Internalization of tenecin 3 by a fungal cellular process is essential forits fungicidal effect on Candida albicans

Tenecin 3 is a glycine-rich, antifungal protein of 78 residues isolated fro m the insect Tenebrio molitor larva. As an initial step towards understandi ng the antifungal mechanism of tenecin 3, we examined how this protein inte racts with the pathogenic fungus Candida albicans to exert its antifungal a ction. Tenecin 3 did not induce the release of a fluorescent dye trapped in the artificial membrane vesicles and it did not perturb the membrane poten tial of C. albicans by the initial interaction. Fluorescence confocal micro scopy and flow cytometric analysis revealed that tenecin 3 is rapidly inter nalized into the cytoplasmic space in energy-dependent and temperature-depe ndent manners. This internalization is also dependent on the ionic environm ent and cellular metabolic states. These results suggest that the internali zation of tenecin 3 into the cytoplasm of C. albicans is mediated by a fung al cellular process. The internalized tenecin 3 is dispersed in the cytopla sm, and the loss of cell viability occurs after this internalization.