Activation mechanism of the insulin receptor revealed by cryo-EM structure of the fully liganded receptor-ligand complex

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Abstract

Insulin signaling controls metabolic homeostasis. Here, we report the cryo-EM structure of full-length insulin receptor (IR) and insulin complex in the active state. This structure unexpectedly reveals that maximally 4 insulins can bind the 'T'-shaped IR dimer at 4 distinct sites related by 2-fold symmetry. Insulins 1 and 1' bind to sites 1 and 1', formed by L1 of one IR protomer and α-CT and FnIII-1 of the other. Insulins 2 and 2' bind to sites 2 and 2' on FnIII-1 of each protomer. Mutagenesis and cellular assays show that both sites 1 and 2 are required for optimal insulin binding and IR activation. We further identify a homotypic FnIII-2-FnIII-2 interaction in mediating the dimerization of membrane proximal domains in the active IR dimer. Our results indicate that binding of multiple insulins at two distinct types of sites disrupts the autoinhibited apo-IR dimer and stabilizes the active dimer.

Data availability

Cryo-EM maps and the corresponding bulit models of insulin receptor/insulin complex have been deposited in EMDB and PDB under the accession codes EMD-20522/EMD-20523 and 6PXV/6PXW, respectively.All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figure2, Figure 3, Figure 4, Figure1-Supplement 1, Figure3-Supplement 2 and Figure3-Supplement 3

The following data sets were generated

1. Uchikawa1 E
2. Choi E
3. Shang G
4. Yu H
5. Bai X-C
(2019) Cryo-EM maps
Protein Data Bank, 6PXV.

http://www.rcsb.org/structure/6PXV
1. Uchikawa1 E
2. Choi E
3. Shang G
4. Yu H
5. Bai X-C
(2019) Cryo-EM maps
Protein Data Bank, 6PXW.

http://www.rcsb.org/structure/6PXW

Article and author information

Author details

Emiko Uchikawa

Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States

Competing interests
The authors declare that no competing interests exist.
Eunhee Choi

Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States

For correspondence
Eunhee.Choi@UTSouthwestern.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-3286-6477
Guijun Shang

Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-0187-7934
Hongtao Yu

Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States

For correspondence
hongtao.yu@utsouthwestern.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-8861-049X
Xiao-chen Bai

Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States

For correspondence
Xiaochen.Bai@UTSouthwestern.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-4234-5686

Funding

Cancer Preventation and Research Institute of Texas (RR160082)

Xiao-chen Bai

Welch Foundation (I-1944)

Xiao-chen Bai

Cancer Preventation and Research Institute of Texas (RP120717-P2)

Hongtao Yu

Cancer Preventation and Research Institute of Texas (RP160667-P2)

Hongtao Yu

Howard Hughes Medical Institute

Hongtao Yu

Welch Foundation (I-1441)

Hongtao Yu

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.