Localization of membrane-associated guanylate kinase (MAGI)-1/BAI-associated protein (BAP) 1 at tight junctions of epithelial cells
Localization of membrane-associated guanylate kinase (MAGI)-1/BAI-associated protein (BAP) 1 at tight junctions of epithelial cells
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DOI：
10.1038/sj.onc.1203153
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发表时间：
1999-12-16
期刊：
影响因子：
8
通讯作者：
Takai, Y
中科院分区：
文献类型：
--
作者：
Ide, N;Hata, Y;Takai, Y
膜相关鸟苷酸激酶-1/BAI-相关蛋白1和突触相关蛋白97/人Discs-大肿瘤抑制基因是突触支架分子S-SCAM和突触后密度-95/SAP90的普遍亚型，它们分别与突触结构有关。SAP97/hDLG定位于上皮细胞连接，可能作为支架蛋白发挥作用，但MAGI-1/BAP1的亚细胞定位或功能尚不清楚。在肠上皮细胞中，MAGI-1/BAP1定位于紧密连接，而SAP97/hDLG定位于细胞间连接。在Madine Darby犬肾(MDCK)细胞中，MAGI-1/BAP1与ZO-1共定位，而SAP97/hDLG与E-钙粘素共定位。在MDCK细胞中，Rad小G蛋白的显性活性突变体和阴性突变体改变了细胞间连接处SAP97/hDLG的数量，但不改变MAGI-1/BAP1的数量。当MDCK细胞被切换到低钙时，E-钙粘附素从质膜上消失，细胞解离。低钙开关后的佛波醇12-肉豆蔻酸酯13-乙酸酯处理诱导了紧密连接样结构。MAGI-1/BAP1与ZO-1一起被招募到这个结构中，而SAP97/hDLG或E-cadherin则没有。提示MAGI-1/BAP1是上皮细胞紧密连接的组成部分，其作用不同于SAP97/hDLG。
Membrane-associated guanylate kinase (MAGI)-1/BAI-associated protein (BAP) 1 and Synapse-associated protein (SAP) 97/human Discs-large tumor suppressor gene (hDLG) are ubiquitous isoforms of synaptic scaffolding molecule (S-SCAM) and Postsynaptic density(PSD)-95/SAP90, both of which are implicated in the structures of synapses, respectively. SAP97/hDLG is localized at epithelial junctions and may function as a scaffolding protein, but the subcellular localization or the function of MAGI-1/BAP1 has not been clarified. In intestinal epithelial cells, MAGI-1/BAP1 was localized at tight junctions, whereas SAP97/hDLG was localized diffusely at cell-cell junctions. In Madine Darby canine kidney (MDCK) cells, MAGI-1/BAP1 was colocalized with ZO-1, whereas SAP97/hDLG was colocalized with E-cadherin. In MDCK cells, dominant active and negative mutants of Rad small G protein changed the amounts of SAP97/hDLG at cell-cell junctions, but not that of MAGI-1/BAP1. When MDCK cells were switched to a low Ca2+ medium, E-cadherin disappeared from the plasma membrane, and cells were dissociated. The phorbol 12-myristate 13-acetate-treatment after the low Ca2+ switch induced a tight junction-like structure. MAGI-1/BAP1 was recruited with ZO-1 to this structure, but SAP97/hDLG or E-cadherin was not. These findings suggest that MAGI-1/BAP1 is a component of tight junctions of epithelial cells, and that its role is different from that of SAP97/hDLG.