CHC22 and CHC17 clathrins have distinct biochemical properties and display differential regulation and function.
CHC22 and CHC17 clathrins have distinct biochemical properties and display differential regulation and function.
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DOI：
10.1074/jbc.m117.816256
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发表时间：
2017-12-22
期刊：
影响因子：
--
通讯作者：
Brodsky FM
中科院分区：
文献类型：
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作者：
Dannhauser PN;Camus SM;Sakamoto K;Sadacca LA;Torres JA;Camus MD;Briant K;Vassilopoulos S;Rothnie A;Smith CJ;Brodsky FM
笼状蛋白是一种细胞质蛋白，在内吞作用和其他膜运输途径中起着重要作用。当被聚集到细胞内膜上时，典型的笼状蛋白三离子组装成多面体蛋白质涂层，促进囊泡的形成并捕获货物分子进行运输。三聚体是由三个笼状蛋白重链亚基三聚而成的。大多数脊椎动物都有两种不同形式的笼状蛋白重链，CHC17和CHC22，产生两种具有不同细胞功能的笼状蛋白。CHC17在细胞膜上形成小泡，用于受体介导的内吞作用，并在细胞器生物发生的跨高尔基网络中形成小泡。CHC22在胰岛素调节的葡萄糖转运蛋白4(GLUT4)的细胞内靶向中起关键作用，在胰岛素抵抗时积聚在GLUT4的固存部位，也参与了神经元的发育。在这里，我们证明了CHC22和CHC17具有相同的形态特征，CHC22形成了三棱柱和网状囊泡外套。然而，细胞内CHC22包被的囊泡与CHC17形成的囊泡不同。CHC22涂层对pH变化更稳定，不会被分解CHC17涂层的酶复合体去除。CHC22不支持胞膜上的囊泡形成或转铁蛋白内吞作用。我们的发现为CHC17和CHC22在人类细胞中的单独调控和不同的功能生态位提供了生化证据。此外，CHC22涂层相对于CHC17涂层具有更高的稳定性，这可能与其在胰岛素抵抗期间过度积聚GLUT4有关。
Clathrins are cytoplasmic proteins that play essential roles in endocytosis and other membrane traffic pathways. Upon recruitment to intracellular membranes, the canonical clathrin triskelion assembles into a polyhedral protein coat that facilitates vesicle formation and captures cargo molecules for transport. The triskelion is formed by trimerization of three clathrin heavy-chain subunits. Most vertebrates have two isoforms of clathrin heavy chains, CHC17 and CHC22, generating two clathrins with distinct cellular functions. CHC17 forms vesicles at the plasma membrane for receptor-mediated endocytosis and at the trans-Golgi network for organelle biogenesis. CHC22 plays a key role in intracellular targeting of the insulin-regulated glucose transporter 4 (GLUT4), accumulates at the site of GLUT4 sequestration during insulin resistance, and has also been implicated in neuronal development. Here, we demonstrate that CHC22 and CHC17 share morphological features, in that CHC22 forms a triskelion and latticed vesicle coats. However, cellular CHC22-coated vesicles were distinct from those formed by CHC17. The CHC22 coat was more stable to pH change and was not removed by the enzyme complex that disassembles the CHC17 coat. Moreover, the two clathrins were differentially recruited to membranes by adaptors, and CHC22 did not support vesicle formation or transferrin endocytosis at the plasma membrane in the presence or absence of CHC17. Our findings provide biochemical evidence for separate regulation and distinct functional niches for CHC17 and CHC22 in human cells. Furthermore, the greater stability of the CHC22 coat relative to the CHC17 coat may be relevant to its excessive accumulation with GLUT4 during insulin resistance.