Akt1 is dynamically modified with O-GlcNAc following treatments with PUGNAc and insulin-like growth factor-1

The Ser/Thr kinase Akt1 is activated by growth factors subsequent to its phosphorylation on Thr308 and Ser473. In the present study, Akt1 was found to be constitutively modified with O-GlcNAc. Treatment of SH-SY5Y cells with O(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), which inhibits the enzymatic removal of O-GlcNAc from proteins, increased cytosolic O-GlcNAc-Akt1 levels. Treatment of cells with insulin-like growth factor-1 (IGF-1) also increased O-GlcNAc-Akt1 levels and increased Akt1 phosphorylation. PUGNAc treatment did not attenuate IGF-1 induced Akt1 phosphorylation. These results indicate that Akt1 can be simultaneously modified with O-GlcNAc and phosphorylated. However, PUGNAc induced the nuclear accumulation of Akt1 suggesting that the O-GlcNAc-modification on Akt1 may play a role in Akt1 nuclear localization.