Unformatted text preview: g the proapoptotic BH3-only proteins
PUMA and Noxa, leading to cell death.
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CELL DEATH AND CELL RENEWAL 11 Survival factor
Receptor tyrosine kinase
PIP3 PIP2 Akt PDK1 P
P P mTOR P mTORC2
PI 3-kinase mTORC1 Active Akt
P P GSK-3 Bad
regulation Bim FIGURE 17.11 The PI 3-kinase pathway and cell survival Many growth factors that signal cell survival activate receptor protein-tyrosine kinases, leading to
activation of PI 3-kinase, formation of PIP3, and activation of the protein kinase,
Akt. Akt then phosphorylates a number of proteins that contribute to cell survival.
Phosphorylation of the BH3-only protein Bad maintains it in an inactive state, as
does phosphorylation of the FOXO transcription factors. In the absence of Akt signaling, activation of Bad promotes apoptosis and activ...
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