DAG1 glycosylations

Dystroglycan, encoded by the gene DAG1, can be cleaved into two proteins, alpha-DAG1 (chain 30-653) and beta-DAG1 (chain 654-895). Alpha-dystroglycan (here designated as DAG1(30-653)) is a cell surface protein that plays an important role in the assembly of the extracellular matrix in muscle, brain, and peripheral nerves by linking the basal lamina to cytoskeletal proteins. Alpha-DAG1(30-653) binds with high affinity to the extracellular matrix component laminin, and the intracellular domain of beta-DAG1(654-895) binds to the cytoskeletal protein dystrophin. Glycosylation is essential for DAG1(30-653) function. DAG1(30-653) is the best characterized O-mannosylated mammalian protein. O-mannose glycans are initiated on DAG1 by the covalent attachment of mannose to serine and threonine residues via an alpha-linkage. Extended O-mannose glycans divide into three categories based on known GlcNAc residue extensions of the initiating mannose (cores M1−M3). The biosynthesis of the three categories are described here. We arbitrarily chose Thr-423, -481 and -367 for these modifications (see Tran et al., 2012 for justification). The M1, M2, and M3 reactions, that run in parallel in the cell, are listed here in a single linear order with their intermediates for display purposes.

Summary from Reactome (R-HSA-8931838), read 2026-09-23.