 1:30 and 1:50 molar ratios with minor secondary structural changes. While exploring the molecular insights of FQs interaction with F-actin, STD NMR combined with MD simulations revealed the importance of the fluorinated quinolone core, which is common to all FQs. These studies also highlight the involvement of R5 amino, bulky piperazine and azabicyclo rings at the R7 position in F-actin’s intermonomer interface binding, ultimately leading to the disruption of F-actin. We propose modifying the identified positions on the quinolone core to enhance the potency of F-actin disruption. For targeting actin mis-aggregation related. neuro degenerative diseases (NDs), these positions can be modified with the functional groups that might increase the lipophilicity of the molecule to cross the BBB.