protein O-linked glycosylation

Definition

Target type: biologicalprocess

A protein glycosylation process in which a carbohydrate or carbohydrate derivative unit is added to a protein via the hydroxyl group of peptidyl-serine, peptidyl-threonine, peptidyl-hydroxylysine, or peptidyl-hydroxyproline, or via the phenol group of peptidyl-tyrosine, forming an O-glycan. [GOC:pr, ISBN:0879695595, RESID:AA0153, RESID:AA0154, RESID:AA0155, RESID:AA0157, RESID:AA0212]

O-linked glycosylation is a crucial post-translational modification that involves the attachment of sugar molecules to the hydroxyl group of serine or threonine residues in proteins. Unlike N-linked glycosylation, which occurs in the endoplasmic reticulum, O-linked glycosylation predominantly takes place in the Golgi apparatus. This process is mediated by glycosyltransferases, enzymes that catalyze the transfer of specific sugar moieties from donor molecules, such as UDP-sugars, to the target protein.

The first step in O-linked glycosylation typically involves the transfer of N-acetylglucosamine (GlcNAc) from UDP-GlcNAc to the hydroxyl group of a serine or threonine residue, forming an O-GlcNAc modification. This modification can occur on cytoplasmic and nuclear proteins, and it plays a role in various cellular processes, including signal transduction, gene expression, and protein stability.

After the initial GlcNAc attachment, a variety of other sugars can be added to the growing glycan chain, including galactose, fucose, sialic acid, and N-acetylgalactosamine (GalNAc). The specific sugar modifications and their arrangement are determined by the glycosyltransferases present in the Golgi apparatus and by the specific protein being glycosylated.

O-linked glycosylation can be further categorized into different types based on the core sugar structure and the linkage to the protein. For example, mucin-type O-glycosylation is characterized by the attachment of GalNAc to serine or threonine residues, followed by the addition of various other sugars. This type of glycosylation is prevalent in mucins, which are proteins that line the surfaces of epithelial tissues and play a role in lubrication and protection.

Another type of O-glycosylation involves the attachment of GlcNAc to serine or threonine residues in specific proteins, such as the epidermal growth factor receptor (EGFR). This modification can influence the receptor's activity and signaling pathways.

O-linked glycosylation is a highly regulated process, and dysregulation of this modification has been implicated in various diseases, including cancer, diabetes, and inflammatory disorders. Understanding the complexities of O-linked glycosylation and its role in cellular functions is essential for developing therapeutic strategies targeting this crucial post-translational modification.'
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Proteins (13)

Compounds (30)