title: The endoplasmic reticulum and casein-containing vesicles contribute to milk fat globule membrane.
abstract: During lactation, mammary epithelial cells secrete huge amounts of milk from their apical side. The current view is that caseins are secreted by exocytosis, whereas milk fat globules are released by budding, enwrapped by the plasma membrane. Owing to the number and large size of milk fat globules, the membrane surface needed for their release might exceed that of the apical plasma membrane. A large-scale proteomics analysis of both cytoplasmic lipid droplets and secreted milk fat globule membranes was used to decipher the cellular origins of the milk fat globule membrane. Surprisingly, differential analysis of protein profiles of these two organelles strongly suggest that, in addition to the plasma membrane, the endoplasmic reticulum and the secretory vesicles contribute to the milk fat globule membrane. Analysis of membrane-associated and raft microdomain proteins reinforces this possibility and also points to a role for lipid rafts in milk product secretion. Our results provide evidence for a significant contribution of the endoplasmic reticulum to the milk fat globule membrane and a role for SNAREs in membrane dynamics during milk secretion. These novel aspects point to a more complex model for milk secretion than currently envisioned.
authors.affiliation: INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France.
authors.forename: Edith
authors.initials: E
authors.lastname: Honvo-Houéto
authors.affiliation: INRA, UMR1319, MICALIS, PAPPSO, F-78352 Jouy-en-Josas Cedex, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Henry
authors.affiliation: INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Chat
authors.affiliation: INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France.
authors.forename: Sarah
authors.initials: S
authors.lastname: Layani
authors.affiliation: INRA, UR1196 Génomique et Physiologie de la Lactation, F-78352 Jouy-en-Josas Cedex, France sandrine.truchet@jouy.inra.fr.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Truchet
mesh_terms: D000818:Animals; D001940:Breast / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D006017:Glycolipids / Q000096:biosynthesis* / Q000378:metabolism*; D006023:Glycoproteins / Q000096:biosynthesis* / Q000378:metabolism*; D006801:Humans; D007774:Lactation / Q000378:metabolism; D066292:Lipid Droplets; D008055:Lipids; D008321:Mammary Glands, Animal / Q000378:metabolism; D042361:Mammary Glands, Human / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism; D008566:Membranes / Q000378:metabolism; D051379:Mice; D008892:Milk / Q000378:metabolism; D040901:Proteomics / Q000379:methods; D050600:SNARE Proteins / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism / Q000502:physiology
chemical_list: D002364:Caseins; D006017:Glycolipids; D006023:Glycoproteins; D008055:Lipids; D050600:SNARE Proteins; C110367:milk fat globule