Regulation and roles of the expression of milk fat globule-characteristic gangliosides in murine mammary gland.

本实验采用小鼠乳腺原代培养细胞和SV-40 A255永生化细胞，研究了妊娠期和哺乳期乳脂肪球特征性糖链表达的机制和作用。原代培养的细胞保持在含有皮质醇和表皮生长因子的基础培养基中，并发现通过在基础培养基中添加催乳素来启动乳汁分泌。GD 1 α神经节苷脂的合成同时被认为是与催乳素刺激下的乳汁分泌相关的事件，并被发现是由GM 1 α 2 -6唾液酸转移酶和神经酰胺乳糖苷β 1 - 4 N-乙酰半乳糖胺转移酶的激活触发的。此外，在分泌乳汁的细胞中，胆固醇磺基转移酶被高度激活，但发现仅用表皮生长因子刺激即可诱导胆固醇磺基转移酶，这表明胆固醇磺基转移酶的诱导与表皮生长因子的刺激无关。 ...更多信息 erase与乳腺上皮细胞的生长有关。对于永生化细胞，在表皮生长因子的刺激下观察到胆固醇磺基转移酶的诱导，但在与原代培养细胞相同的条件下没有观察到乳脂球的产生以及GD 1 α的合成。因此，在乳汁分泌过程中所调节的酶被发现在翻译水平上受到控制。并对硫酸胆固醇和GD 1 α神经节苷脂的可能作用进行了探讨。从观察到胆固醇硫酸盐分布在暴露于胰腺消化酶的十二指肠下的胃肠道上皮细胞中，预期其保护细胞免受消化酶的作用。如预期的那样，发现胆固醇硫酸盐对几种蛋白酶、DNA酶和糖苷酶具有抑制活性，并且发现胆固醇硫酸盐在乳腺上皮细胞中的主要功能之一是保护细胞免受在产乳过程中分泌的几种酶的组织损伤。另一方面，GD 1 α神经节苷脂作为脂肪球膜上主要的负电荷脂质，被阐明为肉毒梭菌A型和E型毒素以及破伤风梭菌毒素的受体分子，表明其具有保护新生儿免受细菌感染的功能。少

I performed the experiments using primary cultuted cells and SV-40A255-immortalized cells of murine mammary gland to clarify the mechanism and roles of the expression of milk fat globule-characteristic carbohydrate chains during the periods of pregnancy and lactation. The primary cultured cells were maintained in the basal medium containing cortisol and epidermal growth factor, and were found to be initiated the secretion of milk by addition of prolactin in the basal medium. Synthesis of GD1alpha ganglioside was simultaneously obserbed as an event associated with the secretion of milk under stimulation with prolactin, and was found to be trigered by activations of GM1balpha2-6 sialyltransferase and ceramide lactoside beta1-4N-acetylgalactosaminyltransferase. Also, cholesterol sulfotransferase was highly activated in the cells with secretion of milk, but it was found to be induced by stimulation with epidermal growth factor alone, indicating that the induction of cholesterol sulfotransf … More erase is associated with the growth of mammary epithelial cells. In the case of immortalized cells, the induction of cholesterol sulfotrasferase was observed under stimulation of epidermal growth factor, but production of milk fat grobule, as well as synthesis of GD1alpha, was not observed under the same condition as that for primary cultured cells. The enzuymes thus regulated during the process of milk secretion were found to be controled at the translational level. Then, I invertigated the possible roles of cholesterol sulfate and GD1alpha ganglioside. From the observation that cholesterol sulfate was distributed in the epithelial cells of gastrointestinal tract under the duodenum, where was exposed to the pancreatic digestive enzymes, it was expected to protect the cells from the action of digestive enzymes. As was expected, cholesterol sulfate was found to possess the inhibitory activity toward several proteases, DNase and glycosidases, and one of the major function of cholesterol sulfate in the epithelial cells of mammary gland was found to protect the cells from tissue injury with several enzymes screted during the production of milk. On the other hand, GD1alpha gangloside as the major negatively charged lipids in the fat globule membrane was clarified to be the receptor molecules for toxins from Cl.botulinum type A and type E,and Cl.tetani, indicating that it fuction to protect neonates from the bacterial infections. Less