Objective: Actin, the main component of microfilament structure in eukaryotic cells, regulates signaling pathways by interacting with actin binding proteins. Our previous studies have shown that depolymerization of filamentous actin (F-actin) occurs following its interaction with fragment A of the toxin in endothelial cells infected with diphtheria toxin and mutant diphtheria toxin (CRM-197) . In this study, it was aimed to determine intracellular trafficking of diphtheria toxin by stabilization of F-actin in endothelial cells.

Material and Methods: Human umbilical vein endothelial cells were cultured and incubated with 0.1 μM jasplakinolide for 30 and 60 minutes respectively. For diphtheria toxin (0.75 nM) treatment, the incubation period with jasplakinolide was limited to 15 minutes. Intracellular stabilization of F-actin and diphtheria toxin traffic were visualized using immunofluorescence microscopy.

Results: Depending on the duration of the incubation period, it was determined that the stress fibers were expressed in the cell membrane of the endothelial cells treated with jasplakinolide. It was shown that diphtheria toxin trafficking was not inhibited in F-actin-stabilized endothelial cells and fragment A was directed to the perinuclear area.

Conclusion: Inhibition of G-actin / F-actin turnover in steady state by intracellular F-actin stabilization does not stop diphtheria toxin trafficking. This result supports studies showing the importance of filamentous actin in toxin trafficking.