United States Department of Agriculture/Agriculture Research Service Children's Nutrition Research Center, Department of Paediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
J Appl Physiol (1985). 2010 Nov;109(5):1448-54. doi: 10.1152/japplphysiol.00428.2010. Epub 2010 Aug 19.
Mammalian target of rapamycin complex 1 (mTORC1) signaling is crucial for the regulation of protein synthesis. Most of known mTORC1 regulators have been isolated and characterized using cell culture systems, and the physiological roles of these regulators have not been fully tested in vivo. Previously we demonstrated that the insulin (INS) and amino acid (AA)-induced activation of mTORC1 is developmentally regulated in skeletal muscle (Suryawan A et al. Am J Physiol Endocrinol Metab 293: E1597-E1605, 2007). The present study aimed to characterize in more detail the effects of the postprandial rise in INS and AA on the activation and abundance of mTORC1 regulators in muscle and how this is modified by development. Overnight fasted 6- and 26-day-old pigs were studied during 1) euinsulinemic-euglycemic-euaminoacidemic conditions (control), 2) euinsulinemic-euglycemic-hyperaminoacidemic clamps (AA), and 3) hyperinsulinemic-euglycemic-euaminoacidemic clamps (INS). INS, but not AA, enhanced the PRAS40 phosphorylation, and this effect was greater in 6- than in 26-day old pigs. Phospholipase D1 (PLD1) abundance and phosphorylation, and the association of PLD1 with Ras homolog enriched in brain (Rheb), were greater in the younger pigs. Neither INS, AA, nor age altered the abundance of Rheb, vacuolar protein sorting 34 (Vps34), or FK506-binding protein 38 (FKBP38). Although INS and AA had no effect, the abundance of ras-related GTP binding B (RagB) and the association of RagB with Raptor were greater in 6- than in 26-day-old pigs. Neither INS, AA, nor age altered AMPK-induced phosphorylation of Raptor. Our results suggest that the enhanced activation of mTORC1 in muscle of neonatal pigs is in part due to regulation by PRAS40, PLD1, and the Rag GTPases.
哺乳动物雷帕霉素靶蛋白复合物 1（mTORC1）信号对于蛋白质合成的调节至关重要。大多数已知的 mTORC1 调节剂已经通过细胞培养系统被分离和鉴定，并且这些调节剂在体内的生理作用尚未被充分测试。先前我们证明，胰岛素（INS）和氨基酸（AA）诱导的 mTORC1 激活在骨骼肌中是发育调控的（Suryawan A 等人。Am J Physiol Endocrinol Metab 293：E1597-E1605，2007）。本研究旨在更详细地描述餐后 INS 和 AA 升高对肌肉中 mTORC1 调节剂的激活和丰度的影响，以及这种影响如何被发育所修饰。过夜禁食的 6 天和 26 天龄猪在以下三种情况下进行研究：1）胰岛素正常-血糖正常-氨基酸正常条件（对照），2）胰岛素正常-血糖正常-氨基酸高的钳夹（AA），和 3）高胰岛素-血糖正常-氨基酸正常的钳夹（INS）。INS，但不是 AA，增强了 PRAS40 的磷酸化，并且这种效应在 6 天龄猪中比在 26 天龄猪中更明显。磷酸脂酶 D1（PLD1）的丰度和磷酸化，以及 PLD1 与脑丰富的 Ras 同源物（Rheb）的结合，在幼猪中更大。INS、AA 或年龄均未改变 Rheb、液泡蛋白分选 34（Vps34）或 FK506 结合蛋白 38（FKBP38）的丰度。尽管 INS 和 AA 没有影响，但 RagB 的丰度和 RagB 与 Raptor 的结合在 6 天龄猪中比在 26 天龄猪中更大。INS、AA 或年龄均未改变 AMPK 诱导的 Raptor 磷酸化。我们的结果表明，新生仔猪肌肉中 mTORC1 的激活增强部分归因于 PRAS40、PLD1 和 Rag GTPases 的调节。
