Mammalian target of rapamycin positively regulates collagen type I production via a phosphatidylinositol 3-kinase-independent pathway
Mammalian target of rapamycin positively regulates collagen type I production via a phosphatidylinositol 3-kinase-independent pathway
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DOI：
10.1074/jbc.m401238200
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发表时间：
2004-05-28
影响因子：
4.8
通讯作者：
Trojanowska, M
中科院分区：
文献类型：
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作者：
Shegogue, D;Trojanowska, M
雷帕霉素的哺乳动物靶标(MTOR)是一种多功能蛋白，参与调节细胞的生长、增殖和分化。本研究的目的是确定mTOR在I型胶原调节中的作用。磷脂酰肌醇(PI)3-激酶的药物抑制剂LY294002显著抑制I型胶原蛋白和mRNA水平。LY294002对胶原α1(I)链的作用更为明显，与胶原α2(I)链相比，α1(I)链在转录和mRNA稳定水平上受到抑制，而α2(I)链通过降低mRNA稳定性而受到抑制。相比之下，添加PI 3-激酶抑制剂Wortmannin并不改变I型胶原稳定状态的mRNA水平。这一观察和使用失活的LY294002类似物的进一步实验表明，胶原mRNA的水平被抑制，而不是PI 3-激酶。其他实验已经证实，mTOR正向调节人成纤维细胞中I型胶原的合成。这些结论基于的结果表明，用一种特定的抑制剂雷帕霉素抑制mTOR活性，会降低胶原mRNA的水平。此外，使用小干扰RNA使mTOR的表达降低约50%，导致胶原mRNA和蛋白水平显著下降(COL1A1下降75%，COL1A2下降28%)。因此，mTOR在调节真皮成纤维细胞I型胶原基因的基础表达中起着至关重要的作用。综上所述，我们的数据表明，经典的PI3-激酶途径，位于PI3-激酶下游的mTOR，不参与真皮成纤维细胞中mTOR依赖的I型胶原合成的调节。由于胶原过度生成是纤维化的一个主要特征，确定mTOR是其调节的关键介质，可能为药物或基因治疗提供合适的靶点。
The mammalian target of rapamycin ( mTOR) is a multifunctional protein involved in the regulation of cell growth, proliferation, and differentiation. The goal of this study was to determine the role of mTOR in type I collagen regulation. The pharmacological inhibitor of phosphatidylinositol (PI) 3-kinase, LY294002, significantly inhibited collagen type I protein and mRNA levels. The effects of LY294002 were more pronounced on the collagen alpha1( I) chain, which was inhibited at the transcriptional and mRNA stability levels versus collagen \alpha2( I) chain, which was inhibited through a decrease in mRNA stability. In contrast, addition of the PI 3-kinase inhibitor, wortmannin, did not alter type I collagen steady-state mRNA levels. This observation and further experiments using an inactive LY294002 analogue suggested that collagen mRNA levels are inhibited independent of PI 3-kinase. Additional experiments have established that mTOR positively regulates collagen type I synthesis in human fibroblasts. These conclusions are based on results demonstrating that inhibition of mTOR activity using a specific inhibitor, rapamycin, reduced collagen mRNA levels. Furthermore, decreasing mTOR expression by about 50% by using small interfering RNA resulted in a significant decrease of collagen mRNA (75% COL1A1 decrease and 28% COL1A2 decrease) and protein levels. Thus, mTOR plays an essential role in regulating basal expression of collagen type I gene in dermal fibroblasts. Together, our data suggest that the classical PI 3-kinase pathway, which places mTOR downstream of PI 3-kinase, is not involved in mTOR-dependent regulation of type I collagen synthesis in dermal fibroblasts. Because collagen overproduction is a main feature of fibrosis, identification of mTOR as a critical mediator of its regulation may provide a suitable target for drug or gene therapy.