Entamoeba mitosomes play an important role in encystation by association with cholesteryl sulfate synthesis

Abstract

Hydrogenosomes and mitosomes are mitochondrion-related organelles (MROs) that have highly reduced and divergent functions in anaerobic/microaerophilic eukaryotes. Entamoeba histolytica, a microaerophilic, parasitic amoebozoan species, which causes intestinal and extraintestinal amoebiasis in humans, possesses mitosomes, the existence and biological functions of which have been a longstanding enigma in the evolution of mitochondria. We previously demonstrated that sulfate activation, which is not generally compartmentalized to mitochondria, is a major function of E. histolytica mitosomes. However, because the final metabolites of sulfate activation remain unknown, the overall scheme of this metabolism and the role of mitosomes in Entamoeba have not been elucidated. In this study we purified and identified cholesteryl sulfate (CS) as a final metabolite of sulfate activation. We then identified the gene encoding the cholesteryl sulfotransferase responsible for synthesizing CS. Addition of CS to culture media increased the number of cysts, the dormant form that differentiates from proliferative trophozoites. Conversely, chlorate, a selective inhibitor of the first enzyme in the sulfate-activation pathway, inhibited cyst formation in a dose-dependent manner. These results indicate that CS plays an important role in differentiation, an essential process for the transmission of Entamoeba between hosts. Furthermore, we show that Mastigamoeba balamuthi, an anaerobic, free-living amoebozoan species, which is a close relative of E. histolytica, also has the sulfate-activation pathway in MROs but does not possess the capacity for CS production. Hence, we propose that a unique function of MROs in Entamoeba contributes to its adaptation to its parasitic life cycle. mitochondrion-related organelles | protist | sulfolipids | differentiation M itochondrion-related organelles (MROs) are derived from canonical mitochondria and are found in a wide range of anaerobic/microaerophilic eukaryotes (1, 2). During the course of evolution MROs have undergone secondary loss of mitochondrial functions; this loss has occurred independently multiple times, resulting in the broad phylogenetic distribution of organisms possessing MROs (2). Furthermore, MROs occasionally acquire novel functions from other organisms by lateral gene transfer (LGT) (1, 3). Hence, MROs are not simply remnants of mitochondria but rather are organelles that display a variety of unique features (1-5).Unique features have been demonstrated in different types of MRO (2-4). Some anaerobic lineages of eukaryotes possess MROs (hydrogenosomes or hydrogen-producing mitochondria) that have remodeled their mitochondria drastically to couple ATP generation with hydrogen production (2-4). Mitosomes, another type of MRO maintained in some organisms that inhabit anaerobic/microaerophilic environments, do not produce ATP or hydrogen and have lost typical mitochondrial functions, such as the tricarboxylic acid (TCA) cycle, electron transport, oxidative phosphorylation, and β-oxidation...

An Interactome-Centered Protein Discovery Approach Reveals Novel Components Involved in Mitosome Function and Homeostasis in Giardia lamblia

“…This may even include general functions in stage-differentiation as recently shown in E . histolytica whose mitosomes are essential for the encystation process [74]. …”

Changes in ultrastructural features of the foraminifera Ammonia spp. in response to anoxic conditions: Field and laboratory observations

“…(phylotype T6) (Nomaki et al, 2016), as 34 S-labeled sulfate was incorporated into the electron dense bodies in specimens incubated in dysoxic conditions. Those authors conclude that the sulfate activation pathway may be related to foraminiferal dormancy or encystment under anoxia in a manner similar to Entamoeba histolytica (Mi-ichi et al, 2011(Mi-ichi et al, , 2015.…”

Diversity and origins of anaerobic metabolism in mitochondria and related organelles

“…While initial reports suggested that the NIF system is dually localized to the cytoplasm and mitosomes [84], more recent proteomic studies have been unable to detect NIF system components in the organelle, calling into question the widely held notion that the main reason for maintaining MROs is the biosynthesis of Fe-S clusters [80]. Currently, the only known function of the MROs of Entamoeba is ATP import via mitochondrial carrier proteins [85] and sulfate activation for the generation of sulfated compounds [80,86]. Mastigamoeba balamuthi is a free-living relative of Entamoeba that inhabits low oxygen freshwater environments [87].…”