Figure 1.

The insulin/insulin growth factor signaling pathway and its activation by reactive oxygen species (ROS). Insulin or other growth factors bind to and activate the insulin receptor or other receptor tyrosine kinases. This binding leads to PI3K and Akt activation either directly or via Ras. Akt phosphorylates and inhibits the activities of Foxo and the Tor inhibitor Tsc1/Tsc2. Activated Tor impairs autophagy and activates protein synthesis, whereas activated Foxo has the opposite effects. Phosphatases inhibit signaling either by catalyzing receptor dephosphorylation or by antagonizing PI3K activity. Pathway activators are shown in blue, and inhibitors in gray. ROS inhibits pathway inhibitors (red) and activates pathway activators (green).