The fungal peptide toxin candidalysin induces distinct membrane repair mechanisms compared to bacterial pore-forming toxins.

The common fungal pathogen, Candida albicans, relies on the pore-forming toxin candidalysin to damage host cells. Cells resist other pore-forming toxins by Ca2+ dependent microvesicle shedding and annexins (cholesterol-dependent cytolysins, CDCs), or annexins and patch repair (aerolysin). However, it is unclear which Ca2+ dependent repair mechanism(s) resists candidalysin. Here, we determined the involvement of different Ca2+ dependent repair mechanisms to candidalysin and compared responses to CDCs and aerolysin using flow cytometry and high-resolution microscopy. We report that candidalysin triggered Ca2+-dependent repair, but patch repair and ceramide failed to provide significant protection. MEK-dependent repair and annexins A1, A2 and A6 contributed partially to repairing damage caused by candidalysin. However, annexin translocation after candidalysin challenge was delayed compared to CDCs or aerolysin challenge. Surprisingly, extracellular Cl- improved cell survival after candidalysin challenge, but not after challenge with a CDC or aerolysin. Finally, we found that candidalysin is removed via extracellular vesicle shedding. These findings reveal that Ca2+ dependent microvesicle shedding protects cells from candidalysin and can be engaged by multiple molecular mechanisms during membrane repair.