Williamson D, Gallagher P, Harber M, Hollon C, Trappe S
Human Performance Laboratory, Ball State University, Muncie, IN 47306, USA.
J Physiol. 2003 Mar 15;547(Pt 3):977-87. doi: 10.1113/jphysiol.2002.036673. Epub 2003 Jan 31.
The purpose of this investigation was to examine the activation (phosphorylation) and total protein content of MAPK signalling cascade proteins (ERK 1/2, p90RSK, Mnk 1, eIF4E, p38 MAPK, JNK/SAPK, MKP 1) at rest and following exercise, in sedentary young and old men. Eight young (22 +/- 1 years; YM) and eight old (79 +/- 3 years; OM) men underwent a resting muscle biopsy of the vastus lateralis; they then performed a knee extensor resistance exercise session (29 contractions at approximately 70 % of max), followed by a post-exercise biopsy. Western immunoblot analysis demonstrated that the OM had higher resting phosphorylation of ERK 1/2, p90RSK, Mnk 1, p38 MAPK and JNK/SAPK proteins versus YM (P < 0.05). The resistance exercise bout caused an increase in phosphorylation of the ERK 1/2, p90RSK and Mnk 1 proteins (P < 0.05) in the YM. Conversely, the OM had a decrease in ERK 1/2, p90RSK, Mnk 1, p38 MAPK and JNK/SAPK phosphorylation (P < 0.05) after the exercise bout. Neither group showed a change in eIF4E phosphorylation. The total amount of protein expression of the MAPK signalling proteins was not different between the YM and OM, except that there was a higher (P < 0.05) MKP 1 protein content in the OM. This investigation is the first to provide evidence that MAPK proteins are differentially activated at rest and in response to a bout of resistance exercise in skeletal muscle of young and old men. These findings may have implications for other processes (e.g. transcription and translation) involved in skeletal muscle type and growth, when examining the changes occurring with ageing muscle before and after resistance exercise/training.
本研究的目的是检测久坐不动的年轻和老年男性在静息状态及运动后，丝裂原活化蛋白激酶（MAPK）信号级联蛋白（细胞外调节蛋白激酶1/2（ERK 1/2）、p90核糖体S6激酶（p90RSK）、丝裂原和应激激活蛋白激酶1（Mnk 1）、真核细胞起始因子4E（eIF4E）、p38丝裂原活化蛋白激酶（p38 MAPK）、应激活化蛋白激酶/应激激活蛋白激酶（JNK/SAPK）、丝裂原活化蛋白激酶磷酸酶1（MKP 1））的激活（磷酸化）情况及总蛋白含量。八名年轻男性（22±1岁；青年组）和八名老年男性（79±3岁；老年组）接受了股外侧肌静息肌肉活检；随后他们进行了一次伸膝抗阻训练（以约最大力量的70%进行29次收缩），训练后再次进行肌肉活检。蛋白质免疫印迹分析表明，与青年组相比，老年组静息时ERK 1/2、p90RSK、Mnk 1、p38 MAPK和JNK/SAPK蛋白的磷酸化水平更高（P<0.05）。抗阻训练使青年组ERK 1/2、p90RSK和Mnk 1蛋白的磷酸化水平升高（P<0.05）。相反，老年组在训练后ERK 1/2、p90RSK、Mnk 1、p38 MAPK和JNK/SAPK的磷酸化水平降低（P<0.05）。两组的eIF4E磷酸化水平均未发生变化。除老年组的MKP 1蛋白含量更高（P<0.05）外，MAPK信号蛋白的总表达量在青年组和老年组之间没有差异。本研究首次提供证据表明，在年轻和老年男性的骨骼肌中，MAPK蛋白在静息状态及对一次抗阻训练的反应中被差异性激活。在研究抗阻运动/训练前后衰老肌肉中发生的变化时，这些发现可能对骨骼肌类型和生长中涉及的其他过程（如转录和翻译）具有启示意义。
