Dynamic Cytoskeletal Glycosylation and Neurodegenerative Disease

O-GlcNAcylation of nucleoplasmic and cytoplasmic proteins is a ubiquitous and highly dynamic modification. It entails the attachment of a single O-linked N-acetylglucosamine (O-GlcNAc) moiety O-glycosidically linked to side-chain hydroxyls of serine and threonine residues. The rapidly expanding list of O-GlcNAcylated proteins includes RNA Polymerase II, nuclear pore, heat shock, and tumor suppressor proteins, nuclear oncogenes, and numerous cytoskeletal and membrane associated proteins. Many sites of O-GlcNAc addition are similar to consensus sites of protein phosphorylation, and in some cases identical. Accordingly, O-GlcNAcylation and O-phosphorylation appear to be reciprocally related on some proteins. All O-GlcNAcylated proteins are phosphoproteins which assemble into tightly regulated reversible multi-protein complexes. Several O-GlcNAcylated proteins are key components involved in cytoskeletal assembly and organization, and defects in their regulated multimerization are implicated in several neurodegenerative disorders. Thus, abnormal cytoskeletal O-GlcNAcylation may promote defects in regulated protein multimerization and potentiate disease.