Dimerization of the insulin-like growth factor II/mannose 6-phosphate receptor
Dimerization of the insulin-like growth factor II/mannose 6-phosphate receptor
复制标题
DOI：
10.1074/jbc.m001273200
复制
发表时间：
2000-06-23
影响因子：
4.8
通讯作者：
MacDonald, RG
中科院分区：
文献类型：
--
作者：
Byrd, JC;Park, JHY;MacDonald, RG
胰岛素样生长因子 II/甘露糖 6-磷酸受体 (IGF2R) 通过其胞质外结构域中的两个结合结构域与溶酶体酶相互作用。我们在随附的文章 (Byrd, J. C., and MacDonald, R. G. (2000) J. Biol. Chem. 275, 18638-18646) 中报道，两个胞质外甘露糖 6-磷酸 (Man-6-P) 结合结构域中只有一个是高亲和力 Man-6-P 配体结合所必需的，这表明，与阳离子依赖性 Man-6-P 受体一样， IGF2R 有助于与溶酶体酶的高亲和力相互作用。在本研究中，我们直接表征了 IGF2R 天然存在和工程形式的形成寡聚结构的能力。虽然凝胶过滤色谱表明纯化的牛 IGF2R 物种以单体形式存在，但天然凝胶电泳允许分离具有不同磷酸甘露糖基配体结合特征的受体的二聚体和单体形式。 IGF2R 形成寡聚复合物的能力得到证实，并通过使用带有表位标记的可溶性 IGF2R 构建体定位到胞质外结构域，该构建体带有跨膜和胞质结构域的缺失。最后，嵌合受体被设计成含有与表皮生长因子受体的胞质结构域融合的IGF2R的胞质外和跨膜结构域，通过测量自磷酸化可以监测嵌合体的二聚化。总的来说，这些结果表明，在没有 Man-6-P 配体的情况下，IGF2R 能够形成寡聚复合物，最有可能是二聚体。
The insulin-like growth factor II/mannose 6-phosphate receptor (IGF2R) interacts with lysosomal enzymes through two binding domains in its extracytoplasmic domain. We report in the accompanying article (Byrd, J. C., and MacDonald, R. G. (2000) J. Biol. Chem. 275, 18638-18646) that only one of the two extracytoplasmic mannose 6-phosphate (Man-6-P) binding domains is necessary for high affinity Man-6-P ligand binding, suggesting that, like the cation-dependent Man-6-P receptor, oligomerization of the IGF2R contributes to high affinity interaction with lysosomal enzymes. In the present study, we have directly characterized both naturally occurring and engineered forms of the IGF2R for their ability to form oligomeric structures. Whereas gel filtration chromatography suggested that purified bovine IGF2R species exist in a monomeric form, native gel electrophoresis allowed for the separation of dimeric and monomeric forms of the receptors with distinct phosphomannosyl ligand binding characteristics. The ability of the IGF2R to form oligomeric complexes was confirmed and localized to the extracytoplasmic domain through the use of epitope-tagged soluble IGF2R constructs bearing deletions of the transmembrane and cytoplasmic domains. Finally, chimeric receptors were engineered containing the extracytoplasmic and transmembrane domains of the IGF2R fused to the cytoplasmic domain of the epidermal growth factor receptor with which dimerization of the chimeras could be monitored by measuring autophosphorylation. Collectively, these results show that the IGF2R is capable of forming oligomeric complexes, most likely dimers, in the absence of Man-6-P ligands.