Core 1 O-glycan and extended Core 1 O-glycan

Core 1 O-glycan is a fundamental carbohydrate structure found on O-glycosylated proteins, most commonly on mucins and a variety of serum glycoproteins[1][7][8][10]. Its canonical form, known as the T-antigen, consists of a galactose (Gal) β1-3 linked to N-acetylgalactosamine (GalNAc), which is attached via O-linkage to serine or threonine residues in proteins[1][7][8][10]. This structure can be further modified by the addition of sialic acid, fucose, or converted into more complex forms including branched (core 2) or elongated ("extended core 1") variants[1][3][7]. Core 1 and its extended forms play critical roles in mediating cell–cell adhesion, recognition, immune cell trafficking, and serve as essential ligands for selectins during inflammation and immune responses[1][3][9]. Abnormalities in the expression, sialylation, or branching of core 1/extended core 1 O-glycans are implicated in cancer, inflammatory bowel disease, and immune dysfunctions[8][9]. Core 1 O-glycans are produced by the enzyme core 1 β1–3 galactosyltransferase (T-synthase), which requires the molecular chaperone Cosmc for activity[8]. The term "Core 1 and extended Core 1 O-glycans" refers to glycan motifs and is not a single discrete therapeutic target, receptor, enzyme, or transporter; thus, it is not itself a conventional drug target[1][3][7][8]. Notes on correctness: This entry groups together a core glycan structure (Core 1 O-glycan, T antigen) and its extended/branched forms, which are not single molecules or protein-based targets but classes of carbohydrate motifs found on many glycoproteins. While essential for cell biology and disease, they are not typical therapeutic targets like receptors or enzymes. Therapies may target glycosylated proteins that bear these motifs, but not the glycan structure itself[1][3].

Other names

T antigen (for Core 1)Galβ1-3GalNAc-O-Ser/Thr (for Core 1)extended core 1 O-glycan