Methionine Induces LAT1 Expression in Dairy Cow Mammary Gland by Activating the mTORC1 Signaling Pathway
Methionine Induces LAT1 Expression in Dairy Cow Mammary Gland by Activating the mTORC1 Signaling Pathway
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蛋氨酸通过激活 mTORC1 信号通路诱导奶牛乳腺中 LAT1 的表达。
DOI：
10.1089/dna.2017.3792
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发表时间：
2017-12-01
影响因子：
3.1
通讯作者：
Hou, Xiaoming
中科院分区：
文献类型：
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作者：
Duan, Xiaoyu;Lin, Ye;Hou, Xiaoming
蛋氨酸是奶牛乳蛋白合成的限制性氨基酸。蛋氨酸对乳蛋白合成的影响取决于其通过氨基酸转运蛋白主动转运到细胞中。L型氨基酸转运蛋白1（LAT1）是一种诱导中性氨基酸转运的蛋白，在哺乳期乳腺中高表达。然而，蛋氨酸对奶牛乳腺中LAT1表达的影响以及控制这一过程的机制知之甚少。在这项研究中，我们表明，奶牛乳腺上皮细胞与蛋氨酸浓度增加24小时的治疗导致LAT1及其相关蛋白4F2重链（4F2hc）的表达增加。在用0.6mM甲硫氨酸处理后出现最大表达水平。甲硫氨酸处理也增加了细胞活力和酪蛋白的合成。Western印迹显示，甲硫氨酸通过激活哺乳动物雷帕霉素靶蛋白复合物1（mTORC 1）信号传导诱导LAT1和4F2hc表达。通过雷帕霉素或raptor siRNA抑制mTORC1信号传导阻止了LAT1和4F2hc的上调。这些结果表明，蛋氨酸可能激活mTORC 1信号通路，进一步增加奶牛乳腺中LAT1和4F2hc的表达，从而影响乳蛋白的合成。
Methionine is the limiting amino acid for milk protein synthesis in dairy cows. The effect of methionine availability on milk protein synthesis is dependent on its active transport into cells through amino acid transporters. L-type amino acid transporter 1 (LAT1), which induces the transport of neutral amino acids, is highly expressed in lactating mammary gland. However, the effect of methionine on LAT1 expression and the mechanism governing this process in dairy cow mammary gland are poorly understood. In this study, we show that treatment of dairy cow mammary epithelial cells with increasing concentrations of methionine for 24h resulted in increased expression of LAT1 and its associated protein 4F2 heavy chain (4F2hc). Maximal expression levels occurred after treatment with 0.6mM methionine. Methionine treatment also increased cell viability and -casein synthesis. Western blots showed that methionine induced LAT1 and 4F2hc expression by activating mammalian target of rapamycin complex 1 (mTORC1) signaling. Inhibition of mTORC1 signaling by rapamycin or raptor siRNA prevented the upregulation of LAT1 and 4F2hc. These results indicate that methionine may activate the mTORC1 signaling pathway and further increase LAT1 and 4F2hc expression in dairy cow mammary gland, thus affecting milk protein synthesis.