Tuning insulin receptor signaling using de novo-designed agonists.

Insulin binding induces conformational changes in the insulin receptor (IR) that activate the intracellular kinase domain and the protein kinase B (AKT) and mitogen-activated protein kinase (MAPK) pathways, regulating metabolism and proliferation. We reasoned that designed agonists inducing different IR conformational changes might induce different downstream responses. We used de novo protein design to generate binders for individual IR extracellular domains and fused them in different orientations with different conformational flexibility. We obtained a series of synthetic IR agonists that elicit a wide range of receptor autophosphorylation, MAPK activation, trafficking, and proliferation responses. We identified designs more potent than insulin, causing longer-lasting glucose lowering in vivo and retaining activity on disease-causing IR mutants, while largely avoiding the cancer cell proliferation induced by insulin. Our findings shed light on how changes in IR conformation and dynamics translate into downstream signaling, and with further development, our synthetic agonists could have therapeutic utility for metabolic and proliferative diseases.