Mechanisms of Receptor Tyrosine Kinase Inhibition

描述(申请人提供)：生长因子受体酪氨酸激酶(RTK)在组织的发育和维持中发挥核心作用，它们的异常激活有助于各种类型的肿瘤的生长和进展。该项目的长期目标是识别和表征新的RTK负调控通路，以努力更好地了解RTK促进肿瘤进展的机制。当前资金阶段的努力将集中在一种名为LRIG1的新型人类富含亮氨酸的跨膜重复蛋白上。LRIG1与哺乳动物ErbB家族RTK的四个成员在物理上相互作用，增强其泛素化和降解，抑制ErbB介导的培养细胞的增殖和转化。我们的两个主要问题涉及LRIG1对ErbB负调控的生化机制，以及LRIG1在体内参与ErbB信号转导。这些问题将以四个具体目标加以解决。1)LRIG1介导的受体泛素化和降解的机制将通过鉴定负责的E3泛素连接酶(S)来评估。2)将采用突变方法对LRIG1分子进行功能解剖，以确定负责与ErbB受体相互作用的区域，以及负责将受体偶联到蛋白质降解机制的区域。负责LRIG1相互作用的受体结构元件也将被确定。3)在转基因小鼠模型中检测LRIG1对ErbB介导的乳腺肿瘤进展的影响。这些研究将涉及将LRIG1-/-小鼠或诱导过表达LRIG1的小鼠转入MMTV-ErbB2系，并评估肿瘤潜伏期、生长速度和转移频率。4)检测LRIG1在人乳腺肿瘤中的表达，并与ErbB受体蛋白过度表达进行相关性研究。该项目将为LRIG1作为ErbB受体功能的负调控因子奠定生物化学基础。

DESCRIPTION (provided by applicant): Growth factor receptor tyrosine kinases (RTKs) play central roles in the development and maintenance of tissues, and their aberrant activation contributes to the growth and progression of a variety of tumor types. The long-term goal of the proposed project is to identify and characterize novel RTK negative regulatory pathways in an effort to better understand the mechanisms by which RTKs contribute to tumor progression. Efforts for the current funding period will focus on a novel human transmembrane leucine-rich repeat protein called LRIG1. LRIG1 physically interacts with each of the four members of the mammalian ErbB family of RTKs, enhances their ubiquitination and degradation, and suppresses ErbB-mediated proliferation and transformation of cultured cells. Our two overarching questions concern the biochemical mechanisms underlying ErbB negative regulation by LRIG1, and the participation of LRIG1 in ErbB signaling in vivo. These questions will be addressed with four specific aims. 1) The mechanisms underlying LRIG1-mediated receptor ubiquitination and degradation will be assessed by identifying the responsible E3 ubiquitin ligase(s). 2) Mutagenesis approaches will be employed to functionally dissect the LRIG1 molecule to identify regions responsible for interacting with ErbB receptors, and regions responsible for coupling receptors to the protein degradation machinery. Receptor structural elements responsible for LRIG1 interaction will also be identified. 3) The ability of LRIG1 to influence ErbB-mediated mammary tumor progression in a transgenic mouse model will be examined. These studies will involve crossing LRIG1-/- mice or mice inducibly overexpressing LRIG1 into an MMTV-ErbB2 line, and assessing tumor latency, growth rate and metastasis frequency. 4) The expression of LRIG1 in human breast tumors will be examined and correlated with ErbB receptor protein overexpression. The proposed project will lay the biochemical foundation for LRIG1 as a negative regulator of ErbB receptor function.