Legionella translocates an E3 ubiquitin ligase that has multiple U-boxes with distinct functions
Legionella translocates an E3 ubiquitin ligase that has multiple U-boxes with distinct functions
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DOI：
10.1111/j.1365-2958.2008.06124.x
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发表时间：
2008-03-01
影响因子：
3.6
通讯作者：
Nagai, Hiroki
中科院分区：
文献类型：
--
作者：
Kubori, Tomoko;Hyakutake, Akihiro;Nagai, Hiroki
嗜肺军团菌具有Dot/Icm IV型分泌系统，用于易位许多破坏宿主细胞功能的“效应蛋白”。在这项研究中，我们确定了19个新的Dot/Icm底物蛋白使用系统的筛选技术。blast分析显示，其中一种底物，我们命名为LubX（军团菌U盒蛋白），含有两个结构域，与真核E3泛素连接酶中发现的U盒结构域具有显着的相似性。LubX的表达在感染时被诱导，并且产生的大部分LubX被易位到宿主细胞中。LubX具有与UbcH 5a或UbcH 5c E2酶结合的泛素连接酶活性，并介导宿主Clk 1（Cdc 2样激酶1）的多聚泛素化。我们证明了其中一个U盒（U盒1）对泛素连接至关重要，另一个U盒（U盒2）介导与Clk 1的相互作用。因此，LubX的两个U盒具有不同的功能，并且U盒2在底物结合中起非典型作用。虽然我们证明了Clk激酶的抑制导致小鼠巨噬细胞内军团菌生长的显著减少，但Clk 1泛素化的后果仍有待阐明。总之，这些数据表明，Clk 1是军团菌在感染过程中调节的靶宿主分子。
Legionella pneumophila has a Dot/Icm type IV secretion system used to translocate a number of 'effector proteins' which subvert host cell functions. In this study, we identified 19 novel Dot/Icm substrate proteins using a systematic screening technique. A blast analysis revealed that one of the substrates, which we named LubX (LegionellaU-box protein), contains two domains that have a remarkable similarity to the U-box, a domain found in eukaryotic E3 ubiquitin ligases. The expression of LubX is induced upon infection, and most of the LubX produced was translocated into the host cells. LubX has ubiquitin ligase activity in conjunction with UbcH5a or UbcH5c E2 enzymes and mediates polyubiquitination of host Clk1 (Cdc2-like kinase 1). We demonstrate that one of the U-boxes (U-box 1) is critical to the ubiquitin ligation, and the other U-box (U-box 2) mediates interaction with Clk1. Thus, the two U-boxes of LubX have distinct functions, and U-box 2 plays a non-canonical role in substrate binding. Although we demonstrate that inhibition of Clk kinase results in a marked reduction of Legionella growth within mouse macrophages, the consequence of Clk1 ubiquitination is still being elucidated. Together, these data suggest that Clk1 is the target host molecule which Legionella modulates during infection.