MICRO ISC · Investigating the function of the microsporidian mitosome using genomics and molecular cell biology
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2005-01-10 → 2007-01-09
- EU contribution
- €161,314
- Participants
- 1
- Scheme
- IIF
Lines connect the coordinator with its partners.
Results in brief
Final Activity Report Summary - MICRO ISC (Investigating the function of the microsporidian mitosome using genomics and molecular cell biology)
Microsporidia are highly specialised obligate intracellular parasites of eukaryotes, including humans, which demonstrate extreme reduction at the molecular, cellular and biochemical level. Even though they were long thought to be early branching eukaryotes lacking mitochondria, they were recently shown to contain a tiny mitochondrial remnant called a mitosome. The function of the mitosome is unknown since microsporidians lack the genes for canonical mitochondrial functions, such as aerobic respiration and heme biosynthesis. The microsporidial genomes encode, however, several components of the mitochondrial iron-sulphur (Fe/S) cluster assembly machinery. During my project I provided the first experimental insights into the metabolic function and localisation of these proteins. I cloned, functionally characterised and localised several central mitochondrial Fe/S cluster assembly components for the microsporidians encephalitozoon cuniculi and trachipleistophora hominis. Several microsporidial proteins could functionally replace their yeast counterparts in Fe/S protein biogenesis. In e. cuniculi, the iron (frataxin) and sulphur, i.e. cysteine desulphurase and Nfs1, donors and the scaffold protein (Isu1) co-located with mitochondrial Hsp70 to the mitosome, with the latter being consistent with the functional site for Fe/S cluster biosynthesis. In t. hominis, mitochondrial Hsp70 and the essential sulphur donor (Nfs1) were still in the mitosome, even though, surprisingly, the main pools of Isu1 and frataxin were cytosolic, creating a conundrum of how these key components of Fe/S cluster biosynthesis coordinated their function. The observation that mitosomes of both species contained critical elements of a Fe/S cluster assembly machinery, which was essential in model eukaryotes for cell survival, strongly argued that this biosynthetic process was a key function of the microsporidian organelle.
Data: CORDIS, © European Union
Project objective
Microsporidia like Trachipleistophora hominis and Encephalitozoon cuniculi, are opportunistic parasites of humans with HIV. Around 50% of cases of serious diarrhoea in AIDS patients are associated with microsporidia - 14 different microsporidia have now been isolated. Despite their importance, the genome and cell biology of microsporidia are poorly understood. I will use a multidisciplinary approach incorporating training in bioinformatics, proteomics, cell and molecular biology to investigate the structu re and function of the recently discovered microsporidian mitosome ' the most highly reduced mitochondrion yet discovered. My work will also further basic understanding of the minimal and essential functions of the mitochondrion itself; an organelle that is vital for eukaryotes. My hypothesis is that the mitosome makes iron sulphur (Fe-S) clusters ' a fundamental process for all eukaryotic cells, and whose dysfunction causes inherited mitochondrial diseases like Friedrichs Ataxia. The E. cuniculi genome en codes seven of the proteins involved in this process, but there is no experimental data on their location or function. I will clone and sequence two of the key genes (Nfs1p, Isu1p) from Trachipleistophora hominis, a more tractable experimental system than Encephalitozoon, and produce antibodies to locate their site of activity. I will also perform in vitro tests of enzyme function. I will do this at Newcastle University with Professor Martin Embley, in whose lab the mitosome was discovered, and where there are state-of-the-art facilities for bioinformatics, cell biology, proteomics and light and electron microscopy. I will also use bioinformatics to search the Encephalitozoon genome for the mitosomal import pathway. Preliminary data suggests that the mitosome may have, uniquely, dispensed with one of the main mitochondrial import pathways. Thus this work will improve understanding of yet another fundamental mitochondrial process ' that of protein import.
Original text from CORDIS.
Participants
- UNIVERSITY OF NEWCASTLE UPON TYNE · NEWCASTLE UPON TYNECoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union