Calcium-dependent mitochondrial extrusion in ciliated protozoa

Abstract

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.

Mitochondrial quality control in the myocardium: Cooperation between protein degradation and mitophagy

“…More recently, this phenomenon has also been described in ciliated protozoan [79]. Mitochondria are expelled in response to heat shock or by clustering of immobilization antigens and elevated intracellular calcium levels.…”

DNA abandonment and the mechanisms of uniparental inheritance of mitochondria and chloroplasts

“…For example, small colorless proplastids in the basal meristem develop into large green chloroplasts in the maize leaf, after which most ptDNA is degraded (Oldenburg and Bendich 2004a) c Resynthesis accompanying orgDNA degradation (turnover) is required during aerobic growth of unicellular eukaryotes (for example, Euglena). Degradation without resynthesis (abandonment) was found in light-grown leaves (where cells no longer divide) for ptDNA of four plants (Bendich 2010b) and mtDNA of maize (Oldenburg et al 2013) d Bendich (2010b) e Biparental or uniparental (for one or the other parent), depending on the species or strain DNA may be extruded from the cell, thus losing their nutritive potential along with the defective orgDNA (Sears 1980;Nagata 2010;Bisharyan and Clark 2011). 5.…”

Mitochondrial DNA: A disposable genome?

“…For example, in response to stimulation, eosinophils abandon their mtDNA by catapulting it into extracellular milieu, while remaining viable [51, 52]. In response to a heat shock and upon antibody-induced clustering of GPI-anchored antigens, ciliated protozoa jettison mitochondria out of the cells without losing viability [53]. In transgenic mice, doxycycline-induced expression of the mutant UNG1 resulted in hippocampal mtDNA depletion [54], which was accompanied by relatively mild behavioral changes such as increased locomotor activity, impaired cognitive abilities, and lack of anxietylike responses [55].…”