Structural requirements for basolateral sorting of the human transferrin receptor in the biosynthetic and endocytic pathways of Madin-Darby canine kidney cells.
Structural requirements for basolateral sorting of the human transferrin receptor in the biosynthetic and endocytic pathways of Madin-Darby canine kidney cells.
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DOI：
10.1083/jcb.137.6.1255
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发表时间：
1997-06-16
期刊：
影响因子：
--
通讯作者：
Trowbridge IS
中科院分区：
文献类型：
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作者：
Odorizzi G;Trowbridge IS
在极化的Madin-Darby犬肾（MDCK）细胞中，转铁蛋白受体（TR）被选择性地传递到基底外侧表面，在那里它通过网格蛋白包被的凹坑和网格将转铁蛋白内化回到基底外侧边界。突变体无尾受体随机排序的生物合成和内吞途径，表明TR的基底外侧排序依赖于位于61个氨基酸的胞质结构域内的信号。为了鉴定TR的基底外侧分选信号，我们分析了在MDCK细胞中表达的一系列突变的人TR。我们发现残基19-41足以从生物合成和内吞途径进行基底外侧分选，并且这是TR胞质尾区包含基底外侧分选信息的唯一区域。基底外侧分选信号不同于该区域内包含的YTRF内化信号，并且不是基于酪氨酸的。详细的功能分析的突变TR表明，残基29-35是最重要的生物合成途径的基底外侧排序。内吞途径的内化受体的基底外侧分选的结构要求是不相同的。最显著的差异是G31 DNS 34改变为YTRF损害了来自生物合成途径的新合成受体的基底外侧分选，但不损害来自内吞途径的内化受体。此外，已经鉴定了选择性地损害来自内吞途径的内化TR的基底外侧分选而不影响新合成的受体的基底外侧分选的突变。这些结果意味着，在识别TR基底外侧分选信号中存在细微的差异，这些信号由位于生物合成和内吞途径内的单独分选机制识别。
In polarized Madin-Darby canine kidney (MDCK) cells, the transferrin receptor (TR) is selectively delivered to the basolateral surface, where it internalizes transferrin via clathrin-coated pits and recycles back to the basolateral border. Mutant tailless receptors are sorted randomly in both the biosynthetic and endocytic pathways, indicating that the basolateral sorting of TR is dependent upon a signal located within the 61–amino acid cytoplasmic domain. To identify the basolateral sorting signal of TR, we have analyzed a series of mutant human TR expressed in MDCK cells. We find that residues 19–41 are sufficient for basolateral sorting from both the biosynthetic and endocytic pathways and that this is the only region of the TR cytoplasmic tail containing basolateral sorting information. The basolateral sorting signal is distinct from the YTRF internalization signal contained within this region and is not tyrosine based. Detailed functional analyses of the mutant TR indicate that residues 29–35 are the most important for basolateral sorting from the biosynthetic pathway. The structural requirements for basolateral sorting of internalized receptors from the endocytic pathway are not identical. The most striking difference is that alteration of G31DNS34 to YTRF impairs basolateral sorting of newly synthesized receptors from the biosynthetic pathway but not internalized receptors from the endocytic pathway. Also, mutations have been identified that selectively impair basolateral sorting of internalized TRs from the endocytic pathway without affecting basolateral sorting of newly synthesized receptors. These results imply that there are subtle differences in the recognition of the TR basolateral sorting signal by separate sorting machinery located within the biosynthetic and endocytic pathways.