Mechanisms of Receptor Tyrosine Kinase Inhibition

描述（由申请人提供）：生长因子受体酪氨酸激酶（RTKs）在组织的发育和维持中起着核心作用，它们的异常激活有助于多种肿瘤类型的生长和进展。该项目的长期目标是识别和表征新的RTK负调控途径，以更好地理解RTK促进肿瘤进展的机制。目前资助期的工作将集中在一种新的人类跨膜富含亮氨酸的重复蛋白LRIG1上。LRIG1与哺乳动物RTKs ErbB家族的四个成员相互作用，增强它们的泛素化和降解，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信号传导。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机制将通过鉴定E3泛素连接酶来评估。2)将采用诱变方法对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。还将确定LRIG1相互作用的受体结构元件。3)我们将在转基因小鼠模型中检测LRIG1影响erbb介导的乳腺肿瘤进展的能力。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细胞系，并评估肿瘤潜伏期、生长速度和转移频率。4)研究LRIG1在人乳腺肿瘤中的表达与ErbB受体蛋白过表达的相关性。该项目将为LRIG1作为ErbB受体功能负调控因子奠定生化基础。

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.