Double-stranded RNA-dependent protein kinase phosphorylation of the alpha-subunit of eukaryotic translation initiation factor 2 mediates apoptosis.
As the molecular processes of complex cell stress signaling pathways are defined, the subsequent challenge is to elucidate how each individual event influences the final biological outcome. Phosphorylation of the translation initiation factor 2 (eIF2alpha)atSer(51) is a molecular signal that inhibits translation in response to activation of any of four diverse eIF2alpha stress kinases. We used gene targeting to replace the wild-type Ser(51) allele with an Ala in the eIF2alpha gene to test the hypothesis that translational control through eIF2alpha phosphorylation is a central death stimulus in eukaryotic cells. Homozygous eIF2alpha mutant mouse embryo fibroblasts were resistant to the apoptotic effects of dsRNA, tumor necrosis factor-alpha, and serum deprivation. TNFalpha treatment induced eIF2alpha phosphorylation and activation of caspase 3 primarily through the dsRNA-activated eIF2alpha kinase PKR. In addition, expression of a phospho-mimetic Ser(51) to Asp mutant eIF2alpha-activated caspase 3, indicating that eIF2alpha phosphorylation is sufficient to induce apoptosis. The proapoptotic effects of PKR-mediated eIF2alpha phosphorylation contrast with the anti-apoptotic response upon activation of the PKR-related endoplasmic reticulum eIF2alpha kinase, PERK. Therefore, divergent fates of death and survival can be mediated through phosphorylation at the same site within eIF2alpha. We propose that eIF2alpha phosphorylation is fundamentally a death signal, yet it may promote either death or survival, depending upon coincident signaling events.
Scheuner
Donalyn
D
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650.
Patel
Rupali
R
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650.
Wang
Feng
F
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650.
Lee
Kuei
K
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650.
Kumar
Kotlo
K
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650.
Wu
Jun
J
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650.
Nilsson
Anders
A
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650.
Karin
Michael
M
Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636.
Kaufman
Randal J
RJ
Departments of Biological Chemistry, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650; Departments of Internal Medicine, Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan 48109-0650. Electronic address: kaufmanr@umich.edu.
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000737:chemistry; D015852:Eukaryotic Initiation Factor-2 / Q000502:physiology*; D006367:HeLa Cells; D006720:Homozygote; D006801:Humans; D051379:Mice; D010766:Phosphorylation; D012330:RNA, Double-Stranded / Q000737:chemistry; D014162:Transfection; D019892:eIF-2 Kinase / Q000737:chemistry*
D015852:Eukaryotic Initiation Factor-2; D012330:RNA, Double-Stranded; D004247:DNA; D019892:eIF-2 Kinase; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases