Figure 2

Mitochondrial apoptotic module. The levels of p53_killer and Akt_u are considered as pro-apoptotic input signals. Total level of Akt is assumed constant and, since the phosphorylated Akt is anti-apoptotic, the unphosphorylated Akt is considered as the pro-apoptotic input (associated with e.g. growth factor withdrawal). Phosphorylated Akt phosphorylates Bad, which then remains bound to Scaffold_14-3-3. When dephosphorylated, Bad binds to Bcl-x_L, leading to the dissociation of Bax from its complexes with Bcl-x_L. Free Bax (via the omitted process of cytochrome c release) turns pro-caspases into active caspases (module output) which induce apoptosis. Arrow-headed lines indicate protein transformations, circle-headed lines – activating (including transcription) or inactivating influence. Light red color indicates pro-apoptotic, and light blue – anti-apoptotic proteins. Symbol Ø is used to denote sink or source.