Brain ischemia and reperfusion activates the eukaryotic initiation factor 2alpha kinase, PERK.
Reperfusion after global brain ischemia results initially in a widespread suppression of protein synthesis in neurons, which persists in vulnerable neurons, that is caused by the inhibition of translation initiation as a result of the phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 (eIF2alpha). To identify kinases responsible for eIF2alpha phosphorylation [eIF2alpha(P)] during brain reperfusion, we induced ischemia by bilateral carotid artery occlusion followed by post-ischemic assessment of brain eIF2alpha(P) in mice with homozygous functional knockouts in the genes encoding the heme-regulated eIF2alpha kinase (HRI), or the amino acid-regulated eIF2alpha kinase (GCN2). A 10-fold increase in eIF2alpha(P) was observed in reperfused wild-type mice and in the HRI-/- or GCN2-/- mice. However, in all reperfused groups, the RNA-dependent protein kinase (PKR)-like endoplasmic reticulum eIF2alpha kinase (PERK) exhibited an isoform mobility shift on SDS-PAGE, consistent with the activation of the kinase. These data indicate that neither HRI nor GCN2 are required for the large increase in post-ischemic brain eIF2alpha(P), and in conjunction with our previous report that eIF2alpha(P) is produced in the brain of reperfused PKR-/- mice, provides evidence that PERK is the kinase responsible for eIF2alpha phosphorylation in the early post-ischemic brain.
Kumar
R
R
Department of Emergency Medicine, Wayne State University, Detroit, Michigan 48201, USA.
Azam
S
S
Sullivan
J M
JM
Owen
C
C
Cavener
D R
DR
Zhang
P
P
Ron
D
D
Harding
H P
HP
Chen
J J
JJ
Han
A
A
White
B C
BC
Krause
G S
GS
DeGracia
D J
DJ
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D011233:Precipitin Tests; D015427:Reperfusion Injury / Q000378:metabolism*; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism*
D019892:eIF-2 Kinase