Membrane PI(4,5)P ₂ and ErbB2 abundance regulate ErbB receptor oligomerization and kinase activation

Because ErbB receptors play distinct roles in regulating diverse cellular functions, the mechanisms governing ErbB receptor activation are likely to be more diverse than previously recognized. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P ₂ ] positively regulates ErbB1 kinase activity, but the role of PI(4,5)P ₂ in regulating other ErbB family members in living cells remains poorly understood. We show that disruption of PI(4,5)P ₂ binding enhances ErbB4 oligomerization and kinase activity while reducing both processes in ErbB1. Analysis of chimeric receptors identified the juxtamembrane (JM) regions of ErbB1 and ErbB4 as key determinants of their distinct responses to PI(4,5)P ₂ during receptor oligomerization and kinase activation. Furthermore, the JM–kinase module of ErbB1 is more active in the presence of PI(4,5)P ₂ , whereas that of ErbB4 is activated by the disruption of PI(4,5)P ₂ binding. In contrast, the JM–kinase module of ErbB2 exhibits weak dependence on PI(4,5)P ₂ . ErbB2 preferentially promotes ErbB4 oligomerization over ErbB1 oligomerization, thereby enhancing ErbB4 activation. Collectively, these findings identify plasma membrane PI(4,5)P ₂ availability and ErbB2 abundance as two factors that jointly govern ErbB receptor oligomerization and activation.