NOVEL HER2 SECRETED PROTEIN THAT BINDS TO P185HER2

描述：（逐字改编自研究者摘要）过度表达 p185 HER-2/neu受体酪氨酸激酶（RTK），但不是其他成员的 人EGF受体家族足以赋予转化表型， 与乳腺癌更积极的临床结果相关， 可能是其他人类癌症。由于控制的临床重要性 p185 HER-2的激活，人们已经进行了大量的努力， 鉴定特异性配体，尽管迄今为止还没有特异性， 亲和配体已被鉴定。p185 HER-2的强致癌活性 可能是由于一个未表征的配体，或异常的能力， p185 HER-2二聚化，这是RTK激活所必需的。我们已经确定 一种新的HER-2基因分泌产物，由一种替代转录物编码 在正常人体组织中表达。蛋白质产物p68 ECDIIIa是 由来自p185的亚结构域I和II以及命名为 ECDIIIa.进一步的实验表明，p68 ECDIIIa特异性结合 p185 HER-2在细胞表面，但可能不刺激酪氨酸磷酸化。 此外，过表达p185 HER-2的癌细胞似乎有一种机制， 用于抑制p68 ECDIIIa表达。我们的假设是 ECDIIIa结构域介导与p185 HER-2的特异性结合， 与p68 ECDIIIa的相互作用阻止p185 HER-2二聚化和随后的 信号转导我们现在建议确定 通过测定p68与p185的结合亲和力和通过 定义它们交互所需的域和子域。的 p68 ECDIIIa对p185 HER-2同源和异源的功能意义 通过重组p68 ECDIIIa的作用来检测信号转导 二聚化，生长因子对异聚受体的结合亲和力， 受体自身磷酸化和促有丝分裂信号转导。我们将使用 异源p68 ECDIIIa表达以检验p68抑制ECDIIIa表达的假设。 肿瘤细胞生长为肿瘤细胞提供选择性压力， 过表达p185。p185 HER-2结合蛋白的结构与功能研究 由HER-2基因本身编码的蛋白质，可能为研究HER-2基因的功能提供新的见解。 理解HER-2在正常发育和人类癌症中的作用。

DESCRIPTION: (adapted verbatim from the investigator's abstract) Overexpression of p185HER-2/neu receptor tyrosine kinase (RTK), but not other members of the human EGF receptor family, is sufficient to confer a transformed phenotype and is associated with more aggressive clinical outcome in breast cancer and possibly other human cancers. Because of the clinical importance of controlling the activation of p185HER-2, intensive efforts have been directed toward the identification of a specific ligand, although to date no specific, high affinity ligand has been identified. The potent oncogenic activity of p185HER-2 may be due to an uncharacterized ligand, or to the exceptional capacity of p185HER-2 to dimerize, which is required for RTK activation. We have identified a novel secreted product of the HER-2 gene encoded by an alternative transcript that is expressed in normal human tissues. The protein product, p68ECDIIIa, is composed of subdomains I and II from p185 and a novel C-terminus designated ECDIIIa. Further experiments show that p68ECDIIIa specifically binds to p185HER-2 at the cell surface, but may not stimulate tyrosine phosphorylation. Moreover, carcinoma cells that overexpress p185HER-2 appear to have a mechanism for repression of p68ECDIIIa expression. Our hypothesis is that the unique ECDIIIa domain mediates specific binding to p185HER-2 and the resulting interaction with p68ECDIIIa prevents p185HER-2 dimerization and subsequent signal transduction. We now propose to determine the mechanism of the interaction of p68 with p185 by determining their binding affinities and by defining the domains and subdomains required for their interaction. The functional significance of p68ECDIIIa to p185HER-2 homomeric and heteromeric signal transduction will be examined by the effects of recombinant p68ECDIIIa on dimerization, growth factor binding affinity to heteromeric receptors, receptor autophosphorylation, and mitogenic signal transduction. We will use heterologous p68ECDIIIa expression to test the hypothesis that p68 inhibits tumor cell growth providing a selective pressure for tumor cells which overexpress p185. Studies on the structural and function of a p185HER-2 binding protein, encoded by the HER-2 gene itself, may provide novel insight for understanding the role of HER-2 in normal development and in human cancers.