Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
Department of Chemistry, University of California, Berkeley, California 94705, United States.
Biochemistry. 2020 Oct 20;59(41):3965-3972. doi: 10.1021/acs.biochem.0c00641. Epub 2020 Oct 5.
Mutations in the epidermal growth factor receptor (EGFR) extracellular domain (ECD) are implicated in the development of glioblastoma multiforme (GBM), which is a highly aggressive form of brain cancer. Of particular interest to GBM is the EGFR variant known as EGFRvIII, which is distinguished by an in-frame deletion of exons 2-7, which encode ECD residues 6-273. Included within the deleted region is an autoinhibitory tether, whose absence, alongside unique disulfide interactions within the truncated ECD, supports assembly of a constitutively active asymmetric kinase dimer. Previous studies have shown that the binding of growth factors to the ECD of wild-type EGFR leads to the formation of two distinct coiled coil dimers in the cytoplasmic juxtamembrane (JM) segment, whose identities correlate with the downstream phenotype. One coiled coil contains leucine residues at the interhelix interface (EGF-type), whereas the other contains charged and polar side chains (TGF-α-type). It has been proposed that growth-factor-dependent structural changes in the ECD and adjacent transmembrane helix are transduced into distinct JM coiled coils. Here, we show that, in the absence of this growth-factor-induced signal, the JM of EGFRvIII adopts both EGF-type and TGF-α-type structures, providing direct evidence for this hypothesis. These studies confirm that the signals that define JM coiled coil identity begin within the ECD, and support a model in which growth-factor-induced conformational changes are transmitted from the ECD through the transmembrane helix to favor different coiled coil isomers within the JM.
表皮生长因子受体 (EGFR) 细胞外结构域 (ECD) 的突变与多形性胶质母细胞瘤 (GBM) 的发生有关，GBM 是一种高度侵袭性的脑癌。特别引起 GBM 关注的是一种称为 EGFRvIII 的 EGFR 变体，它的特征是外显子 2-7 的框内缺失，这些外显子编码 ECD 残基 6-273。缺失区域内包含一个自动抑制的系绳，其缺失以及截断 ECD 内独特的二硫键相互作用，支持组成一个组成性激活的不对称激酶二聚体。先前的研究表明，生长因子与野生型 EGFR 的 ECD 结合导致细胞浆近膜 (JM) 段内形成两个不同的卷曲螺旋二聚体，其身份与下游表型相关。一个卷曲螺旋在螺旋间界面含有亮氨酸残基 (EGF 型)，而另一个卷曲螺旋含有带电荷和极性侧链 (TGF-α 型)。有人提出，ECD 和相邻跨膜螺旋的生长因子依赖性结构变化被转导为不同的 JM 卷曲螺旋。在这里，我们表明，在没有这种生长因子诱导信号的情况下，EGFRvIII 的 JM 采用 EGF 型和 TGF-α 型结构，为这一假说提供了直接证据。这些研究证实了定义 JM 卷曲螺旋身份的信号始于 ECD，并且支持这样一种模型，即生长因子诱导的构象变化从 ECD 通过跨膜螺旋传递，以有利于 JM 内不同的卷曲螺旋异构体。
