Hsc70 chaperones clathrin and primes it to interact with vesicle membranes
Hsc70 chaperones clathrin and primes it to interact with vesicle membranes
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DOI：
10.1074/jbc.275.12.8439
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发表时间：
2000-03-24
影响因子：
4.8
通讯作者：
Eisenberg, E
中科院分区：
文献类型：
--
作者：
Jiang, RF;Gao, BC;Eisenberg, E
当Hsc70在依赖于辅助蛋白和ATP的反应中脱包膜时，会发生一轮快速脱包膜，随后是非常缓慢的稳态脱包膜。我们现在表明，这种双相时间过程的发生是因为Hsc70顺序地与解离的网格蛋白三链形成两种类型的复合物。第一轮网格蛋白脱膜是由预稳态组装蛋白(AP)-网格蛋白- hsc70 - adp复合物的形成驱动的。然后，在ADP与ATP交换之后，形成一个稳定的ap -网格蛋白-Hsc70-ATP复合物，结合Hsc70，阻止进一步的脱膜，这种稳定的复合物仅在APs存在的脱膜过程中形成；在没有APs的情况下，Hsc70迅速从未包被的网格蛋白上解离并继续进行解包，无论是与ATP还是ADP络合，稳态络合物与预稳态络合物的性质都有很大的不同，因为它不能被抗网格蛋白抗体免疫沉淀，而且很容易被快速蛋白液相色谱分离。值得注意的是，当稳态配合物与未包被的囊泡膜在ATP中孵化时，稳态前的配合物发生了变化，这表明稳态配合物中的网格蛋白三螺旋离子重新结合到膜上，再次被Hsc70包被。我们认为Hsc70不仅可以揭开网格蛋白的外壳，还可以作为其伴侣，防止其在细胞质中不适当地聚合，并引物改造网格蛋白包被的坑。
When Hsc70 uncoats clathrin-coated vesicles in an auxilin- and ATP dependent reaction, a single round of rapid uncoating occurs followed by very slow steady-state uncoating. We now show that this biphasic time course occurs because Hsc70 sequentially forms two types of complex with the dissociated clathrin triskelions. The first round of clathrin uncoating is driven by formation of a pre steady-state assembly protein (AP)-clathrin-Hsc70-ADP complex. Then, following exchange of ADP with ATP, a steady-state AP-clathrin-Hsc70-ATP complex forms that ties up Hsc70, preventing further uncoating, This steady-state complex forms only during uncoating in the presence of APs; in the absence of APs, Hsc70 rapidly dissociates from the uncoated clathrin and continues to carry out uncoating, Whether it is complexed with ATP or ADP, the steady-state complex has very different properties from the pre-steady-state complex in that it cannot be immunoprecipitated by anti-clathrin antibodies and is readily dissociated by fast protein liquid chromatography. Remarkably, when the steady-state complex is incubated with uncoated vesicle membranes in ATP, the pre steady state complex reforms, suggesting that the clathrin triskelions in the steady-state complex rebind to the membranes and are again uncoated by Hsc70. We propose that Hsc70 not only uncoats clathrin but also chaperones it to prevent it from inappropriately polymerizing in the cell cytosol and primes it to reform clathrin coated pits.