A novel ER J-protein DNAJB12 accelerates ER-associated degradation of membrane proteins including CFTR.
A novel ER J-protein DNAJB12 accelerates ER-associated degradation of membrane proteins including CFTR.
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DOI：
10.1247/csf.10023
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发表时间：
2010-12
影响因子：
1.5
通讯作者：
Yo-hei Yamamoto;Taiji Kimura;S. Momohara;Masato Takeuchi;T. Tani;Y. Kimata;H. Kadokura;K. Kohno
中科院分区：
文献类型：
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作者：
Yo-hei Yamamoto;Taiji Kimura;S. Momohara;Masato Takeuchi;T. Tani;Y. Kimata;H. Kadokura;K. Kohno
已知胞质Hsc 70/Hsp 70有助于内质网（ER）相关的膜蛋白降解。然而，至少在哺乳动物细胞中，其伴侣ER定位的J-蛋白的这种细胞事件尚未确定。在这里，我们提出这种缺失的蛋白质是DNAJB 12。蛋白酶保护试验和免疫荧光研究表明，DNAJB 12是一个ER定位的单跨膜蛋白，携带一个面向胞质的J结构域。利用免疫共沉淀法，我们发现DNAJB 12能够结合Hsc 70，从而可以募集Hsc 70到ER膜。值得注意的是，DNAJB 12的细胞过表达加速了包括囊性纤维化跨膜传导调节因子（CFTR）在内的错误折叠的膜蛋白的降解，而不是错误折叠的管腔蛋白。CFTR的DNAJB 12依赖性降解受到蛋白酶体抑制剂lactacystin的影响，这表明该过程需要泛素-蛋白酶体系统。相反，敲低DNAJB 12表达减弱了CFTR的降解。因此，DNAJB 12是一种新的哺乳动物ER定位的J蛋白，在膜蛋白的质量控制中起着至关重要的作用。
Cytosolic Hsc70/Hsp70 are known to contribute to the endoplasmic reticulum (ER)-associated degradation of membrane proteins. However, at least in mammalian cells, its partner ER-localized J-protein for this cellular event has not been identified. Here we propose that this missing protein is DNAJB12. Protease protection assay and immunofluorescence study revealed that DNAJB12 is an ER-localized single membrane-spanning protein carrying a J-domain facing the cytosol. Using co-immunoprecipitation assay, we found that DNAJB12 is able to bind Hsc70 and thus can recruit Hsc70 to the ER membrane. Remarkably, cellular overexpression of DNAJB12 accelerated the degradation of misfolded membrane proteins including cystic fibrosis transmembrane conductance regulator (CFTR), but not a misfolded luminal protein. The DNAJB12-dependent degradation of CFTR was compromised by a proteasome inhibitor, lactacystin, suggesting that this process requires the ubiquitin-proteasome system. Conversely, knockdown of DNAJB12 expression attenuated the degradation of CFTR. Thus, DNAJB12 is a novel mammalian ER-localized J-protein that plays a vital role in the quality control of membrane proteins.