Structural Studies of Growth Factor Receptor Function

描述(申请人提供)：受体酪氨酸激酶(RTK)在许多动物组织中调节细胞生长和分化。在人类体内发现了20种不同类别的RTK，包括胰岛素受体、表皮生长因子(EGF)和血管内皮生长因子(VEGF)。RTK由一个胞外配体结合区、一个跨膜区域和一个胞浆酪氨酸激酶组成。与胞外区的配基结合触发了该激酶活性的激活，从而导致下游靶标的磷酸化，并启动了一系列信号级联反应。RTK的不适当激活可能导致细胞生长失控，58个人类RTK中有28个的变化与某种形式的癌症有关。例如，在20-25%的人类乳腺癌中发现EGF受体同系物ErbB2/HER2的过度表达，并与更具侵袭性的肿瘤和更差的预后相关。抑制RTK已被证明是一种有效的抗癌策略，抗EGF受体(Erbitux)和ErbB2/HER2(Herceptin)的单抗已分别被批准用于治疗结直肠癌和乳腺癌。我的实验室最近开发了一种方法，简化了富含半胱氨酸的糖蛋白的表达，其中包括大多数RTK胞外区，用于X射线结构研究。这些方法使我们能够确定人表皮生长因子受体(EGFR)家族的所有四个成员以及ErbB2/HER2与赫赛汀和另一种治疗性抗体Omnitarg的纤维结合的晶体结构。结合其他实验室的结果，这些结构已经为EGFR家族带来了新的信号模型，并为抗癌药物靶向该家族的机制提供了洞察力。我们的第一个目标是扩展这些研究，并确定具有结合配体的特定对EGFR家族成员的胞外区域的晶体结构，以更好地了解该家族内信号转导的性质和特异性。我们的第二个目标是对EGFR家族成员的两个下游信号效应器进行生化和结构研究，以更好地了解EGFR产生的信号是如何在细胞内传递和调节的。我们的第三个目标是启动两类相关RTK的结构研究，包括巨噬细胞集落刺激因子(MCSF)、干细胞因子(SCF)、Flt3配体和血管内皮生长因子的受体，以更好地了解它们在正常和疾病状态下的功能。

DESCRIPTION (provided by applicant): Receptor tyrosine kinases (RTKs) mediate cell growth and differentiation in many animal tissues. Twenty different classes of RTKs are found in humans and include receptors for insulin, epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF). RTKs consist of an extracellular ligand-binding region, a single membrane-spanning region, and a cytoplasmic tyrosine kinase. Ligand binding to the extracellular region triggers activation of the kinase activity, which leads to phosphorylation of downstream targets and initiation of a signaling cascade. Inappropriate activation of RTKs can lead to uncontrolled cell growth, and alterations in 28 of the 58 human RTKs have been associated with some form of cancer. For example, overexpression of the EGF receptor homologue ErbB2/HER2 is found in 20-25% of human breast cancers and is associated with more aggressive tumors and a poorer prognosis. Inhibiting RTKs has proven an effective anticancer strategy, and monoclonal antibodies against the EGF receptor (Erbitux) and ErbB2/HER2 (Herceptin) have been approved for the treatment of colorectal and breast cancer, respectively. My laboratory has recently developed methods that simplify expression of cysteine-rich glycoproteins, which includes most RTK extracellular regions, for X-ray structural studies. These methods have enabled us to determine crystal structures of the extracellular regions of all four members of the human EGF receptor (EGFR) family as well as ErbB2/HER2 complexed with the Fabs of Herceptin and another therapeutic antibody, Omnitarg. Combined with results from other labs, these structures have led to new models of signaling for the EGFR family and provided insight into the mechanism of anticancer agents targeting this family. Our first aim is to extend these studies and determine crystal structures of the extracellular regions of specific pairs of EGFR family members with bound ligand to better understand the nature of signaling and specificity within this family. Our second aim is to perform biochemical and structural studies of two downstream effectors of signaling by EGFR family members to better understand how EGFR generated signals are transmitted and regulated within the cell. Our third aim is to initiate structural studies of two related classes of RTKs, which include the receptors for macrophage colony-stimulating factor (MCSF), stem cell factor (SCF), Flt3 Ligand, and VEGF, to better understand their function in normal and disease states.