AP-1B-Mediated Protein Sorting Regulates Polarity and Proliferation of Intestinal Epithelial Cells in Mice
AP-1B-Mediated Protein Sorting Regulates Polarity and Proliferation of Intestinal Epithelial Cells in Mice
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DOI：
10.1053/j.gastro.2013.05.013
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发表时间：
2013-09-01
期刊：
影响因子：
29.4
通讯作者：
Ohno, Hiroshi
中科院分区：
文献类型：
--
作者：
Hase, Koji;Nakatsu, Fubito;Ohno, Hiroshi
背景与目的：在上皮细胞中，蛋白分选机制调节产生和维持细胞极性的质膜蛋白的定位。网格蛋白-衔接蛋白（AP）复合物AP-1B在极化上皮细胞中特异性表达，在那里它调节膜蛋白的基底外侧分选。然而，人们对其生理意义知之甚少。方法：我们分析了编码AP-1B mu 1B亚基的Ap 1 m2缺陷小鼠（Ap 1 m2（-/-）小鼠）的肠上皮细胞，并将其与129/B6/CD 1同窝出生小鼠（对照组）进行比较。腹腔注射二苯并氮杂卓抑制Notch信号传导，注射IWR 1抑制β-连环蛋白信号传导。收集肠组织样品并通过免疫荧光分析进行分析。结果：Ap 1 m2（-/-）小鼠出现肠上皮细胞增生。肠上皮细胞的极性被破坏，所示的外观异位微绒毛样结构的侧质膜和基底外侧膜蛋白，包括低密度脂蛋白受体和E-钙粘蛋白的定位错误。因此，E-钙粘蛋白-β-连环蛋白复合物在粘附连接处被破坏，导致β-连环蛋白的核转位。这导致由β-连环蛋白/转录因子4（Tcf 4）复合物调节的基因上调，并增加肠上皮细胞的增殖。结论：AP-1B是小鼠肠细胞蛋白分选和极化所必需的。肠上皮中AP-1B的缺失导致E-钙粘蛋白的错误定位、β-连环蛋白/Tcf 4复合物的活化、增殖和增生。
BACKGROUND & AIMS: In epithelial cells, protein sorting mechanisms regulate localization of plasma membrane proteins that generate and maintain cell polarity. The clathrin-adaptor protein (AP) complex AP-1B is expressed specifically in polarized epithelial cells, where it regulates basolateral sorting of membrane proteins. However, little is known about its physiological significance. METHODS: We analyzed the intestinal epithelia of mice deficient in Ap1m2 (Ap1m2(-/-) mice), which encodes the AP-1B mu 1B subunit, and compared it with 129/B6/CD1 littermates (controls). Notch signaling was inhibited by intraperitoneal injection of dibenzazepine, and beta-catenin signaling was inhibited by injection of IWR1. Intestinal tissue samples were collected and analyzed by immunofluorescence analysis. RESULTS: Ap1m2(-/-) mice developed intestinal epithelial cell hyperplasia. The polarity of intestinal epithelial cells was disrupted, as indicated by the appearance of ectopic microvilli-like structures on the lateral plasma membrane and mislocalization of basolateral membrane proteins, including the low-density lipoprotein receptor and E-cadherin. The E-cadherin-beta-catenin complex therefore was disrupted at the adherens junction, resulting in nuclear translocation of beta-catenin. This resulted in up-regulation of genes regulated by beta-catenin/transcription factor 4 (Tcf4) complex, and increased the proliferation of intestinal epithelial cells. CONCLUSIONS: AP-1B is required for protein sorting and polarization of intestinal cells in mice. Loss of AP-1B in the intestinal epithelia results in mislocalization of E-cadherin, activation of beta-catenin/Tcf4 complex, proliferation, and hyperplasia.