aPKC acts upstream of PAR-1b in both the establishment and maintenance of mammalian epithelial polarity
aPKC acts upstream of PAR-1b in both the establishment and maintenance of mammalian epithelial polarity
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DOI：
10.1016/j.cub.2004.08.021
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发表时间：
2004-08-24
期刊：
影响因子：
9.2
通讯作者：
Ohno, S
中科院分区：
文献类型：
--
作者：
Suzuki, A;Hirata, M;Ohno, S
背景：aPKC和PARA在各种情况下都需要细胞极性。在哺乳动物上皮细胞中，aPKC定位于紧密连接（TJs），在细胞间不对称连接的发展中起着不可或缺的作用，而细胞间不对称连接是建立和维持顶基底极性所必需的。另一方面，哺乳动物的PAR-1激酶之一PAR-1b/EMK1/ MARK2与aPKC互补地定位于外侧膜，但对其在上皮细胞顶基极性中的作用以及与aPKC的功能关系知之甚少。结果：我们证明PAR-1b对于极化MDCK细胞膜结构域的不对称发育至关重要。然而，它不是aPKC连接定位和TJs形成所必需的，这表明PAR-1b在上皮细胞极化过程中作用于aPKC下游。另一方面，aPKC磷酸化PAR-1b的苏氨酸595，增强其与14-3-3/PAR-5的结合。在极化的MDCK细胞中，T595磷酸化和14-3-3结合仅在PAR-1b的可溶性形式中被观察到，冈田酸处理诱导PAR-1b从侧膜上依赖T595解离。此外，T595A突变不仅会导致PAR-1b渗漏到根尖膜，还会导致膜结构域发育异常。这些结果表明，在极化上皮细胞中，aPKC在TJs磷酸化PAR-1b，并与14-3-3合作，促进PAR-1b与侧膜的解离，调节PAR-1b活性，促进膜结构域的发育。结论：这些结果表明，哺乳动物aPKC在PAR-1b的上游参与上皮细胞极性的建立和维持。
Background: aPKC and PARA are required for cell polarity in various contexts. In mammalian epithelial cells, aPKC localizes at tight junctions(TJs) and playsan indispensable role in the development of asymmetric intercellular junctions essential for the establishment and maintenance of apicobasal polarity. On the other hand, one of the mammalian PAR-1 kinases, PAR-1b/EMK1/ MARK2, localizes to the lateral membrane in a complimentary manner with aPKC, but little is known about its role in apicobasal polarity of epithelial cells as well as its functional relationship with aPKC.Results: We demonstrate that PAR-1b is essential for the asymmetric development of membrane domains of polarized MDCK cells. Nonetheless, it is not required for the junctional localization of aPKC nor the formation of TJs, suggesting that PAR-1b works downstream of aPKC during epithelial cell polarization. On the other hand, aPKC phosphorylates threonine 595 of PAR-1b and enhances its binding with 14-3-3/PAR-5. In polarized MDCK cells, T595 phosphorylation and 14-3-3 binding are observed only in the soluble form of PAR-1b, and okadaic acid treatment induces T595-dependent dissociation of PAR-1b from the lateral membrane. Furthermore, T595A mutation induces not only PAR-1b leakage into the apical membrane, but also abnormal development of membrane domains. These results suggest that in polarized epithelial cells, aPKC phosphorylates PAR-1b at TJs, and in cooperation with 14-3-3, promotes the dissociation of PAR-1b from the lateral membrane to regulate PAR-1b activity for the membrane domain development.Conclusions: These results suggest that mammalian aPKC functions upstream of PAR-1b in both the establishment and maintenance of epithelial cell polarity.