Ubiquitin-like modifier 1 ligating enzyme 1 (UFL1) has been characterized as a ubiquitin-like (Ubl) protein that affects a range of cellular processes across various pathways. In this study, mouse mammary epithelial cells (HC11 cell line) and UFL1 knockout (KO) mice were used to establish UFL1 knockdown models to explore the influence of UFL1 on milk protein and fat synthesis in the mouse mammary gland and the underlying mechanisms. This is the first study to show UFL1 localization in mouse mammary epithelial cells. UFL1 depletion by transfected UFL1 siRNA (siUFL1) caused aggravated apoptosis. In addition, UFL1 depletion suppressed milk protein synthesis-related protein level in vivo and in vitro. Conversely, ACACA and FASN expressions increased in UFL1-deficient mice. Moreover, UFL1 depletion increased triglyceride synthesis levels and inhibited the p-JNK expression. Importantly, the expression of proteins related to milk protein synthesis was decreased in JNK- and UFL1-deficient cells, whereas proteins related to milk fat synthesis showed the opposite trend, indicating that UFL1 affects milk protein and fat synthesis via the suppression of JNK activation. Overall, our findings indicate that UFL1 plays a key role in mammary milk and fat synthesis via JNK activation.

中文翻译：

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UFM1特异性连接酶1连接酶1通过JNK信号通路介导小鼠乳腺上皮细胞中的乳蛋白和脂肪合成相关基因表达。

泛素样修饰物1连接酶1（UFL1）已被表征为泛素样（Ubl）蛋白，可影响跨各种途径的一系列细胞过程。在这项研究中，小鼠乳腺上皮细胞（HC11细胞系）和UFL1敲除（KO）小鼠用于建立UFL1敲除模型，以研究UFL1对小鼠乳腺中乳蛋白和脂肪合成的影响及其潜在机制。这是第一个显示UFL1在小鼠乳腺上皮细胞中定位的研究。转染的UFL1 siRNA（siUFL1）消耗UFL1会导致凋亡加剧。此外，UFL1耗竭抑制体内和体外的乳蛋白合成相关蛋白水平。相反，ACACA和FASN表达在UFL1缺陷型小鼠中增加。此外，UFL1消耗增加了甘油三酸酯的合成水平，并抑制了p-JNK表达。重要的是，在缺乏JNK和UFL1的细胞中，与牛奶蛋白质合成有关的蛋白质表达降低，而与牛奶脂肪合成有关的蛋白质却呈现相反的趋势，表明UFL1通过抑制JNK激活影响牛奶蛋白质和脂肪合成。总体而言，我们的发现表明UFL1在通过JNK激活的乳汁和脂肪合成中起关键作用。