The Membrane Activity of the Amphibian Temporin B PeptideAnalog TB_KKG6K Sheds Light on the Mechanism That KillsCandida albicans
Temporin B (TB) is a 13-amino-acid-long, cationic peptide secreted by the granular glands of the European frog Rana temporaria. We recently showed that the modified TB peptide analog TB_KKG6K rapidly killed planktonic and sessile Candida albicans at low micromolar concentrations and was neither hemolytic nor cytotoxic to mammalian cells in vitro. The present study aimed to shed light into its mechanism of action, with a focus on its fungal cell membrane activity. We utilized different fluorescent dyes to prove that it rapidly induces membrane depolarization and permeabilization. Studies on model membrane systems revealed that the TB analog undergoes hydrophobic and electrostatic membrane interactions, showing a preference for anionic lipids, and identified phosphatidylinositol and cardiolipin as possible peptide targets.
Fluorescence microscopy using fluorescein isothiocyanate-labeled TB_KKG6K in the presence of the lipophilic dye FM4-64 indicated that the peptide compromises membrane integrity and rapidly enters C. albicans cells in an energy-independent manner.
Peptide-treated cells analyzed by cryo-based electron microscopy exhibited no signs of
cell lysis; however, subcellular structures had disintegrated, suggesting that intracellular
activity may form part of the killing mechanism of the peptide. Taken together, this
study proved that TB_KKG6K compromises C. albicans membrane function, which
explains the previously observed rapid, fungicidal mode of action and supports its great
potential as a future anti-Candida therapeutic
comments