首页>
外文期刊>The biochemical journal
>GLUT4 translocation precedes the stimulation of glucose uptake by insulin in muscle cells: potential activation of GLUT4 via p38 mitogen-activated protein kinase
【24h】
GLUT4 translocation precedes the stimulation of glucose uptake by insulin in muscle cells: potential activation of GLUT4 via p38 mitogen-activated protein kinase
pWe previously reported that SB203580, an inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), attenuates insulin-stimulated glucose uptake without altering GLUT4 translocation. These results suggested that insulin might activate GLUT4 via a p38 MAPK-dependent pathway. Here we explore this hypothesis by temporal and kinetic analyses of the stimulation of GLUT4 translocation, glucose uptake and activation of p38 MAPK isoforms by insulin. In L6 myotubes stably expressing GLUT4 with an exofacial Myc epitope, we found that GLUT4 translocation (it/isub1/2/sub = 2.5min) preceded the stimulation of 2-deoxyglucose uptake (it/isub1/2/sub = 6min). This segregation of glucose uptake from GLUT4 translocation became more apparent when the two parameters were measured at 22°C. Preincubation with the p38 MAPK inhibitors SB202190 and SB203580 reduced insulin-stimulated transport of either 2-deoxyglucose or 3-iO/i-methylglucose by 40–60%. Pretreatment with SB203580 lowered the apparent transport iV/isubmax/sub of insulin-mediated 2-deoxyglucose and 3-iO/i-methylglucose without any significant change in the apparent iK/isubm/sub for either hexose. The ICsub50/sub values for the partial inhibition of 2-deoxyglucose uptake by SB202190 and SB203580 were 1 and 2iμ/iM respectively, and correlated with the ICsub50/sub for full inhibition of p38 MAPK by the two inhibitors in myotubes (2 and 1.4iμ/iM, respectively). Insulin caused a dose- (ECsub50/sub = 15nM) and time- (it/isub1/2/sub = 3min) dependent increase in p38 MAPK phosphorylation, which peaked at 10min (2.3±0.3-fold). iIn vitro/i kinase assay of immunoprecipitates from insulin-stimulated myotubes showed activation of p38α (2.6±0.3-fold) and p38β (2.3±0.2-fold) MAPK. These results suggest that activation of GLUT4 follows GLUT4 translocation and that both mechanisms contribute to the full stimulation of glucose uptake by insulin. Furthermore, activation of GLUT4 may occur via an SB203580-sensitive pathway, possibly involving p38 MAPK./p
展开▼
机译：>我们先前曾报道SB203580是p38丝裂原活化蛋白激酶（p38 MAPK）的抑制剂，可减弱胰岛素刺激的葡萄糖摄取，而不会改变GLUT4的转运。这些结果表明，胰岛素可能通过p38 MAPK依赖性途径激活GLUT4。在这里，我们通过对胰岛素刺激GLUT4易位，葡萄糖摄取和激活p38 MAPK亚型的时间和动力学分析来探索这一假设。在稳定表达具有颜面部Myc表位的GLUT4的L6肌管中，我们发现GLUT4易位（ t 1/2 = 2.5min）在刺激2-脱氧葡萄糖摄取（< i> t 1/2 = 6分钟）。当在22°C下测量这两个参数时，葡萄糖从GLUT4易位的分离变得更加明显。与p38 MAPK抑制剂SB202190和SB203580的预温育可将胰岛素刺激的2-脱氧葡萄糖或3-O-甲基葡萄糖的转运减少40-60％。 SB203580预处理降低了胰岛素介导的2-脱氧葡萄糖和3- O 甲基葡萄糖的表观转运 V max ，而表观没有任何明显变化 K m 表示己糖。 SB202190和SB203580部分抑制2-脱氧葡萄糖摄取的IC 50 值分别为1和2 μ，并与IC 50 可以通过肌管中的两种抑制剂（分别为2和1.4μM）完全抑制p38 MAPK。胰岛素引起p38 MAPK磷酸化的剂量依赖性（EC 50 = 15nM）和时间依赖性（ t 1/2 = 3min），在10分钟时达到峰值（2.3±0.3倍）。胰岛素刺激的肌管的免疫沉淀物的体外激酶测定表明，p38α（2.6±0.3倍）和p38β（2.3±0.2倍）MAPK被激活。这些结果表明，GLUT4的激活遵循GLUT4易位，并且这两种机制都有助于完全刺激胰岛素吸收葡萄糖。此外，GLUT4的激活可能通过SB203580敏感途径发生，可能涉及p38 MAPK。
展开▼
