Human insulin-like growth factor-I (IGF-I) is a single-chain 70-amino-acid polypeptide with structural homology to insulin and human IGF-II. IGF-I plays a key role in growth, differentiation, and development via autocrine, paracrine and endocrine mechanisms. It is a mitogen and also has effects on cell migration and differentiation.
IGF-I signals by binding to the type 1 insulin-like growth factor receptor (IGF-1R) and also to the insulin receptor (IR), resulting in the activation of the AKT signaling pathway. IGF-I also binds to each of the six IGF-binding proteins (IGFBPs). This binding also regulates the biological function of IGF-I. IGF-I is highly conserved across species, suggesting an important role for the peptide.
