Expression and in vitro anticancer activity of Lp16-PSP, a member of the YjgF/YER057c/UK114 protein family from the mushroom Lentinula edodes C91-3

Abstract

Latcripin-16 (Lp16-PSP) is a gene that was extracted as a result of de novo characterization of the Lentinula edodes strain C91-3 transcriptome. The aim of the present study was to clone, express, and investigate the selective in vitro anticancer potential of Lp16-PSP in human cell lines. Lp16-PSP was analyzed using bioinformatics tools, cloned in a prokaryotic expression vector pET32a (+) and transformed into E. coli Rosetta gami. It was expressed and solubilized under optimized conditions. The differential scanning fluorometry (DSF)-guided refolding method was used with modifications to identify the proper refolding conditions for the Lp16-PSP protein. To determine the selective anticancer potential of Lp16-PSP, a panel of human cancerous and non-cancerous cell lines was used. Lp16-PSP protein was identified as endoribonuclease L-PSP protein and a member of the highly conserved YjgF/YER057c/UK114 protein superfamily. Lp16-PSP was expressed under optimized conditions (37°C for 4h following induction with 0.5mM isopropyl β-D-1-thiogalactopyranoside). Solubilization was achieved with mild solubilization buffer containing 2M urea using the freeze-thaw method. The DSF guided refolding method identified the proper refolding conditions (50mM Tris-HCl, 100mM NaCl, 1mM EDTA, 400mM Arginine, 0.2mM GSH and 2mM GSSG; pH 8.0) for Lp16-PSP, with a melting transition of ~ 58°C. A final yield of ~ 16mg of purified Lp16-PSP from 1L of culture was obtained following dialysis and concentration by PEG 20,000. A Cell Counting Kit-8 assay revealed the selective cytotoxic effect of Lp16-PSP. The HL-60 cell line was demonstrated to be most sensitive to Lp16-PSP, with an IC50 value of 74.4 ± 1.07µg/ml. The results of the present study suggest that Lp16-PSP may serve as a potential anticancer agent; however, further investigation is required to characterize this anticancer effect and to elucidate the molecular mechanism underlying the action of Lp16-PSP.