Characterization of a novel fungal immunomodulatory protein, FIP-SJ75 shuffled from Ganoderma lucidum, Flammulina velutipes and Volvariella volvacea

FIP-SJ75, a novel fungal immunomodulatory protein gene, was shuffled from the genes of three different mushroom species: Ganoderma lucidum, Flammulina velutipes, and Volvariella volvacea. Based on the expression of FIP-SJ75 gene in Escherichia coli, recombinant FIP-SJ75 (rFIP-SJ75) was routinely confirmed, consisting of 115 amino acids, and six peptides were identified by LC/Q-TOF MS with a coverage rate of 84.3%. Bioactivity assay in vitro indicated that rFIP-SJ75 promoted the proliferation of RAW264.7 cells at a range of 1-8 mu g/mL, and significantly activated RAW264.7 cells in a dose-dependent manner. Real-time PCR revealed rFIP-SJ75 obviously promoted pro-inflammatory genes (TNF-alpha and IL-6), but reduced the expression of anti-inflammatory genes (IL-10 and TGF-beta 1) at the transcriptional level. These data implied that rFIP-SJ75 possessed immunomodulatory activity in macrophages by promoting macrophage M1 polarization and initiating pro-inflammatory responses, which could lay the foundation for rFIP-SJ75 to become a stable immunomodulator resource for further research and potential applications.