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Verathamjamras C, Sriwitool TE, Netsirisawan P, Chaiyawat P, Chokchaichamnankit D, Prasongsook N, Srisomsap C, Svasti J, Champattanachai V. Aberrant RL2 O-GlcNAc antibody reactivity against serum-IgA1 of patients with colorectal cancer. Glycoconjugate journal 2021 38(1) 33608772
Abstract:
O-GlcNAcylation, a single attachment of N-acetylglucosamine (GlcNAc) on serine and threonine residues, plays important roles in normal and pathobiological states of many diseases. Aberrant expression of O-GlcNAc modification was found in many types of cancer including colorectal cancer (CRC). This modification mainly occurs in nuclear-cytoplasmic proteins; however, it can exist in some extracellular and secretory proteins. In this study, we investigated whether O-GlcNAc-modified proteins are present in serum of patients with CRC. Serum glycoproteins of CRC patients and healthy controls were enriched by wheat germ agglutinin, a glycan binding protein specifically binds to terminal GlcNAc and sialic acid. Two-dimensional gel electrophoresis, RL2 O-GlcNAc immunoblotting, affinity purification, and mass spectrometry were performed. The results showed that RL2 O-GlcNAc antibody predominantly reacted against serum immunoglobulin A1 (IgA1). The levels of RL2-reacted IgA were significantly increased while total IgA were not different in patients with CRC compared to those of healthy controls. Analyses by ion trap mass spectrometry using collision-induced dissociation and electron-transfer dissociation modes revealed one O-linked N-acetylhexosamine modification site at Ser268 located in the heavy constant region of IgA1; unfortunately, it cannot be discriminated whether it was N-acetylglucosamine or N-acetylgalactosamine because of their identical molecular mass. Although failed to demonstrate unequivocally it was O-GlcNAc, these data indicated that serum-IgA had an aberrantly increased reactivity against RL2 O-GlcNAc antibody in CRC patients. This specific glycosylated form of serum-IgA1 will expand the spectrum of aberrant glycosylation which provides valuable information to cancer glycobiology.
O-GlcNAc proteins:
IGHA1
Species: Homo sapiens
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Netsirisawan P, Chaiyawat P, Chokchaichamnankit D, Lirdprapamongkol K, Srisomsap C, Svasti J, Champattanachai V. Decreasing O-GlcNAcylation affects the malignant transformation of MCF-7 cells via Hsp27 expression and its O-GlcNAc modification. Oncology reports 2018 40(4) 30106436
Abstract:
O-GlcNAcylation is a dynamic posttranslational modification of nucleoplasmic proteins. Previously, we reported that the O-GlcNAcylation level was increased in primary breast and colorectal cancer tissues. However, its precise roles in cancer development and progression are still largely unexplored. The aim of the present study was to investigate the roles of O-GlcNAcylation in the malignant transformation of cancer cell lines. O-GlcNAcylation level was examined in six cancer cell lines including breast (MCF-7 and MDA-MB-231), colorectal (SW480 and SW620), and liver (SK-Hep1 and HepG2). We found that the levels of O-GlcNAcylation and O-GlcNAc transferase (OGT), an O-GlcNAc catalyzing enzyme, were obviously increased in all cancerous cells, except SK-Hep1, when compared to normal cells. Reducing O-GlcNAcylation using RNA interference against OGT showed a marked reduction in OGT and O-GlcNAcylation levels. Surprisingly, siOGT had no effect on cell growth under conventional monolayer cultures. However, it inhibited anchorage-independent growth in soft agar cultures of all cancer cells, except SK-Hep1. Under anoikis resistance conditions performed by spheroid cultures, siOGT treatment decreased viability only in MCF-7, SW480, and SW620 cells. Among them, OGT knockdown in MCF-7 cells revealed a high inhibitory effect on colony and spheroid cultures. Using two-dimensional gel electrophoresis and mass spectrometric analysis, heat shock protein 27 (Hsp27) was found to be the highest upregulated protein upon OGT knockdown. Immunoblots revealed that the Hsp27 protein level was increased but its O-GlcNAc modification level was decreased in siOGT-treated cells. These changes were associated with the inhibition of MCF-7 cell transformation. Notably, double knockdown of OGT and Hsp27 showed a reversal in the inhibitory effect on colony and spheroid cultures. Collectively, these results indicate that O-GlcNAcylation is required for anoikis resistance and anchorage-independent growth of MCF-7 cells. Blocking this glycosylation by OGT knockdown may regulate both Hsp27 protein expression and its O-GlcNAc modification levels. This alteration may play vital roles in malignant transformation.