Exocyst function is regulated by effector phosphorylation.
Exocyst function is regulated by effector phosphorylation.
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DOI：
10.1038/ncb2226
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发表时间：
2011-05
影响因子：
21.3
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中科院分区：
文献类型：
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外囊复合物通过与小GTP酶的相互作用将囊泡束缚在融合位点。G蛋白RalA位于Glut4囊泡上，并在胰岛素激活后与外泌囊结合，但随后必须脱离以确保连续的胞吐作用。在这里，我们报告说，识别后的外囊激活RalA，脱离发生通过磷酸化的效应Sec5，而不是RalA失活。Sec5在G蛋白结合结构域中经历磷酸化，变构减少RalA相互作用。磷酸化事件由蛋白激酶C催化，并由外囊相关磷酸酶逆转。将Sec5的磷酸化位点突变引入丙氨酸或天冬氨酸会破坏胰岛素刺激的Glut4胞吐作用，以及极化上皮细胞和斑马鱼胚胎发育过程中的其他运输过程。因此，外泌囊通过与G蛋白接合、脱离和重新接合的回路充当外泌囊泡的“看门人”。
The exocyst complex tethers vesicles at sites of fusion through interactions with small GTPases. The G-protein RalA resides on Glut4 vesicles, and binds to the exocyst after activation by insulin, but must then disengage to ensure continuous exocytosis. Here we report that after recognition of the exocyst by activated RalA, disengagement occurs through phosphorylation of its effector Sec5, rather than RalA inactivation. Sec5 undergoes phosphorylation in the G-protein binding domain, allosterically reducing RalA interaction. The phosphorylation event is catalyzed by protein kinase C and is reversed by an exocyst-associated phosphatase. Introduction of Sec5 bearing mutations of the phosphorylation site to either alanine or aspartate disrupts insulin-stimulated Glut4 exocytosis, as well as other trafficking processes in polarized epithelial cells and during development of zebrafish embryos. The exocyst thus serves as a “gatekeeper” for exocytic vesicles through a circuit of engagement, disengagement, and re-engagement with G proteins.