NOVEL HER2 SECRETED PROTEIN THAT BINDS TO P185HER2

描述：(逐字改编自调查员的摘要)过度表达 P185HER-2/neu受体酪氨酸激酶(RTK)，而不是 人EGF受体家族，足以赋予转化的表型和 与乳腺癌更具侵袭性的临床结局相关 可能是其他人类癌症。因为控制的临床重要性 随着p185HER-2的激活，密集的努力已经指向 特定配基的鉴定，尽管到目前为止还没有特定的、高的 亲和配基已经确定。P185HER-2的强致癌活性 可能是由于一种未表征的配体，或者由于具有特殊的能力 P185HER-2二聚化，这是RTK激活所必需的。我们已经确定了 由另一种转录物编码的HER-2基因的新分泌产物 它在正常的人体组织中表达。蛋白质产物p68ECDIIIa是 由来自p185的亚区I和II和一个新的C-末端组成 ECDIIIa进一步的实验表明，p68ECDIIa特异性地结合到 P185HER-2存在于细胞表面，但不能刺激酪氨酸磷酸化。 此外，过表达p185HER-2的癌细胞似乎有一个机制 用于抑制p68ECDIIa表达。我们的假设是独一无二的 ECDIIa结构域介导与p185HER-2的特异性结合 与p68ECDIIa的相互作用阻止了p185HER-2的二聚化和随后的 信号转导。我们现在建议确定 测定p68与p185的结合亲和力及相互作用 定义它们交互所需的域和子域。这个 P68ECDIIa对p185HER-2同聚体和异构体的功能意义 信号转导将通过重组p68ECDIIIa的作用来检验 关于二聚化，生长因子与异构体受体的亲和力， 受体自磷酸化和有丝分裂信号转导。我们将使用 P68ECDIIa异源表达验证p68抑制假说 肿瘤细胞的生长为肿瘤细胞提供了选择性压力 过度表达P185。P185HER-2结合蛋白的结构和功能研究 由HER-2基因本身编码的蛋白质可能为 了解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.