Autophagy is involved in starvation response and cell death in Blastocystis

Previous studies have demonstrated that colony forms of Blastocystis undergo cell death with numerous membrane-bound vesicles containing organelles located within the central vacuole, resembling morphological features of autophagy. In this study, we investigated whether Blastocystis underwent autophagy upon amino acid starvation and rapamycin treatment. Concurrently, we provide new insight into a possible function of the central vacuole. The use of the autophagy marker monodansylcadaverine, and the autophagy inhibitors 3-methyladenine and wortmannin, showed the existence of autophagy in amino-acid-starved and rapamycin-treated Blastocystis. Confocal microscopy and transmission electron microscopy studies also showed morphological changes that were suggestive of autophagy. The unusually large size of the autophagic compartments within the parasite central vacuole was found to be unique in Blastocystis. In addition, autophagy was found to be triggered when cells were exposed to the cytotoxic antibody mAb 1D5, and autophagy was intensified in the presence of the caspase inhibitor zVAD.fmk. Taken together, our results suggest that the core machinery for autophagy is conserved in Blastocystis, and that it plays an important role in the starvation response and cell death of the parasite.