FUNCTIONAL CHARACTERIZATION OF ECHINOCOCCUS GRANULOSUS ANTIGEN B (EgAgB) APOLIPOPROTEINS

SILVA V; FERREYRA ANA; KENNEDY MW; B. CÓRSICO

La Plata

Congreso; 8th International Conference on Lipid Binding Proteins (8ICLBP); 2013

LBPS

The parasite Echinococcus granulosus has a very restricted lipid metabolism, therefore the uptake, transportation and delivery of lipids between parasite tissues is essential for parasite viability and growth. In this scenario, Antigen B (EgAgB), an abundant lipoprotein in the parasite, has been postulated as one of its most important lipid carriers. This antigen is a complex of 230 kDa with a high content of lipids, including highly hydrophobic lipids and a variety of phospholipids. The EgAgB ability to bind these lipids relies on its protein moiety, referred to as EgAgB apolipoproteins. They belong to a novel, cestode-specific, lipoprotein family known as Hydrophobic Ligand Binding Proteins and include different isoforms encoded by a multigene family (EgAgB1-EgAgB5). The aim of this work is to analyze the lipid binding properties of EgAgB apolipoproteins. For this purpose, three recombinant subunits (EgAgB1, EgAgB2 and EgAgB3) were over expressed and delipidated by RP-HPLC. We found that these subunits are able to bind anthroyloxy-fatty acids with high affinity and to transfer them to phospholipids membranes containing an energy transfer acceptor of the anthroyloxy group donor. These results suggest that EgAgB subunits are capable to directly interact with model membranes. Thus the possibility that EgAgB could interact with cell membranes to uptake or deliver their lipids should be considered. In this regard, EgAgB has been also described as an immunomodulator molecule, binding and down-regulating inflammatory properties in myeloid cells. Taken this information together, we analyzed the ability of EgAgB subunits to interact with monocytes/macrophages. We found that EgAgB1 and EgAgB3 showed the highest ability to bind them. The characterization of these molecular interactions would help us to identify the receptor(s) involved in this recognition, allowing a major understanding of EgAgB´s function in E. granulosus lipid metabolism and as a potential immunomodulator.