Microsporidia are small intracellular parasites capable of forming spores. They are important human pathogens and are encountered in patients with HIV/AIDS. Despite their medical importance, very little is known about their biology. Until recently, microsporidia were thought to lack mitochondria. However, remnant mitochondria called mitosomes have been identified in these parasites. These lack ATP but contain components for mitochondrial iron-sulphur cluster biosynthesis. The scientific objective of the EU-funded 'Exploring the fundamental biology of microsporidian mitosomes' (MICMIT) project was to further study the biology of these organelles. To this end, scientists developed a novel immunocapture- based method for isolating mitosomes from the intracellular parasite Trachipleistophora hominis and the mucosal parasite Giardia lamblia. Proteomic analyses of the isolated mitosomes identified new candidate mitosomal proteins for both species. Importantly, microsporidian mitosomes from the different species had strong similarities in their functional proteomes indicating an evolutionary conservation of essential components. Scientists confirmed the presence of the iron-sulphur cluster biosynthesis pathway but discovered differences in the way the different microsporidia exported pathway products. Alongside novel transporter proteins, they also discovered a key player of parasitic DNA and RNA biosynthesis. Instead of producing ATP, the Ynk1 yeast homologue aids the parasite in stealing early substrates from host cells. These are used to carry out interconversions and obtain vital components such as DNA and RNA. Collectively, the work by the MICMIT study provides fundamental knowledge on the biology of important human parasites. Given the medical importance of microsporidia, the findings of the project could be utilised to develop novel drugs that target one or more of the identified molecules.
Microsporidia, parasite, biosynthetic, mitosomes, ATP, iron-sulphur cluster, Ynk1 yeast homologue