Insertion of a synthetic switch into insulin provides metabolite-dependent regulation of hormone–receptor activation

Abstract

Ligand-dependent conformational switches are ubiquitous in biological macromolecules, from allosteric proteins to RNA riboswitches. Molecular design of artificial switches provides a general strategy to test relationships between macromolecular structure and function. The present study exploited recent structures of complexes between an ancestral signaling protein (insulin) and the ectodomain of its cellular receptor to insert a metabolite-regulated switch into the hormone. Whereas binding of ligands often stabilizes structure, this design envisioned metabolite-dependent “opening” of a closed, inactive insulin conformation. Assessment of hormone-directed receptor autophosphorylation and a downstream signaling cascade in liver-derived cells demonstrated that binding of metabolite (a monosaccharide) enabled hormonal signaling. These results suggest a mechanism-based strategy to design “smart” glucose-responsive analogs to more safely treat insulin-dependent diabetes mellitus.