Molecular Determinants of Lactation Success

牛奶是一种复杂的液体，能够维持人类婴儿6个月或更长时间的全部营养， 以及在产后早期的关键时期提供保护，防止感染和常见的儿童疾病， 期乳脂质提供了新生儿生长所需的大部分热量，此外， 将脂溶性维生素传递给婴儿的主要机制和必需脂肪酸的来源 新生儿膜合成和类二十烷酸和其他生物活性脂质信号的合成所需 分子。为了满足新生儿的热量和营养需求，一种独特的顶泌机制在哺乳动物中进化出来。 哺乳动物有效地分泌大量的脂质进入牛奶。来自人类和动物模型的证据 表明顶浆分泌脂质对启动和维持泌乳也很重要， 干扰这一过程会增加泌乳失败的风险。我们实验室的工作表明， 顶浆分泌脂质包括三个机制上不同的步骤：（1）形成专门的“对接” CLD和顶端质膜（APM）之间的接触;（2）对接CLD的膜固定， 部分由高尔基体衍生的分泌囊泡驱动;和（3）膜包被的CLD释放到 腔空间作为三层膜涂层结构，称为乳脂球（MFG），由顶浆分泌 分裂过程我们以前确定了亲酪蛋白（Btn），乳腺特异性 跨膜蛋白、细胞质氧化还原酶、黄嘌呤氧化还原酶（XOR）和CLD外壳 蛋白质，围脂蛋白-2（Plin 2）对小鼠顶浆分泌脂质分泌很重要。重要的是，我们已经证明 这些蛋白质的基因缺失会干扰CLD分泌，并损害或阻止泌乳。 本研究的目的是：（1）探讨顶浆分泌脂质的机制， 假设催乳素和催产素独立调节这一过程的离散步骤;（2）定义如何 顶浆分泌脂质影响顶膜特性、分泌囊泡运输、泌乳和 确定XOR、Btn和Plin 2之间相互作用的关键分子决定因素 介导顶浆分泌脂质。所提出的研究利用了新颖的XOR、Btn和Plin 2 我们实验室开发的基因敲除小鼠模型，定量高分辨率成像，以及创新的 生理和生物化学分析以及顶浆分泌脂质分泌的细胞培养模型来完成这些 目标.

Milk is a complex fluid capable of sustaining the total nutrition of the human infant for 6 months or longer, as well as providing protection against infection and common childhood illnesses during the critical early postnatal period. Milk lipids provide the majority of the calories required for neonatal growth, in addition to being the primary mechanism for transferring fat-soluble vitamins to infants and the source of essential fatty acids needed for neonatal membrane synthesis and the synthesis of eicosanoids and other bioactive lipid signalling molecules. To meet caloric and nutritional demands of newborns, a unique apocrine mechanism evolved in mammals to efficiently secrete large quantities of lipid into milk. Evidence from humans and animal models suggest that apocrine lipid secretion is also important for initiating and sustaining lactation, and that interference with this process increases the risk of lactation failure. Work from our laboratories indicates that apocrine lipid secretion involves three mechanistically distinct steps: (1) formation of specialized “docking” contacts between CLD and the apical plasma membrane (APM); (2) membrane envelopment of docked CLD, driven in part by Golgi derived secretory vesicles; and (3) release of membrane enveloped CLD into the luminal space as trilaminar membrane coated structures, referred to as milk fat globules (MFG), by an apocrine scission process. We previously identified interactions between butyrophilin (Btn), a mammary gland specific transmembrane protein, the cytoplasmic redox enzyme, xanthine oxidoreductase (XOR), and the CLD coat protein, perilipin-2 (Plin2) as important for apocrine lipid secretion in mice. Importantly, we have demonstrated that genetic deletion of either of these proteins interferes with CLD secretion, and impairs or prevents lactation. The goals of this proposal are: (1) to investigate the mechanism of apocrine lipid secretion and test the hypothesis that prolactin and oxytocin independently regulate discrete steps of this process; (2) define how apocrine lipid secretion affects apical membrane properties, secretory vesicle trafficking, lactogenesis and lactation success; and (3) to define critical molecular determinants of interactions between XOR, Btn and Plin2 that mediate apocrine lipid secretion. The proposed studies take advantage of novel XOR, Btn and Plin2 knockout mouse models developed in our laboratories, quantitative high resolution imaging, and innovative physiological and biochemical analyses and cell culture models of apocrine lipid secretion to accomplish these goals.