School of Life Science and Technology, Harbin Institute of Technology , Harbin , China.
Faculty of Education, Wakayama University , Wakayama , Japan.
Am J Physiol Endocrinol Metab. 2019 Jun 1;316(6):E1081-E1092. doi: 10.1152/ajpendo.00478.2018. Epub 2019 Apr 9.
Musclin is a muscle-secreted cytokine that disrupts glucose uptake and glycogen synthesis in type 2 diabetes. The purpose of this study was to investigate the mechanisms responsible for the regulation of musclin gene expression in response to treatment with palmitate. RNA sequencing results showed that biological processes activated by palmitate are mainly enriched in endoplasmic reticulum (ER) stress. The protein kinase RNA-like ER kinase (PERK) signaling pathway is involved in the regulation of musclin expression induced by palmitate. Chromatin immunoprecipitation data showed that activating transcription factor 4 (ATF4)-downstream of PERK-bound to the promoter of the C/EBPβ gene. Notably, C/EBPβ also contains a binding site in the region -94-52 of the musclin gene promoter. Knockdown or knockout of PERK and ATF4 using short hairpin RNA or CRISPR-Cas9 decreased the expression of C/EBPβ and musclin induced by palmitate. Furthermore, knockdown and knockout of C/EBPβ alleviated the high expression of musclin in response to treatment with palmitate. Moreover, CRISPR-Cas9 knockout of the region -94-52 in which C/EBPβ binds to the promoter of musclin abrogated the induction of high musclin expression caused by palmitate. Collectively, these findings suggest that treatment with palmitate activates the PERK/ATF4 signaling pathway, which in turn increases the expression of C/EBPβ. C/EBPβ binds directly to the promoter of the musclin gene and upregulates its expression.
肌球蛋白是一种肌肉分泌的细胞因子，可破坏 2 型糖尿病患者的葡萄糖摄取和糖原合成。本研究旨在探讨棕榈酸处理调节肌球蛋白基因表达的机制。RNA 测序结果表明，棕榈酸激活的生物学过程主要富集在内质网（ER）应激中。蛋白激酶 RNA 样 ER 激酶（PERK）信号通路参与调节棕榈酸诱导的肌球蛋白表达。染色质免疫沉淀数据显示，PERK 下游的激活转录因子 4（ATF4）与 C/EBPβ 基因启动子结合。值得注意的是，C/EBPβ 在肌球蛋白基因启动子的-94-52 区域也含有一个结合位点。使用短发夹 RNA 或 CRISPR-Cas9 敲低或敲除 PERK 和 ATF4 可降低棕榈酸诱导的 C/EBPβ 和肌球蛋白表达。此外，敲低和敲除 C/EBPβ 可减轻棕榈酸处理后肌球蛋白的高表达。此外，CRISPR-Cas9 敲除 C/EBPβ 结合到肌球蛋白启动子的-94-52 区域，可消除棕榈酸诱导的肌球蛋白高表达。总之，这些发现表明，棕榈酸处理激活 PERK/ATF4 信号通路，进而增加 C/EBPβ 的表达。C/EBPβ 直接与肌球蛋白基因的启动子结合，上调其表达。
