O-glycan processing

Definition

Target type: biologicalprocess

The stepwise addition of carbohydrate or carbohydrate derivative residues to the initially added O-linked residue (usually GalNAc) to form a core O-glycan structure. [GOC:mah, GOC:pr, PMID:10580130]

O-glycan processing is a complex and essential biological process that involves the synthesis, modification, and degradation of O-linked glycans, which are sugar chains attached to serine or threonine residues of proteins. The process begins in the endoplasmic reticulum (ER), where O-glycosylation, the attachment of the first sugar, N-acetylglucosamine (GlcNAc), to the protein backbone occurs. This step is catalyzed by an enzyme called polypeptide N-acetylgalactosaminyltransferase (ppGalNAcT).

After the initial GlcNAc attachment, the O-glycan undergoes a series of modifications and extensions in the Golgi apparatus, a cellular compartment responsible for protein sorting and modification. These modifications include the addition of various sugar residues, such as galactose, fucose, sialic acid, and N-acetylglucosamine, by specific glycosyltransferases.

The specific structure and sequence of sugar residues in an O-glycan are determined by the interplay of multiple factors, including the specific protein substrate, the expression and activity of glycosyltransferases and glycosidases, and the cellular environment.

O-glycan processing plays a crucial role in various biological processes, including:
- Protein folding and stability: O-glycans can influence protein structure and prevent aggregation.
- Cell signaling: O-glycans can act as receptors for extracellular ligands and modulate signaling pathways.
- Cell adhesion and migration: O-glycans are involved in cell-cell and cell-matrix interactions, influencing cell adhesion and movement.
- Immune recognition: O-glycans on the surface of cells can be recognized by immune cells and influence immune responses.

Defects in O-glycan processing can lead to various diseases, including cancer, inflammation, and developmental disorders. Understanding the intricate mechanisms of O-glycan processing is crucial for developing novel therapeutic strategies targeting these diseases.'
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Proteins (18)

Compounds (17)