Biochemical and functional characterization of recombinant fungal immunomodulatory proteins (rFIPs)

Identification a novel Ganoderma FIP gene from Ganoderma capense and its functional expression in Pichia pastoris

Ganoderma capense is a precious medicinal fungus in China. In this study, a novel fungal immunomodulatory protein gene, named as FIP-gca, was cloned from G. capense by homologous cloning. Sequencing analysis indicated that FIP-gca was composed of 336 bp, which encoded a polypeptide of 110 amino acids. Protein sequence blasting and phylogenetic analysis showed that FIP-gca shared homology with other Ganoderma FIPs. FIP-gca was effectively expressed in Pichia pastoris GS115 at an expression level of 166.8 mg/L and purified using HisTrap™ fast-flow prepack columns. The immunomodulation capacity of rFIP-gca was demonstrated by that rFIP-gca could obviously stimulate cell proliferation and increase IL-2 secretion of murine spleen lymphocytes. Besides, antitumor activity of rFIP-gca towards human stomach cancer AGS cell line was evaluated in vitro. Cell wound scratch assay proved that rFIP-gca could inhibit migration of AGS cells. And flow cytometry assay revealed that rFIP-gca could significantly induce apoptosis of AGS cells. rFIP-gca was able to induce 18.12% and 22.29% cell apoptosis at 0.3 μM and 0.6 μM, respectively. Conclusively, the novel FIP-gca gene from G. capense has been functionally expressed in Pichia and rFIP-gca exhibited ideal immunomodulation and anti-tumour activities, which implies its potential application and study in future.

Glycosylation Contributes to Thermostability and Proteolytic Resistance of rFIP-nha (Nectria haematococca)

Glycosylation is an important post-translational modification of proteins, contributing to protein function, stability and subcellular localization. Fungal immunomodulatory proteins (FIPs) are a group of small proteins with notable immunomodulatory activity, some of which are glycoproteins. In this study, the impact of glycosylation on the bioactivity and biochemical characteristics of FIP-nha (from Nectria haematococca) is described. Three rFIP-nha glycan mutants (N5A, N39A, N5+39A) were constructed and expressed in Pichia pastoris to study the functionality of the specific N-glycosylation on amino acid N5 and N39. Their protein characteristics, structure, stability and activity were tested. WT and mutants all formed tetramers, with no obvious difference in crystal structures. Their melting temperatures were 82.2 °C (WT), 81.4 °C (N5A), 80.7 °C (N39A) and 80.1 °C (N5+39A), indicating that glycosylation improves thermostability of rFIP-nha. Digestion assays showed that glycosylation on either site improved pepsin resistance, while 39N-glycosylation was important for trypsin resistance. Based on the 3D structure and analysis of enzyme cleavage sites, we conclude that glycosylation might interfere with hydrolysis via increasing steric hindrance. WT and mutants exerted similar bioactivity on tumor cell metabolism and red blood cells hemagglutination. Taken together, these findings indicate that glycosylation of FIP-nha impacts its thermostability and digestion resistance.

FIP-nha, a fungal immunomodulatory protein from Nectria haematococca, induces apoptosis and autophagy in human gastric cancer cells via blocking the EGFR-mediated STAT3/Akt signaling pathway

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FIP-nha, a new FIP discovered beyond Basidiomycota, has been demonstrated a broad spectrum of antitumor activity and cell selectivity against human cancers.

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FIP-nha inhibited the growth, induced apoptosis and autophagy of gastric cancer cells through competitively binding to EGFR with EGF to blocking the EGFR-mediated STAT3/Akt pathway.

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FIP-nha may be a potential chemotherapy drug that targeted EGFR to treat human gastric cancer.

FIP-nha, a fungal immunomodulatory protein from Nectria haematococca, has been demonstrated a broad spectrum of antitumor activity and cell selectivity against human cancers in our previous study. However, the effect and mechanism of FIP-nha on gastric cancer remains unclear. In this study, we systematically observed the cytotoxicity, biological effect, regulatory mechanism and interaction target of FIP-nha on human gastric cancer cell lines, AGS and SGC7901. Our results demonstrated that FIP-nha inhibited the growth of AGS and SGC7901 cells in a dose-dependent manner and exerted proapoptotic effects on both cells as confirmed by flow cytometry, DAPI staining and western blot analysis. Additionally, the exposure of AGS and SGC7901 to FIP-nha induced autophagy as indicated by western blot analysis, GFP-LC3 and mCherry-GFP-LC3 transfection and acridine orange staining. Furthermore, we found that FIP-nha decreased the phosphorylation of EGFR, STAT3 and Akt and inhibited activation effect of ligand factor EGF to EGFR and its downstream signal molecule STAT3 and Akt. Finally, we proved that FIP-nha located on the surface of gastric cancer cells and bound directly to the transmembrane protein of EGFR by immunoprecipitation, cellular localization, molecular docking, microscale thermophoresis assay. The above findings indicated that FIP-nha inhibited the growth of gastric cancer and induced apoptosis and autophagy through competitively binding to EGFR with EGF to blocking the EGFR-mediated STAT3/Akt pathway. In summary, our study provided novel insights regarding the activity of FIP-nha against gastric cancer and contributed to the clinical application of FIP-nha as a potential chemotherapy drugs that targeted EGFR for human gastric cancer.

Ganoderma immunomodulatory proteins: mushrooming functional FIPs

Fungal immunomodulatory protein (FIP) is a novel functional protein family with specific immunomodulatory activity identified from several macro-fungi. A variety of biological activities of FIPs have been reported, such as anti-allergy, anti-tumor, mitogenic activity, and immunomodulation. Among all known FIPs, the firstly discovered FIP was isolated from Ganoderma lucidum, and most FIP members were from Ganoderma genus. Compared with other FIPs, Ganoderma FIPs possess some advantageous bioactivities, like stronger anti-tumor activity. Therein, gene sequences, protein structural features, biofunctions, and recombinant expression of Ganoderma FIPs were summarized and addressed, focusing on elucidating their anti-tumor activity and molecular mechanisms. Combined with current advances, development potential and application of Ganoderma FIPs were also prospected. KEY POINTS: • More than a dozen of reported FIPs are identified from Ganoderma species. • Ganoderma immunomodulatory proteins have superior anti-tumor activity with promising prospects and application. • Current review comprehensively addresses characterization, biofunctions, and anti-tumor mechanisms of Ganoderma FIPs.

Narrative Review: Bioactive Potential of Various Mushrooms as the Treasure of Versatile Therapeutic Natural Product

Mushrooms have remained an eternal part of traditional cuisines due to their beneficial health potential and have long been recognized as a folk medicine for their broad spectrum of nutraceuticals, as well as therapeutic and prophylactic uses. Nowadays, they have been extensively investigated to explain the chemical nature and mechanisms of action of their biomedicine and nutraceuticals capacity. Mushrooms belong to the astounding dominion of Fungi and are known as a macrofungus. Significant health benefits of mushrooms, including antiviral, antibacterial, anti-parasitic, antifungal, wound healing, anticancer, immunomodulating, antioxidant, radical scavenging, detoxification, hepatoprotective cardiovascular, anti-hypercholesterolemia, and anti-diabetic effects, etc., have been reported around the globe and have attracted significant interests of its further exploration in commercial sectors. They can function as functional foods, help in the treatment and therapeutic interventions of sub-optimal health states, and prevent some consequences of life-threatening diseases. Mushrooms mainly contained low and high molecular weight polysaccharides, fatty acids, lectins, and glucans responsible for their therapeutic action. Due to the large varieties of mushrooms present, it becomes challenging to identify chemical components present in them and their beneficial action. This article highlights such therapeutic activities with their active ingredients for mushrooms.

Differences in Antioxidants, Polyphenols, Protein Digestibility and Nutritional Profile between Ganoderma lingzhi from Industrial Crops in Asia and Ganoderma lucidum from Cultivation and Iberian Origin

Carpophores of Ganoderma lingzhi (GZ) from industrial crops in China were analysed and compared with carpophores of three Iberian strains of cultivated Ganoderma lucidum (GL) (Aveiro, Madrid, Palencia) previously genetically characterized. The genetic determination of all the fungi in the study coincided with the identification provided by the companies and entities that supplied the samples. Cultivation time ranged between 107 and 141 days. The analysis of total phenol content showed to be 56.8% higher for GL from Palencia than for GZ. Intraspecific variation was a maximum of 56% from GL. The content of antioxidants, both intraspecific and interspecific, was found to be strain-dependent with a maximum variation of 78.5%. The nutritional analysis shows that there are differences in dietary fiber, protein, ash and sodium content between GL and GZ. In fatty acids analysis, only trans fatty acids showed significant differences, being higher in GL. Protein profile and digestibility of GZ and GL-Madrid mushroom proteins were evaluated by digestion with simulated gastric fluid and were different. The two species were perfectly differentiated according to their protein profile. These results should be considered for nutritional and industrial applications.

Functional evaluation of a recombinant fungal immunomodulatory protein from L. rhinocerus produced in P. pastoris and E. coli host expression systems

Fungal immunomodulatory proteins (FIPs) are bioactive proteins with immunomodulatory properties. We previously reported the heterologous production in Escherichia coli of FIP-Lrh from Tiger milk mushroom (Lignosus rhinocerus) with potent cytotoxic effect on cancer cell lines. However, protein produced in E. coli lacks post-translational modifications and may be contaminated with lipopolysaccharide (LPS) endotoxin. Therefore, in this study, yFIP-Lrh produced in Pichia pastoris was functionally compared with eFIP-Lrh produced in E. coli. Expression construct of FIP-Lrh cDNA in pPICZα was generated, transformed into P. pastoris X-33 and Mut⁺ transformants were verified by colony PCR. Induction with 0.5% or 1% methanol resulted in a secreted 13.6 kDa yFIP-Lrh which was subsequently purified and verified using LCMS/MS analysis. Size exclusion chromatography confirmed eFIP-Lrh as a homodimer whereas the larger size of yFIP-Lrh may indicate post-translational modification despite negative for glycoproteins staining. At lower concentration (4-8 μg/mL), yFIP-Lrh induced significantly higher Th1 (IFN-γ, TNF-α) and Th2 (IL-6, IL-4, IL-5, IL-13) cytokines production in mice splenocytes, whereas 16 μg/mL eFIP-Lrh induced significantly higher pro-inflammatory cytokines (TNF-α, IL-6, IL-10), possibly due to higher residual LPS endotoxin (0.082 EU/mL) in eFIP-Lrh compared to negligible level in yFIP-Lrh (0.001 EU/mL). Furthermore, yFIP-Lrh showed higher cytotoxic effect on MCF-7 and HeLa cancer cells. Since both recombinant proteins of FIP-Lrh have the same peptide sequence, besides glycosylation, other post-translational modifications in yFIP-Lrh may account for its enhanced immunomodulatory and anti-proliferative activities. In conclusion, P. pastoris is preferred over E. coli for production of a functionally active yFIP-Lrh devoid of endotoxin contamination. KEY POINTS: • FIP-Lrh can induced production of Th1 and Th2 cytokines by mouse splenocytes. • Higher cytotoxic effect on cancer cells observed for yeast compared to E. coli produced FIP-Lrh. • P. pastoris allows production of an endotoxin-free and functionally active recombinant FIP-Lrh.

Identification and Functional Characterization of a Novel Immunomodulatory Protein From Morchella conica SH

A novel fungal immunomodulatory protein (FIP) was found in the precious medical and edible mushroom Morchella conica SH, defined as FIP-mco, which belongs to the FIP family. Phylogenetic analyses of FIPs from different origins were performed using Neighbor-Joining method. It was found that FIP-mco belonged to a new branch of the FIP family and may evolved from a different ancestor compared with most other FIPs. The cDNA sequence of FIP-mco was cloned and expressed in the yeast Pichia Pastoris X33. The recombinant protein of FIP-mco (rFIP-mco) was purified by agarose Ni chromatography and determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. The protein rFIP-mco could significantly suppress the proliferation of A549 and HepG2 cells at the concentration of 15 and 5 μg/ml, respectively, and inhibited the migration and invasion of human A549 and HepG2 cells at the concentration of 15 and 30 μg/ml respectively in vitro. Further, rFIP-mco can significantly reduce the expression levels of TNF-α, IL-1β, and IL-6 in the THP1 cells (human myeloid leukemia mononuclear cells). In order to explore the potential mechanism of the cytotoxicity effect of rFIP-mco on A549 and HepG2 cells, cell cycle and apoptosis assay in the two cancer cells were conducted. The results demonstrated that G0/G1 to S-phase arrest and increased apoptosis may contribute to the proliferation inhibition by rFIP-mco in the two cancer cells. Molecular mechanism of rFIP-mco's reduction effect on the inflammatory cytokines was also studied by suppression of the NF-κB signaling pathway. It showed that suppression of NF-κB signaling is responsible for the reduction of inflammatory cytokines by rFIP-mco. The results indicated the prospect of FIP-mco from M. conica SH as an effective and feasible source for cancer therapeutic studies and medical applications.

Immunomodulatory Effects of Edible and Medicinal Mushrooms and Their Bioactive Immunoregulatory Products

Mushrooms have been valued as food and health supplements by humans for centuries. They are rich in dietary fiber, essential amino acids, minerals, and many bioactive compounds, especially those related to human immune system functions. Mushrooms contain diverse immunoregulatory compounds such as terpenes and terpenoids, lectins, fungal immunomodulatory proteins (FIPs) and polysaccharides. The distributions of these compounds differ among mushroom species and their potent immune modulation activities vary depending on their core structures and fraction composition chemical modifications. Here we review the current status of clinical studies on immunomodulatory activities of mushrooms and mushroom products. The potential mechanisms for their activities both in vitro and in vivo were summarized. We describe the approaches that have been used in the development and application of bioactive compounds extracted from mushrooms. These developments have led to the commercialization of a large number of mushroom products. Finally, we discuss the problems in pharmacological applications of mushrooms and mushroom products and highlight a few areas that should be improved before immunomodulatory compounds from mushrooms can be widely used as therapeutic agents.

New advances and potentials of fungal immunomodulatory proteins for therapeutic purposes

Fungal immunomodulatory proteins (FIPs) are fascinating small and heat-stable bioactive proteins in a distinct protein family due to similarities in their structures and sequences. They are found in fungi, including the fruiting bodies producing fungi comprised of culinary and medicinal mushrooms. Structurally, most FIPs exist as homodimers; each subunit consisting of an N-terminal α-helix dimerization and a C-terminal fibronectin III domain. Increasing numbers of identified FIPs from either different or same fungal species clearly indicates the growing research interests into its medicinal properties which include immunomodulatory, anti-inflammation, anti-allergy, and anticancer. Most FIPs increased IFN-γ production in peripheral blood mononuclear cells, potentially exerting immunomodulatory and anti-inflammatory effects by inhibiting overproduction of T helper-2 (Th2) cytokines common in an allergy reaction. Recently, FIP from Ganoderma microsporum (FIP-gmi) was shown to promote neurite outgrowth for potential therapeutic applications in neuro-disorders. This review discussed FIPs' structural and protein characteristics, their recombinant protein production for functional studies, and the recent advances in their development and applications as pharmaceutics and functional foods.

Current Understanding of the Structure and Function of Fungal Immunomodulatory Proteins

Fungal immunomodulatory proteins (FIPs) are a group of proteins found in fungi, which are extensively studied for their immunomodulatory activity. Currently, more than 38 types of FIPs have been described. Based on their conserved structure and protein identity, FIPs can be classified into five subgroups: Fve-type FIPs (Pfam PF09259), Cerato-type FIPs (Pfam PF07249), PCP-like FIPs, TFP-like FIPs, and unclassified FIPs. Among the five subgroups, Fve-type FIPs are the most studied for their hemagglutinating, immunomodulating, and anti-cancer properties. In general, these small proteins consist of 110–125 amino acids, with a molecular weight of ~13 kDa. The other four subgroups are relatively less studied, but also show a noticeable influence on immune cells. In this review, we summarized the protein modifications, 3-dimensional structures and bioactivities of all types of FIPs. Moreover, structure-function relationship of FIPs has been discussed, including relationship between carbohydrate binding module and hemagglutination, correlation of oligomerization and cytokine induction, relevance of glycosylation and lymphocyte activation. This summary and discussion may help gain comprehensive understanding of FIPs' working mechanisms and scope future studies.

Efficacy of fungal immunomodulatory protein to promote swine immune responses against porcine reproductive and respiratory syndrome virus infection

Fungal immunomodulatory protein (FIP) is one of the bioactive compounds of edible mushrooms, which has been shown to trigger type 1 T helper (Th1) pathway activation in research with mice. This study was designated to assess immunomodulatory effects of recombinant FIP-Flammulina velutipes (rFIP-fve) on swine and the protective efficacy against PRRSV infection. In the in vitro evaluations, rFIP-fve significantly triggered up-regulation of IL-2 and IFN-γ mRNA in porcine PBMCs and stimulated natural killer cytotoxicity. Porcine pulmonary alveolar macrophages (PAMs) treated with rFIP-fve showed prolonged life times, up-regulation of both MHC I and II molecules and enhanced abilities to present antigen. In the in vivo trial, two doses of 2 mg rFIP-fve significantly reduced drops in the CD4/CD8 ratio after PRRSV challenge, and the cytokine mRNA profile of PBMC revealed a tendency of IFN-γ up-regulation and a decrease in IL-10 in the rFIP-treated group. Moreover, administration of rFIP-fve also decreased the PRRSV viremia with 1 log10 in titer (p = 0.07) and alleviated the severity of clinical signs after PRRSV challenge. Conclusively, these results illustrate the in vitro and in vivo immunological changes of rFIP-fve administered to pigs and reveal its potential to be used as an immunomodulatory therapeutic against PRRSV infection.

Optimization of the fermentation parameters for the production of Ganoderma lucidum immunomodulatory protein by Pichia pastoris

In order to obtain a better fermentation parameter for the production of recombinant Ganoderma lucidum immunomodulatory protein (rFIP-glu), an engineered Pichia pastoris GS115 was investigated on the fermentation time, temperature, methanol concentration and initial pH of media, while immunomodulatory activities of the rFIP-glu was confirmed. L₉(3³) orthogonal experiment were firstly employed to optimize various fermentation parameters in the shake-flask level. The optimized fermentation parameters were subsequently verified in a 5 L fermenter. Biological activities including cell viability and tumor necrosis factor-alpha (TNF-α) mRNA of the rFIP-glu were evaluated on murine macrophage RAW264.7 cells. The results showed that the yield of rFIP-glu was up to 368.71 μg/ml in the shake-flask, and 613.47 μg/ml in the 5 L fermenter, when the Pichia pastoris was incubated in basic media with the methanol concentration 1.0% and initial pH 6.5, and with constant shaking at 280 rpm for 4 days at 26 °C. In vitro assays of biological activity indicated that rFIP-glu had significant toxicity against RAW264.7 cells, and possessed the ability to induce TNF-α mRNA expression in macrophage RAW264.7 cells. In conclusion, engineered P. pastoris showed a good fermentation property under the optimum fermentation parameters. It could be a candidate industrial strain for further study.

Ganoderma proteins and their potential applications in cosmetics

Ganoderma have been regarded as a traditional source of natural bioactive compounds for centuries and have recently been exploited for potential components in the cosmetics industry. Besides Ganoderma polysaccharides and triterpenes, multiple proteins have been found in Ganoderma. With the in-depth study of these proteins, various pharmacological functions of Ganoderma have become important in the discovery and development of new products. In the review, we summarized and discussed the kinds and characteristics of Ganoderma proteins, especially on fungal immunomodulatory proteins (FIPs) which can be potentially developed into cosmeceuticals or nutricosmetics and are a suitable target for production using established biotechnological methods. Furthermore, we discuss their pharmacological activities of the proteins with a focus on their pharmacological functions related to cosmetics, such as antioxidant activity, inhibition of melanin, antibacterial activity, and regulation of inflammatory mediators. Numerous other questions also are addressed before the proteins can be widely accepted and used as cosmetic additives.

Recombinant Expression and Bioactivity Comparison of Four Typical Fungal Immunomodulatory Proteins from Three Main Ganoderma Species

Background

More than a dozen of fungal immunomodulatory proteins (FIPs) have been identified to date, most of which are from Ganoderma species. However, little is known about the similarities and differences between different Ganoderma FIPs’ bioactivities. In the current study, two FIP genes termed FIP-gap1 and FIP-gap2 from G. applanatum, along with LZ-8 and FIP-gsi, another two representative Ganoderma FIP genes from G. lucidum and G. sinense were functionally expressed in Pichia. Subsequently, bioactivities of four recombinant Ganoderma FIPs were demonstrated and compared.

Results

All the four Ganoderma FIP genes could be effectively expressed in P. pastoris GS115 at expression levels ranging from 197.5 to 264.3 mg L^− 1 and simply purified by one step chromatography using HisTrap™ FF prepack columns. Amino acid sequence analysis showed that they all possessed the FIP conserved fragments. The homologies of different Ganoderma FIPs were from 72.6 to 86.4%. In vitro haemagglutination exhibited that FIP-gap1, FIP-gsi and LZ-8 could agglutinate human, sheep and mouse red blood cells but FIP-gap2 agglutinated none. Besides, the immunomodulation activities of these Ganoderma FIPs were as: rFIP-gap2 > rFIP-gap1 > rLZ-8 and rFIP-gsi in terms of proliferation stimulation and cytokine induction on murine splenocytes. Additionally, the cytotoxic activity of different FIPs was: rFIP-gap1 > rLZ-8 > rFIP-gsi > rFIP-gap2, examined by their inhibition of three human carcinomas A549, Hela and MCF-7.

Conclusions

Taken together, four typical Ganoderma FIP genes could be functionally expressed in P. pastoris, which might supply as feasible efficient resources for further study and application. Both similarities and differences were indeed observed between Ganoderma FIPs in their amino acid sequences and bioactivities. Comprehensively, rFIP-gaps from G. applanatum proved to be more effective in immunomodulation and cytotoxic assays in vitro than rLZ-8 (G. lucidum) and rFIP-gsi (G. sinense).

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0488-0) contains supplementary material, which is available to authorized users.

Purification, identification and functional characterization of an immunomodulatory protein from Pleurotus eryngii

Pleurotus eryngii contains bioactive compounds that can activate the immune system. Here we report the identification, purification, and functional characterization of the bioactive P. eryngii protein (PEP) 1b. PEP 1b was discovered to be a 21.9 kDa protein with the ability to induce the M1-polarization of the macrophage cell line RAW 264.7 cells. Biochemical measurements showed that PEP 1b stimulated nitric oxide (NO), IL-1β, IL-6 and TNF-α production and regulated inducible NO synthase. Phosphorylation and inhibitor studies revealed that PEP 1b promoted the translocation of NF-kB from the cytosol to the nucleus allowing the induction of target gene expression and NO production. The phosphorylation of JNK and ERK1/2 was found to be necessary for NO production. Each phosphorylation pathway was found to require a Toll-like receptor (TLR) 4 as a prerequisite for PEP 1b-induced NO production. This study suggests that PEP 1b is an immunomodulatory protein that can boost cellular immune responses through the activation of the TLR4-NF-κB and MAPK signaling pathways.

Optimized Triton X-114 assisted lipopolysaccharide (LPS) removal method reveals the immunomodulatory effect of food proteins

SCOPE

Investigations into the immunological response of proteins is often masked by lipopolysaccharide (LPS) contamination. We report an optimized Triton X-114 (TX-114) based LPS extraction method for β-lactoglobulin (BLG) and soy protein extract suitable for cell-based immunological assays.

METHODS AND RESULTS

Optimization of an existing TX-114 based phase LPS extraction method resulted in >99% reduction of LPS levels. However, remaining TX-114 was found to interfere with LPS and protein concentration assays and decreased viability of THP-1 macrophages and HEK-Blue 293 cells. Upon screening a range of TX-114 extraction procedures, TX-114-binding beads were found to most effectively lower TX-114 levels without affecting protein structural properties. LPS-purified proteins showed reduced capacity to activate TLR4 compared to non-treated proteins. LPS-purified BLG did not induce secretion of pro-inflammatory cytokines from THP-1 macrophages, as non-treated protein did, showing that LPS contamination masks the immunomodulatory effect of BLG. Both HEK293 cells expressing TLR4 and differentiated THP-1 macrophages were shown as a relevant model to screen the protein preparations for biological effects of LPS contamination.

CONCLUSION

The reported TX-114 assisted LPS-removal from protein preparations followed by bead based removal of TX-114 allows evaluation of natively folded protein preparations for their immunological potential in cell-based studies.

FIP-sch2, a new fungal immunomodulatory protein from Stachybotrys chlorohalonata, suppresses proliferation and migration in lung cancer cells

Fungal immunomodulatory protein (FIP)-sch2, an immunomodulatory protein identified in the ascomycete Stachybotrys chlorohalonata by a sequence similarity search, is a novel member of the FIP family. FIP-sch2 shares high sequence identity, structure, and evolutionary conservation with previously reported FIPs. It was satisfactorily expressed in Escherichia coli with a glutathione S-transferase (GST) tag and purified by GST-affinity magnetic beads. To characterize the direct antitumor effects, human lung adenocarcinoma A549 cells were treated with different concentrations of recombinant FIP (rFIP)-sch2 in vitro, and the results showed that rFIP-sch2 could reduce cell viability dose-dependently with a half-maximal inhibitory concentration (IC₅₀) of 9.48 μg/mL. Furthermore, rFIP-sch2 at 8 μg/mL could significantly induce apoptosis and interrupt migration in A549 cells. Notably, the antitumor effect of rFIP-sch2 was equivalent to that of rLZ-8 but was obviously increased compared to rFIP-fve. In addition, the exploration of the antitumor mechanism suggested that rFIP-sch2 induced lung cancer cell death by activating apoptosis and inhibiting migration. Our results indicated that rFIP-sch2 was a promising candidate for use in future cancer therapy.

Identification and Characterisation of a Novel Protein FIP-sch3 from Stachybotrys chartarum

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.

Characterisation of a New Fungal Immunomodulatory Protein from Tiger Milk mushroom, Lignosus rhinocerotis

Lignosus rhinocerotis (Tiger milk mushroom) is an important folk medicine for indigenous peoples in Southeast Asia. We previously reported its de novo assembled 34.3 Mb genome encoding a repertoire of proteins including a putative bioactive fungal immunomodulatory protein. Here we report the cDNA of this new member (FIP-Lrh) with a homology range of 54–64% to FIPs from other mushroom species, the closest is with FIP-glu (LZ-8) (64%) from Ganoderma lucidum. The FIP-Lrh of 112 amino acids (12.59 kDa) has a relatively hydrophobic N-terminal. Its predicted 3-dimensional model has identical folding patterns to FIP-fve and contains a partially conserved and more positively charged carbohydrates binding pocket. Docking predictions of FIP-Lrh on 14 glycans commonly found on cellular surfaces showed the best binding energy of −3.98 kcal/mol to N-acetylgalactosamine and N-acetylglucosamine. Overexpression of a 14.9 kDa soluble 6xHisFIP-Lrh was achieved in pET-28a(+)/BL21 and the purified recombinant protein was sequence verified by LC-MS/MS (QTOF) analysis. The ability to haemagglutinate both mouse and human blood at concentration ≥0.34 μM, further demonstrated its lectin nature. In addition, the cytotoxic effect of 6xHisFIP-Lrh on MCF-7, HeLa and A549 cancer cell lines was detected at IC₅₀ of 0.34 μM, 0.58 μM and 0.60 μM, respectively.

Recombinant FIP-gat, a Fungal Immunomodulatory Protein from Ganoderma atrum, Induces Growth Inhibition and Cell Death in Breast Cancer Cells

FIP-gat, an immunomodulatory protein isolated from Ganoderma atrum, is a new member of the FIP family. Little is known, however, about its expressional properties and antitumor activities. It was availably expressed in Escherichia coli with a total yield of 29.75 mg/L. The migration of recombinant FIP-gat (rFIP-gat) on SDS-PAGE corresponded to the predicted molecular mass, and the band was correctly detected by a specific antibody. To characterize the direct effects of rFIP-gat on MDA-MB-231 breast cancer cells, MDA-MB-231 cells were treated with different concentrations of rFIP-gat in vitro; the results showed that this protein could reduce cell viability dose-dependently with a median inhibitory concentration (IC50) of 9.96 μg/mL and agglutinate the MDA-MB-231 cells at a concentration as low as 5 μg/mL. Furthermore, FIP-gat at a concentration of 10 μg/mL can induce significant growth inhibition and cell death in MDA-MB-231 cells. Notably, FIP-gat treatment triggers significant cell cycle arrest at the G1/S transition and pronounced increase in apoptotic cell population. Molecular assays based on microarray and real-time PCR further revealed the potential mechanisms encompassing growth arrest, apoptosis, and autophagy underlying the phenotypic effects.

Identification and functional characterization of a novel fungal immunomodulatory protein from Postia placenta

In this study, a previously unknown fungal immunomodulatory protein (FIP), here called FIP-ppl, was identified from the basidiomycete fungus Postia placenta by searching its genome sequence database using known FIPs as baits, which was the first basidiomycete FIP to be identified outside the order of edible macro fungi. The gene FIP-ppl was synthesized and expressed in Escherichia coli to produce a glutathione S-transferase (GST) fusion protein. The fusion protein was purified on a GST affinity column and the protein tag was removed using in situ thrombin cleavage. The purified recombinant protein (rFIP-ppl) displayed hemagglutination activity toward rabbit red blood cells but not against human red blood cells. RFIP-ppl stimulated mouse splenocyte cell proliferation and enhanced interleukin-2 (IL-2) release. Antitumor assays indicated that rFIP-ppl had significant cell proliferation inhibitory activity and apoptotic effects in human tumor cells with more pronounced inhibiting proliferation and inducing apoptotic effects on gastric tumor cells (MGC823) than against hepatoma (HepG2) cells. This study confirms an alternative means of identifying, producing, and isolating new FIPs. It may provide convenient access to FIP-ppl with potential human therapeutic applications.

Lectins from edible mushrooms

Mushrooms are famous for their nutritional and medicinal values and also for the diversity of bioactive compounds they contain including lectins. The present review is an attempt to summarize and discuss data available on molecular weights, structures, biological properties, N-terminal sequences and possible applications of lectins from edible mushrooms. It further aims to update and discuss/examine the recent advancements in the study of these lectins regarding their structures, functions, and exploitable properties. A detailed tabling of all the available data for N-terminal sequences of these lectins is also presented here.

Recombinant expression of a novel fungal immunomodulatory protein with human tumor cell antiproliferative activity from Nectria haematococca

To our best knowledge, all of the fungal immunomodulatory proteins (FIPs) have been successfully extracted and identified in Basidomycetes, with only the exception of FIP from ascomycete Nectria haematococca (FIP-nha) discovered through homology alignment most recently. In this work, a gene encoding FIP-nha was synthesized and recombinantly expressed in an Escherichia coli expression system. SDS-PAGE and MALDI-MS analyses of recombinant FIP-nha (rFIP-nha) indicated that the gene was successfully expressed. The yield of the bioactive FIP-nha protein was 42.7 mg/L. In vitro assays of biological activity indicated that the rFIP-nha caused hemagglutination of human and rabbit red blood cells, significantly stimulated mouse spleen lymphocyte proliferation, and enhanced expression of interleukin-2 (IL-2) released from mouse splenocytes, revealing a strong antitumor effect against HL60, HepG2 and MGC823. Through this work, we constructed a rapid and efficient method of FIP production, and suggested that FIP-nha is a valuable candidate for use in future medical care and pharmaceutical products.