Calcium-dependent mitochondrial extrusion in ciliated protozoa.

Here we demonstrate that ciliated protozoa can jettison mitochondria as intact organelles, releasing their contents to the extracellular space either in a soluble form, or in association with membrane vesicles at the cell periphery. The response is triggered by lateral clustering of GPI-anchored surface antigens, or by heat shock. In the first instance, extrusion is accompanied by elevated levels of intracellular calcium and is inhibited by Verapamil and BAPTA-AM arguing strongly for the involvement of calcium in triggering the response. Cells survive mitochondrial discharge raising the interesting possibility that extrusion is an early evolutionary adaptation to cell stress.