Structural requirements and sequence motifs for polarized sorting and endocytosis of LDL and Fc receptors in MDCK cells.
Structural requirements and sequence motifs for polarized sorting and endocytosis of LDL and Fc receptors in MDCK cells.
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DOI：
10.1083/jcb.126.4.991
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发表时间：
1994-08
影响因子：
7.8
通讯作者：
Mellman, I
中科院分区：
文献类型：
--
作者：
Matter, K;Yamamoto, E M;Mellman, I
在MDCK细胞中，大多数膜蛋白的基底外侧分选已被证明依赖于不同的胞质结构域决定簇。这些信号可分为与网格蛋白包被的凹坑定位信号相关的信号和不相关的信号。LDL受体具有两个含酪氨酸的信号，每类一个，其可以独立地将来自高尔基复合体和内体的受体靶向至基底外侧质膜。我们现在已经研究了这两种决定因素的活性所需的其他结构特征。我们发现，这两个依赖于，至少在一定程度上，对集群的1-3个酸性氨基酸位于COOH端侧的每个酪氨酸。虽然也发现与每个酪氨酸相邻的单个残基是关键的，但两个信号的不同之处在于，只有包被的坑无关的信号可以耐受苯丙氨酸代替其酪氨酸残基。我们还发现，基底外侧靶向的“包被坑相关”信号的结构要求是不同的快速内吞作用所需的。除了共享一个共同的酪氨酸残基，没有功能的NPXY基序包被坑定位所需的基底外侧靶向。我们还研究了小鼠巨噬细胞Fc受体（FcRII-B2）的基底外侧靶向，该受体含有酪氨酸非依赖性包被的凹坑定位信号。基底侧运输和内吞作用被发现依赖于一个共同的二亮氨酸型基序。因此，基底外侧靶向决定簇，如包被的凹坑结构域，可以包含含酪氨酸或含二亮氨酸的信号。这些基序附近的氨基酸决定了它们是否作为内吞作用、基底外侧靶向作用或两者的决定因素。
In MDCK cells, basolateral sorting of most membrane proteins has been shown to depend on distinct cytoplasmic domain determinants. These signals can be divided into those which are related to signals for localization at clathrin-coated pits and those which are unrelated. The LDL receptor bears two tyrosine-containing signals, one of each class, that can independently target receptors from the Golgi complex and from endosomes to the basolateral plasma membrane. We have now investigated the other structural features required for the activity of both determinants. We find that both depend, at least in part, on clusters of 1-3 acidic amino acids located on the COOH-terminal side of each tyrosine. While single residues adjacent to each tyrosine were also found to be critical, the two signals differed in that only the coated pit-unrelated signal could tolerate a phenylalanine in place of its tyrosine residue. We also found that the structural requirements for basolateral targeting of the "coated pit-related" signal were distinct from those required for rapid endocytosis. Apart from sharing a common tyrosine residue, no feature of the NPXY motif for coated pit localization was required for basolateral targeting. We also investigated basolateral targeting of the mouse macrophage Fc receptor (FcRII-B2) which contains a tyrosine-independent coated pit localization signal. Basolateral transport and endocytosis were found to depend on a common dileucine-type motif. Thus, basolateral targeting determinants, like coated pit domains, can contain either tyrosine- or di-leucine-containing signals. The amino acids in the vicinity of these motifs determine whether they function as determinants for endocytosis, basolateral targeting, or both.