1. RET Recognition of GDNF-GFRα1 Ligand by a Composite Binding Site Promotes Membrane-Proximal Self-Association
- Author
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Andrew Purkiss, Fabienne Beuron, Agata Nawrotek, Svend Kjaer, Massimo Santoro, Phillip P. Knowles, Kerry M. Goodman, Neil Q. McDonald, Roger George, Edward P. Morris, and Emily M. Burns
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities ,endocrine system ,Glial Cell Line-Derived Neurotrophic Factor Receptors ,endocrine system diseases ,Molecular Sequence Data ,Plasma protein binding ,CHO Cells ,General Biochemistry, Genetics and Molecular Biology ,Antibodies ,Cell membrane ,Epitopes ,Protein structure ,Cricetulus ,Cricetinae ,Glial cell line-derived neurotrophic factor ,medicine ,Animals ,Humans ,Amino Acid Sequence ,Glial Cell Line-Derived Neurotrophic Factor ,Binding site ,Ternary complex ,lcsh:QH301-705.5 ,Zebrafish ,Binding Sites ,biology ,Chemistry ,Cell Membrane ,Proto-Oncogene Proteins c-ret ,Zebrafish Proteins ,Ligand (biochemistry) ,Recombinant Proteins ,Cell biology ,Protein Structure, Tertiary ,Rats ,medicine.anatomical_structure ,Biochemistry ,lcsh:Biology (General) ,biology.protein ,Sequence Alignment ,Protein Binding - Abstract
SummaryThe RET receptor tyrosine kinase is essential to vertebrate development and implicated in multiple human diseases. RET binds a cell surface bipartite ligand comprising a GDNF family ligand and a GFRα coreceptor, resulting in RET transmembrane signaling. We present a hybrid structural model, derived from electron microscopy (EM) and low-angle X-ray scattering (SAXS) data, of the RET extracellular domain (RETECD), GDNF, and GFRα1 ternary complex, defining the basis for ligand recognition. RETECD envelopes the dimeric ligand complex through a composite binding site comprising four discrete contact sites. The GFRα1-mediated contacts are crucial, particularly close to the invariant RET calcium-binding site, whereas few direct contacts are made by GDNF, explaining how distinct ligand/coreceptor pairs are accommodated. The RETECD cysteine-rich domain (CRD) contacts both ligand components and makes homotypic membrane-proximal interactions occluding three different antibody epitopes. Coupling of these CRD-mediated interactions suggests models for ligand-induced RET activation and ligand-independent oncogenic deregulation.
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