Ternary SNARE complexes are enriched in lipid rafts during mast cell exocytosis
Ternary SNARE complexes are enriched in lipid rafts during mast cell exocytosis
复制标题
DOI：
10.1111/j.1600-0854.2006.00490.x
复制
发表时间：
2006-11-01
期刊：
影响因子：
4.5
通讯作者：
Roche, Paul A.
中科院分区：
文献类型：
--
作者：
Puri, Niti;Roche, Paul A.
脂筏是富含胆固醇和鞘糖脂的膜微区，参与细胞内蛋白质运输的调节。在胞吐过程中，一类称为SNARE的蛋白质介导分泌颗粒-质膜融合。为了研究脂筏在分泌颗粒胞吐中的作用，我们检测了大鼠嗜碱性白血病（RBL）肥大细胞中SNARE蛋白和SNARE复合物的脂筏结合。SNARE蛋白SNAP-23与脂筏标记物共定位，并且存在于RBL细胞中的洗涤剂不溶性脂筏微结构域中。相比之下，只有少量（< 20%）的质膜SNARE syntaxin 4或颗粒相关SNARE囊泡相关膜蛋白（VAMP）-2存在于这些微结构域中。尽管如此，基本上所有的突触融合蛋白4和大多数的VAMP-2在这些筏存在于SNARE复合物含有SNAP-23，而基本上没有这些复合物存在于非筏膜。尽管SNAP-23是通过棕榈酰化来膜锚定的，跨膜蛋白突触融合蛋白4与脂筏的结合是因为其与SNAP-23结合。在刺激肥大细胞胞吐后，突触融合蛋白4和VAMP-2在筏中的量增加了两倍，并且这些蛋白质现在存在于筏相关的磷酸-SNAP-23/突触融合蛋白4/VAMP-2复合物中，揭示了SNARE融合复合物在调节胞吐过程中的差异关联。
Lipid rafts are membrane microdomains rich in cholesterol and glycosphingolipids that have been implicated in the regulation of intracellular protein trafficking. During exocytosis, a class of proteins termed SNAREs mediate secretory granule-plasma membrane fusion. To investigate the role of lipid rafts in secretory granule exocytosis, we examined the raft association of SNARE proteins and SNARE complexes in rat basophilic leukemia (RBL) mast cells. The SNARE protein SNAP-23 co-localized with a lipid raft marker and was present in detergent-insoluble lipid raft microdomains in RBL cells. By contrast, only small amounts (< 20%) of the plasma membrane SNARE syntaxin 4 or the granule-associated SNARE vesicle-associated membrane protein (VAMP)-2 were present in these microdomains. Despite this, essentially all syntaxin 4 and most of VAMP-2 in these rafts were present in SNARE complexes containing SNAP-23, while essentially none of these complexes were present in nonraft membranes. Whereas SNAP-23 is membrane anchored by palmitoylation, the association of the transmembrane protein syntaxin 4 with lipid rafts was because of its binding to SNAP-23. After stimulating mast cells exocytosis, the amount of syntaxin 4 and VAMP-2 present in rafts increased twofold, and these proteins were now present in raft-associated phospho-SNAP-23/syntaxin 4/VAMP-2 complexes, revealing differential association of SNARE fusion complexes during the process of regulated exocytosis.