Abstract |
Heat shock results in inhibition of general protein synthesis. In thermotolerant cells, protein synthesis is still rapidly inhibited by heat stress, but protein synthesis recovers faster than in naive heat-shocked cells, a phenomenon known as translational thermotolerance. Here we investigate the effect of overexpressing a single heat shock protein on cap-dependent and cap-independent initiation of translation during recovery from a heat shock. When overexpressing alphaB-crystallin or Hsp27, cap-dependent initiation of translation was protected but no effect was seen on cap-independent initiation of translation. When Hsp70 was overexpressed however, both cap-dependent and -independent translation were protected. This finding indicates a difference in the mechanism of protection mediated by small or large heat shock proteins. Phosphorylation of alphaB-crystallin and Hsp27 is known to significantly decrease their chaperone activity; therefore, we tested phosphorylation mutants of these proteins in this system. AlphaB-crystallin needs to be in its non-phosphorylated state to give protection, whereas phosphorylated Hsp27 is more potent in protection than the unphosphorylatable form. This indicates that chaperone activity is not a prerequisite for protection of translation by small heat shock proteins after heat shock. Furthermore, we show that in the presence of 2-aminopurine, an inhibitor of kinases, among which is double-stranded RNA-activated kinase, the protective effect of overexpressing alphaB-crystallin is abolished. The synthesis of the endogenous Hsps induced by the heat shock to test for thermotolerance is also blocked by 2-aminopurine. Most likely the protective effect of alphaB-crystallin requires synthesis of the endogenous heat shock proteins. Translational thermotolerance would then be a co-operative effect of different heat shock proteins.
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Authors | Linda Doerwald, Carla Onnekink, Siebe T van Genesen, Wilfried W de Jong, Nicolette H Lubsen |
Journal | The Journal of biological chemistry
(J Biol Chem)
Vol. 278
Issue 50
Pg. 49743-50
(Dec 12 2003)
ISSN: 0021-9258 [Print] United States |
PMID | 14523008
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- HSP27 Heat-Shock Proteins
- HSP70 Heat-Shock Proteins
- HSPB1 protein, human
- Heat-Shock Proteins
- Hsbp1 protein, mouse
- Molecular Chaperones
- Neoplasm Proteins
- RNA, Messenger
- alpha-Crystallin B Chain
- 2-Aminopurine
- Luciferases
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Topics |
- 2-Aminopurine
(chemistry, metabolism)
- Animals
- Blotting, Western
- Cells, Cultured
- Electrophoresis, Polyacrylamide Gel
- Genes, Reporter
- HSP27 Heat-Shock Proteins
- HSP70 Heat-Shock Proteins
(chemistry)
- HeLa Cells
- Heat-Shock Proteins
- Hot Temperature
- Humans
- Luciferases
(metabolism)
- Mice
- Models, Genetic
- Molecular Chaperones
- Mutation
- Neoplasm Proteins
(physiology)
- Phosphorylation
- Promoter Regions, Genetic
- Protein Biosynthesis
- RNA, Messenger
(metabolism)
- Reverse Transcriptase Polymerase Chain Reaction
- Temperature
- Time Factors
- Transfection
- alpha-Crystallin B Chain
(physiology)
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