Structure-function relationship of the insulin receptor on cell proliferation and metabolism

PROJECT SUMMARY Dysfunction in insulin receptor (IR) signaling is implicated in various metabolic disorders, including diabetes and cancer. Since the discovery of insulin more than a century ago, considerable effort has been made to elucidate its metabolic function. Given the high incidence of patients with both diabetes and cancer and the links between tumorigenesis and hyperinsulinemia (or elevated insulin level in the blood), there is a pressing need to reassess insulin’s “mitotic” function via activation of the MAPK signaling pathway. The primary objective of my research is to understand the molecular mechanism and biological function of biased agonism of IR activation by designer ligands. Additionally, I aim to use these designer ligands as tools to elucidate the regulatory mechanism of IR trafficking system. Recently, we functionally characterized and determined the cryo-EM structures of insulin-bound and designer ligand-bound IR. Notably, we observed that designer ligand induces a distinct active conformation of IR compared to insulin and exhibits biased agonism against the MAPK signaling pathway through the same IR. Furthermore, my preliminary data demonstrates that the designer ligand reduces IR levels in vivo and in cultured cells by promoting the degradation of internalized IR, rather than recycling it back to the cell surface. These results raise immediate questions: (i) how do different IR active conformations induce biased agonism and modulate downstream signaling pathways, (ii) what are the biological outcomes of the biased agonism against the MAPK signaling pathway, and (iii) which regulators sort IR for recycling or degradation? To address these questions, in Aim 1, I will elucidate the mechanism and biological function of biased agonism of designer ligands in cultured cells and mice. In Aim2, I will use designer ligands as tools to identify regulators of IR trafficking by proximity-dependent biotinylation proteomics. By combining cell biology, biochemistry, proteomics, and mouse physiology, I aim to establish structure- to-function relationship between IR, its downstream signaling pathways, and physiological processes. This research project will be conducted at Columbia University under the co-mentorship from Dr. Eunhee Choi and Dr. Domenico Accili. The collaborative environment at Columbia, coupled with distinct yet complimenting expertise of my sponsors in structural biology, cell signaling, and physiology, provides me with unparalleled access to a wealth of resources, both intellectual and technical. These resources are crucial for the successful execution and accomplishment of my proposed multidisciplinary research project and training.