Internalization and recycling pathways of the thyrotropin receptor
Internalization and recycling pathways of the thyrotropin receptor
复制标题
DOI：
10.1210/me.13.10.1751
复制
发表时间：
1999-10-01
影响因子：
--
通讯作者：
Milgrom, E
中科院分区：
文献类型：
--
作者：
Baratti-Elbaz, C;Ghinea, N;Milgrom, E
迄今为止，关于TSH受体的细胞内运输的信息很少。在本研究中，我们使用了稳定转染的L细胞，表达TSH受体，I-125标记的TSH，和抗受体抗体，以及金结合的抗受体单克隆抗体和激素。后者使我们能够通过电子显微镜研究TSH受体的细胞分布和内吞作用。该受体最初定位于质膜适当的网格蛋白包被的坑，但被排除在光滑的囊泡开放到细胞表面。它通过网格蛋白包被的囊泡内化。组成性内吞占细胞表面受体分子的10%。与激素孵育后，内吞作用增加3倍。大多数内化的受体分子（90%）被回收到细胞表面，而激素在溶酶体中降解。这种受体的再循环被莫能菌素抑制。电子显微镜和共聚焦显微镜的研究中重复的人甲状腺细胞的原代培养物，并显示出的分布，和内吞途径，非常相似的转染L细胞中观察到的。先前的研究表明LH受体被高比例内吞并在溶酶体中降解。与转铁蛋白受体的共聚焦显微镜和共定位研究证实，高度同源的LH和TSH受体表现出，当在相同的细胞中表达时，非常不同的细胞运输特性。LH/TSH受体嵌合体的使用表明，跨膜-细胞内结构域包含将蛋白质定向到回收或降解途径的信息。细胞外结构域似乎在内化的程度中起作用。这些观察现在应该允许识别所涉及的分子信号。
Scant information is available to date on the intracellular trafficking of the TSH receptor. In the present study we have used stably transfected L cells that express the TSH receptor, I-125-labeled TSH, and antireceptor antibodies as well as gold-conjugated antireceptor monoclonal antibodies and hormone. The latter allowed us to study, by electron microscopy, the cellular distribution and endocytosis of TSH receptor. The receptor was initially localized on the plasmalemma proper and in clathrin-coated pits but was excluded from smooth vesicles open to the cell surface. It was internalized through clathrin-coated vesicles. Constitutive endocytosis represented 10% of cell surface receptor molecules. Endocytosis was increased 3-fold by incubation with hormone. The majority of internalized receptor molecules (90%) was recycled to the cell surface, whereas the hormone was degraded in lysosomes. This recycling of receptor was inhibited by administration of monensin. Electron microscopic and confocal microscopic studies were repeated in primary cultures of human thyroid cells and showed a distribution, and endocytosis pathways, very similar to those observed in transfected L cells. A previous study has shown the LH receptor to be endocytosed in high proportion and to be degraded in lysosomes. Confocal microscopy and colocalization studies with transferrin receptor confirmed that the highly homologous LH and TSH receptors exhibit, when expressed in the same cells, very different cellular trafficking properties. The use of LH/TSH receptor chimeras showed that transmembrane-intracellular domains contain information orienting the protein toward recycling or degradative pathways. The extracellular domain seems to play a role in the extent of internalization. These observations should now allow the identification of the molecular signals involved.