Electron Tomography Revels that Milk Lipids Originate from Endoplasmic Reticulum Domains with Novel Structural Features.
Electron Tomography Revels that Milk Lipids Originate from Endoplasmic Reticulum Domains with Novel Structural Features.
复制标题
电子断层扫描揭示乳脂起源于具有新颖结构特征的内质网结构域。
DOI：
10.1007/s10911-019-09438-y
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发表时间：
2019
影响因子：
2.5
通讯作者：
McManaman,JamesL
中科院分区：
文献类型：
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作者：
Ladinsky,MarkS;Mardones,GonzaloA;Orlicky,DavidJ;Howell,KathrynE;McManaman,JamesL
脂滴（Lipid drops，LD）是来源于内质网（Endoplasmic reticulum，ER）的一种动态调节的细胞器，参与中性脂质的储存、运输和代谢。在哺乳动物的乳腺上皮细胞（MEC）中，完整的LD通过一种新的顶分泌机制完整地分泌到乳汁中形成乳脂。完整LD的分泌和泌乳MEC分泌的相对大量的脂质增加了对负责脂质合成和LD形成的细胞过程的需求。由于对LD-ER相互作用的了解有限，这些过程至今还没有很好的定义。为了克服这些局限性，我们使用快速冷冻和冷冻替代方法结合三维电子断层扫描和高分辨率免疫定位来定义LD与ER在妊娠和哺乳大鼠MEC中的相互作用。使用这些方法，我们确定了不同的ER结构域，有助于脂滴的形成和稳定，并具有独特的功能，以前未被认识或不完全赞赏。我们的研究结果表明，新生的脂滴内的ER腔和协会的形成和成熟的液滴与结构独特的区域的ER脑池，其特征在于存在的perilipin-2，一种蛋白质参与脂滴的形成，和酶参与脂质合成。这些数据表明，牛奶脂质来源于LD-ER结构域与新的结构特征，并提出了一种机制，初始液滴形成在ER腔和随后的成熟液滴与ER池。
Lipid droplets (LD) are dynamically-regulated organelles that originate from the endoplasmic reticulum (ER), and function in the storage, trafficking and metabolism of neutral lipids. In mammary epithelial cells (MEC) of lactating animals, intact LD are secreted intact into milk to form milk lipids by a novel apocrine mechanism. The secretion of intact LD and the relatively large amounts of lipid secreted by lactating MEC increase demands on the cellular processes responsible for lipid synthesis and LD formation. As yet these processes are poorly defined due to limited understanding of LD-ER interactions. To overcome these limitations, we used rapid-freezing and freeze-substitution methods in conjunction with 3D electron tomography and high resolution immunolocalization to define interactions between LD with ER in MEC of pregnant and lactating rats. Using these approaches, we identified distinct ER domains that contribute to lipid droplet formation and stabilization and which possess unique features previously unrecognized or not fully appreciated. Our results show nascent lipid droplets within the ER lumen and the association of both forming and mature droplets with structurally unique regions of ER cisternae, characterized by the presence of perilipin-2, a protein implicated in lipid droplet formation, and enzymes involved in lipid synthesis. These data demonstrate that milk lipids originate from LD-ER domains with novel structural features and suggest a mechanism for initial droplet formation in the ER lumen and subsequent maturation of the droplets in association with ER cisternae.