Ubiquitin-proteasome-mediated degradation of keratin intermediate filaments in mechanically stimulated A549 cells
Ubiquitin-proteasome-mediated degradation of keratin intermediate filaments in mechanically stimulated A549 cells
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DOI：
10.1074/jbc.m801635200
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发表时间：
2008-09-12
影响因子：
4.8
通讯作者：
Ridge, Karen M.
中科院分区：
文献类型：
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作者：
Jaitovich, Ariel;Mehta, Semil;Ridge, Karen M.
我们以前报道，剪切应力诱导磷酸化和分解角蛋白中间丝（IF）。剪切应力还诱导角蛋白IF的时间和应变依赖性降解，当前的研究检查了暴露于0-24 h剪切应力（7.5-30达因/ cm（2））的人A549细胞中角蛋白降解的机制。发现泛素与从剪切应力细胞免疫沉淀的角蛋白共价结合，并且用蛋白酶体抑制剂MG 132预处理防止角蛋白IF网络的降解。重要的是，K8 Ser-73的磷酸化是剪切应力介导的角蛋白IF网络的泛素化、分解和降解所必需的。免疫荧光显微镜显示，剪切应力导致在对照细胞中观察到的角蛋白原纤维的薄阵列被重组成核周聚集体，称为侵袭体，并且泛素也与这种结构相关。最后，E2酶，UbcH 5 b，-c，和Ubc 3，但不是E2- 25 K所需的剪切应力介导的泛素-蛋白酶体降解角蛋白。这些数据表明，剪切应力通过磷酸化和泛素-蛋白酶体途径促进角蛋白IF网络的分解和降解。
We previously reported that shear stress induces phosphorylation and disassembly of keratin intermediate filaments (IFs). Shear stress also induces a time- and strain-dependent degradation of keratin IFs, and the current study examines the mechanisms involved in degradation of keratin proteins in human A549 cells exposed to 0-24 h of shear stress (7.5-30 dynes/ cm(2)). Ubiquitin was found to be covalently associated with keratin proteins immunoprecipitated from shear-stressed cells, and pretreatment with the proteasomal inhibitor MG132 prevented the degradation of the keratin IF network. Importantly, phosphorylation of K8 Ser-73 is required for the shear stress-mediated ubiquitination, disassembly, and degradation of the keratin IF network. Immunofluorescence microscopy revealed that shear stress caused the thin array of keratin fibrils observed in control cells to be reorganized into a perinuclear aggregate, known as an aggresome, and that ubiquitin was also associated with this structure. Finally, the E2 enzymes, UbcH5b, -c, and Ubc3, but not E2-25K are required for the shear stress-mediated ubiquitin-proteasomal degradation of keratin proteins. These data suggest that shear stress promotes the disassembly and degradation of the keratin IF network via phosphorylation and the ubiquitin- proteasome pathway.