Ligand-induced transmembrane conformational coupling in monomeric EGFR

EGFR regulates cellular processes across the animal kingdom. Here, the authors show that transmembrane conformational coupling is the first step in EGFR signaling, providing evidence for the existence of transmembrane intramolecular conformational changes in a single pass membrane protein. Single pass cell surface receptors regulate cellular processes by transmitting ligand-encoded signals across the plasma membrane via changes to their extracellular and intracellular conformations. This transmembrane signaling is generally initiated by ligand binding to the receptors in their monomeric form. While subsequent receptor-receptor interactions are established as key aspects of transmembrane signaling, the contribution of monomeric receptors has been challenging to isolate due to the complexity and ligand-dependence of these interactions. By combining membrane nanodiscs produced with cell-free expression, single-molecule Forster Resonance Energy Transfer measurements, and molecular dynamics simulations, we report that ligand binding induces intracellular conformational changes within monomeric, full-length epidermal growth factor receptor (EGFR). Our observations establish the existence of extracellular/intracellular conformational coupling within a single receptor molecule. We implicate a series of electrostatic interactions in the conformational coupling and find the coupling is inhibited by targeted therapeutics and mutations that also inhibit phosphorylation in cells. Collectively, these results introduce a facile mechanism to link the extracellular and intracellular regions through the single transmembrane helix of monomeric EGFR, and raise the possibility that intramolecular transmembrane conformational changes upon ligand binding are common to single-pass membrane proteins.

Automated summary

In this study, the authors show that transmembrane conformational coupling is the first step in EGFR signaling, providing evidence for the existence of transmembrane intramolecular conformational changes in a single pass membrane protein. They also found that ligand binding induces intracellular conformational changes within monomeric EGFR, and implicate a series of electrostatic interactions in the conformational coupling. These results suggest that intramolecular transmembrane conformational changes upon ligand binding may be common to single-pass membrane proteins.