Differential phosphorylation at Ser473 and Thr308 of Akt-1 in rat brain following hypoglycemic coma.

We analyzed both total Akt-1 and phosphorylation of Akt-1 at residues Ser473 and Thr308 (phospho-Akt-1(Ser474) and phospho-Akt-1(Thr308), respectively) in the outer and inner layers of cortex following 30 min of hypoglycemic coma by Western blot analyses and confocal microscopy. The total amount of Akt-1 was not altered in any area examined. Phospho-Akt-1(Ser474), however, increased significantly in both layers of cortex at 0 and 30 min of recovery, but returned to control level at 3 h of recovery. In the vulnerable area (outer layer of cortex), no upregulation of phospho-Akt-1(Thr308) was observed at any time points examined. In the resistant area like inner layer of cortex, however, phospho-Akt-1(Thr308) was significantly over the control level at 3 h of recovery. Confocal microscopy result indicates that most of phospho-Akt-1(Thr308) had already moved into nucleus at 3 h of recovery. Our results suggest that Akt-1, when phosphorylated at Thr308, may play a protective role for neurons in the resistant regions of the brain.