Gaisano H Y, Ghai M, Malkus P N, Sheu L, Bouquillon A, Bennett M K, Trimble W S
Department of Medicine, University of Toronto, Ontario, Canada.
Mol Biol Cell. 1996 Dec;7(12):2019-27. doi: 10.1091/mbc.7.12.2019.
Syntaxins are cytoplasmically oriented integral membrane soluble NEM-sensitive factor receptors (SNAREs; soluble NEM-sensitive factor attachment protein receptors) thought to serve as targets for the assembly of protein complexes important in regulating membrane fusion. The SNARE hypothesis predicts that the fidelity of vesicle traffic is controlled in part by the correct recognition of vesicle SNAREs with their cognate target SNARE partner. Here, we show that in the exocrine acinar cell of the pancreas, multiple syntaxin isoforms are expressed and that they appear to reside in distinct membrane compartments. Syntaxin 2 is restricted to the apical plasma membrane whereas syntaxin 4 is found most abundantly on the basolateral membranes. Surprisingly, syntaxin 3 was found to be localized to a vesicular compartment, the zymogen granule membrane. In addition, we show that these proteins are capable of specific interaction with vesicle SNARE proteins. Their nonoverlapping locations support the general principle of the SNARE hypothesis and provide new insights into the mechanisms of polarized secretion in epithelial cells.
Syntaxins是面向细胞质的整合膜可溶性NEM敏感因子受体（SNAREs；可溶性NEM敏感因子附着蛋白受体），被认为是调节膜融合中重要的蛋白质复合物组装的靶点。SNARE假说预测，囊泡运输的保真度部分受囊泡SNARE与其同源靶标SNARE伙伴的正确识别控制。在这里，我们表明，在胰腺的外分泌腺泡细胞中，多种Syntaxin亚型表达，并且它们似乎位于不同的膜区室中。Syntaxin 2局限于顶端质膜，而Syntaxin 4在基底外侧膜上含量最丰富。令人惊讶的是，Syntaxin 3被发现定位于一个囊泡区室，即酶原颗粒膜。此外，我们表明这些蛋白质能够与囊泡SNARE蛋白发生特异性相互作用。它们不重叠的定位支持了SNARE假说的一般原则，并为上皮细胞极化分泌的机制提供了新的见解。
