Computational model for the IGF-II/IGF2r complex that is predictive of mutational and surface plasmon resonance data
Philippe Roche1, James Brown, Adam Denley
1Division of Structural Biology, University of Oxford, Henry Wellcome Building for Genomic Medicine, Oxford, United Kingdom. robert@strubi.ox.ac.uk
Abstract:
Insulin-like growth factors (IGFs) are key regulators of cell proliferation, differentiation, and transformation, and are thus pivotal in cancer, especially breast, prostate, and colon neoplasm. Their potent mitogenic and anti-apoptotic actions depend primarily on their availability to bind to the signaling IGF cell surface receptors. One mechanism by which IGF-II availability is thought to be modulated is by binding to the nonsignaling IGF-II receptor (IGF2R). This binding is essentially mediated by domain 11 in the multidomain IGF2R extracellular region. The crystal structure of domain 11 of the human IGF-II receptor (IGF2R-d11) has identified a putative IGF-II binding site, and a nuclear magnetic resonance (NMR) solution structure for the IGF-II ligand has also been characterized. These structures have now been used to model in silico the protein-protein interaction between IGF-II and IGF2R-d11 using the program 3D-Dock. Because the IGF-II data comprise an ensemble of 20 structures, all of which satisfy the NMR constraints, the docking procedure was applied to each member of the ensemble. Only those models in which residue Ile1572 of IGF2R-d11, known to be essential for the binding of IGF-II, was at the interface were considered further. These plausible complexes were then critically assessed using an array of analysis techniques including consideration of additional mutagenesis data. One model was strongly supported by these analyses and is discussed here in detail. Furthermore, we demonstrate in vitro experimental support for this model by studying the binding of chimeras of IGF-I and IGF-II to IGF2R fragments.
Insights
Insulin-like growth factors (IGFs) regulate cell growth and are crucial in cancer. This study models the interaction between IGF-II and its receptor (IGF2R) to understand IGF-II availability and its role in cancer development.
Area of Science:
- Molecular biology
- Biochemistry
- Structural biology
Background:
- Insulin-like growth factors (IGFs) are critical regulators of cell proliferation, differentiation, and transformation, playing a pivotal role in cancers like breast, prostate, and colon.
- The availability of IGF-II for signaling IGF receptors is modulated by binding to the non-signaling IGF-II receptor (IGF2R).
- Domain 11 of IGF2R (IGF2R-d11) is essential for mediating IGF-II binding.
Purpose of the Study:
- To model the in silico protein-protein interaction between IGF-II and IGF2R-d11.
- To identify the specific binding interface and structural basis for IGF-II and IGF2R-d11 interaction.
- To provide experimental validation for the proposed binding model.
Main Methods:
- Utilized crystal structure of IGF2R-d11 and NMR solution structure of IGF-II.
- Employed 3D-Dock program for in silico modeling of protein-protein interaction.
- Applied ensemble docking using 20 IGF-II structures and filtered models based on essential residue Ile1572.
- Validated models using mutagenesis data and in vitro binding assays with IGF chimeras.
Main Results:
- A plausible in silico model of the IGF-II and IGF2R-d11 complex was generated.
- The model highlights the critical role of residue Ile1572 in IGF2R-d11 for IGF-II binding.
- In vitro experiments using IGF chimeras provided supporting evidence for the proposed binding model.
Conclusions:
- The study presents a detailed structural model for IGF-II binding to IGF2R domain 11.
- This model enhances understanding of IGF-II availability regulation.
- The findings contribute to comprehending the role of IGF signaling in cancer and offer potential therapeutic targets.
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