Basic Amino Acids Within the Juxtamembrane Domain of the Epidermal Growth Factor Receptor Regulate Receptor Dimerization and Auto-phosphorylation.

Epidermal growth factor receptor (EGFR) dysregulation is observed in many human cancers and is both a cause of oncogenesis and a target for chemotherapy. We previously showed that partial charge neutralization of the juxtamembrane (JX) region of EGFR via the EGFR R1-6 mutant construct induces constitutive receptor activation and transformation of NIH 3T3 cells, both from the plasma membrane and from the ER when combined with the ER-retaining L417H mutation (Bryant et al. in J Biol Chem 288:34930-34942, 2013). Here, we use chemical crosslinking and immunoblotting to show that these mutant constructs form constitutive, phosphorylated dimers in both the plasma membrane and the ER. Furthermore, we combine this electrostatic perturbation with conformationally-restricted receptor mutants to provide evidence that activation of EGFR R1-6 dimers requires functional coupling both between the EGFR extracellular dimerization arms and between intracellular tyrosine kinase domains. These findings provide evidence that the electrostatic charge of the JX region normally serves as a negative regulator of functional dimerization of EGFR.