A Novel Core Fucose-specific Lectin from the Mushroom Pholiota squarrosa

Fuc alpha 1-6 oligosaccharide has a variety of biological functions and serves as a biomarker for hepatocellular carcinoma because of the elevated presence of fucosylated alpha-fetoprotein ( AFP) in this type of cancer. In this study we purified a novel Fuc alpha 1-6-specific lectin from the mushroom Pholiota squarrosa by ion-exchange chromatography and affinity chromatography on thyroglobulin-agarose. The purified lectin was designated as PhoSL ( P. squarrosa lectin). SDS-PAGE, MALDI-TOF mass spectrometry, and N-terminal amino acid sequencing indicate that PhoSL has a molecular mass of 4.5 kDa and consists of 40 amino acids (NH2-APVPVTKLVCDGDTYKCTAYLDFGDGRWVAQWDTNVFHTG-OH). Isoelectric focusing of the lectin showed bands near pI 4.0. The lectin activity was stable between pH 2.0 and 11.0 and at temperatures ranging from 0 to 100 degrees C for incubation times of 30 min. When PhoSL was investigated with frontal affinity chromatography using 132 pyridylaminated oligosaccharides, it was found that the lectin binds only to core alpha 1-6-fucosylated N-glycans and not to other types of fucosylated oligosaccharides, such as alpha 1-2-, alpha 1-3-, and alpha 1-4-fucosylated glycans. Furthermore, PhoSL bound to alpha 1-6-fucosylated AFP but not to non-fucosylated AFP. In addition, PhoSL was able to demonstrate the differential expression of alpha 1-6fucosylation between primary and metastatic colon cancer tissues. Thus, PhoSL will be a promising tool for analyzing the biological functions of alpha 1-6 fucosylation and evaluating Fuc alpha 1-6 oligosaccharides as cancer biomarkers.