Placing a Disrupted Degradation Motif at the C Terminus of Proteasome Substrates Attenuates Degradation without Impairing Ubiquitylation
Placing a Disrupted Degradation Motif at the C Terminus of Proteasome Substrates Attenuates Degradation without Impairing Ubiquitylation
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DOI：
10.1074/jbc.m113.453027
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发表时间：
2013-05-03
影响因子：
4.8
通讯作者：
Ravid, Tommer
中科院分区：
文献类型：
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作者：
Alfassy, Omri S.;Cohen, Itamar;Ravid, Tommer
泛素-蛋白酶体系统消除蛋白质需要存在顺式作用降解信号。努力辨别错误折叠的蛋白酶体底物的降解信号，迄今揭示了一个一般的机制，即隐藏的疏水基序的曝光提供了一个降解determinate.We以前的特点是这样一个决定因素，采用酵母动粒蛋白Ndc 10作为模型底物。Ndc 10本质上是一种稳定的蛋白质，当暴露位于C末端区域的疏水性基序时会迅速降解。降解基序包括两个不同的基本元件：DegA，包括两个两亲性螺旋，和DegB，Ndc 10的松散结构的C-末端尾部内的疏水序列。在这里，我们表明，DegB的疏水性是无关的底物的泛素化含有Ndc 10降解基序，但蛋白酶体降解是必不可少的。突变DegB，其中的疏水序列被破坏，作为一个占主导地位的降解抑制元件时，表达在C-末端区域的泛素依赖性和非依赖性底物的26 S蛋白酶体。该突变体稳定了酵母和哺乳动物细胞中的底物，表明了模块化识别部分。的突变DegB的主导功能提供了一个强大的实验工具，用于评估在完整的细胞中的特定蛋白酶体底物的稳定的生理意义，并研究相关的病理效应。
Protein elimination by the ubiquitin-proteasome system requires the presence of a cis-acting degradation signal. Efforts to discern degradation signals of misfolded proteasome substrates thus far revealed a general mechanism whereby the exposure of cryptic hydrophobic motifs provides a degradation determinant.We have previously characterized such a determinant, employing the yeast kinetochore protein Ndc10 as a model substrate. Ndc10 is essentially a stable protein that is rapidly degraded upon exposure of a hydrophobic motif located at the C-terminal region. The degradation motif comprises two distinct and essential elements: DegA, encompassing two amphipathic helices, and DegB, a hydrophobic sequence within the loosely structured C-terminal tail of Ndc10. Here we show that the hydrophobic nature of DegB is irrelevant for the ubiquitylation of substrates containing the Ndc10 degradation motif, but is essential for proteasomal degradation. Mutant DegB, in which the hydrophobic sequence was disrupted, acted as a dominant degradation inhibitory element when expressed at the C-terminal regions of ubiquitin-dependent and -independent substrates of the 26S proteasome. This mutant stabilized substrates in both yeast and mammalian cells, indicative of a modular recognition moiety. The dominant function of the mutant DegB provides a powerful experimental tool for evaluating the physiological implications of stabilization of specific proteasome substrates in intact cells and for studying the associated pathological effects.