Wednesday 29 October 2003
second messenger in signal transduction
PIP3 signals activates the kinase PDK1 (3-phosphoinositide-dependent protein kinase-1), which in turn activates the kinase AKT, also known as protein kinase B (PKB).
Proteins phosphorylated by activated AKT promote cell survival.
Phosphorylation of Ikappa-B kinase leads to activation of the transcription factor NF-kB to oppose apoptosis. Bad is a protein in the Bcl-2 gene family that opposes Bcl-2 to induce apoptosis. Phosphorylation of Bad by AKT blocks anti-apoptotic activity to promote cell survival.
Similarly, phosphorylation of the protease caspase 9 or forkhead transcription factors by AKT block the induction of apoptosis by these factors. AKT promotes cell survival and opposes apoptosis by a variety of routes. (Biocarta)
PI3K/PTEN/AKT signaling pathway