Ligand-induced transmembrane conformational coupling in monomeric EGFR
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. While receptor-receptor interactions are established as key aspects of transmembrane signaling, the contribution from the single helix of a monomeric receptor has been challenging to isolate due to the complexity and ligand-dependence of the receptor-receptor interactions. By combining membrane nanodiscs produced wtih 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 are common to single-pass membrane proteins.