Molecular Dissection of IGF2R Growth Suppressor Activity

说明（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（IGF 2 R）， 负责转运携带甘露糖-6-磷酸（Man-6-P）的溶酶体 酶到其适当的细胞内目的地，用于介导摄取 以及随后的促分裂原胰岛素样生长因子11的降解 （IGF-II），以及促进生长抑制剂的活化，转化 生长因子-b（TGF-β）。每一项活动都符合 IGF 2 R作为肿瘤抑制因子的作用，但问题是 IGF 2 R的配体结合功能负责细胞生长 抑制剂活性尚未直接涉及。该项目将测试 IGF 2 R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， 以下具体目的：1）测量生长抑制作用 野生型IGF 2 R与Man-6-P与IGF-II结合中突变的受体 功能协调发展的用野生型IGF 2 R cDNA转染的IGF 2 R缺陷细胞系 结合IGF-II或Man-6-P缺陷的表达构建体或IGF 2 R突变体 将分析配体相对于载体转染的 对照我们的预期是，野生型IGF 2 R表达的增加将导致IGF 2 R基因的表达增加。 抑制细胞生长，突变体将表现出这种损害 生长抑制活性。2)为了确定癌症相关的 M6 P/IGF 2 R错义或截短突变对生长抑制活性的影响 IGF2R我们预计错义突变将表现出减少 IGF 2 R功能和截短突变体可能具有新的显性负性 方面的影响. 3)为了评估受体的生长抑制作用， 依赖于IGF 2 R的受体前和后结合事件的活性 二聚化，即高亲和力配体结合的发展和增强 内化这些研究将有助于了解受体的功能。 肿瘤抑制功能，并允许合理设计策略， IGF 2 R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.