Towards an understanding of Mesocestoides vogae fatty acid binding proteins' roles

Molecular Characteristics of the Fatty-Acid-Binding Protein (FABP) Family in Spirometra mansoni-A Neglected Medical Tapeworm

The plerocercoid larva of the tapeworm Spirometra mansoni can parasitize humans and animals, causing serious parasitic zoonosis. The molecular characteristics and adaptive parasitism mechanism of Spirometra tapeworms are still unknown. In this study, 11 new members of the fatty-acid-binding protein (FABP) family were characterized in S. mansoni. A clustering analysis showed 11 SmFABPs arranged into two groups, and motif patterns within each group had similar organizations. RT-qPCR showed that SmFABPs were highly expressed in the adult stage, especially in gravid proglottid. A high genetic diversity of SmFABPs and relative conservation of FABPs in medical platyhelminthes were observed in the phylogenetic analysis. Immunolocalization revealed that natural SmFABP is mainly located in the tegument and parenchymal tissue of the plerocercoid and the uterus, genital pores, and cortex of adult worms. rSmFABP can build a more stable holo form when binding with palmitic acid to protect the hydrolytic sites of the protein. A fatty acid starvation induction test suggested that SmFABP might be involved in fatty acid absorption, transport, and metabolism in S. mansoni. The findings in this study will lay the foundation to better explore the underlying mechanisms of FABPs involved in Spirometra tapeworms as well as related taxa.

Dimerization, host-parasite communication and expression studies of an Echinococcus granulosus 2DBD nuclear receptor

Nuclear receptors (NRs) are ligand-modulated transcription factors that regulate various biological processes, such as metabolism, development and reproduction. Although NRs with two DNA-binding domains (2DBD) were identified in Schistosoma mansoni (Platyhelminth, Trematoda) more than fifteen years ago, these proteins have been poorly studied. 2DBD-NRs could become attractive therapeutic targets to combat parasitic diseases such as cystic echinococcosis since this type of protein is absent in vertebrate hosts. Cystic echinococcosis is a worldwide zoonosis caused by the larval stage of the parasitic platyhelminth Echinococcus granulosus (Cestoda) that generates an important public health problem and a significant economic loss. Recently, our research group identified four 2DBD-NRs in E. granulosus, named Eg2DBDα, Eg2DBDα.1 (an isoform of Eg2DBDα), Eg2DBDβ, and Eg2DBDγ. This work demonstrated that Eg2DBDα.1 forms homodimers through the E and F regions, whereas its interaction with EgRXRβa could not be detected. In addition, the stimulation of Eg2DBDα.1 homodimerization by intermediate host serum was shown, suggesting that at least one lipophilic molecule from bovine serum could bind to Eg2DBDα.1. Finally, Eg2DBDs expression studies in the protoscolex larval stage were performed, indicating that Eg2dbdγ is not expressed, whereas Eg2dbdα has the highest expression level followed by Eg2dbdβ and Eg2dbdα.1 in decreased order. Overall, these findings provide new insights into the mechanism of action of Eg2DBDα.1 and its potential role in host-parasite communication.

Echinococcus granulosus fatty acid binding proteins subcellular localization

Two fatty acid binding proteins, EgFABP1 and EgFABP2, were isolated from the parasitic platyhelminth Echinococcus granulosus. These proteins bind fatty acids and have particular relevance in flatworms since de novo fatty acids synthesis is absent. Therefore platyhelminthes depend on the capture and intracellular distribution of host's lipids and fatty acid binding proteins could participate in lipid distribution. To elucidate EgFABP's roles, we investigated their intracellular distribution in the larval stage by a proteomic approach. Our results demonstrated the presence of EgFABP1 isoforms in cytosolic, nuclear, mitochondrial and microsomal fractions, suggesting that these molecules could be involved in several cellular processes.