Translational regulation of milk protein synthesis

牛奶中的蛋白质为婴儿的生长提供了理想的氨基酸组成。此外，从牛奶蛋白发酵或消化中提取的生物活性多肽在治疗和预防包括肥胖、动脉粥样硬化、动脉高血压和2型糖尿病在内的人类代谢综合征症状方面具有功能价值。牛乳蛋白质组由80%的酪蛋白和20%的乳清蛋白组成。这四种酪蛋白分别命名为1-、AS2-、B-和K-酪蛋白，它们是两亲性的，聚集成被称为酪蛋白胶束的表面活性粒子，由于它们作为新型胃肠道营养和药物输送纳米粒的有趣性质，近年来引起了人们的注意。酪蛋白翻译过程中胶束的形成过程和乳腺上皮细胞内囊泡的运输过程，以及单个酪蛋白在囊泡内聚集过程中的作用还没有完全阐明。我们的目标是利用体外、体内和电子技术相结合的方法研究酪蛋白合成的翻译调节。我们将使用无细胞翻译来产生假设，以解释人和牛酪蛋白翻译效率的差异。我们还将扩大无细胞体系中的蛋白质产量，以便研究酪蛋白胶束的形成和稳定性。我们将应用沉默RNA协议来探索哺乳动物雷帕霉素靶标(MTOR)和整合应激反应(ISR)网络在培养的乳腺上皮细胞酪蛋白分泌的营养和激素调控中的作用。我们的发现将导致体内测试，使用分裂乳房方案，通过乳头通道将mTOR和ISR抑制剂注入两个单侧季度，并评估乳房mTOR和ISR信号蛋白在磷酸化状态下的对侧反应。这些数据将用于将牛奶蛋白质合成的翻译控制模型参数化，该模型可用于设计新的实验方案。对牛奶蛋白mRNAs翻译的关注对于奶牛营养领域来说是新的，可能会在牛奶中的酪蛋白分布、酪蛋白胶束的营养包裹特性以及改善人类营养的能力方面产生重大的新发现。

The protein of milk supplies an ideal amino acid profile for infant growth. In addition, bioactive peptides derived from fermentation or digestion of milk proteins possess functional value in treatment and prevention of symptoms of the human metabolic syndrome including obesity, atherogenesis, arterial hypertension, and type 2 diabetes. The bovine milk proteome is 80% casein and 20% whey proteins. The four caseins, designated as1-, as2-, ß- and K-casein are amphipathic and aggregate into surfactant particles called casein micelles that have drawn attention in recent years due to their interesting properties as novel gastrointestinal nutrient and drug delivery nanoparticles. The process of micelle formation during casein translation and vesicular transport in the mammary epithelial cell, and the roles of each individual casein in the intravesicular aggregation process have not yet been fully elucidated. Our objectives are to study the translational regulation of casein synthesis using a combination of in vitro, in vivo and in silico techniques. We will use cell-free translation to generate hypotheses to explain differences in translational efficiency of human and bovine caseins. We will also scale up protein yields from the cell-free system to enable study of casein micelle formation and stability. We will apply silencing RNA protocols to probe the role of mammalian target of rapamycin (mTOR) and integrated stress response (ISR) networks in nutritional and hormonal manipulations of casein secretion from mammary epiothelial cells in culture. Our findings will lead to tests in vivo, using a split-udder protocol where mTOR and ISR inhibitors are infused into two unilateral quarters through the teat canals, and contralateral responses in phosphorylation state of mammary mTOR and ISR signalling proteins are evaluated. The data will be used to parametize a model of translational control of milk protein synthesis that can be used to design new experimental protocols. The focus on translation of milk protein mRNAs is novel for the dairy cow nutrition field and may generate significant new findings in terms of the casein profile in milk, the nutrient-encapsulating properties of casein micelles, and the ability to improve human nutrition.