HETERODIMERIZATION IN ERBB RECEPTORS

描述（由申请人提供）： EGF受体是一种经典的受体酪氨酸激酶，具有细胞外配体结合结构域和细胞内酪氨酸激酶结构域。EGF的结合诱导EGF受体与其自身或与受体酪氨酸激酶的ErbB家族的其它成员的二聚化，其中ErbB 2是优选的二聚化配偶体。EGF受体的二聚化导致通过形成不对称激酶二聚体刺激其细胞内酪氨酸激酶活性。在这种不对称二聚体中，一个激酶结构域充当另一个激酶结构域的激活剂。由于这种机制，在受体二聚体中一次只能激活一个激酶结构域。根据目前的模型，受体的磷酸化然后以反式发生，并且仅在受体二聚体的情况下发生。虽然这个模型非常简单，但不能解释EGFR同二聚体和EGFR/ErbB 2异二聚体功能的所有方面。 EGF受体有八种不同的配体，它们能够在同一细胞系中诱导不同的反应。其分子基础尚不清楚，但已假设配体诱导EGF受体的不同构象。由于缺乏适当的工具，这一假设尚未得到实验性的解决。使用荧光素酶片段互补成像，我们已经记录了EGF受体对其不同配体的响应的明显差异，表明这种方法对EGF受体构象的配体特异性变化敏感。我们还使用放射性配体结合研究来记录受体构象的更微妙的差异，这些差异反映在配体结合的变构特性的差异中。 靶向ErbB受体的治疗策略取决于对这些受体如何相互作用以及与其配体相互作用以及如何调节的充分理解。拟议工作的目标是开发一个EGFR/ErbB 2激活模型，该模型与所有现存数据一致，并了解EGF受体介导的信号转导中配体特异性差异的分子基础。为此，该基金的具体目标是：1）开发EGFR/ErbB 2异源二聚体激活和磷酸化的准确模型; 2）测试不同EGF受体配体诱导EGF受体不同构象的假设; 3）定量EGF受体最早信号应答的配体特异性差异。我们将使用放射性配体结合以及分子成像和传统的激酶测定来测试我们的假设。这些研究将为ErbB靶向治疗药物的开发和利用提供一个更准确和全面的基础，为研究策略和临床选择奠定基础。 公共卫生相关性： ErbB受体在多种人类肿瘤中突变或过度表达，包括乳腺癌、肺癌和结肠癌。因此，重要的是要确定这些受体之间的相互作用，使信号转导的分子机制可以理解和新的治疗干预策略可以确定。

DESCRIPTION (provided by applicant): The EGF receptor is a classical receptor tyrosine kinase with an extracellular ligand binding domain and an intracellular tyrosine kinase domain. Binding of EGF induces dimerization of the EGF receptor with itself or with other members of the ErbB family of receptor tyrosine kinases with ErbB2 being the preferred dimerization partner. Dimerization of the EGF receptor leads to the stimulation of its intracellular tyrosine kinase activity via the formation of an asymmetric kinase dimer. In this asymmetric dimer, one kinase domain serves as the activator of the other kinase domain. As a result of this mechanism, only one kinase domain can be activated at a time in the receptor dimer. According to the current model, phosphorylation of the receptor then occurs in trans and only takes place in the context of receptor dimers. While appealingly simple, this model cannot explain all aspects of EGFR homodimer and the EGFR/ErbB2 heterodimer function. The EGF receptor has eight different ligands and they are capable of inducing different responses in the same cell line. The molecular basis for this is unknown but it has been hypothesized that the ligands induce different conformations of the EGF receptor. This hypothesis has not been experimentally addressed due to the lack of appropriate tools. Using luciferase fragment complementation imaging, we have documented distinct differences in the response of the EGF receptor to its different ligands, indicating that this method is sensitive to ligand-specific changes in EGF receptor conformation. We have also used radioligand binding studies to document more subtle differences in receptor conformation reflected in differences in the allosteric properties of ligand binding. Therapeutic strategies for targeting ErbB receptors hinge on having a full understanding of how these receptors interact with each other and with their ligands and how they are regulated. The goal of the proposed work is to develop a model of EGFR/ErbB2 activation that is consistent with all extant data and to understand the molecular basis for ligand-specific differences in EGF receptor-mediated signaling. To this end, the specific aims of this grant are to: 1) Develop an accurate model for the activation and phosphorylation in the EGFR/ErbB2 heterodimer; 2) Test the hypothesis that different EGF receptor ligands induce different conformations of the EGF receptor; 3) Quantify ligand-specific differences in the earliest signaling response of the EGF receptor. We will use radioligand binding as well as molecular imaging and traditional kinase assays to test our hypotheses. These studies will provide a more accurate and comprehensive foundation upon which to base research strategies and clinical choices for the development and utilization of ErbB-targeted therapeutics. PUBLIC HEALTH RELEVANCE: ErbB receptors are mutated or over-expressed in a variety of human tumors, including breast, lung and colon cancers. It is therefore important to define the interactions among these receptors so that the molecular mechanism of signal transduction can be understood and new strategies for therapeutic intervention can be identified.