p90 Ribosomal S6 Kinase and p70 Ribosomal S6 Kinase Link Phosphorylation of the Eukaryotic Chaperonin Containing TCP-1 to Growth Factor, Insulin, and Nutrient Signaling
p90 Ribosomal S6 Kinase and p70 Ribosomal S6 Kinase Link Phosphorylation of the Eukaryotic Chaperonin Containing TCP-1 to Growth Factor, Insulin, and Nutrient Signaling
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DOI：
10.1074/jbc.m900097200
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发表时间：
2009-05-29
影响因子：
4.8
通讯作者：
Blenis, John
中科院分区：
文献类型：
--
作者：
Abe, Yuki;Yoon, Sang-Oh;Blenis, John
包含TCP-1的伴侣蛋白（CCT）是一种大的多亚基复合物，在真核细胞中介导蛋白质折叠。CCT参与新合成多肽的折叠，包括肌动蛋白、微管蛋白和几种细胞周期调节剂;因此，CCT在细胞骨架组织和细胞分裂中起重要作用。在这里，我们确定伴侣蛋白CCT作为p90核糖体S6激酶（RSK）和p70核糖体S6激酶（S6 K）的一种新的生理底物。RSK磷酸化CCT的β亚基，以响应激活Ras-有丝分裂原活化蛋白激酶（MAPK）途径的肿瘤促进剂或生长因子。通过质谱法将CCT β Ser-260鉴定为RSK位点，并通过定点诱变进行确认。RSK依赖性Ser-260磷酸化对MEK抑制剂UO 126和RSK抑制剂BID-1870敏感。胰岛素弱激活RSK，但强烈激活磷酸肌醇3-激酶（PI 3 K）-哺乳动物雷帕霉素靶蛋白（mTOR）途径，并利用S6 K调节CCT β磷酸化。因此，Ras-MAPK和PI 3 K-mTOR通路在各种哺乳动物细胞中响应于多种激动剂而汇聚于CCT β Ser-260磷酸化。我们还表明，RNA干扰介导的内源性CCT β的敲低导致受损的细胞增殖，可以用异位表达的小鼠CCT β野生型或磷酸化模拟突变体S260 D，但不是磷酸化缺陷突变体S260 A来拯救。虽然CCT β调节的分子机制尚不清楚，但我们的研究结果表明癌基因和生长因子信号传导与伴侣蛋白CCT介导的细胞活性之间存在联系。
Chaperonin containing TCP-1 (CCT) is a large multisubunit complex that mediates protein folding in eukaryotic cells. CCT participates in the folding of newly synthesized polypeptides, including actin, tubulin, and several cell cycle regulators; therefore, CCT plays an important role in cytoskeletal organization and cell division. Here we identify the chaperonin CCT as a novel physiological substrate for p90 ribosomal S6 kinase (RSK) and p70 ribosomal S6 kinase (S6K). RSK phosphorylates the beta subunit of CCT in response to tumor promoters or growth factors that activate the Ras-mitogen-activated protein kinase (MAPK) pathway. CCT beta Ser-260 was identified as the RSK site by mass spectrometry and confirmed by site-directed mutagenesis. RSK-dependent Ser-260 phosphorylation was sensitive to the MEK inhibitor UO126 and the RSK inhibitor BID-1870. Insulin weakly activates RSK but strongly activates the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathway and utilizes S6K to regulate CCT beta phosphorylation. Thus, the Ras-MAPK and PI3K-mTOR pathways converge on CCT beta Ser-260 phosphorylation in response to multiple agonists in various mammalian cells. We also show that RNA interference-mediated knockdown of endogenous CCT beta causes impaired cell proliferation that can be rescued with ectopically expressed murine CCT beta wild-type or phosphomimetic mutant S260D, but not the phosphorylation-deficient mutant S260A. Although the molecular mechanism of CCT beta regulation remains unclear, our findings demonstrate a link between oncogene and growth factor signaling and chaperonin CCT-mediated cellular activities.