COP9-Associated CSN5 Regulates Exosomal Protein Deubiquitination and Sorting
COP9-Associated CSN5 Regulates Exosomal Protein Deubiquitination and Sorting
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DOI：
10.2353/ajpath.2009.080861
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发表时间：
2009-04-01
影响因子：
6
通讯作者：
Zhang, Huang-Ge
中科院分区：
文献类型：
--
作者：
Liu, Yuelong;Shah, Spandan V.;Zhang, Huang-Ge
沉积到多泡体内腔中的泛素化内体蛋白被分选用于溶酶体介导的降解或作为外泌体分泌到细胞外环境中。细胞货物蛋白分选的机制目前尚不清楚。在这项研究中，我们发现COP 9信号体（CSN）相关蛋白CSN 5定量调节被分选到外泌体中的蛋白质。外泌体蛋白的Western印迹分析表明，与从用乱序siRNA转染的293细胞的上清液中分离的外泌体相比，CSN 5的小干扰（si）RNA敲低导致泛素化和非泛素化外泌体蛋白（包括热休克蛋白70）的水平增加。此外，用JAB 1/MPN/Mov 34金属酶结构域缺失的CSN 5转染的293细胞产生具有更高水平的泛素化热休克蛋白70的外泌体，其不影响非泛素化热休克蛋白70水平。CSN 5的COP 9相关去泛素活性的丧失也导致被分选到外泌体中的HIV Gag的增强以及HIV-1释放的促进，表明COP 9相关CSN 5以CSN 5 JAB 1/MPN/Mov 34金属酶结构域依赖性和非依赖性方式调节许多外泌体蛋白的分选。我们认为COP 9相关的CSN 5以去泛素化活性依赖和非依赖的方式调节外泌体蛋白质分选，这与目前蛋白质对外泌体的泛素依赖性分选的想法相反。(Am J Pathol 2009，174：1415-1425; DOI：10.2353/ajpath.2009.080861）
Ubiquitinated endosomal proteins that are deposited into the lumens of multivesicular bodies are either sorted for lysosomal-mediated degradation or secreted as exosomes into the extracellular milieu. The mechanisms that underlie the sorting of cellular cargo proteins are currently unknown. In this study, we show that the COP9 signalosome (CSN)-associated protein CSN5 quantitatively regulated proteins that were sorted into exosomes. Western blot analysis of exosomal proteins indicated that small interfering (si)RNA knockdown of CSN5 results in increased levels of both ubiquitinated and non-ubiquitinated exosomal proteins, including heat shock protein 70, in comparison with exosomes isolated from the supernatants of 293 cells transfected with scrambled siRNA. Furthermore, 293 cells transfected with JAB1/MPN/Mov34 metalloenzyme domain-deleted CSN5 produced exosomes with higher levels of ubiquitinated heat shock protein 70, which did not affect non-ubiquitinated heat shock protein 70 levels. The loss of COP9-associated deubiquitin activity of CSN5 also led to the enhancement of HIV Gag that was sorted into exosomes as well as the promotion of HIV-1 release, suggesting that COP9-associated CSN5 regulates the sorting of a number of exosomal proteins in both a CSN5 JAB1/MPN/Mov34 metalloenzyme domain-dependent and -independent manner. We propose that COP9-associated CSN5 regulates exosomal protein sorting in both a deubiquitinating activity-dependent and -independent manner, which is contrary to the current idea of ubiquitin-dependent sorting of proteins to exosomes. (Am J Pathol 2009, 174:1415-1425; DOI: 10.2353/ajpath.2009.080861)