Ras signalling and apoptosis.

Activated Ras proteins have either positive or negative effects on the regulation of apoptosis depending on cell type and other factors. In part, this is due to the ability of Ras to control directly multiple effector pathways, including PI3-kinase, which provides a universal survival signal, and Raf, which can inhibit survival. The mechanisms remain partly unclear, however, especially with regard to Raf effects on apoptosis regulation. Recently Ras has been shown to be able to protect cells from apoptosis either through activation of PKB/Akt via PI3-kinase, or through activation of NF-kappa B.