Involvement of Hsp90 in signaling and stability of 3-phosphoinositide-dependent kinase-1
Involvement of Hsp90 in signaling and stability of 3-phosphoinositide-dependent kinase-1
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DOI：
10.1074/jbc.m106736200
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发表时间：
2002-03-22
影响因子：
4.8
通讯作者：
Tsuruo, T
中科院分区：
文献类型：
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作者：
Fujita, N;Sato, S;Tsuruo, T
丝氨酸/苏氨酸激酶Akt被认为介导许多抗凋亡反应的生物学作用。筛选药物，可以干扰Akt信号通路显示，热休克蛋白90抑制剂（如格尔德霉素，根赤霉素，及其类似物）诱导Akt去磷酸化，这导致Akt失活和细胞凋亡。Hsp 90抑制剂在体外不直接影响Akt激酶活性。因此，我们研究了Hsp 90抑制剂对上游Akt激酶、磷脂酰肌醇-3-OH激酶（PI 3 K）和3-磷酸肌醇依赖性蛋白激酶-1（PDK 1）的影响。Hsp 90抑制剂对PI 3 K蛋白表达无影响。相反，用Hsp 90抑制剂处理细胞减少了PDK 1的量，而不直接抑制PDK 1激酶活性。我们发现PDK 1的激酶结构域对于与Hsp 90形成复合物是必不可少的，并且Hsp 90抑制剂抑制PDK 1与Hsp 90的结合。PDK 1降解机制表明，抑制PDK 1与Hsp 90的结合导致PDK 1的蛋白酶体依赖性降解。蛋白酶体抑制剂的处理增加了Hsp 90转运蛋白处理的细胞中洗涤剂不溶性PDK 1的量。因此，PDK 1与Hsp 90的结合调节其稳定性、溶解性和信号传导。由于Akt与Hsp 90的结合也参与了Akt激酶活性的维持，因此Hsp 90在PDK 1-Akt生存信号通路中起着重要作用。
Serine/threonine kinase Akt is thought to mediate many biological actions toward anti-apoptotic responses. Screening of drugs that could interfere with the Akt signaling pathway revealed that Hsp90 inhibitors (e.g. geldanamycin, radicicol, and its analogues) induced Akt dephosphorylation, which resulted in Akt inactivation and apoptosis of the cells. Hsp90 inhibitors did not directly affect Akt kinase activity in vitro. Thus, we examined the effects of Hsp90 inhibitors on upstream Akt kinases, phosphatidylinositide-3-OH kinase (PI3K) and 3-phosphoinositide-dependent protein kinase-1 (PDK1). Hsp90 inhibitors had no effect on PI3K protein expression. In contrast, treatment of the cells with Hsp90 inhibitors decreased the amount of PDK1 without directly inhibiting PDK1 kinase activity. We found that the kinase domain of PDK1 was essential for complex formation with Hsp90 and that Hsp90 inhibitors suppressed PDK1 binding to Hsp90. PDK1 degradation mechanisms revealed that inhibition of PDK1 binding to Hsp90 caused proteasome-dependent degradation of PDK1. Treatment of proteasome inhibitors increased the amount of detergent-insoluble PDK1 in Hsp90 inhibitor-treated cells. Therefore, the association of PDK1 with Hsp90 regulates its stability, solubility, and signaling. Because Akt binding to Hsp90 is also involved in the maintenance of Akt kinase activity, Hsp90 plays an important role in PDK1-Akt survival signaling pathway.