Prolactin and epidermal growth factor stimulate adipophilin synthesis in HC11 mouse mammary epithelial cells via the PI3-kinase/Akt/mTOR pathway
- 作者：Alain Pauloin ; alain.pauloin@jouy.inra.fr ; Eric Chanat
- 关键词：A.U. ; arbitrary unit ; ADRP ; adipocyte differentiation-related protein ; BSA ; bovine serum albumin ; CIS ; cytokine-inducible SH2-containing proteins ; ECL ; electrochemiluminescence ; EGF ; epidermal growth factor ; EGFr ; EGF receptor ; ER ; endoplasmic reticulum
- 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Cell Research
- 出版年：2012
- 期刊代码：20_01674889
- 类别：bio
- 出版时间：May, 2012
- 卷：1823
- 期：5
- 页码：987-996
- 文件大小：1530 K
摘要
The aim of the present study is to estimate the role played by cortisol, prolactin (PRL) and epidermal growth factor (EGF) in the synthesis of adipocyte differentiation-related protein (ADRP) as compared to the well-studied regulation of飥?尾-casein synthesis by these hormones in the mammary epithelial cell line HC11. This comparison between a cytoplasmic lipid droplet-associated protein, which is strictly specific to both lipid accumulation and secretion by lactating mammary epithelial cells, and an archetypal milk protein is useful for evaluating the extent to which a mechanistic relationship exists between biosynthesis, transport and secretion of these two major milk components. We found that cortisol inhibits PRL-stimulated ADRP synthesis, as opposed to its known stimulating effect on 尾-casein synthesis. The involvement of PRL and EGF in ADRP synthesis was explored by means of a battery of inhibitors. The Jak2 inhibitor AG490 provoked a stimulation of ADRP synthesis whereas it totally suppressed that of 尾-casein. The use of AG1478, a specific inhibitor of EGF receptor phosphorylation, or of PD98059, a specific MEK inhibitor, revealed that the Ras/Raf/MEK/ERK1/2 pathway has no significant influence on ADRP levels. Inhibition of JNK was also ineffective. In contrast, incubation of the cells with SB 203580, a specific inhibitor of p38, slightly stimulated ADRP synthesis and induced a proportional dose-response inhibition of PRL-induced 尾-casein synthesis. Finally, cell treatment with wortmannin or LY294002 revealed that both PRL and EGF positively regulate ADRP and 尾-casein synthesis through PI3-kinase signaling. Because both the Akt inhibitor MK-2206 and the mTOR inhibitor rapamycin provoked a strong diminution of PRL-induced synthesis of the two proteins, and because oleate induced phosphorylation of Akt, we concluded that, in the mammary epithelial cell line HC11, the PI3-kinase/Akt/mTOR signaling pathway strongly participates in 尾-casein synthesis and is a main regulator of ADRP expression.