Terminal sialic acid on cell-surface sialoglycan

Terminal sialic acid is a negatively charged nine-carbon monosaccharide found at the outermost (terminal) position of glycan chains on cell-surface glycoproteins and glycolipids, forming sialoglycans[2][5]. Sialic acids mediate key biological processes by modulating cell–cell adhesion, migration, signal transduction, protection from proteases and glycosidases, and by masking underlying antigens, thereby preventing recognition by immune lectins and receptors[6][5][1]. These terminal sugars act as critical ligands for sialic acid-binding immunoglobulin-like lectins (Siglecs), which function as immune regulators, and for selectins, which regulate cellular trafficking and inflammation[4][6]. Sialylation, the process of adding sialic acids to glycan chains, profoundly influences cell fate, clearance from circulation, and recognition of “self” by the immune system[4][7]. Aberrations in terminal sialic acid expression are associated with tumor immune evasion, enhanced metastatic behavior, infectious disease mechanisms, and chronic inflammation, making them an emerging therapeutic target and disease biomarker[7][2][1][4].

Other names

Terminal sialic acidCell-surface sialic acidCell-surface sialoglycan terminal sialic acidSialoglycan terminal sugar

Inhibiting terminal sialic acid or its synthetic enzymes can unmask Siglecs, leading to altered immune recognition or clearance by immune cells. Blocking sialylation can reduce masking of “self” and enhance immune attack on cancerous or infected cells. Inhibition enhances complement activation or opsonization. Some therapies may block cancer cell rolling/adhesion by interfering with selectin–sialoglycan interactions.