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Unformatted text preview: ation of FOXO stimulates
transcription of another BH3-only protein, Bim. Additional targets of Akt that have
been implicated in regulation of apoptosis include the protein kinase GSK-3 and
additional transcription factors, such as p53 and NF-kB, both of which are regulated by Akt and GSK-3 phosphorylation. Translational regulation by GSK-3 and by
the mTOR pathway (see Figure 15.33) may also affect cell survival. c ontrolling the activation of caspase-9 and cell survival in response to
growth factor stimulation.
In contrast to the cell stress and growth factor signaling pathways that
regulate the intrinsic pathway of apoptosis, some secreted polypeptides
activate receptors that induce cell death via the extrinsic pathway of apoptosis. These receptors directly activate a distinct initiator caspase, caspase-8
( Figure 17.12). The polypeptides that signal cell death by this pathway
belong to the tumor necrosis factor (TNF) family. They bind to members of
the TNF receptor family, which can induce apoptosis in a...
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