Biochem. J. (2006) 397
(187–194) (Printed in Great Britain)
Phosphorylation of the a subunit of translation initiation factor-2 by PKR mediates protein synthesis inhibition in the mouse brain during status epilepticus
Larissa S. CARNEVALLI*1,2, Catia M. PEREIRA*1, Carolina B. JAQUETA†, Viviane S. ALVES*, Vanessa N. PAIVA*, Krishna M. VATTEM‡, Ronald C. WEK‡, Luiz Eugênio A. M. MELLO† and Beatriz A. CASTILHO*3
*Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, Rua Botucatu, 862, São Paulo, SP 04023-062, Brazil, †Departamento de Fisiologia, Universidade Federal de São Paulo, Rua Botucatu, 862, São Paulo, SP, Brazil, and ‡Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, U.S.A.
In response to different cellular stresses, a family of protein kinases phosphorylates eIF2a (a subunit of eukaryotic initiation factor-2), contributing to regulation of both general and genespecific translation proposed to alleviate cellular injury or alternatively induce apoptosis. Recently, we reported eIF2a(P) (phosphorylated eIF2a) in the brain during SE (status epilepticus) induced by pilocarpine in mice, an animal model of TLE (temporal lobe epilepsy) [Carnevalli, Pereira, Longo, Jaqueta, Avedissian, Mello and Castilho (2004) Neurosci. Lett. 357, 191–194]. We show in the present study that one eIF2a kinase family member, PKR (double-stranded-RNA-dependent protein kinase), is activated in the cortex and hippocampus at 30 min of SE, reflecting the levels of eIF2a(P) in these areas. In PKR-deficient animals subjected to SE, eIF2a phosphorylation was clearly evident coincident with activation of a secondary eIF2a kinase, PEK/PERK (pancreatic eIF2a kinase/RNA-dependent-protein-kinase-like endoplasmic reticulum kinase), denoting a compensatory mechanism between the two kinases. The extent of eIF2a phosphorylation correlated with the inhibition of protein synthesis in the brain, as determined from polysome profiles. We also found that C57BL/6 mice, which enter SE upon pilocarpine administration but are more resistant to seizure-induced neuronal degeneration, showed very low levels of eIF2a(P) and no inhibition of protein synthesis during SE. These results taken together suggest that PKR-mediated phosphorylation of eIF2a contributes to inhibition of protein synthesis in the brain during SE and that sustained high levels of eIF2a phosphorylation may facilitate ensuing cell death in the most affected areas of the brain in TLE.
Key words: double-stranded-RNA-dependent protein kinase (PKR), pilocarpine, status epilepticus, a subunit of eukaryotic initiation factor-2 (eIF2a), temporal lobe epilepsy model, translation initiation.
Abbreviations used: ATF4, activating transcription factor 4; dsRNA, double-stranded RNA; eIF2a, a subunit of eukaryotic initiation factor-2; eIF2a(P), phosphorylated eIF2a; 4E-BP1, eIF4E-binding protein 1; ER, endoplasmic reticulum; GADD34, growth-arrest and DNA-damage-inducible protein 34; HRI, haem-regulated eIF2a kinase; HRP, horseradish peroxidase; IRES, internal ribosomal entry site; ISR, integrated stress response; PKR, dsRNA-dependent protein kinase; PEK/PERK, pancreatic eIF2a kinase/RNA-dependent-protein-kinase-like ER kinase; PACT, PKR-activating protein; PP1, protein phosphatase 1; RPL32, ribosomal protein L32; SE, status epilepticus; TLE, temporal lobe epilepsy.
1These authors have contributed equally to this work.
2Present address: Genome Research Institute, University of Cincinnati, Cincinnati, OH, U.S.A.
3To whom correspondence should be addressed (email bac@ecb.epm.br).
Received 8 October 2005/13 February 2006; accepted 22 February 2006
Published as BJ Immediate Publication 22 February 2006, doi:10.1042/BJ20051643
The Biochemical Society, London ©2006
Editorial Advisory Panel
RSS feeds
Table of contents by email
My BJ toolbox
