Temperature sensitivity of phospho-Ser(473)-PKB/AKT.
The phospho-PKB/Akt status is often used as surrogate marker to measure activation of the PI3K/Akt/mTOR signal transduction pathway. Though, inconsistencies of the p-Ser(473)-PKB/Akt status have raised doubts in the validity of p-Ser(473)-PKB/Akt phosphorylation as endpoint. Here, we determined that p-Ser(473)-PKB/Akt but not p-Thr(308)-PKB/Akt phosphorylation is highly temperature sensitive. p-Ser(473)-PKB/Akt phosphorylation was rapidly reduced to levels below 50% on exposure to 20-25 degrees C in murine and human cell lines including cells expressing constitutively active PI3K or lacking PTEN. Down-regulation of p-Ser(473)-PKB/Akt was reversible and re-exposure to physiological temperature resulted in increased p-Ser(473)-PKB/Akt phosphorylation levels. Phosphatase activity at low temperature was sustained at 75% baseline level and phosphatase inhibition prevented p-Ser(473)-PKB/Akt dephosphorylation induced by the low temperature shift. Interestingly temperature-dependent deregulation of the p-Ser(473)-PKB/Akt status was also observed in response to irradiation. Thus our data demonstrate that minimal additional stress factors deregulate the PI3K/Akt-survival pathway and the p-Ser(473)-PKB/Akt status as experimental endpoint.
Oehler-Jänne
Christoph
C
Department of Radiation Oncology, University Hospital Zurich, CH-8091 Zurich, Switzerland.
von Bueren
André O
AO
Vuong
Van
V
Hollenstein
Andreas
A
Grotzer
Michael A
MA
Pruschy
Martin
M
D000818:Animals; D002460:Cell Line; D015536:Down-Regulation; D006358:Hot Temperature; D006801:Humans; D051379:Mice; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010768:Phosphoserine / Q000378:metabolism*; D010769:Phosphothreonine / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*
D010769:Phosphothreonine; D010768:Phosphoserine; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase