Amino acids regulate skeletal muscle PHAS-I and p70 S6-kinase phosphorylation independently of insulin.
Amino acids regulate skeletal muscle PHAS-I and p70 S6-kinase phosphorylation independently of insulin.
复制标题
氨基酸独立于胰岛素调节骨骼肌 PHAS-I 和 p70 S6 激酶磷酸化。
DOI：
10.1152/ajpendo.2000.279.2.e301
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Barrett,EJ
中科院分区：
文献类型：
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作者：
Long,W;Saffer,L;Wei,L;Barrett,EJ
重新进食可以逆转禁食时肌肉蛋白质的损失。负责这种逆转的生理调节和细胞控制部位还没有完全确定。磷酸化热酸稳定蛋白(PHAS-I)的磷酸化可以释放真核细胞起始因子4E(EIF4E)，并通过加速翻译起始来刺激蛋白质合成。P70S6-激酶(P70S6K)的磷酸化被认为参与了一些核糖体蛋白和其他在转录起始点附近有多嘧啶簇的蛋白质的合成的调节。我们检测了饲料是否增加了PHAs-I和p70S6k的磷酸化，并在体内测定了胰岛素和氨基酸对大鼠骨骼肌PHAs-I和p70S6k磷酸化的单独影响。肌肉取自自由喂养和隔夜禁食的大鼠(n=5)。其余禁食大鼠分别给予胰岛素(3min U·μ−1·kg−1，正常血糖钳夹)、氨基酸或两者合用。冷冻夹住腓肠肌，通过定量Western blotts上可见的几种磷酸化形式来测量PHAs-I和p70S6k的磷酸化。我们观察到，摄食增加了PHAs-I和p70S6K的磷酸化(P<；0.05)。单独输入氨基酸就能重现喂食的效果。生理性高胰岛素血症使p70S6K蛋白表达增加(P<；0.05)，但不影响PHAs-I的磷酸化(P=0.98)。在氨基酸输注中加入胰岛素并不比单独加入氨基酸更能促进PHAs-I和p70S6k的磷酸化。我们的结论是，单独的氨基酸输注增强了大鼠骨骼肌中蛋白质合成途径的激活。这种作用不依赖于血浆胰岛素的增加，并模拟了正常喂养过程中蛋白质合成的激活。
Refeeding reverses the muscle protein loss seen with fasting. The physiological regulators and cellular control sites responsible for this reversal are incompletely defined. Phosphorylation of phosphorylated heat-acid stabled protein (PHAS-I) frees eukaryotic initiation factor 4E (eIF4E) and stimulates protein synthesis by accelerating translation initiation. Phosphorylation of p70 S6-kinase (p70S6k) is thought to be involved in the regulation of the synthesis of some ribosomsal proteins and other selected proteins with polypyrimidine clusters near the transcription start site. We examined whether phosphorylation of PHAS-I and p70S6kwas increased by feeding and determined the separate effects of insulin and amino acids on PHAS-I and p70S6kphosphorylation in rat skeletal muscle in vivo. Muscle was obtained from rats fed ad libitum or fasted overnight (n= 5 each). Other fasted rats were infused with insulin (3 μU · min−1· kg−1, euglycemic clamp), amino acids, or the two combined. Gastrocnemius was freeze-clamped, and PHAS-I and p70S6kphosphorylation was measured by quantifying the several phosphorylated forms of these proteins seen on Western blots. We observed that feeding increased phosphorylation of both PHAS-I and p70S6k(P< 0.05). Infusion of amino acids alone reproduced the effect of feeding. Physiological hyperinsulinemia increased p70S6K(P< 0.05) but not PHAS-I phosphorylation (P= 0.98). Addition of insulin to amino acid infusion was no more effective than amino acids alone in promoting PHAS-I and p70S6kphosphorylation. We conclude that amino acid infusion alone enhances the activation of the protein synthetic pathways in vivo in rat skeletal muscle. This effect is not dependent on increases in plasma insulin and simulates the activation of protein synthesis that accompanies normal feeding.