A dileucine motif targets E-cadherin to the basolateral cell surface in Madin-Darby canine kidney and LLC-PK1 epithelial cells
A dileucine motif targets E-cadherin to the basolateral cell surface in Madin-Darby canine kidney and LLC-PK1 epithelial cells
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DOI：
10.1074/jbc.m101907200
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发表时间：
2001-06-22
影响因子：
4.8
通讯作者：
Teasdale, RD
中科院分区：
文献类型：
--
作者：
Miranda, KC;Khromykh, T;Teasdale, RD
E-钙粘蛋白是一种主要的上皮细胞黏附连接蛋白，在细胞间黏附和细胞极性中起着核心作用。新合成的E-钙粘蛋白是针对基底侧细胞表面的，我们利用E-钙粘蛋白与在Madin-Darby犬肾和LLC-PK1上皮细胞表达的白细胞介素2α(IL-2α)受体外膜融合的嵌合体，分析了E-钙粘蛋白胞浆尾部的靶向信息，含有E-钙粘素胞浆尾部全长或膜近端半部分的嵌合体正确地靶向于基外区。对膜近端尾部区域的序列分析表明，存在一个高度保守的二亮氨酸基序，通过突变分析该基序可能是一个靶向信号。该基序的消除导致了Tac/E-钙粘蛋白碱侧定位的丧失，准确地指出这一二亮氨酸信号是碱侧靶向E-钙粘素的必要条件和充分条件，无法结合β-连环蛋白的截断突变体被正确地靶向，表明与目前的理解相反，β-连环蛋白不是基侧转运所必需的。我们的结果还提供了证据，证明二亮氨酸介导的靶向在UC-PK细胞中保持不变，尽管该细胞系中基于酪氨酸的基侧蛋白的极性发生了变化，这些结果首次提供了对E-钙粘附素如何靶向基侧膜的直接见解。
E-cadherin is a major adherens junction protein of epithelial cells, with a central role in cell-cell adhesion and cell polarity. Newly synthesized E-cadherin is targeted to the basolateral cell surface, We analyzed targeting information in the cytoplasmic tail of E-cadherin by utilizing chimeras of E-cadherin fused to the ectodo- main of the interleukin-2 alpha (IL-2 alpha) receptor expressed in Madin-Darby canine kidney and LLC-PK1 epithelial cells, Chimeras containing the full-length or membrane-proximal half of the E-cadherin cytoplasmic tail were correctly targeted to the basolateral domain. Sequence analysis of the membrane-proximal tail region revealed the presence of a highly conserved dileucine motif, which was analyzed as a putative targeting signal by mutagenesis. Elimination of this motif resulted in the loss of Tac/E-cadherin basolateral localization, pinpointing this dileucine signal as being both necessary and sufficient for basolateral targeting of E-cadherin, Truncation mutants unable to bind beta -catenin were correctly targeted, showing, contrary to current understanding, that beta -catenin is not required for basolateral trafficking. Our results also provide evidence that dileucine mediated targeting is maintained in UC-PK, cells despite the altered polarity of basolateral proteins with tyrosine-based signals in this cell line, These results provide the first direct insights into how E-cadherin is targeted to the basolateral membrane.