Affiliations: 1) Biology Centre of the Czech Academy of Sciences, Institute of Entomology, Ceske Budejovice, Czechia; 2) University of South Bohemia, Faculty of Science, Ceske Budejovice, Czechia
Keywords: c. innate immunity; j. homeostasis
IDGFs (Imaginal Dish Growth Factors) are a family of chitinase-like proteins secreted into the insect hemolymph from the fat body and hemocytes, they also represent important component secreted from salivary glands and silk glands of insects. IDGFs lost the hydrolytic activity of true chitinases but they are still able to bind carbohydrate moieties. They are implicated in multiple functions, including extracellular matrix reorganization, cell growth stimulation, wound healing, insect hemolymph clotting, antimicrobial activity, detoxification and also insect silk spinning. With its crystal structure determined, Drosophila IDGF2 is the best characterized member of the IDGF family. IDGF2 possess a unique shaped carbohydrate binding domain which is different from chitinases and other chitinase-like proteins.
We conducted a glycan array screen to find the binding partner of IDGF2. We established a functional in vivo assay based on the ability of IDGF2 to induce genes involved in innate immunity and inflammation. We compared the induction of wild-type and binding domain mutant forms of IDGF2. Moreover, we also examined the mutant protein distribution in tissue.
In the present study, we have identified Galα1-3(Fucα1-2)Galβ1 carbohydrate moiety as the preferred binding partner of IDGF2. Unlike other known chitinase-like proteins, IDGF2 does not bind to N-acetylglucosamine. Furthermore, we proved that the function of IDGF2 depends on its binding ability.
Our work brings new insights about insect chitinase-like proteins binding abilities, which are crucial for their function as modulators of host response in insects as well as mammals.