COPII-coated membranes function as transport carriers of intracellular procollagen I.
COPII-coated membranes function as transport carriers of intracellular procollagen I.
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DOI：
10.1083/jcb.201702135
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发表时间：
2017-06-05
期刊：
影响因子：
--
通讯作者：
Schekman R
中科院分区：
文献类型：
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作者：
Gorur A;Yuan L;Kenny SJ;Baba S;Xu K;Schekman R
外壳蛋白复合体II(COPII)对I型前胶原(PC1)等大分子物质的分泌是必不可少的，但缺乏COPII囊泡作为PC1从内质网运输的证据。使用高分辨率显微镜和体外重组囊泡萌发试验，Gorur等人。显示COPII囊泡携带PC1。外壳蛋白复合体II(COPII)对于300 nm I型前胶原(PC1)分子等大型物质从内质网(ER)到高尔基体(Golgi)的运输至关重要。先前的工作表明，CUL3-KLHL12复合体使内质网出口部位的COPII囊泡直径增加到300 nm以上，并加速PC1的分泌。然而，大的COPII囊泡作为PC1运输载体的作用并没有得到明确的证明。在这项研究中，利用随机光学重建显微镜、相关光学电子显微镜和活细胞成像，我们证明了流动的COPII包裹的囊泡的存在，这些囊泡完全包裹着货物PC1，并且物理上与内质网分离。我们还开发了一种无细胞的COPII囊泡发芽反应，将PC1重新捕获到大的COPII囊泡中。这一过程需要COPII蛋白和COPII亚单位SAR1的GTPase活性。我们得出结论，大的COPII囊泡是PC1的真正载体。
The coat protein complex II (COPII) is essential for the secretion of large cargo, such as procollagen I (PC1), but evidence that COPII vesicles act as PC1 transport carriers from the ER was lacking. Using high-resolution microscopy and in vitro reconstituted vesicle budding assays, Gorur et al. show that COPII vesicles carry PC1. The coat protein complex II (COPII) is essential for the transport of large cargo, such as 300-nm procollagen I (PC1) molecules, from the endoplasmic reticulum (ER) to the Golgi. Previous work has shown that the CUL3-KLHL12 complex increases the size of COPII vesicles at ER exit sites to more than 300 nm in diameter and accelerates the secretion of PC1. However, the role of large COPII vesicles as PC1 transport carriers was not unambiguously demonstrated. In this study, using stochastic optical reconstruction microscopy, correlated light electron microscopy, and live-cell imaging, we demonstrate the existence of mobile COPII-coated vesicles that completely encapsulate the cargo PC1 and are physically separated from ER. We also developed a cell-free COPII vesicle budding reaction that reconstitutes the capture of PC1 into large COPII vesicles. This process requires COPII proteins and the GTPase activity of the COPII subunit SAR1. We conclude that large COPII vesicles are bona fide carriers of PC1.