mTOR is essential for the proteotoxic stress response, HSF1 activation and heat shock protein synthesis.
mTOR is essential for the proteotoxic stress response, HSF1 activation and heat shock protein synthesis.
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DOI：
10.1371/journal.pone.0039679
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Calderwood SK
中科院分区：
文献类型：
--
作者：
Chou SD;Prince T;Gong J;Calderwood SK
雷帕霉素（TOR）的靶点是一种高分子量蛋白激酶，其响应于有丝分裂原和营养物质可用性的变化而调节细胞中的许多过程。在这里，我们已经表明，在人类组织培养细胞中的mTOR在蛋白毒性应激反应中起着关键作用，并且通过RNA干扰降低mTOR水平导致对热休克的敏感性增加。这种效应伴随着合成热休克蛋白（HSP）的能力急剧下降，包括Hsp 70，Hsp 90和Hsp 110。由于HSP转录受热休克转录因子1（HSF 1）调节，我们研究了mTOR是否可以直接磷酸化该因子。事实上，我们确定mTOR可以直接磷酸化HSF 1的丝氨酸326，转录激活的关键残基。HSF 1在热休克后立即在S326上磷酸化，并被其他细胞应激物包括蛋白酶体抑制剂和亚砷酸钠触发。将S326突变为丙氨酸导致失去激活HSF 1调节的启动子-报告基因构建体的能力，表明mTOR和S326在应激期间HSP基因的转录调节中的直接作用。由于已知mTOR存在于至少两种细胞内复合物中，mTORC 1和mTOR 2，我们检查了哪种复合物可能与HSF 1相互作用。事实上，mTORC 1抑制剂雷帕霉素阻止了HSF 1-S326磷酸化，表明该复合物参与了应激中的HSF 1调节。因此，我们的实验表明mTORC 1在蛋白毒性应激的转录反应中起关键作用。
The target of rapamycin (TOR) is a high molecular weight protein kinase that regulates many processes in cells in response to mitogens and variations in nutrient availability. Here we have shown that mTOR in human tissue culture cells plays a key role in responses to proteotoxic stress and that reduction in mTOR levels by RNA interference leads to increase sensitivity to heat shock. This effect was accompanied by a drastic reduction in ability to synthesize heat shock proteins (HSP), including Hsp70, Hsp90 and Hsp110. As HSP transcription is regulated by heat shock transcription factor 1 (HSF1), we examined whether mTOR could directly phosphorylate this factor. Indeed, we determined that mTOR could directly phosphorylate HSF1 on serine 326, a key residue in transcriptional activation. HSF1 was phosphorylated on S326 immediately after heat shock and was triggered by other cell stressors including proteasome inhibitors and sodium arsenite. Null mutation of S326 to alanine led to loss of ability to activate an HSF1-regulated promoter-reporter construct, indicating a direct role for mTOR and S326 in transcriptional regulation of HSP genes during stress. As mTOR is known to exist in at least two intracellular complexes, mTORC1 and mTOR2 we examined which complex might interact with HSF1. Indeed mTORC1 inhibitor rapamycin prevented HSF1-S326 phosphorylation, suggesting that this complex is involved in HSF1 regulation in stress. Our experiments therefore suggest a key role for mTORC1 in transcriptional responses to proteotoxic stress.
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