The Role of GAB1:JNK2alpha2 Complex in Glial Tumorigenesis

描述（由申请人提供）：被称为多形性胶质母细胞瘤的高级别人脑肿瘤，其特征是细胞增殖增加、细胞凋亡抵抗和血管增强。对分子机制的研究强烈暗示了受体酪氨酸激酶途径。该项目的目的是研究这些酪氨酸激酶受体的下游途径，以期提高我们对胶质肿瘤发生的理解。对这些途径的更好理解将有希望引导我们改进针对恶性脑肿瘤的治疗方法。Albert Wong博士实验室之前的研究表明，JNK2a2的表达促进了几种致瘤表型，包括细胞生长和致瘤性。他的实验室还克隆了Gab1对接蛋白，这是受体酪氨酸激酶途径的重要组成部分，促进细胞生长、存活和血管的形成。有强有力的证据表明，Gab1在JNK和ERK的功能中起重要的辅助作用。ERK结合Gab1中存在的Met结合域（MBD），这可以导致ERK磷酸化Gab1。Gab1对ERK的功能至关重要，因为ERK缺乏核定位信号（NLS），而是依赖于它与Gab1的关联，而Gab1确实有一个NLS，以进入细胞核。研究发现，在H2O2刺激下，Gab1对JNK的激活至关重要，JNK也与Gab1相关。基于这些原因，我们认为Gab1是细胞中JNK2a2功能的重要组成部分。该项目的目的是确定Gab1: JNK2a2复合物在介导JNK2a2信号传导中的作用及其在胶质肿瘤发生中的作用。在第一个具体目标中，我们将首先在Gab1上建立与JNK2a2相互作用的位点。使用这些信息，在特定的Aim #2中，我们将确定Gab1: JNK2a2复合物直接相互作用的位置。如果我们发现活性Gab1: JNK2a2复合物定位于细胞核，我们将确认这是由于Gab1的核运输。在具体目标#3中，我们将确定Gab1:JNK2a2复合物在介导AKT和PI 3-激酶激活中的作用。利用Gab1的显性阴性突变体干扰与JNK2a2的结合，我们将证明这对干扰胶质肿瘤表型的几个方面有影响。最终，这些信息可能有助于设计脑肿瘤信号通路下调的治疗方法。简而言之，我们正在研究恶性脑肿瘤的分子生物学，希望找到更好的治疗方案。

DESCRIPTION (provided by applicant): The high grade human brain tumors known as glioblastoma multiforme are characterized by an increase in cell proliferation, resistance to apoptosis, and enhanced vascularity. The search for the molecular mechanisms has strongly implicated receptor tyrosine kinases pathways. The objective of this project is to study the downstream pathways for these tyrosine kinase receptors in hopes to improve our understanding of glial tumorigenesis. A better understanding of these pathways will hopefully lead us to improved therapeutics directed at malignant brain tumors. Previous work in the lab of Dr. Albert Wong has shown that expression of JNK2a2 promotes several tumorigenic phenotypes including cell growth and tumorigenicity. His lab also cloned the Gab1 docking protein, which is an essential component in receptor tyrosine kinases pathways that promotes cell growth, survival, and vascularity. There is strong evidence that Gab1 acts as an important accessory for JNK and ERK function. ERK binds to the Met binding domain (MBD) present in Gab1 and this can result in Gab1 phosphorylation by ERK. Gab1 is essential for ERK function as ERK lacks a nuclear localization signal (NLS) and instead relies on its association with Gab1, which does have a NLS, for importation into the nucleus. It has been found that Gab1 is essential for the activation of JNK following stimulation by H2O2 and that JNK also associates with Gab1. For these reasons, we believe that Gab1 is an essential component for JNK2a2 function in cells. The goal of this project is to determine the role of the Gab1: JNK2a2 complex in mediating JNK2a2 signaling and its role in glial tumorigenesis. In the first specific aim, we will first establish the site on Gab1 that interacts with JNK2a2. Using this information, in specific Aim #2, we will determine where the Gab1: JNK2a2 complexes directly interact. Should we find that the active Gab1: JNK2a2 complex localizes to the nucleus, we will confirm that this is due to the nuclear transport by Gab1. In specific aim #3, we will determine the role of the Gab1:JNK2a2 complex in mediating AKT and PI 3-kinase activation. Using dominant negative mutants of Gab1 that interfere with the binding to JNK2a2, we will show that this has an effect on interfering with several aspects of the glial tumor phenotypes. Ultimately, this information may be useful for designing therapeutics for the downregulation of signaling pathways in brain tumors. In plain language, we are studying the molecular biology of malignant brain tumors in hope to find better treatment options for this tumor.