Dynamics of clathrin and adaptor proteins during endocytosis
Dynamics of clathrin and adaptor proteins during endocytosis
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DOI：
10.1152/ajpcell.00160.2006
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发表时间：
2006-11-01
影响因子：
5.5
通讯作者：
Simon, Sanford M.
中科院分区：
文献类型：
--
作者：
Rappoport, Joshua Z.;Kemal, Shahrnaz;Simon, Sanford M.
内吞接头复合体AP-2与细胞表面的大多数网状蛋白阳性斑点共存。然而，我们先前观察到AP-2被排除在内化笼蛋白包裹的小泡(CCV)之外。目前的研究定量地证明了AP-2在新生CCV内化前几秒钟从内吞作用部位脱离。相反，胞质膜上的另一种网状蛋白接头--胞外蛋白与网状蛋白一起消失了。这表明，在整个内吞作用过程中，Eepsin仍然是CCV的一个组成部分。细胞表面的网状蛋白斑点代表一个不同的群体：大多数(70%)的斑点在4分钟的时间内消失，而少数(22%)的斑点在~gt；=30分钟保持不变。静态的网状蛋白斑点经历不断的亚基交换，这表明虽然它们是静态结构，但这些斑点包括功能性的网状蛋白分子，而不是死端的聚集体。这些结果支持这样一个模型，即AP-2在内吞作用之前起到货物分拣的作用，而替代适配器，如epsin，实际上将货物连接到新生内吞小泡周围的网状蛋白外壳。这些数据还支持静态网状蛋白的作用，为内吞作用提供了一个成核部位。
The endocytic adaptor complex AP-2 colocalizes with the majority of clathrin-positive spots at the cell surface. However, we previously observed that AP-2 is excluded from internalizing clathrin-coated vesicles (CCVs). The present studies quantitatively demonstrate that AP-2 disengages from sites of endocytosis seconds before internalization of the nascent CCV. In contrast, epsin, an alternate adaptor for clathrin at the plasma membrane, disappeared, along with clathrin. This suggests that epsin remains an integral part of the CCV throughout endocytosis. Clathrin spots at the cell surface represent a heterogeneous population: a majority (70%) of the spots disappeared with a time course of 4 min, whereas a minority (22%) remained static for >= 30 min. The static clathrin spots undergo constant subunit exchange, suggesting that although they are static structures, these spots comprise functional clathrin molecules, rather than dead-end aggregates. These results support a model where AP-2 serves a cargo-sorting function before endocytosis, whereas alternate adaptors, such as epsin, actually link cargo to the clathrin coat surrounding nascent endocytic vesicles. These data also support a role for static clathrin, providing a nucleation site for endocytosis.