Heat shock protein 70 inhibits apoptosis downstream of cytochrome c release and upstream of caspase-3 activation

C. Y. Li, J. S. Lee, Young-Gyu Ko, J. I. Kim, J. S. Seo

Research output: Contribution to journalArticle

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Abstract

Heat shock protein 70 (HSP70) has been shown to act as an inhibitor of apoptosis. We have also observed an inhibitory effect of HSP70 on apoptotic cell death both in preheated U937 and stably transfected HSP70-overexpressing U937 (U937/HSP70) cells. However, the molecular mechanism whereby HSP70 prevents apoptosis still remains to be solved. To address this issue, we investigated the effect of HSP70 on apoptotic processes in an in vitro system. Caspase-3 cleavage and DNA fragmentation were detected in cytosolic fractions from normal cells upon addition of dATP, but not from preheated U937 or U937/hsp70 cells. Moreover, the addition of purified recombinant HSP70 to normal cytosolic fractions prevented caspase-3 cleavage and DNA fragmentation, suggesting that HSP70 prevents apoptosis upstream of caspase-3 processing. Because cytochrome c was still released from mitochondria into the cytosol by lethal heat shock despite prevention of caspase-3 activation and cell death in both preheated U937 and U937/hsp70 cells, it was evident that HSP70 acts downstream of cytochrome c release. Results obtained in vitro with purified deletion mutants of HSP70 showed that the carboxyl one-third region (from amino acids 438 to 641) including the peptide-binding domain and the carboxyl-terminal EEVD sequence was essential to prevent caspase-3 processing. From these results, we conclude that HSP70 acts as a strong suppressor of apoptosis acting downstream of cytochrome c release and upstream of caspase-3 activation.

Original languageEnglish
Pages (from-to)25665-25671
Number of pages7
JournalJournal of Biological Chemistry
Volume275
Issue number33
DOIs
Publication statusPublished - 2000 Aug 18
Externally publishedYes

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HSP70 Heat-Shock Proteins
Cytochromes c
Caspase 3
Chemical activation
Apoptosis
U937 Cells
DNA Fragmentation
Cell death
Cell Death
Mitochondria
DNA
Processing
Recombinant Proteins
Cytosol
Shock
Hot Temperature

ASJC Scopus subject areas

  • Biochemistry

Cite this

Heat shock protein 70 inhibits apoptosis downstream of cytochrome c release and upstream of caspase-3 activation. / Li, C. Y.; Lee, J. S.; Ko, Young-Gyu; Kim, J. I.; Seo, J. S.

In: Journal of Biological Chemistry, Vol. 275, No. 33, 18.08.2000, p. 25665-25671.

Research output: Contribution to journalArticle

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