Figure 1
From: Targeting insulin-like growth factor axis in hepatocellular carcinoma
Binding of insulin and IGF ligands to their receptors. Insulin receptor and IGF-1 receptor are both tyrosine kinases. IGF-2R functions as a clearance site for IGF-2. Insulin receptor and IGF-1R are homologous and form hemireceptors. IGF-1 binds to IGF-1R and to IGF-1R/Insulin Receptor hemireceptor; it binds to insulin receptor only at very high concentrations. IGF-2 binds to IGF-1R, IGF-2R and binds to insulin receptor only during early fetal development. Insulin binds to insulin receptor, and it binds to IGF-1R/Insulin Receptor hemireceptor at high concentration. Signal transduction is activated after the activation of IGF-1R, IGF-1R/Insulin Receptor hemireceptor and insulin receptor; however, IGF-2R activation results in no signal downstream. Solid lines represent high affinity binding, dotted lines indicate weak binding.