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Communication Dans Un Congrès Année : 2012

SNARE proteins and milk products secretion

Résumé

Introduction. Casein micelles and milk fat globules (MFGs) are major milk components both of which being secreted at the apical side of the mammary epithelial cell (MEC) during lactation. Caseins are released by exocytosis while MFGs are excreted by budding, being enwrapped by the apical plasma membrane. Nevertheless, the molecular mechanisms involved in milk products secretion are still not fully deciphered. Due to their size (4 µm average diameter in bovine), the expulsion of MFGs obviously requires a very important amount of membrane. This could be partly provided by the exocytosis of secretory vesicles containing caseins but other sources of membranes are likely. Moreover, the secretion of these various milk products seems to be coordinated at the time of suckling, suggesting the existence of regulatory mechanisms common to the processes of protein exocytosis and lipid budding. In this context, we investigated the role of SNARE proteins (soluble N-ethylmaleimide-sensitive factor activating protein receptor) which are the core fusion machinery of cell membranes in the secretion of milk products. [br/] Results. We previously showed that SNARE proteins are expressed in the mouse mammary gland at different physiological stages, and especially during lactation, and that some of these proteins are actually associated with caseins containing secretory vesicles and/or with intracellular lipid droplets (LDs), as well as with MFGs [1]. Our results showed that SNAP-23 is associated with both LDs and MFGs, and that this protein is often present at the interface between the casein containing vesicles and the LDs at the apical pole of MECs. SNAP-23 has already been demonstrated at the membrane of bovine MFGs [2] and could play a role in intracellular growth of LDs [3]. We have also observed other SNARE proteins such as VAMP-8 and Sec22B at the surface of mouse MFGs. Interestingly, VAMP-8 is associated with both casein containing vesicles and intracellular LDs in the MECs of lactating mouse. The differential analysis of proteins associated with intracellular LDs and MFGs by mass spectrometry provides important informations concerning the compartments providing membrane for the secretion of MFGs. [br/] Conclusion. Taken together, our results suggest that the membrane allowing the secretion of MFGs comes from several compartments, including at least caseins containing secretory vesicles and the endoplasmic reticulum. Moreover, it is likely that the protein SNAP-23 is a common actor to both secretory vesicles exocytosis and budding of MFGs, thus constituting a potential regulatory point for the coordinated secretion of milk products. [br/] Perspectives. The functional role of SNAP-23 in the secretion of milk products will be determined using tools such as botulinum toxin E (BoNT/E) and siRNAs directed against SNAP-23.[br/] References. [1] Chat et al., 2011, Eur J Cell Biol 90(5):401-13. [2] Reinhardt & Lippolis, 2008, J Dairy Sci 91(6):2307-18. [3] Boström et al., 2007, Nat Cell Biol 9(11):1286-93.

Domaines

Biologie animale
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Dates et versions

hal-01204362 , version 1 (23-09-2015)

Identifiants

  • HAL Id : hal-01204362 , version 1
  • PRODINRA : 269303

Citer

Edith Honvo Houeto, Celine Henry, Sophie Chat, Sarah Layani-Moreno, Eric Chanat, et al.. SNARE proteins and milk products secretion. 15. Annual Meeting Club Exocytose-Endocytose, Club Exocytose-Endocytose. Paris, FRA., May 2012, L'Isle sur la Sorgue, France. ⟨hal-01204362⟩
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