Wilson Chris, Hargreaves Mark, Howlett Kirsten F
Center for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Melbourne, Victoria, Australia.
Am J Physiol Endocrinol Metab. 2006 Feb;290(2):E341-6. doi: 10.1152/ajpendo.00314.2005. Epub 2005 Sep 27.
The subcellular localization of insulin signaling proteins is altered by various stimuli such as insulin, insulin-like growth factor I, and oxidative stress and is thought to be an important mechanism that can influence intracellular signal transduction and cellular function. This study examined the possibility that exercise may also alter the subcellular localization of insulin signaling proteins in human skeletal muscle. Nine untrained males performed 60 min of cycling exercise (approximately 67% peak pulmonary O2 uptake). Muscle biopsies were sampled at rest, immediately after exercise, and 3 h postexercise. Muscle was fractionated by centrifugation into the following crude fractions: cytosolic, nuclear, and a high-speed pellet containing membrane and cytoskeletal components. Fractions were analyzed for protein content of insulin receptor, insulin receptor substrate (IRS)-1 and -2, p85 subunit of phosphatidylinositol 3-kinase, Akt, and glycogen synthase kinase-3 (GSK-3). There was no significant change in the protein content of the insulin signaling proteins in any of the crude fractions after exercise or 3 h postexercise. Exercise had no significant effect on the phosphorylation of IRS-1 Tyr612 in any of the fractions. In contrast, exercise increased (P < 0.05) the phosphorylation of Akt Ser473 and GSK-3alpha/beta Ser9/21 in the cytosolic fraction only. In conclusion, exercise can increase phosphorylation of downstream insulin signaling proteins specifically in the cytosolic fraction but does not result in changes in the subcellular localization of insulin signaling proteins in human skeletal muscle. Change in the subcellular protein localization is therefore an unlikely mechanism to influence signal transduction pathways and cellular function in skeletal muscle after exercise.
胰岛素信号蛋白的亚细胞定位会受到多种刺激的影响而发生改变，这些刺激包括胰岛素、胰岛素样生长因子I以及氧化应激，并且被认为是一种能够影响细胞内信号转导和细胞功能的重要机制。本研究探讨了运动是否也可能改变人类骨骼肌中胰岛素信号蛋白的亚细胞定位。九名未经训练的男性进行了60分钟的骑行运动（约为峰值肺氧摄取量的67%）。在运动前、运动结束后即刻以及运动后3小时采集肌肉活检样本。通过离心将肌肉分离成以下粗提组分：胞质、细胞核以及包含膜和细胞骨架成分的高速沉淀组分。对各组分进行分析，检测胰岛素受体、胰岛素受体底物（IRS）-1和-2、磷脂酰肌醇3激酶的p85亚基、Akt以及糖原合酶激酶-3（GSK-3）的蛋白质含量。运动后或运动后3小时，任何粗提组分中胰岛素信号蛋白的蛋白质含量均无显著变化。运动对任何组分中IRS-1 Tyr612的磷酸化均无显著影响。相比之下，运动仅使胞质组分中Akt Ser473和GSK-3α/β Ser9/21的磷酸化增加（P < 0.05）。总之，运动可特异性增加胞质组分中胰岛素下游信号蛋白的磷酸化，但不会导致人类骨骼肌中胰岛素信号蛋白的亚细胞定位发生变化。因此，亚细胞蛋白定位的改变不太可能是运动后影响骨骼肌信号转导途径和细胞功能的机制。
