SPIKE1 Signals Originate from and Assemble Specialized Domains of the Endoplasmic Reticulum
SPIKE1 Signals Originate from and Assemble Specialized Domains of the Endoplasmic Reticulum
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DOI：
10.1016/j.cub.2010.11.016
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发表时间：
2010-12-07
期刊：
影响因子：
9.2
通讯作者：
Szymanski, Daniel B.
中科院分区：
文献类型：
--
作者：
Zhang, Chunhua;Kotchoni, Simeon O.;Szymanski, Daniel B.
在叶表皮中，错综复杂的叶状铺面细胞使用植物的Rho（ROP）小GTP酶来整合肌动蛋白和微管组织，并通过分泌途径运输[1-5]。细胞信号传导的发生是因为鸟嘌呤核苷酸交换因子（GEF）促进ROP活化及其与指导细胞生长机制的效应蛋白的相互作用[6]。在拟南芥中，SPIKE 1（SPK 1）是唯一的DOCK家族GEF [7，8]。SPK 1促进叶表皮的极化生长和细胞-细胞粘附;然而，其在细胞中的作用模式尚不清楚。脊椎动物DOCK蛋白在质膜上展开[9，10]。同样，目前的模型将SPK 1活性和/或活性ROP置于植物质膜上，并调用皮层细胞骨架的局部图案化作为形状控制的机制[1，4，6，11]。在本文中，我们发现，SPK 1是一种外周膜蛋白，积累在，并促进形成，一个专门的领域的内质网（ER）称为ER出口网站（ERES）。SPK 1信号由ERES点源的分布式网络产生，并维持早期分泌途径的稳态。ERES是从ER出口货物的地点[12]。我们的研究结果开辟了意想不到的领域植物G蛋白生物学和重新定义ERES作为一个亚细胞位置的信号整合在形态发生。
In the leaf epidermis, intricately lobed pavement cells use Rho of plants (ROP) small GTPases to integrate actin and microtubule organization with trafficking through the secretory pathway [1-5]. Cell signaling occurs because guanine nucleotide exchange factors (GEFs) promote ROP activation and their interactions with effector proteins that direct the cell growth machineries [6]. In Arabidopsis, SPIKE1 (SPK1) is the lone DOCK family GEF [7, 8]. SPK1 promotes polarized growth and cell-cell adhesion in the leaf epidermis; however, its mode of action in cells is not known. Vertebrate DOCK proteins are deployed at the plasma membrane [9, 10]. Likewise, current models place SPK1 activity and/or active ROP at the plant plasma membrane and invoke the localized patterning of the cortical cytoskeleton as the mechanism for shape control [1, 4, 6, 11]. In this paper, we find that SPK1 is a peripheral membrane protein that accumulates at, and promotes the formation of, a specialized domain of the endoplasmic reticulum (ER) termed the ER exit site (ERES). SPK1 signals are generated from a distributed network of ERES point sources and maintain the homeostasis of the early secretory pathway. The ERES is the location for cargo export from the ER [12]. Our findings open up unexpected areas of plant G protein biology and redefine the ERES as a subcellular location for signal integration during morphogenesis.