Human Molecular Genetics Advance Access published online on March 16, 2009
Human Molecular Genetics, doi:10.1093/hmg/ddp123
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Short 42°C heat shock induces phosphorylation and degradation of Cdc25A which depends on p38MAPK, Chk2, and 14.3.3
1 Institute of Clinical Pathology, Medical University of Vienna, Vienna, Austria 2 Department of Medicinal Genetics, Medical University of Vienna, Vienna, Austria 3 Department of Medicine I, Institute of Cancer Research, Medical University of Vienna, Vienna, Austria
* Corresponding author: Georg Krupitza, Institute of Clinical Pathology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria. Tel.: +43-1 40400 Ext. 3487 Fax: +43-1 40400 3707 e-mail: georg.krupitza{at}meduniwien.ac.at
Received January 14, 2009; Revised March 12, 2009; Accepted March 12, 2009
The effects of heat shock (HS; 42°C) on the cell cycle and underlying molecular mechanisms are astonishingly unexplored. Here we show that HS caused rapid Cdc25A degradation and a reduction of cell cycle progression. Cdc25A degradation depended on Ser75-Cdc25A phosphorylation caused by p38MAPK and Chk2 which phosphorylated Ser177-Cdc25A that is specific for 14.3.3 binding. Upon HS Cdc25A rapidly co-localised with 14.3.3 in the perinuclear space that was accompanied with a decrease of nuclear Cdc25A protein levels. Consistently, a 14.3.3 binding deficient Cdc25A double mutant (Ser177/Ala-Tyr507/Ala) was not degraded in response to heat shock and there was no evidence for an increased co-localisation of Cdc25A with 14.3.3 in the cytosol. Therefore, upon HS, p38, Chk2, and 14.3.3 were antagonists of Cdc25A stability. On the other hand, Cdc25A was protected by Hsp90 in HEK293 cells because the specific inhibition of Hsp90 with Geldanamycin caused Cdc25A degradation in HEK293 implicating that Cdc25A is an Hsp90 client. Specific inhibition of Hsp90 together with HS caused and accelerated degradation of Cdc25A and was highly cytotoxic. The results presented here show for the first time that Cdc25A is degraded by moderate heat shock and protected by Hsp90. We describe the mechanisms explaining HS-induced cell cycle retardation and provide a rationale for a targeted hyperthermia cancer therapy.