Exploring the diversity of mitochondrion related organelles in Cryptosporidium species

Abstract

Cryptosporidium is an apicomplexan parasite that causes widespread diarrhoeal disease in both humans and animals. It is a parasite that is responsible for large waterborne outbreaks of Cryptosporidiosis. Humans are thought to acquire the parasite by the ingestion of oocysts, which are shed in the stool of infected animals or humans. Research has been done on this parasite, however up till now there has not been a treatment against this. Cryptosporidium have lost their mitochondrial genome and therefore various mitochondrial pathways have been conserved in some of these species. Using bioinformatics analysis, we summarized the differences and similarities in the metabolic pathways in the mitosomes of six Cryptosporidium species (C. parvum, C. hominis, C. tyzzeri, C. ubiquitum, C.andersoni and C.muris) . As only C. parvum and C. hominis pathways have been mapped on KEGG Pathway Database, amino acid sequences were extracted for proteins involved in glycolysis/gluconeogenesis (map00010), TCA cycle (map00020), protein import machinery (map03060), pentose phosphate pathway (map00030), pyruvate metabolism (map00620) and oxidative phosphorylation (map00190). Amino acid sequences for the protein coding genes were run in BlastP on CryptoDB using the set parameters. The gene results were analyzed and used to produce diagrams to show the metabolic pathways in the mitosomes of the Cryptosporidium species.In this study we show that the essential TCA cycle enzymes were present in the gastric species C. andersoni and C.muris, whereas C.parvum, C.hominis, C.tyzzeri and C.ubiquitum only retain the membrane bound malate-quinone oxidoreductase (MQO) and pyruvate synthase. All species investigated showed a highly reduced protein import machinery in comparison to P.falciparum, and conserved glycolysis/gluconeogenesis proteins and Fe-S (iron-sulfur) cluster assembly, suggesting that these two pathways are the main ways in which the parasite acquires energy.Our results from the CryptoDB Blast search for the Protein Import Machinery and other pathways investigated contained some putative protein coding genes which needs to be experimentally validated. The Tim 9-10 which is responsible for transporting hydrophobic proteins to the inner mitochondrial membrane was annotated as uncharacterized in three protein coding genes: C.hominis (GY17_00000465), C.parvum (cgd6_4450) and C.tyzzeri (CTYZ_00001648). Further studies such as PCR analysis as well as Western blotting can be used to characterize the protein present and molecular structural analysis carried out to find out the shape and immunofluorescent assays as well as neutralization assays used to assess the function of the protein. The results from this study can be helpful to direct further research in understanding the functions of the mitosomes of these species and could be pivotal in developing new therapeutic drugs that are used to target various pathways in Cryptosporidium species.