Heat shock-induced, caspase-3-independent rapid breakdown of Akt and consequent alteration of its total phosphorylation/activity level

The immediate effect of a 15-min heat shock was examined on the level and t he activity of Akt. Following heat shock, the Akt level decreased by 15-70% in a temperature-dependent and phosphorylation status-independent manner. This decrease of Akt level was not prevented by caspase inhibitors. At 48 d egrees C, the extent of the breakdown was so immense that the total phospho rylation/activity level of Akt was not increased over the control level, im plying that the total cellular activity of Akt governed by the level and th e molar activity does not necessarily undergo the ensuing change. (C) 2000 Academic Press.