Dolichyl-diphosphooligosaccharide--protein glycosyltransferase 48 kDa subunit

DDOST encodes the 48 kDa subunit of the oligosaccharyl transferase (OST) complex, which catalyzes the cotranslational transfer of a conserved glycan (Glc₃Man₉GlcNAc₂) from dolichol-pyrophosphate to asparagine residues within nascent proteins. This N-glycosylation reaction occurs at the endoplasmic reticulum translocon and requires all OST subunits for maximal activity (UniProt: P39656). The DDOST subunit is essential for assembly of both SST3A- and SST3B-containing OST complexes and functions in the context of protein folding and trafficking across the ER membrane.

Mutations in DDOST cause congenital disorder of glycosylation 1R (CDG1R; MIM 614507), a multisystem disease characterized by defective N-glycoprotein biosynthesis and presenting with neurological involvement, developmental delay, hypotonia, and immunodeficiency (UniProt: P39656). The critical role of N-glycosylation in neuronal development and function underscores the protein's relevance to nervous system pathology.

In Alzheimer's disease, DDOST is upregulated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics). The mean log2 fold-change is 0.37 across subcellular fractions in TMT-labeled quantitative proteomics, suggesting elevated OST complex capacity in the AD brain environment. Whether this reflects compensatory glycosylation stress or contributes to disease pathogenesis warrants further investigation.