title: Prolactin and epidermal growth factor stimulate adipophilin synthesis in HC11 mouse mammary epithelial cells via the PI3-kinase/Akt/mTOR pathway.
abstract: 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 β-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 β-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 β-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 β-casein synthesis. Finally, cell treatment with wortmannin or LY294002 revealed that both PRL and EGF positively regulate ADRP and β-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 β-casein synthesis and is a main regulator of ADRP expression.
authors.affiliation: INRA, UR1196 Génomique et Physiologie de la Lactation, R-78350 Jouy-en-Josas, France. alain.pauloin@jouy.inra.fr
authors.forename: Alain
authors.initials: A
authors.lastname: Pauloin
authors.forename: Eric
authors.initials: E
authors.lastname: Chanat
mesh_terms: D000818:Animals; D002364:Caseins / Q000378:metabolism; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008321:Mammary Glands, Animal / Q000166:cytology; D008565:Membrane Proteins / Q000096:biosynthesis*; D051379:Mice; D008954:Models, Biological; D019301:Oleic Acid / Q000494:pharmacology; D000070780:Perilipin-2; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011388:Prolactin / Q000494:pharmacology*; D014176:Protein Biosynthesis / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D012756:Sheep; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D002364:Caseins; D004815:Epidermal Growth Factor; D053614:Janus Kinase 2; D008565:Membrane Proteins; D019301:Oleic Acid; D000070780:Perilipin-2; D019869:Phosphatidylinositol 3-Kinases; D011388:Prolactin; D047428:Protein Kinase Inhibitors; D011500:Protein Synthesis Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D016755:Proto-Oncogene Proteins c-jun; D050799:STAT5 Transcription Factor; D058570:TOR Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C000602983:Plin2 protein, mouse; C494093:Stat5a protein, mouse; C546843:mTOR protein, mouse