Insulin receptor Arg717 and IGF-1 receptor Arg704 play a key role in ligand binding and in receptor activation

• Published in: Open biology Vol. 13; no. 11; p. 230142
• Main Authors: Kertisová, Anna, Žáková, Lenka, Macháčková, Kateřina, Marek, Aleš, Šácha, Pavel, Pompach, Petr, Jiráček, Jiří, Selicharová, Irena
• Format: Journal Article
• Language: English
• Published: The Royal Society 08.11.2023
• Subjects: mutagenesis in vitro; peptide hormone; receptor modification; receptor tyrosine kinase; structure–function
• ISSN: 2046-2441; 2046-2441
• DOI: 10.1098/rsob.230142

The insulin receptor (IR, with its isoforms IR-A and IR-B) and the insulin-like growth factor 1 receptor (IGF-1R) are related tyrosine kinase receptors. Recently, the portfolio of solved hormone–receptor structures has grown extensively thanks to advancements in cryo-electron microscopy. However, the dynamics of how these receptors transition between their inactive and active state are yet to be fully understood. The C-terminal part of the alpha subunit ( α CT) of the receptors is indispensable for the formation of the hormone-binding site. We mutated the α CT residues Arg717 and His710 of IR-A and Arg704 and His697 of IGF-1R. We then measured the saturation binding curves of ligands on the mutated receptors and their ability to become activated. Mutations of Arg704 and His697 to Ala in IGF-1R decreased the binding of IGF-1. Moreover, the number of binding sites for IGF-1 on the His697 IGF-1R mutant was reduced to one-half, demonstrating the presence of two binding sites. Both mutations of Arg717 and His710 to Ala in IR-A inactivated the receptor. We have proved that Arg717 is important for the binding of insulin to its receptor, which suggests that Arg717 is a key residue for the transition to the active conformation.