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

Simple Summary: The purpose of this study was to investigate the members, gene expression patterns, and molecular characteristics of the Spirometra mansoni fatty-acid-binding protein family. We screened and characterized 11 new SmFABP genes and divided them into two groups based on conservative motifs. All 11 genes were highly expressed in the adult stage. We found that SmFABPs had a high genetic diversity and the FABPs in medical platyhelminthes were relatively conserved. When rSmFABP is combined with palmitic acid, a more stable holographic morphology can be established to protect the hydrolysis site of FABP. 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.