Caractérisation des protéines SNARE potentiellement impliquées dans la sécrétion des produits du lait
Résumé
The mammary gland is a complex tissue which function is to ensure the offspring’s feeding by producing and secreting milk during lactation. Casein micelles and fat globules (MFGs) are essential constituents of milk and are both secreted at the apical side of mammary epithelial cells (MECs) during lactation. MFGs are excreted by budding, being enwrapped by the apical plasma membrane, while caseins contained in transport vesicles are released by exocytosis. The lactogenic hormone prolactin (PRL) not only induces the synthesis of caseins but also an increase of arachidonic acid (AA) in MECs, which may accelerate the apical transport and possibly the exocytosis of caseins (secretagogue effect of PRL). Nevertheless, the molecular mechanisms governing casein exocytosis are, to date, not fully deciphered. By forming stable ternary complexes, SNARE (Soluble NSF Attachment Receptor) proteins constitute the core fusion machinery for cellular membrane trafficking and exocytosis events in many cell types. In addition, SNAREs have recently been described as target for AA, thus promoting exocytosis in neuroendocrine cells. We therefore attempted to identify the SNARE proteins involved in caseins secretion in the mouse mammary gland during lactation. An exciting possibility is that the SNAREs involved in caseins’ exocytosis can be the target of AA released in response to PRL.