Degradation of endocytosed epidermal growth factor and virally ubiquitinated major histocompatibility complex class I is independent of mammalian ESCRTII
Degradation of endocytosed epidermal growth factor and virally ubiquitinated major histocompatibility complex class I is independent of mammalian ESCRTII
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DOI：
10.1074/jbc.m508632200
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发表时间：
2006-02-24
影响因子：
4.8
通讯作者：
Luzio, JP
中科院分区：
文献类型：
--
作者：
Bowers, K;Piper, SC;Luzio, JP
在哺乳动物细胞的内吞途径中的多泡体处的蛋白质分选模型在很大程度上依赖于从酵母获得的数据。这些数据表明四个ESCRT复合物在多泡体蛋白分选中的重要作用。然而，推定的哺乳动物ESCRTII复合物（hVps 25 p，hVps 22 p和hVps 36 p）没有被证明在内体转运中的功能作用。我们的特点是人类ESCRTII复合物，并调查其功能的内体运输。人ESCRTII蛋白彼此相互作用，与hVps 20 p（ESCRTIII的组分）相互作用，并与它们的酵母同源物相互作用。我们的相互作用数据从酵母双杂交研究沿着与实验纯化的蛋白质建议的N-末端结构域的hVps 22 p在形成一个异源四聚体ESCRTII复合物的重要作用。尽管人ESCRTII存在于细胞质和细胞核中，但在显性阴性hVps 4 Bp过表达时，它可以被募集到内体。有趣的是，我们发现，哺乳动物ESCRTII的小干扰RNA耗竭不影响表皮生长因子的降解，表皮生长因子是多泡体蛋白分选途径的已知货物。我们还表明，去泛素化酶AMSH（与STAM（信号转导衔接子分子）的SH 3结构域相关的分子）和UBPY（泛素异肽酶Y）的耗竭对表皮生长因子降解具有相反的影响，UBPY耗竭导致内体急剧肿胀。另一个货物，主要组织相容性复合物I类在表达卡波西肉瘤相关疱疹病毒蛋白K3的细胞中的下调，在ESCRTII耗尽的细胞中不受影响。我们的数据表明，哺乳动物ESCRTII可能是多余的，货物特异性，或不需要在多泡体蛋白分选。
Models for protein sorting at multivesicular bodies in the endocytic pathway of mammalian cells have relied largely on data obtained from yeast. These data suggest the essential role of four ESCRT complexes in multivesicular body protein sorting. However, the putative mammalian ESCRTII complex (hVps25p, hVps22p, and hVps36p) has no proven functional role in endosomal transport. We have characterized the human ESCRTII complex and investigated its function in endosomal trafficking. The human ESCRTII proteins interact with one another, with hVps20p (a component of ESCRTIII), and with their yeast homologues. Our interaction data from yeast two-hybrid studies along with experiments with purified proteins suggest an essential role for the N-terminal domain of hVps22p in the formation of a heterotetrameric ESCRTII complex. Although human ESCRTII is found in the cytoplasm and in the nucleus, it can be recruited to endosomes upon overexpression of dominant-negative hVps4Bp. Interestingly, we find that small interference RNA depletion of mammalian ESCRTII does not affect degradation of epidermal growth factor, a known cargo of the multivesicular body protein sorting pathway. We also show that depletion of the deubiquitinating enzymes AMSH (associated molecule with the SH3 domain of STAM (signal transducing adaptor molecule)) and UBPY (ubiquitin isopeptidase Y) have opposite effects on epidermal growth factor degradation, with UBPY depletion causing dramatic swelling of endosomes. Down-regulation of another cargo, the major histocompatibility complex class I in cells expressing the Kaposi sarcoma-associated herpesvirus protein K3, is unaffected in ESCRTII-depleted cells. Our data suggest that mammalian ESCRTII may be redundant, cargo-specific, or not required for protein sorting at the multivesicular body.