Caspase-mediated cleavage of eukaryotic translation initiation factor subunit 2alpha.
Eukaryotic translation initiation factor 2alpha (eIF-2alpha), a target molecule of the interferon-inducible double-stranded-RNA-dependent protein kinase (PKR), was cleaved in apoptotic Saos-2 cells on treatment with poly(I).poly(C) or tumour necrosis factor alpha. This cleavage occurred with a time course similar to that of poly(ADP-ribose) polymerase, a well-known caspase substrate. In addition, eIF-2alpha was cleaved by recombinant active caspase-3 in vitro. By site-directed mutagenesis, the cleavage site was mapped to an Ala-Glu-Val-Asp(300) downward arrowGly(301) sequence located in the C-terminal portion of eIF-2alpha. PKR phosphorylates eIF-2alpha on Ser(51), resulting in the suppression of protein synthesis. PKR-mediated translational suppression was repressed when the C-terminally cleaved product of eIF-2alpha was overexpressed in Saos-2 cells, even though PKR can phosphorylate this cleaved product. These results suggest that caspase-3 or related protease(s) can modulate the efficiency of protein synthesis by cleaving the alpha subunit of eIF-2, a key component in the initiation of translation.
Satoh
S
S
Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Hijikata
M
M
Handa
H
H
Shimotohno
K
K
D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011070:Poly I-C / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D014176:Protein Biosynthesis; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019892:eIF-2 Kinase / Q000378:metabolism
D061945:Caspase Inhibitors; D015852:Eukaryotic Initiation Factor-2; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; D010768:Phosphoserine; D003513:Cycloheximide; D011065:Poly(ADP-ribose) Polymerases; D019892:eIF-2 Kinase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D011070:Poly I-C