C-terminal phosphorylation of Hsp70 and Hsp90 regulates alternate binding to co-chaperones CHIP and HOP to determine cellular protein folding/degradation balances
C-terminal phosphorylation of Hsp70 and Hsp90 regulates alternate binding to co-chaperones CHIP and HOP to determine cellular protein folding/degradation balances
复制标题
DOI：
10.1038/onc.2012.314
复制
发表时间：
2013-06-20
期刊：
影响因子：
8
通讯作者：
Vojtesek, B.
中科院分区：
文献类型：
--
作者：
Muller, P.;Ruckova, E.;Vojtesek, B.
热休克蛋白Hsp 90和Hsp 70促进蛋白质折叠，但也可以指导蛋白质进行泛素介导的降解。调节这些相反活性的机制涉及HSP在其C-末端与辅分子伴侣（包括CHIP和HOP）结合。我们在体外证明了Hsp 70和Hsp 90的末端C-末端含有CK 1、CK 2和GSK 3-β等激酶靶向的磷酸化位点。Hsp 90和Hsp 70的磷酸化阻止与CHIP的结合，从而增强与HOP的结合。高度增殖的细胞含有与HOP复合的磷酸化分子伴侣，并且磷酸化模拟和非磷酸化的Hsp突变蛋白显示磷酸化与增加的增殖速率直接相关。我们还证明，原发性人类癌症含有高水平的磷酸化伴侣，并显示出增加的HOP蛋白和mRNA水平。这些数据鉴定了Hsp 70和Hsp 90的C-末端磷酸化作为调节共分子伴侣结合的开关，并表明癌细胞通过共分子伴侣表达和分子伴侣修饰的协同作用而具有升高的蛋白质折叠环境。除了鉴定负责调节正常细胞中分子伴侣介导的蛋白质折叠/降解平衡的途径外，这些数据还提供了新的机制来解释在人类癌细胞中观察到的异常分子伴侣活性，并对抗分子伴侣疗法在癌症治疗中的应用产生影响。
Heat shock proteins Hsp90 and Hsp70 facilitate protein folding but can also direct proteins for ubiquitin-mediated degradation. The mechanisms regulating these opposite activities involve Hsp binding to co-chaperones including CHIP and HOP at their C-termini. We demonstrated that the extreme C-termini of Hsp70 and Hsp90 contain phosphorylation sites targeted by kinases including CK1, CK2 and GSK3-beta in vitro. The phosphorylation of Hsp90 and Hsp70 prevents binding to CHIP and thus enhances binding to HOP. Highly proliferative cells contain phosphorylated chaperones in complex with HOP and phospho-mimetic and non-phosphorylable Hsp mutant proteins show that phosphorylation is directly associated with increased proliferation rate. We also demonstrate that primary human cancers contain high levels of phosphorylated chaperones and show increased levels of HOP protein and mRNA. These data identify C-terminal phosphorylation of Hsp70 and Hsp90 as a switch for regulating co-chaperone binding and indicate that cancer cells possess an elevated protein folding environment by the concerted action of co-chaperone expression and chaperone modifications. In addition to identifying the pathway responsible for regulating chaperone-mediated protein folding/degradation balances in normal cells, the data provide novel mechanisms to account for the aberrant chaperone activities observed in human cancer cells and have implications for the application of anti-chaperone therapies in cancer treatment.