Cell Death in Protists without Mitochondria

Abstract

Some protozoans, such as Trichomonad species, do not possess mitochondria. Most of the time, they harbor another type of membrane-bounded organelle, called hydrogenosome from its capacity to produce H(2). This is the case for the human parasite Trichomonas vaginalis. Some other parasites, such as the protist Giardia lamblia, do not harbor any of these organelles. From this observation arises naturally a naive question: How do cells die when the mitochondrion, the cornerstone of apoptotic process, is absent? Data strongly suggest that the mitochondrion and the hydrogenosome arose from a common ancestral endosymbiont. But hydrogenosomes do not appear to directly substitute for mitochondria in apoptotic functions. Thus, it appears judicious to examine more closely the genome of unicellular cells, which do not harbor mitochondria, and search for new molecules that could participate in the apoptotic process in these microorganisms.

Glucosylceramide synthesis inhibition affects cell cycle progression, membrane trafficking, and stage differentiation in Giardia lamblia

“…Lastly, the presence of an active GCS and the high responsiveness to ceramide in this divergent parasite support the hypothesis that GlcCer synthesis and bioactive sphingolipids have conare scarce. Morphological features of PCD following proapoptotic drugs, including chromatin condensation, apoptotic bodies, and cytoplasmic vacuolation, have been reported; however, our understanding of PCD in G. lamblia is limited as the parasite does not harbor bona fi de mitochondria, key components in the apoptotic pathways, and typical PCD-mediating proteins, such as caspases, have not been identifi ed in the parasite genome so far ( 54 ). Ceramide is an early mediator of cell cycle arrest and apoptosis, acting upstream of caspase-dependent and independent signaling pathways (reviewed in Ref.…”

Trichomoniasis – are we giving the deserved attention to the most common non-viral sexually transmitted disease worldwide?

“…The role of these resistant forms in the trichomonads life cycle is still not understood. In addition to its unique features, T. vaginalis presents hydrogenosomes instead of mitochondria, organelles that are involved in the metabolism adaptation to the hostile infection environment, including specific pathways of cell death 181920.…”

Inhibition of the Rumen Ciliate Entodinium caudatum by Antibiotics

“…Even though mitosomes are not involved in energy production, antibiotics can still inhibit E. caudatum by inhibiting Fe-S cluster formation in its mitosomes. In addition, many antibiotics, such as aminoglycoside antibiotics (Rizzi and Hirose, 2007), penicillin (Matsuda et al, 2002), and chloramphenicol (Holt et al, 1997), induce apoptotic cell death of mammalian cells, and mitochondria are believed to mediate apoptosis in mammalian cells (Xiong et al, 2014) and aerobic protists (Chose et al, 2003). However, it is not known if mitosomes are also involved in apoptosis.…”