This study was conducted to investigate the effects of different concentrations of insulin (INS) in medium on expression levels of αsl-casein ( CSN1S1) gene, mammalian target of rapamycin (mTOR) and Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway related genes. Hol-stein bovine mammary epithelial cells were treated with different concentrations (0, 2. 5, 25. 0, 250. 0 and 5 000.0 ng/mL) of INS, respectively. The expression levels of CSN1S1 gene, mTOR and JAK-STAT signaling pathway related genes were determined by real-time quantitative PCR. The results showed as follows: compared with 0 ng/mL group, INS could promote the expression levels of CSMS1, short-prolactin receptors (S-PRLR), protein kinase B (PKB) and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) genes, and increase the expression levels of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5A (STAT5A) genes. Especially, the expression levels of these genes in 25 ng/mL group were the highest. The results indicate that INS can improve the expression level of CSN1S1 gene. The mechanism is as follows: firstly, INS can promote hormone receptor expression, and then promote genetic transcription; secondly , INS can promote the positive regulation expression of mTOR and JAK-STAT signaling pathways related genes, and highly improve the expression of CSN1S1 gene, which provides a material foundation for increasing milk protein synthesis at the translation level.%本文旨在通过在培养液中添加不同浓度胰岛素(INS),研究其对奶牛乳腺上皮细胞中αs1-酪蛋白(CSNl Sl)基因、雷帕霉素靶蛋白(mTOR)信号通路及Janus激酶-信号传导和转录活化因子(JAK-STAT)信号通路相关基因表达的影响.试验选用中国荷斯坦奶牛的乳腺上皮细胞进行体外培养,在无血清无激素的培养基中分别添加0(对照)、2.5、25.0、250.0、5 000.0 ng/mL INS,利用实时荧光定量PCR方法检测CSNlSl基因、mTOR和JAK-STAT信号通路中相关基因表达量.结果表明:与0 ng/mL组相比,添加不同浓度的INS后均能提高CSNlSl、短型催乳素受体(S-PRLR)及mTOR信号通路中上游蛋白激酶B(PKB)、mTOR和下游真核翻译起始因子4E结合蛋白1(4E-BP1)基因表达量,并且能够增加JAK-STAT信号通路中Janus激酶2(JAK2)和信号转导和转录激活因子5A(STAT5A)基因表达量,当INS浓度为25.0 ng/mL时各正向调节基因表达量最高.此结果提示,添加外源INS能提高奶牛乳腺上皮细胞CSNlSl基因表达量,其作用机理:一是添加INS后能够促进激素受体基因的表达,进而促进转录的启动;二是促进乳蛋白合成的mTOR和JAK-STAT信号通路中各正向调节基因的表达,进而使CSNlSl等乳蛋白合成基因能高水平表达,为进一步通过翻译水平增加乳蛋白的合成奠定了物质基础.
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