Structural and Binding Properties of Two Paralogous Fatty Acid Binding Proteins of Taenia solium Metacestode

Abstract

BackgroundFatty acid (FA) binding proteins (FABPs) of helminths are implicated in acquisition and utilization of host-derived hydrophobic substances, as well as in signaling and cellular interactions. We previously demonstrated that secretory hydrophobic ligand binding proteins (HLBPs) of Taenia solium metacestode (TsM), a causative agent of neurocysticercosis (NC), shuttle FAs in the surrounding host tissues and inwardly transport the FAs across the parasite syncytial membrane. However, the protein molecules responsible for the intracellular trafficking and assimilation of FAs have remained elusive.Methodology/Principal FindingsWe isolated two novel TsMFABP genes (TsMFABP1 and TsMFABP2), which encoded 133- and 136-amino acid polypeptides with predicted molecular masses of 14.3 and 14.8 kDa, respectively. They shared 45% sequence identity with each other and 15–95% with other related-members. Homology modeling demonstrated a characteristic β-barrel composed of 10 anti-parallel β-strands and two α-helices. TsMFABP2 harbored two additional loops between β-strands two and three, and β-strands six and seven, respectively. TsMFABP1 was secreted into cyst fluid and surrounding environments, whereas TsMFABP2 was intracellularly confined. Partially purified native proteins migrated to 15 kDa with different isoelectric points of 9.2 (TsMFABP1) and 8.4 (TsMFABP2). Both native and recombinant proteins bound to 11-([5-dimethylaminonaphthalene-1-sulfonyl]amino)undecannoic acid, dansyl-DL-α-amino-caprylic acid, cis-parinaric acid and retinol, which were competitively inhibited by oleic acid. TsMFABP1 exhibited high affinity toward FA analogs. TsMFABPs showed weak binding activity to retinol, but TsMFABP2 showed relatively high affinity. Isolation of two distinct genes from an individual genome strongly suggested their paralogous nature. Abundant expression of TsMFABP1 and TsMFABP2 in the canal region of worm matched well with the histological distributions of lipids and retinol.Conclusions/SignificanceThe divergent biochemical properties, physiological roles and cellular distributions of the TsMFABPs might be one of the critical mechanisms compensating for inadequate de novo FA synthesis. These proteins might exert harmonized or independent roles on lipid assimilation and intracellular signaling. The specialized distribution of retinol in the canal region further implies that cells in this region might differentiate into diverse cell types during metamorphosis into an adult worm. Identification of bioactive systems pertinent to parasitic homeostasis may provide a valuable target for function-related drug design.

Fasciola hepatica Fatty Acid Binding Protein Induces the Alternative Activation of Human Macrophages

“…A number of protocols have been designed to purify native FABPs from humans and parasites (28)(29)(30). In this study, Fh12 was purified from soluble extracts of adult flukes following a preoptimized protocol that combines separation by molecular sieving chromatography and two consecutive rounds of preparative isoelectric focusing (IEF) using ampholyte mixes with a wide range of pH values (23).…”

Phyletic Distribution of Fatty Acid-Binding Protein Genes

“…Multiple gene duplications have occurred in this subfamily, giving rise to 16 iLBPs including 12 FABP s in vertebrates [1,4–6]. More than 30 FABP genes have been found in a wide range of invertebrates [2,7,8]. …”

Towards an Understanding of Mesocestoides vogae Fatty Acid Binding Proteins’ Roles

“…Low fatty acid aqueous solubility would strongly imply that specific and efficient mechanisms must exist to transport and target these compounds between and within cells. MvFABPs are good candidates to participate in M. vogae Tt FA intracellular distribution acting as counterparts of other lipid binding proteins involved in shuttling FAs to the surrounding host tissue [36] . In the present studies we investigate the intracellular distribution of MvFABPa and MvFABPb and the co-localization with fluorescent FA in vivo captured.…”