Inhibition of Apoptosis
Pathway Description:
Cell survival requires the active inhibition of apoptosis, which is accomplished by inhibiting the expression of pro-apoptotic factors as well as promoting the expression of anti-apoptotic factors. The PI3K pathway, activated by many survival factors, leads to the activation of Akt, an important player in survival signaling. Pten negatively regulates the PI3K pathway. Activated Akt inhibits the pro-apoptotic Bcl-2 family member Bad, Bax, caspase-9, GSK-3 and FoxO1 by phosphorylation. Many growth factors and cytokines induce anti-apoptotic Bcl-2 family members. The Jaks and Src phosphorylate and activate Stat3, which in turn induces the expression of Bcl-xL and Bcl-2. Erk1/2 and PKC activate p90RSK, which activates CREB and induces the expression of Bcl-xL and Bcl-2. These Bcl-2 family members protect the integrity of mitochondria, preventing cytochrome c release and the subsequent activation of caspase-9. TNF-α may activate both pro-apoptotic and anti-apoptotic pathways: TNF-α can induce apoptosis by activating caspase-8 and -10, but can also inhibit apoptosis signaling via NF-κB, which induces the expression of anti-apoptotic genes such as Bcl-2. cIAP1/2 inhibit TNF-α signaling by binding to TRAF2. FLIP inhibits the activation of caspase-8.
Selected Reviews:
- Beere HM (2004) “The stress of dying”: the role of heat shock proteins in the regulation of apoptosis. J. Cell. Sci. 117(Pt 13), 2641–51.
- Franke TF, Hornik CP, Segev L, Shostak GA, Sugimoto C (2003) PI3K/Akt and apoptosis: size matters. Oncogene 22(56), 8983–98.
- Pommier Y, Sordet O, Antony S, Hayward RL, Kohn KW (2004) Apoptosis defects and chemotherapy resistance: molecular interaction maps and networks. Oncogene 23(16), 2934–49.
CST would like to thank Prof. Junying Yuan, Harvard Medical School, Boston, Massachusetts, for reviewing this diagram.
created January 2002 • revised January 2007
