Characterization of a new fungal immunomodulatory protein, FIP-dsq2 from Dichomitus squalens

FIP-dsq2, a new immunomodulatory protein, was identified in Basidiomycota Dichomitus squalens by gene mining. FIP-dsq2 contained 111 amino acids with a molecular weight of 12.51 kDa. FIP-dsq2 had a homology range of 51–65% to the reported FIPs. The predicted 3-dimensional model had more similar identical folding patterns in LZ-8 than for FIP-fve. Evolutionary analysis indicated substantial phylogenetic differences were existed with the other FIPs. Overexpression of a 14.07 kDa soluble recombinant FIP-dsq2 (rFIP-dsq2) was achieved in Rosetta (pGEX-6P-1) and the purified recombinant protein was homodimer verified by gel filtration chromatography analysis. Antitumour ability of rFIP-dsq2 to human lung adenocarcinoma A549 cells was between LZ-8 and FIP-fve. The cytotoxic effect of rFIP-dsq2 in A549 cancer cells was dose-dependent and the half-maximal inhibitory concentration (IC₅₀) was 15.08 μg/mL. Furthermore, rFIP-dsq2 at 8 μg/mL could significantly induce apoptosis and interrupt migration in A549 cells. In addition, the antitumour-mechanism exploration suggested that rFIP-dsq2 inhibited A549 proliferation uniquely via apoptotic cell death pathway. The results stated that rFIP-dsq2 was a promising candidate for use in future lung cancer therapy.