Li Xin, Low Seng Hui, Miura Masumi, Weimbs Thomas
Department of Cell Biology, Lerner Research Institute, and Urological Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA.
Am J Physiol Renal Physiol. 2002 Nov;283(5):F1111-22. doi: 10.1152/ajprenal.00185.2002.
The apical- and basolateral-specific distribution of target soluble N-ethylmaleimide-sensitive factor attachment protein receptors (t-SNAREs) of the syntaxin family appear to be critical for polarity in epithelial cells. To test whether differential SNARE expression and/or subcellular localization may contribute to the known diversity of trafficking phenotypes of epithelial cell types in vivo, we have investigated the distribution of syntaxins 2, 3, and 4 in epithelial cells along the renal tubule. Syntaxins 3 and 4 are restricted to the apical and basolateral domains, respectively, in all cell types, indicating that their mutually exclusive localizations are important for cell polarity. The expression level of syntaxin 3 is highly variable, depending on the cell type, suggesting that it is regulated in concert with the cellular requirement for apical exocytic pathways. While syntaxin 4 localizes all along the basal and lateral plasma membrane domains in vivo, it is restricted to the lateral membrane in Madin-Darby canine kidney (MDCK) cells in two-dimensional monolayer culture. When cultured as cysts in collagen, however, MDCK cells target syntaxin 4 correctly to the basal and lateral membranes. Unexpectedly, the polarity of syntaxin 2 is inverted between different tubule cell types, suggesting a role in establishing plasticity of targeting. The vesicle-associated (v)-SNARE endobrevin is highly expressed in intercalated cells and colocalizes with the H(+)-ATPase in alpha- but not beta-intercalated cells, suggesting its involvement in H(+)-ATPase trafficking in the former cell type. These results suggest that epithelial membrane trafficking phenotypes in vivo are highly variable and that different cell types express or localize SNARE proteins differentially as a mechanism to achieve this variability.
syntaxin家族的靶可溶性N - 乙基马来酰亚胺敏感因子附着蛋白受体（t - SNAREs）在顶端和基底外侧的特异性分布似乎对上皮细胞的极性至关重要。为了测试不同的SNARE表达和/或亚细胞定位是否可能导致体内上皮细胞类型已知的转运表型多样性，我们研究了肾小管上皮细胞中syntaxins 2、3和4的分布。在所有细胞类型中，syntaxins 3和4分别局限于顶端和基底外侧结构域，这表明它们相互排斥的定位对细胞极性很重要。syntaxin 3的表达水平高度可变，取决于细胞类型，这表明它与顶端胞吐途径的细胞需求协同调节。虽然syntaxin 4在体内定位于整个基底和外侧质膜结构域，但在二维单层培养的Madin - Darby犬肾（MDCK）细胞中，它局限于外侧膜。然而，当在胶原蛋白中培养成囊肿时，MDCK细胞将syntaxin 4正确地靶向基底和外侧膜。出乎意料的是，syntaxin 2的极性在不同的肾小管细胞类型之间发生反转，这表明它在建立靶向可塑性中起作用。囊泡相关（v）-SNARE内体蛋白在闰细胞中高度表达，并与α - 而非β - 闰细胞中的H(+) - ATP酶共定位，表明它参与了前一种细胞类型中H(+) - ATP酶的转运。这些结果表明，体内上皮细胞膜转运表型高度可变，并且不同细胞类型以实现这种变异性的机制差异表达或定位SNARE蛋白。
