title: Oleate and linoleate stimulate degradation of β-casein in prolactin-treated HC11 mouse mammary epithelial cells.
abstract: Although virtually all cells store neutral lipids as cytoplasmic lipid droplets, mammary epithelial cells have developed a specialized function to secrete them as milk fat globules. We have used the mammary epithelial cell line HC11 to evaluate the potential connections between the lipid and protein synthetic pathways. We show that unsaturated fatty acids induce a pronounced proliferation of cytoplasmic lipid droplets and stimulate the synthesis of adipose differentiation-related protein. Unexpectedly, the cellular level of beta-casein, accumulated under lactogenic hormone treatment, decreases following treatment of the cells with unsaturated fatty acids. In contrast, saturated fatty acids have no significant effect on either cytoplasmic lipid droplet proliferation or cellular beta-casein levels. We demonstrate that the action of unsaturated fatty acids on the level of beta-casein is post-translational and requires protein synthesis. We have also observed that proteasome inhibitors potentiate beta-casein degradation, indicating that proteasomal activity can destroy some cytosolic protein(s) involved in the process that negatively controls beta-casein levels. Finally, lysosome inhibitors block the effect of unsaturated fatty acids on the cellular level of beta-casein. Our data thus suggest that the degradation of beta-casein occurs via the microautophagic pathway.
authors.affiliation: INRA, UR1196 Génomique et Physiologie de la Lactation Domaine de Vilvert, 78352, Jouy-en-Josas, France. alain.pauloin@jouy.inra.fr
authors.forename: Alain
authors.initials: A
authors.lastname: Pauloin
authors.forename: Sophie
authors.initials: S
authors.lastname: Chat
authors.forename: Christine
authors.initials: C
authors.lastname: Péchoux
authors.forename: Catherine
authors.initials: C
authors.lastname: Hue-Beauvais
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Droineau
authors.forename: Laurent
authors.initials: L
authors.lastname: Galio
authors.forename: Eve
authors.initials: E
authors.lastname: Devinoy
authors.forename: Eric
authors.initials: E
authors.lastname: Chanat
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000502:physiology; D002364:Caseins / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D019787:Linoleic Acid / Q000378:metabolism* / Q000494:pharmacology; D050356:Lipid Metabolism / Q000187:drug effects / Q000502:physiology; D008055:Lipids / Q000502:physiology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D019301:Oleic Acid / Q000378:metabolism* / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism* / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000502:physiology
chemical_list: D002364:Caseins; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D008055:Lipids; D061988:Proteasome Inhibitors; D019301:Oleic Acid; D011388:Prolactin; D019787:Linoleic Acid; D046988:Proteasome Endopeptidase Complex