Differential localization of syntaxin isoforms in polarized Madin-Darby canine kidney cells
Differential localization of syntaxin isoforms in polarized Madin-Darby canine kidney cells
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DOI：
10.1091/mbc.7.12.2007
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发表时间：
1996-12-01
影响因子：
3.3
通讯作者：
Mostov, KE
中科院分区：
文献类型：
--
作者：
Low, SH;Chapin, SJ;Mostov, KE
突触融合蛋白是膜融合机制中的一个重要组成部分，在囊泡对接和融合过程中起着靶向膜受体的作用。先前已经在哺乳动物细胞中鉴定了突触融合蛋白家族的几种同种型，其中一些定位于质膜。我们研究了这些假定的质膜突触融合蛋白在极化上皮细胞，其特征在于存在不同的顶端和基底侧质膜域的亚细胞定位。发现突触融合蛋白2、3和4内源性存在于Madin-Darby犬肾细胞中。用共聚焦免疫荧光显微镜研究了突触融合蛋白1A、1B、2、3和4在稳定转染的Madin-Darby犬肾细胞系中的定位。每种突触融合蛋白亚型被发现具有独特的定位模式。突触融合蛋白1A和1B只存在于细胞内结构，很少或没有明显的质膜染色。与此相反，突触融合蛋白2被发现在顶端和基底外侧表面，而质膜定位的突触融合蛋白3和4分别限于顶端或基底外侧域。因此，突触融合蛋白是第一个已知的质膜融合机制的差异定位在极化细胞中的成分，这表明它们可能在靶向特异性中发挥核心作用。
Syntaxins, integral membrane proteins that are part of the ubiquitous membrane fusion machinery, are thought to act as target membrane receptors during the process of vesicle docking and fusion. Several isoforms of the syntaxin family have been previously identified in mammalian cells, some of which are localized to the plasma membrane. We investigated the subcellular localization of these putative plasma membrane syntaxins in polarized epithelial cells, which are characterized by the presence of distinct apical and basolateral plasma membrane domains. Syntaxins 2, 3, and 4 were found to be endogenously present in Madin-Darby canine kidney cells. The localization of syntaxins 1A, 1B, 2, 3, and 4 in stably transfected Madin-Darby canine kidney cell lines was studied with confocal immunofluorescence microscopy. Each syntaxin isoform was found to have a unique pattern of localization. Syntaxins 1A and 1B were present only in intracellular structures, with little or no apparent plasma membrane staining. In contrast, syntaxin 2 was found on both the apical and basolateral surface, whereas the plasma membrane localization of syntaxins 3 and 4 were restricted to the apical or basolateral domains, respectively. Syntaxins are therefore the first known components of the plasma membrane fusion machinery that are differentially localized in polarized cells, suggesting that they may play a central role in targeting specificity.