Figure 1

Insulin-like growth factor pathway. Bioavailability of the ligands IGF-1 and IGF-2 is regulated by IGF binding proteins. The insulin receptor and IGF-1R are tyrosine kinase cell-surface receptors that recruit and phosphorylate adaptor proteins belonging to the insulin receptor substrate or SHC family, leading to activation of the PI3K/Akt and MAPK signaling cascades. IGF-2R lacks an intracellular tyrosine kinase domain and leads to IGF-2 degradation. IGF-1, insulin-like growth factor-1; IGF-1R, insulin-like growth factor-1 receptor; IGF-2, insulin-like growth factor-2; IGF-2R, insulin-like growth factor-2 receptor; IRS, insulin receptor substrate; MAPK, mitogen-activated protein kinase; P13K/Akt, phosphatidylinositide 3-kinase/Akt; SHC, Src homology 2 domain-containing transforming protein 1.