Abstract
In this study, a novel FIP named FIP-sch3 has been identified and characterised. FIP-sch3 was identified in the ascomycete Stachybotrys chartarum, making it the second FIP to be identified outside the order of Basidiomycota. Recombinant FIP-sch3 (rFIP-shc3) was produced in Escherichia coli and purified using GST-affinity magnetic beads. The bioactive characteristics of FIP-sch3 were compared to those of well-known FIPs LZ-8 from Ganoderma lucidum and FIP-fve from Flammulina velutipes, which were produced and purified using the same method. The purified rFIP-sch3 exhibited a broad spectrum of anti-tumour activity in several types of tumour cells but had no cytotoxicity in normal human embryonic kidney 293 cells. Assays that were implemented to study these properties indicated that rFIP-sch3 significantly suppressed cell proliferation, induced apoptosis and inhibited cell migration in human lung adenocarcinoma A549 cells. The anti-tumour effects of rFIP-sch3 in A549 cells were comparable to those of rLZ-8, but they were significantly greater than those of rFIP-fve. Molecular assays that were built on real-time PCR further revealed potential mechanisms related to apoptosis and migration and that underlie phenotypic effects. These results indicate that FIP-shc3 has a unique anti-tumour bioactive profile, as do other FIPs, which provide a foundation for further studies on anti-tumour mechanisms. Importantly, this study also had convenient access to FIP-sch3 with potential human therapeutic applications.
Highlights
Fungal immunomodulatory proteins (FIPs) are a class of small proteins that share similar sequence and structural characteristics [1]
The phylogenetic tree showed that FIP-gja, FIPgat, LZ-8, FIP-gts, FIP-gmi, FIP-cru, FIP-gap, FIP-fve, and FIP-vvo were clustered into one lineage, indicating that they are highly conserved in molecular evolution
The cells that were treated with FIP-fve and the untreated cells maintained their normal shapes and grew normally. These results demonstrate that recombinant FIPs (rFIPs)-sch3 treatment is clearly toxic to all the above tumour cell lines, and rLZ-8 treatment is toxic to four of them (MCF-7, A549, HeLa and HepG2 cells), but rFIPfve is toxic to none of the five tumour cell lines in this low dose group
Summary
Fungal immunomodulatory proteins (FIPs) are a class of small proteins that share similar sequence and structural characteristics [1]. FIPs are assigned to their own family of proteins. FIP family proteins exhibit sequence identity that is greater than 57% and are made up of approximately 110 amino acid residues with a molecular weight of approximately 13 kDa. FIPs lack His, Cys and Met residues but are rich in Asp and Val residues [2]. The crystal structures of FIP-fve from Flammulina velutipes (PDB entry: 1OSY) [3], LZ-8 (FIP-glu) from Ganoderma lucidum (PDB entry: 3F3H) [4] and FIP-gmi from G. microsporum (PDB entry: 3KCW) have been resolved. FIP-fve and LZ-8 are homodimers, and FIP-gmi is a homotetramer.
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