Molecular Dissection of IGF2R Growth Suppressor Activity

描述（由申请人提供）：通过其许多配体结合功能， 胰岛素样生长因子 II/甘露糖 6-磷酸受体 (IGF2R) 是 负责运输含甘露糖 6-磷酸 (Man-6-P) 的溶酶体 酶到达适当的细胞内目的地，以介导吸收 以及随后有丝分裂原、胰岛素样生长因子 11 的降解 (IGF-II)，并促进生长抑制剂的激活，转化 生长因子-b (TGF-b)。这些活动中的每一项都符合 提出了 IGF2R 作为肿瘤抑制因子的作用，但其具体作用是什么？ IGF2R 的配体结合功能负责细胞生长 抑制活性尚未得到直接解决。本项目将测试 假设 IGF2R 的生长抑制活性取决于 其 IGF-II 和 Man-6-F 结合功能的有效操作，通过 以下具体目标： 1）测量生长抑制作用 野生型 IGF2R 与 Man-6-P 与 IGF-II 结合中突变的受体 功能。用野生型 IGF2R cDNA 转染的 IGF2R 缺陷细胞系 结合 IGF-II 或 Man-6-P 存在缺陷的表达构建体或 IGF2R 突变体 将分析配体相对于载体转染的增殖 控制。我们的预期是，野生型 IGF2R 表达的增加将 抑制细胞生长，并且突变体将表现出这种损害 生长抑制活性。 2) 确定癌症相关的影响 M6P/IGF2R 错义或截短突变对生长抑制活性的影响 IGF2R 的。我们预计错义突变将表现出减少 IGF2R 功能以及截短突变体可能具有新的显性失活 影响。 3) 评估对受体生长抑制的贡献 依赖于 IGF2R 的受体前和受体结合事件后的活性 二聚化，即开发高亲和力配体结合并增强 内化。这些研究将有助于了解受体的 肿瘤抑制功能并允许合理设计利用的策略 IGF2R 在癌症预防和治疗中的作用。

DESCRIPTION (provided by applicant): Through its many ligand-binding functions, the insulin-like growth factor Il/mannose 6-phosphate receptor (IGF2R) is responsible for transporting mannose-6-phosphate (Man-6-P)-bearing lysosomal enzymes to their appropriate intracellular destination, for mediating uptake and subsequent degradation of the mitogen, insulin-like growth factor 11 (IGF-II), and for facilitating activation of the growth inhibitor, transforming growth factor-b (TGF-b). Each of these activities is consistent with the proposed role of the IGF2R as a tumor suppressor, yet the question of which ligand-binding functions of the IGF2R are responsible for the cell-growth suppressor activity have not been directly addressed. This project will test the hypothesis that the IGF2R's growth suppressor activity depends on the efficient operation of both its IGF-II and Man-6-F binding functions, by the following specific aims: 1) To measure the growth-suppressive effects of wild-type IGF2R vs. receptors mutated in the Man-6-P vs. IGF-II binding functions. IGF2R-deficient cell lines transfected with wild-type IGF2R cDNA expression constructs or IGF2R mutants defective in binding IGF-II or Man-6-P ligands will be analyzed for proliferation relative to vector-transfected controls. Our expectation is that increased wild-type IGF2R expression will inhibit cell growth, and that the mutants will show impairment of this growth-suppressive activity. 2) To determine the effects of cancer-associated M6P/IGF2R missense or truncation mutations on the growth-suppressive activity of the IGF2R. We expect that missense mutations will exhibit reductions in IGF2R function and that truncation mutants may have novel dominant-negative effects. 3) To assess the contribution to the receptor's growth-suppressive activity of pre- and post-receptor binding events that depend on IGF2R dimerization, i.e. development of high-affinity ligand binding and enhanced internalization. These studies will contribute to understanding the receptor's tumor suppressor function and permit rational design of strategies that exploit the IGF2R in cancer prevention and therapy.