Analysis of the role of Hsp25 phosphorylation reveals the importance of the oligomerization state of this small heat shock protein in its protective function against TNFα- and hydrogen peroxide-induced cell death
✍ Scribed by Xavier Préville; Heidi Schultz; Ursula Knauf; Matthias Gaestel; André-Patrick Arrigo
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 367 KB
- Volume
- 69
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
The role of murine Hsp25 phosphorylation in the protection mediated by this protein against TNF␣-or H 2 O 2 -mediated cytotoxicity was investigated in L929 cell lines expressing wild type (wt-) or nonphosphorylatable (mt-) Hsp25. We show that mt-Hsp25, in which the phosphorylation sites, serines 15 and 86, were replaced by alanines, is still efficient in decreasing intracellular reactive oxygen species levels and in raising glutathione cellular content, leading the protective activity of mt-Hsp25 against oxidative stress to be identical to that of wt-Hsp25. To independently investigate the role of Hsp25 phosphorylation, we blocked TNF␣-induced phosphorylation of wt-Hsp25 using SB203580, a specific inhibitor of the P38 MAP kinase. This treatment did not abolish the protective activity of Hsp25 against TNF␣. The pattern of Hsp25 oligomerization was also analyzed, showing mt-Hsp25 to constitutively display large native sizes, as does wt-Hsp25 after TNF␣ treatment in the presence of SB203580. Our results, therefore, are consistent with the possibility that the hyperaggregated form of Hsp25 is responsible for the protective activity against oxidative stress and that the phosphorylation of serines 15 and/or 86 by interfering with this structural reorganization, may lead to the inactivation of Hsp25 protective activity.