The Role of Glycans and Glycosyltransferases Involved in N-glycan Branching in Cancer, COPD, Alzheimer's Disease, and Redox Regulation.

Glycosyltransferases that biosynthesize glycans and their genes (glycogenes) play important roles in health and disease. In general, pathophysiological changes are defined by comparing knock-out (KO) or knock-in mice generated using CRISPR-Cas9 and other technologies to normal mice. Next, target molecules such as glycoproteins, glycolipids, and proteoglycans to which various biosynthetic glycans bind were identified. As a result, we found that N-glycan branches biosynthesized by glycosyltransferases are intrinsically involved in Alzheimer's disease, cancer metastasis, epithelial mesenchymal transition (EMT)/mesenchymal epithelial transition (MET), type 2 diabetes, chronic obstructive pulmonary disease (COPD), and ulcerative colitis. For example, the addition of core fucose biosynthesized by α1,6-fucosyltransferase (Fut8) leads to dysregulation of TGF-β receptors. Bisecting N-acetylglucosamine (GlcNAc) biosynthesized by β-1,4-GlcNAc transferase III (GnT-III) affects the subcellular localization of Beta-site Amyloid Precursor Protein Cleaving Enzyme 1 (β-secretase 1, referred to as BACE1). β1,6GlcNAc branching biosynthesized by GnT-V leads to the modification of matrix metalloproteinase (MMP). Identification and characterization of N-glycan structures on these proteins were performed using a glycoproteomic approach based on lectin blotting, western blotting, liquid chromatography-electron spray ionization mass spectrometry, and histochemical staining. Recently, studies concerning redox regulation of N-glycans, termed Glyco-Redox, have emerged as a promising approach. Functional and pathophysiological glycan studies are one of the main goals of glycobiology research. In this review, we describe the role of N-glycan branching glycosyltransferases and their biosynthesized glycans in relation to various diseases, such as cancer metastasis, COPD, Alzheimer's disease, and ulcerative colitis.