氨基酸和胰岛素诱导新生仔猪骨骼肌中 mTORC1 的激活涉及 Sestin2-GATOR2、Rag A/C-mTOR 和 RHEB-mTOR 复合物的形成。
Amino Acid- and Insulin-Induced Activation of mTORC1 in Neonatal Piglet Skeletal Muscle Involves Sestin2-GATOR2, Rag A/C-mTOR, and RHEB-mTOR Complex Formation.
机构信息
US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX.
出版信息
J Nutr. 2018 Jun 1;148(6):825-833. doi: 10.1093/jn/nxy044.
BACKGROUND
Feeding stimulates protein synthesis in skeletal muscle of neonates and this response is regulated through activation of mechanistic target of rapamycin complex 1 (mTORC1). The identity of signaling components that regulate mTORC1 activation in neonatal muscle has not been fully elucidated.
OBJECTIVE
We investigated the independent effects of the rise in amino acids (AAs) and insulin after a meal on the abundance and activation of potential regulators of mTORC1 in muscle and whether the responses are modified by development.
METHODS
Overnight-fasted 6- and 26-d-old pigs were infused for 2 h with saline (control group) or with a balanced AA mixture (AA group) or insulin (INS group) to achieve fed levels while insulin or AAs, respectively, and glucose were maintained at fasting levels. Muscles were analyzed for potential mTORC1 regulatory mechanisms and results were analyzed by 2-factor ANOVA followed by Tukey's post hoc test.
RESULTS
The abundances of DEP domain-containing mTOR-interacting protein (DEPTOR), growth factor receptor bound protein 10 (GRB10), and regulated in development and DNA damage response 2 (REDD2) were lower (65%, 73%, and 53%, respectively; P < 0.05) and late endosomal/lysosomal adaptor, MAPK and mTOR activator 1/2 (LAMTOR1/2), vacuolar H+-ATPase (V-ATPase), and Sestrin2 were higher (94%, 141%, 145%, and 127%, respectively; P < 0.05) in 6- than in 26-d-old pigs. Both AA and INS groups increased phosphorylation of GRB10 (P < 0.05) compared with control in 26- but not in 6-d-old pigs. Formation of Ras-related GTP-binding protein A (RagA)-mTOR, RagC-mTOR, and Ras homolog enriched in brain (RHEB)-mTOR complexes was increased (P < 0.05) and Sestrin2-GTPase activating protein activity towards Rags 2 (GATOR2) complex was decreased (P < 0.05) by both AA and INS groups and these responses were greater (P < 0.05) in 6- than in 26-d-old pigs.
CONCLUSION
The results suggest that formation of RagA-mTOR, RagC-mTOR, RHEB-mTOR, and Sestrin2-GATOR2 complexes may be involved in the AA- and INS-induced activation of mTORC1 in skeletal muscle of neonates after a meal and that enhanced activation of the mTORC1 signaling pathway in neonatal muscle is in part due to regulation by DEPTOR, GRB10, REDD2, LAMTOR1/2, V-ATPase, and Sestrin2.
背景
喂养可刺激新生儿骨骼肌中的蛋白质合成，这种反应通过机械靶标雷帕霉素复合物 1（mTORC1）的激活来调节。调节新生儿肌肉中 mTORC1 激活的信号成分的身份尚未完全阐明。
目的
我们研究了餐后氨基酸（AA）和胰岛素升高对肌肉中 mTORC1 潜在调节剂丰度和激活的独立影响，以及这些反应是否受发育的影响。
方法
overnight-fasted 6- 和 26-天龄的猪分别输注生理盐水（对照组）、AA 混合物（AA 组）或胰岛素（INS 组）2 小时，以达到进食水平，同时分别维持胰岛素或 AA 和葡萄糖在空腹水平。分析肌肉中潜在的 mTORC1 调节机制，并通过双因素方差分析（ANOVA） followed by Tukey 的事后检验进行结果分析。
结果
DEP 结构域包含的 mTOR 相互作用蛋白（DEPTOR）、生长因子受体结合蛋白 10（GRB10）和发育和 DNA 损伤反应调节因子 2（REDD2）的丰度分别降低（分别为 65%、73%和 53%；P < 0.05），晚期内体/溶酶体衔接蛋白、MAPK 和 mTOR 激活物 1/2（LAMTOR1/2）、液泡 H+-ATP 酶（V-ATPase）和 Sestrin2 的丰度分别升高（分别为 94%、141%、145%和 127%；P < 0.05），6 天龄猪的丰度低于 26 天龄猪。与对照组相比，AA 组和 INS 组均增加了 26 天龄猪的 GRB10 磷酸化（P < 0.05）。Ras 相关 GTP 结合蛋白 A（RagA）-mTOR、RagC-mTOR 和 Ras 同源物富集在脑中（RHEB）-mTOR 复合物的形成增加（P < 0.05），而 Rag 2（GATOR2）复合物的 Sestrin2-GTPase 激活蛋白活性降低（P < 0.05），这两组的反应在 6 天龄猪中大于 26 天龄猪（P < 0.05）。
结论
结果表明，RagA-mTOR、RagC-mTOR、RHEB-mTOR 和 Sestrin2-GATOR2 复合物的形成可能参与了餐后 AA 和 INS 诱导的新生儿骨骼肌中 mTORC1 的激活，而新生儿肌肉中 mTORC1 信号通路的增强激活部分归因于 DEPTOR、GRB10、REDD2、LAMTOR1/2、V-ATPase 和 Sestrin2 的调节。
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