Effect of brain ischemia and reperfusion on the localization of phosphorylated eukaryotic initiation factor 2 alpha.
Postischemic brain reperfusion is associated with a substantial and long-lasting reduction of protein synthesis in selectively vulnerable neurons. Because the overall translation initiation rate is typically regulated by altering the phosphorylation of serine 51 on the alpha-subunit of eukaryotic initiation factor 2 (eIF-2 alpha), we used an antibody specific to phosphorylated eIF-2 alpha [eIF-2(alpha P)] to study the regional and cellular distribution of eIF-2(alpha P) in normal, ischemic, and reperfused rat brains. Western blots of brain postmitochondrial supernatants revealed that approximately 1% of all eIF-2 alpha is phosphorylated in controls, eIF-2(alpha P) is not reduced by up to 30 minutes of ischemia, and eIF-2(alpha P) is increased approximately 20-fold after 10 and 90 minutes of reperfusion. Immunohistochemistry shows localization of eIF-2(alpha P) to astrocytes in normal brains, a massive increase in eIF-2(alpha P) in the cytoplasm of neurons within the first 10 minutes of reperfusion, accumulation of eIF-2(alpha P) in the nuclei of selectively vulnerable neurons after 1 hour of reperfusion, and morphology suggesting pyknosis or apoptosis in neuronal nuclei that continue to display eIF-2(alpha P) after 4 hours of reperfusion. These observations, together with the fact that eIF-2(alpha P) inhibits translation initiation, make a compelling case that eIF-2(alpha P) is responsible for reperfusion-induced inhibition of protein synthesis in vulnerable neurons.
DeGracia
D J
DJ
Department of Emergency Medicine, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Sullivan
J M
JM
Neumar
R W
RW
Alousi
S S
SS
Hikade
K R
KR
Pittman
J E
JE
White
B C
BC
Rafols
J A
JA
Krause
G S
GS
D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D010766:Phosphorylation; D051381:Rats; D015427:Reperfusion Injury / Q000378:metabolism*; D019892:eIF-2 Kinase / Q000032:analysis / Q000378:metabolism*
D019892:eIF-2 Kinase