This receptor binds insulin-like growth factor 1 (IGF1) with a high affinity and IGF2 with a lower affinity. It has a tyrosine-protein kinase activity, which is necessary for the activation of the IGF1-stimulated downstream signaling cascade. When present in a hybrid receptor with INSR, binds IGF1. Ref.19 shows that hybrid receptors composed of IGF1R and INSR isoform Long are activated with a high affinity by IGF1, with low affinity by IGF2 and not significantly activated by insulin, and that hybrid receptors composed of IGF1R and INSR isoform Short are activated by IGF1, IGF2 and insulin. In contrast, Ref.21 shows that hybrid receptors composed of IGF1R and INSR isoform Long and hybrid receptors composed of IGF1R and INSR isoform Short have similar binding characteristics, both bind IGF1 and have a low affinity for insulin.

Adams, T.E. et al. (2000) Cell. Mol. Life Sci. 57, 1050-1093
Baserga, R. et al. (2000) Oncogene 19, 5574-5581
Scheidegger, K.J. et al. (2000) J. Biol. Chem. 275, 38921-38928.
O'Connor R, et al. Mol Cell Biol 1997 Jan; 17(1): 427-35