A model for p21 regulation by the PI3-kinase/PTEN signaling pathway. Growth factor signaling stimulates PI3-kinase and induces an increase in PIP-3 levels at the plasma membrane; PTEN converts PIP-3 back to PIP-2. An increase in PIP-3 causes AKT activation. AKT phosphorylates GSK-3 causing the inhibition of GSK-3. In the absence of GSK3 activity, p21 levels rise. AKT also activates mTOR, causing an increase in S6 phosphorylation and translation of proteins, which in turn leads to an increase of p21. The p21 causes an inhibition of cell cycle progression.
Yohn et al. BMC Urology 2011 11:19 doi:10.1186/1471-2490-11-19