EGF acts as a ligand of the EGF receptor (EGFR) to activate the EGFR-mediated signaling pathways and is involved in the regulation of cell physiology. However, the roles of EGFR mediated signaling pathways in the regulation of lipid metabolism in goat mammary epithelial cells (GMECs) are poorly understood. To evaluate the impact of EGF on GMECs, the triglyceride (TG) content and lipid droplet were detected, using TG assay and immunofluorescence. Further, expression of lipogenic genes, the protein kinase B (Akt), phospholipase C-γ1 (PLC-γ1) and extracellular signal-regulated kinases (ERK)1/2 signaling pathways were measured by real-time polymerase chain reaction and Western blot, respectively. The results showed that the mRNA expression of EGFR gene was significantly upregulated in lactating goat mammary gland tissues compared to non-lactation period (p < 0.05). TG contents in EGF-treated GMECs were significantly increased (p < 0.05), and an increase of lipid droplets was also detected. In vitro studies demonstrated that the mRNA levels of lipogenesis-related FASN, ACC, SCD1, LXRa, LXRb and SP1 genes were positively correlated to the mRNA level of EGFR gene shown by gene overexpression and silencing (p < 0.05). The phosphorylations of Akt, ERK1/2 and PLC-γ1 in GMECs were greatly upregulated in the presence of EGF, and specific inhibitors were capable of blocking the phosphorylation of Akt, ERK1/2 and PLC-γ1. Compared with EGF-treated GMECs, the mRNA levels of FASN, ACC and SCD1 were significantly decreased in GMECs co-treated with PLC-γ1 and Akt inhibitor and EGF (p < 0.05), and TG content was also dropped significantly. These observations implied that EGFR plays an important role in regulating de novo fatty acid synthesis in GMECs, mainly mediated by Akt and PLC-γ1 signaling pathways.

中文翻译：

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表皮生长因子主要通过PLC-γ1/ Akt信号通路刺激乳山羊乳腺上皮细胞中的脂肪酸合成。

EGF充当EGF受体（EGFR）的配体，以激活EGFR介导的信号通路，并参与细胞生理的调节。然而，人们对EGFR介导的信号通路在山羊乳腺上皮细胞（GMECs）脂质代谢调节中的作用了解甚少。为了评估EGF对GMEC的影响，使用TG分析和免疫荧光检测了甘油三酸酯（TG）含量和脂质滴。此外，通过实时聚合酶链反应和Western印迹测量了生脂基因，蛋白激酶B（Akt），磷脂酶C-γ1（PLC-γ1）和细胞外信号调节激酶（ERK）1/2信号通路的表达。 ， 分别。结果表明EGFR的mRNA表达与非哺乳期相比，该基因在哺乳的山羊乳腺组织中显着上调（p <0.05）。经EGF处理的GMEC中的TG含量显着增加（p <0.05），并且还检测到脂质滴的增加。体外研究表明，与脂肪生成相关的FASN，ACC，SCD1，LXRa，LXRb和SP1基因的mRNA水平与基因过表达和沉默显示的EGFR基因mRNA水平呈正相关（p<0.05）。在存在EGF的情况下，GMEC中Akt，ERK1 / 2和PLC-γ1的磷酸化大大上调，并且特定的抑制剂能够阻断Akt，ERK1 / 2和PLC-γ1的磷酸化。与EGF处理的GMEC相比，与PLC-γ1和Akt抑制剂及EGF共同处理的GMEC中，FASN，ACC和SCD1的mRNA水平显着降低（p <0.05），TG含量也显着下降。这些观察结果暗示，EGFR在调节GMEC中从头脂肪酸合成中起重要作用，主要由Akt和PLC-γ1信号传导途径介导。