Graduate School of Science and Technology, Shinshu University, Minamiminowa, Nagano, Japan.
Graduate School of Medicine, Science and Technology, Shinshu University, Minamiminowa, Nagano, Japan.
Anim Sci J. 2019 Aug;90(8):1026-1032. doi: 10.1111/asj.13246. Epub 2019 Jun 14.
It has been reported that the expression of β-casein, a representative milk protein, increases when mammary epithelial cells are exposed to mild heat stress at 39°C. However, the direct effects and detailed molecular mechanisms have not yet been elucidated. In this study, we investigated the relationship between an increase in β-casein expression and the unfolded protein response (UPR) under mild heat stress. After reaching confluence, HC11 cells were incubated at 37°C (control) or 39°C (mild heat stress) without differentiation medium, and the expression levels of β-casein and UPR-related genes were assessed. It was revealed that, even with this mild heat treatment (39°C), β-casein expression in HC11 cells increased at the transcriptional level without differentiation induction. The expression levels of X-box binding protein 1 (XBP1) and activating transcription factor 6 alpha (ATF6α) were significantly higher in cells cultured at 39°C compared to those cultured at 37°C. Moreover, the increase in β-casein mRNA expression levels by mild heat treatment was suppressed in XBP1 or ATF6α knockdown cells generated by siRNA for XBP1 or ATF6α respectively. Thus, these results demonstrate that ATF6α and XBP1 is involved in the increase of β-casein expression following mild heat treatment.
据报道，当乳腺上皮细胞暴露于 39°C 的轻度热应激时，β-酪蛋白（一种代表性的牛奶蛋白）的表达会增加。然而，其直接作用和详细的分子机制尚未阐明。在这项研究中，我们研究了在轻度热应激下，β-酪蛋白表达的增加与未折叠蛋白反应（UPR）之间的关系。当细胞达到汇合状态后，将 HC11 细胞在 37°C（对照）或 39°C（轻度热应激）下孵育，不添加分化培养基，并评估β-酪蛋白和 UPR 相关基因的表达水平。结果表明，即使进行这种轻度热处理（39°C），HC11 细胞中的β-酪蛋白在没有诱导分化的情况下，在转录水平上增加。与在 37°C 下培养的细胞相比，在 39°C 下培养的细胞中 X 盒结合蛋白 1（XBP1）和激活转录因子 6 阿尔法（ATF6α）的表达水平显著升高。此外，通过 XBP1 或 ATF6α 的 siRNA 分别敲低 XBP1 或 ATF6α 生成的细胞中，轻度热处理引起的β-酪蛋白 mRNA 表达水平的增加受到抑制。因此，这些结果表明，在轻度热应激后，ATF6α 和 XBP1 参与了β-酪蛋白表达的增加。
