αS1-casein, which is essential for efficient ER-to-Golgi casein transport, is also present in a tightly membrane-associated form

BMC Cell Biology

Research Article

Joëlle Leonil¹  Eric Chanat²  Annabelle Le Parc² 

[1] INRA, UMR1253 Science et Technologie du Lait et de l'Œuf, F-35000, Rennes, France;INRA, UR1196 Génomique et Physiologie de la Lactation, Domaine de Vilvert, F-78352, Jouy-en-Josas cedex, France;

关键词: Endoplasmic Reticulum;    Saponin;    Secretory Pathway;    Rough Endoplasmic Reticulum;    Casein Micelle;   

DOI  :  10.1186/1471-2121-11-65

 received in 2010-05-06, accepted in 2010-08-12,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundCaseins, the main milk proteins, aggregate in the secretory pathway of mammary epithelial cells into large supramolecular structures, casein micelles. The role of individual caseins in this process and the mesostructure of the casein micelle are poorly known.ResultsIn this study, we investigate primary steps of casein micelle formation in rough endoplasmic reticulum-derived vesicles prepared from rat or goat mammary tissues. The majority of both αS1- and β-casein which are cysteine-containing casein was dimeric in the endoplasmic reticulum. Saponin permeabilisation of microsomal membranes in physico-chemical conditions believed to conserve casein interactions demonstrated that rat immature β-casein is weakly aggregated in the endoplasmic reticulum. In striking contrast, a large proportion of immature αS1-casein was recovered in permeabilised microsomes when incubated in conservative conditions. Furthermore, a substantial amount of αS1-casein remained associated with microsomal or post-ER membranes after saponin permeabilisation in non-conservative conditions or carbonate extraction at pH11, all in the presence of DTT. Finally, we show that protein dimerisation via disulfide bond is involved in the interaction of αS1-casein with membranes.ConclusionsThese experiments reveal for the first time the existence of a membrane-associated form of αS1-casein in the endoplasmic reticulum and in more distal compartments of the secretory pathway of mammary epithelial cells. Our data suggest that αS1-casein, which is required for efficient export of the other caseins from the endoplasmic reticulum, plays a key role in early steps of casein micelle biogenesis and casein transport in the secretory pathway.

【 授权许可】

Unknown   
© Le Parc et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.