All Publications

  • Activation of the insulin receptor by insulin-like growth factor 2 NATURE COMMUNICATIONS An, W., Hall, C., Li, J., Hung, A., Wu, J., Park, J., Wang, L., Bai, X., Choi, E. 2024; 15 (1): 2609


    Insulin receptor (IR) controls growth and metabolism. Insulin-like growth factor 2 (IGF2) has different binding properties on two IR isoforms, mimicking insulin's function. However, the molecular mechanism underlying IGF2-induced IR activation remains unclear. Here, we present cryo-EM structures of full-length human long isoform IR (IR-B) in both the inactive and IGF2-bound active states, and short isoform IR (IR-A) in the IGF2-bound active state. Under saturated IGF2 concentrations, both the IR-A and IR-B adopt predominantly asymmetric conformations with two or three IGF2s bound at site-1 and site-2, which differs from that insulin saturated IR forms an exclusively T-shaped symmetric conformation. IGF2 exhibits a relatively weak binding to IR site-2 compared to insulin, making it less potent in promoting full IR activation. Cell-based experiments validated the functional importance of IGF2 binding to two distinct binding sites in optimal IR signaling and trafficking. In the inactive state, the C-terminus of α-CT of IR-B contacts FnIII-2 domain of the same protomer, hindering its threading into the C-loop of IGF2, thus reducing the association rate of IGF2 with IR-B. Collectively, our studies demonstrate the activation mechanism of IR by IGF2 and reveal the molecular basis underlying the different affinity of IGF2 to IR-A and IR-B.

    View details for DOI 10.1038/s41467-024-46990-6

    View details for Web of Science ID 001190084300009

    View details for PubMedID 38521788

    View details for PubMedCentralID PMC10960814

  • The insulin receptor endocytosis. Progress in molecular biology and translational science Wu, J., Park, S. H., Choi, E. 2023; 194: 79-107


    Insulin signaling controls multiple aspects of animal physiology. At the cell surface, insulin binds and activates the insulin receptor (IR), a receptor tyrosine kinase. Insulin promotes a large conformational change of IR and stabilizes the active conformation. The insulin-activated IR triggers signaling cascades, thus controlling metabolism, growth, and proliferation. The activated IR undergoes internalization by clathrin- or caveolae-mediated endocytosis. The IR endocytosis plays important roles in insulin clearance from blood, and distribution and termination of the insulin signaling. Despite decades of extensive studies, the mechanism and regulation of IR endocytosis and its contribution to pathophysiology remain incompletely understood. Here we discuss recent findings that provide insights into the molecular mechanisms and regulatory pathways that mediate the IR endocytosis.

    View details for DOI 10.1016/bs.pmbts.2022.06.020

    View details for PubMedID 36631202

  • Molecular basis for the role of disulfide-linked aCTs in the activation of insulin-like growth factor 1 receptor and insulin receptor ELIFE Li, J., Wu, J., Hall, C., Bai, X., Choi, E., Gallagher, E. J. 2022; 11


    The insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF1R) control metabolic homeostasis and cell growth and proliferation. The IR and IGF1R form similar disulfide bonds linked homodimers in the apo-state; however, their ligand binding properties and the structures in the active state differ substantially. It has been proposed that the disulfide-linked C-terminal segment of α-chain (αCTs) of the IR and IGF1R control the cooperativity of ligand binding and regulate the receptor activation. Nevertheless, the molecular basis for the roles of disulfide-linked αCTs in IR and IGF1R activation are still unclear. Here, we report the cryo-EM structures of full-length mouse IGF1R/IGF1 and IR/insulin complexes with modified αCTs that have increased flexibility. Unlike the Γ-shaped asymmetric IGF1R dimer with a single IGF1 bound, the IGF1R with the enhanced flexibility of αCTs can form a T-shaped symmetric dimer with two IGF1s bound. Meanwhile, the IR with non-covalently linked αCTs predominantly adopts an asymmetric conformation with four insulins bound, which is distinct from the T-shaped symmetric IR. Using cell-based experiments, we further showed that both IGF1R and IR with the modified αCTs cannot activate the downstream signaling potently. Collectively, our studies demonstrate that the certain structural rigidity of disulfide-linked αCTs is critical for optimal IR and IGF1R signaling activation.

    View details for DOI 10.7554/eLife.81286

    View details for Web of Science ID 000895778300001

    View details for PubMedID 36413010

    View details for PubMedCentralID PMC9731570

  • Activation of the insulin receptor by an insulin mimetic peptide NATURE COMMUNICATIONS Park, J., Li, J., Mayer, J. P., Ball, K. A., Wu, J., Hall, C., Accili, D., Stowell, M. B., Bai, X., Choi, E. 2022; 13 (1): 5594


    Insulin receptor (IR) signaling defects cause a variety of metabolic diseases including diabetes. Moreover, inherited mutations of the IR cause severe insulin resistance, leading to early morbidity and mortality with limited therapeutic options. A previously reported selective IR agonist without sequence homology to insulin, S597, activates IR and mimics insulin's action on glycemic control. To elucidate the mechanism of IR activation by S597, we determine cryo-EM structures of the mouse IR/S597 complex. Unlike the compact T-shaped active IR resulting from the binding of four insulins to two distinct sites, two S597 molecules induce and stabilize an extended T-shaped IR through the simultaneous binding to both the L1 domain of one protomer and the FnIII-1 domain of another. Importantly, S597 fully activates IR mutants that disrupt insulin binding or destabilize the insulin-induced compact T-shape, thus eliciting insulin-like signaling. S597 also selectively activates IR signaling among different tissues and triggers IR endocytosis in the liver. Overall, our structural and functional studies guide future efforts to develop insulin mimetics targeting insulin resistance caused by defects in insulin binding and stabilization of insulin-activated state of IR, demonstrating the potential of structure-based drug design for insulin-resistant diseases.

    View details for DOI 10.1038/s41467-022-33274-0

    View details for Web of Science ID 000857704600011

    View details for PubMedID 36151101

    View details for PubMedCentralID PMC9508239

  • Synergistic activation of the insulin receptor via two distinct sites NATURE STRUCTURAL & MOLECULAR BIOLOGY Li, J., Park, J., Mayer, J. P., Webb, K. J., Uchikawa, E., Wu, J., Liu, S., Zhang, X., Stowell, M. B., Choi, E., Bai, X. 2022; 29 (4): 357-+


    Insulin receptor (IR) signaling controls multiple facets of animal physiology. Maximally four insulins bind to IR at two distinct sites, termed site-1 and site-2. However, the precise functional roles of each binding event during IR activation remain unresolved. Here, we showed that IR incompletely saturated with insulin predominantly forms an asymmetric conformation and exhibits partial activation. IR with one insulin bound adopts a Γ-shaped conformation. IR with two insulins bound assumes a Ƭ-shaped conformation. One insulin binds at site-1 and another simultaneously contacts both site-1 and site-2 in the Ƭ-shaped IR dimer. We further show that concurrent binding of four insulins to sites-1 and -2 prevents the formation of asymmetric IR and promotes the T-shaped symmetric, fully active state. Collectively, our results demonstrate how the synergistic binding of multiple insulins promotes optimal IR activation.

    View details for DOI 10.1038/s41594-022-00750-6

    View details for Web of Science ID 000780744900001

    View details for PubMedID 35361965

    View details for PubMedCentralID PMC9115778

  • Thamnolia vermicularis extract improves learning ability in APP/PS1 transgenic mice by ameliorating both A beta and Tau pathologies ACTA PHARMACOLOGICA SINICA Li, C., Gu, X., Lei, M., Wu, J., Jin, J., Shi, X., Zhu, Z., Rukachaisirikul, V., Hu, L., Wen, T., Shen, X. 2017; 38 (1): 9-28


    Considering the complicated pathogenesis of Alzheimer's disease (AD), multi-targets have become a focus in the discovery of drugs for treatment of this disease. In the current work, we established a multi-target strategy for discovering active reagents capable of suppressing both Aβ level and Tau hyperphosphorylation from natural products, and found that the ethanol extract of Thamnolia vermicularis (THA) was able to improve learning ability in APP/PS1 transgenic mice by inhibiting both Aβ levels and Tau hyperphosphorylation. SH-SY5Y and CHO-APP/BACE1 cells and primary astrocytes were used in cell-based assays. APP/PS1 transgenic mice [B6C3-Tg(APPswe, PS1dE9)] were administered THA (300 mg·kg-1·d-1, ig) for 100 d. After the administration was completed, the learning ability of the mice was detected using a Morris water maze (MWM) assay; immunofluorescence staining, Congo red staining and Thioflavine S staining were used to detect the senile plaques in the brains of the mice. ELISA was used to evaluate Aβ and sAPPβ contents, and Western blotting and RT-PCR were used to investigate the relevant signaling pathway regulation in response to THA treatment. In SH-SY5Y cells, THΑ (1, 10, 20 μg/mL) significantly stimulated PI3K/AKT/mTOR and AMPK/raptor/mTOR signaling-mediated autophagy in the promotion of Aβ clearance as both a PI3K inhibitor and an AMPK indirect activator, and restrained Aβ production as a suppressor against PERK/eIF2α-mediated BACE1 expression. Additionally, THA functioned as a GSK3β inhibitor with an IC50 of 1.32±0.85 μg/mL, repressing Tau hyperphosphorylation. Similar effects on Aβ accumulation and Tau hyperphosphorylation were observed in APP/PS1 transgenic mice treated with THA. Furthermore, administration of THA effectively improved the learning ability of APP/PS1 transgenic mice, and markedly reduced the number of senile plaques in their hippocampus and cortex. The results highlight the potential of the natural product THA for the treatment of AD.

    View details for DOI 10.1038/aps.2016.94

    View details for Web of Science ID 000393540900002

    View details for PubMedID 27694908

    View details for PubMedCentralID PMC5220549