AMSH, an ESCRT-III associated enzyme, deubiquitinates cargo on MVB/late endosomes
AMSH, an ESCRT-III associated enzyme, deubiquitinates cargo on MVB/late endosomes
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DOI：
10.1247/csf.06023
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发表时间：
2006-01-01
影响因子：
1.5
通讯作者：
Tanaka, Nobuyuki
中科院分区：
文献类型：
--
作者：
Kyuuma, Masanao;Kikuchi, Kazu;Tanaka, Nobuyuki
包括细胞表面蛋白在内的囊泡货物的适当分选对于许多细胞功能至关重要。泛素化货物靶向内体并被溶酶体酶消化。我们以前确定AMSH，去泛素化酶（DUB），参与囊泡运输。在这里，我们纯化AMSH结合蛋白，CHMP 3，这是一个ESCRT-III亚基。ESCRT-III在成熟的内体上起作用，表明AMSH也可能在MVB/晚期内体中起作用。缺乏CHMP 3结合能力的AMSH突变体的表达导致了具有泛素化货物积累的异常内体。然而，CHMP 3结合能力不是AMSH体外DUB活性或其内体定位所必需的，这表明，在体内，内体货物的去泛素化是CHMP 3依赖性的。当无催化活性的AMSH表达或AMSH耗尽时，泛素化的货物也在内涵体上积累。这些结果表明AMSH的DUB活性和其CHMP 3结合能力都是从内体清除泛素化货物所必需的。
The appropriate sorting of vesicular cargo, including cell-surface proteins, is critical for many cellular functions. Ubiquitinated cargo is targeted to endosomes and digested by lysosomal enzymes. We previously identified AMSH, a deubiquitination enzyme (DUB), to be involved in vesicular transport. Here, we purified an AMSH-binding protein, CHMP3, which is an ESCRT-III subunit. ESCRT-III functions on maturing endosomes, indicating AMSH might also play a role in MVB/late endosomes. Expression of an AMSH mutant lacking CHMP3-binding ability resulted in aberrant endosomes with accumulations of ubiquitinated cargo. Nevertheless, CHMP3-binding capability was not essential for AMSH's in vitro DUB activity or its endosomal localization, suggesting that, in vivo, the deubiquitination of endosomal cargo is CHMP3-dependent. Ubiquitinated cargo also accumulated on endosomes when catalytically inactive AMSH was expressed or AMSH was depleted. These results suggest that both the DUB activity of AMSH and its CHMP3-binding ability are required to clear ubiquitinated cargo from endosomes.