Inhibition of Receptor Dimerization as a Novel Negative Feedback Mechanism of EGFR Signaling

Dimerization of the epidermal growth factor receptor (EGFR) is crucial for initiating signal transduction. We employed raster image correlation spectroscopy to continuously monitor the EGFR monomer-dimer equilibrium in living cells. EGFR dimer formation upon addition of EGF showed oscillatory behavior with a periodicity of about 2.5 min, suggesting the presence of a negative feedback loop to monomerize the receptor. We demonstrated that monomerization of EGFR relies on phospholipase Cγ, protein kinase C, and protein kinase D (PKD), while being independent of Ca2+ signaling and endocytosis. Phosphorylation of the juxtamembrane threonine residues of EGFR (T654/T669) by PKD was identified as the factor that shifts the monomer-dimer equilibrium of ligand bound EGFR towards the monomeric state. The dimerization state of the receptor correlated with the activity of an extracellular signal-regulated kinase, downstream of the EGFR. Based on these observations, we propose a novel, negative feedback mechanism that regulates EGFR signaling via receptor monomerization.

表皮生长因子受体（EGFR）的二聚化对于启动信号转导至关重要。本研究采用光栅图像相关光谱学技术，对活细胞中EGFR单体-二聚体平衡进行持续监测。在添加表皮生长因子（EGF）后，EGFR的二聚化表现出约2.5分钟的周期性振荡行为，这表明存在一个负反馈回路以实现受体的单体化。实验证明，EGFR的单体化依赖于磷脂酶Cγ、蛋白激酶C和蛋白激酶D（PKD），且与Ca2+信号传导和内吞作用无关。蛋白激酶D（PKD）对EGFR近膜丝氨酸残基（T654/T669）的磷酸化被确认为影响配体结合EGFR的单体-二聚体平衡，使其偏向单体状态的关键因素。受体的二聚化状态与EGFR下游的细胞外信号调节激酶（ERK）的活性相关。基于这些观察结果，我们提出了一种新的负反馈机制，该机制通过受体单体化调节EGFR的信号传导。