Title : A novel post-translational modification in nerve terminals: O-linked N-acetylglucosamine phosphorylation
Abstract :
- Protein phosphorylation and glycosylation are the most common post-translational modifications observed in biology, frequently on the same protein
- Assembly protein AP180 is a synapse-specific phosphoprotein and O-linked beta-N-acetylglucosamine (O-GlcNAc) modified glycoprotein
- AP180 is involved in the assembly of clathrin coated vesicles in synaptic vesicle endocytosis
- Unlike other types of O-glycosylation, O-GlcNAc is nucleocytoplasmic and reversible
- It was thought to be a terminal modification, that is, the O-GlcNAc was not found to be additionally modified in any way
- We now show that AP180 purified from rat brain contains a phosphorylated O-GlcNAc (O-GlcNAc-P) within a highly conserved sequence
- O-GlcNAc or O-GlcNAc-P, but not phosphorylation alone, was found at Thr-310
- Analysis of synthetic GlcNAc-6-P produced identical fragmentation products to GlcNAc-P from AP180
- 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
- Sequence similarities suggest there may be a common motif within AP180 involving glycosyl phosphorylation and dual flanking phosphorylation sites within 4 amino acid residues
- 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
Output (sent_index, trigger,
protein,
sugar,
site):
- 2. glycoprotein, , glycoprotein, -, -
- 6. contains, , AP180, O-GlcNAc-P, -
- 6. contains, , AP180, a phosphorylated O-GlcNAc, -
- 7. found, , -, O-GlcNAc-P, Thr-310
- 7. found, , -, O-GlcNAc, Thr-310
- 8. AP180, , AP180, GlcNAc-P, -
Output(Part-Of) (sent_index,
protein,
site):
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):
- 7. AP180, O-GlcNAc-P, Thr-310
- 7. AP180, O-GlcNAc, Thr-310