PMID: 21500857

 

    Legend: Sugar

Title : A novel post-translational modification in nerve terminals: O-linked N-acetylglucosamine phosphorylation.

Abstract :
  1. Protein phosphorylation and glycosylation are the most common post-translational modifications observed in biology, frequently on the same protein
  2. Assembly protein AP180 is a synapse-specific phosphoprotein and O-linked beta-N-acetylglucosamine (O-GlcNAc) modified glycoprotein
  3. AP180 is involved in the assembly of clathrin coated vesicles in synaptic vesicle endocytosis
  4. Unlike other types of O-glycosylation, O-GlcNAc is nucleocytoplasmic and reversible
  5. It was thought to be a terminal modification, that is, the O-GlcNAc was not found to be additionally modified in any way
  6. We now show that AP180 purified from rat brain contains a phosphorylated O-GlcNAc (O-GlcNAc-P) within a highly conserved sequence
  7. O-GlcNAc or O-GlcNAc-P, but not phosphorylation alone, was found at Thr-310
  8. Analysis of synthetic GlcNAc-6-P produced identical fragmentation products to GlcNAc-P from AP180
  9. Direct O-linkage of GlcNAc-P to a Thr residue was confirmed by electron transfer dissociation MS. A second AP180 tryptic peptide was also glycosyl phosphorylated, but the site of modification was not assigned
  10. Sequence similarities suggest there may be a common motif within AP180 involving glycosyl phosphorylation and dual flanking phosphorylation sites within 4 amino acid residues
  11. This novel type of protein glycosyl phosphorylation adds a new signaling mechanism to the regulation of neurotransmission and more complexity to the study of O-GlcNAc modification.