Sorting nexin 27 regulates basal and stimulated brush border trafficking of NHE3.
Sorting nexin 27 regulates basal and stimulated brush border trafficking of NHE3.
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DOI：
10.1091/mbc.e14-12-1597
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发表时间：
2015-06-01
影响因子：
3.3
通讯作者：
Donowitz M
中科院分区：
文献类型：
--
作者：
Singh V;Yang J;Cha B;Chen TE;Sarker R;Yin J;Avula LR;Tse M;Donowitz M
在极化上皮细胞中，SNX27 调节 PDZ 结构域定向 NHE3 从内体到质膜的运输，并增加刷状缘 NHE3 的稳定性。这使得 SNX27 成为上皮细胞极化分选的重要调节因子。分选 nexin 27 (SNX27) 包含一个 PDZ 结构域，该结构域在系统发育上与 NHERF 蛋白的 PDZ 结构域相关。对非上皮细胞的研究表明，这种蛋白质位于核内体中，以 PDZ 结构域依赖性方式调节货物蛋白的运输。然而，SNX27 在上皮细胞中货物蛋白运输中的作用尚未得到充分探索。在这里，我们表明 SNX27 主要通过 SNX27 PDZ 结构域直接与 NHE3（C 端）相互作用。使用野生型和 SNX27 的 PDZ 结构域突变体 (GYGF → GAGA) 进行的敲低和重建实验相结合，证明 SNX27 的 PDZ 结构域对于维持极化上皮细胞中 NHE3 的基础活性和 NHE3 的表面表达是必需的。基于生物素化的肠上皮细胞回收和降解研究表明，NHE3 从早期内体到质膜的胞吐作用（而非内吞作用）需要 SNX27。 SNX27 还需要调节 NHE3 在质膜上的保留。本研究的结果扩展了我们对 PDZ 介导的货物蛋白从内体到上皮细胞质膜再循环的理解。
In polarized epithelial cells, SNX27 regulates PDZ domain–directed trafficking of NHE3 from endosomes to the plasma membrane and increases the stability of brush border NHE3. This establishes SNX27 as an important regulator of polarized sorting in epithelial cells. Sorting nexin 27 (SNX27) contains a PDZ domain that is phylogenetically related to the PDZ domains of the NHERF proteins. Studies on nonepithelial cells have shown that this protein is located in endosomes, where it regulates trafficking of cargo proteins in a PDZ domain–dependent manner. However, the role of SNX27 in trafficking of cargo proteins in epithelial cells has not been adequately explored. Here we show that SNX27 directly interacts with NHE3 (C-terminus) primarily through the SNX27 PDZ domain. A combination of knockdown and reconstitution experiments with wild type and a PDZ domain mutant (GYGF → GAGA) of SNX27 demonstrate that the PDZ domain of SNX27 is required to maintain basal NHE3 activity and surface expression of NHE3 in polarized epithelial cells. Biotinylation-based recycling and degradation studies in intestinal epithelial cells show that SNX27 is required for the exocytosis (not endocytosis) of NHE3 from early endosome to plasma membrane. SNX27 is also required to regulate the retention of NHE3 on the plasma membrane. The findings of the present study extend our understanding of PDZ-mediated recycling of cargo proteins from endosome to plasma membrane in epithelial cells.