Translation inhibition in apoptosis: caspase-dependent PKR activation and eIF2-alpha phosphorylation

J Biol Chem. 2001 Nov 9;276(45):41620-8. doi: 10.1074/jbc.M103674200. Epub 2001 Sep 12.


The protein kinase PKR is a major player in the cellular antiviral response, acting mainly by phosphorylation of the alpha-subunit of the eukaryotic translation initiation factor 2 (eIF2-alpha) to block de novo protein synthesis. PKR activation requires binding of double-stranded RNA or PACT/RAX proteins to its regulatory domain. Since several reports have demonstrated that translation is inhibited in apoptosis, we investigated whether PKR and eIF2-alpha phosphorylation contribute to this process. We show that PKR is proteolysed and that eIF2-alpha is phosphorylated at the early stages of apoptosis induced by various stimuli. Both events coincide with the onset of caspase activity and are prevented by caspase inhibitors. Using site-directed mutagenesis we show that PKR is specifically proteolysed at Asp(251) during cellular apoptosis. This site is cleaved in vitro by recombinant caspase-3, caspase-7, and caspase-8 and not by the proinflammatory caspase-1 and caspase-11. The released kinase domain efficiently phosphorylates eIF2-alpha at the cognate Ser(51) residue, and its overexpression in mammalian cells impairs the translation of its own mRNA and of reporter mRNAs. Our results demonstrate a new and caspase-dependent activation mode for PKR, leading to eIF2-alpha phosphorylation and translation inhibition in apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis*
  • Caspases / physiology*
  • Enzyme Activation
  • Eukaryotic Initiation Factor-2 / metabolism*
  • Humans
  • Jurkat Cells
  • Phosphorylation
  • Protein Biosynthesis*
  • eIF-2 Kinase / metabolism*


  • Eukaryotic Initiation Factor-2
  • eIF-2 Kinase
  • Caspases