Rab8A and Rab13 are activated by insulin and regulate GLUT4 translocation in muscle cells
Rab8A and Rab13 are activated by insulin and regulate GLUT4 translocation in muscle cells
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DOI：
10.1073/pnas.1009523107
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发表时间：
2010-11-16
影响因子：
11.1
通讯作者：
Klip, Amira
中科院分区：
文献类型：
--
作者：
Sun, Yi;Bilan, Philip J.;Klip, Amira
骨骼肌是膳食葡萄糖处置的主要部位，该功能依赖于胰岛素介导的GLUT 4囊泡胞吐至其细胞表面。在骨骼肌和脂肪细胞中，这种反应涉及Akt信号传导至Rab-GAP（GTP酶激活蛋白）AS 160/TBC 1D 4。有趣的是，AS 160靶向的Rabs似乎不同，Rab 8A参与肌肉细胞中的GLUT 4胞吐，Rab 10参与脂肪细胞中的GLUT 4胞吐，胰岛素对它们的激活作用尚不清楚。Rabs 8A、10和13属于Rab-GTP酶的相同亚家族。在这里，我们表明，胰岛素促进GTP加载Rab 13和Rab 8A，但不Rab 10在大鼠L 6肌细胞，Rab 8A激活Rab 13之前。siRNA介导的Rab 13敲低阻断了胰岛素诱导的肌肉细胞表面GLUT 4的增加，该增加被Rab 13直系同源物而不是Rab 8A所拯救。组成型活性AS 160降低了表面GLUT 4的基础和胰岛素刺激水平，过表达Rab 8A或Rab 13可逆转这种效应，这表明两种Rabs都是GLUT 4运输背景下AS 160-GAP活性的靶点。Rab 13有一个更广泛的细胞内分布的Rab 8A的核周限制相比，和胰岛素促进Rab 13与GLUT 4在细胞周边的共定位。我们的结论是Rab 13和Rab 8A是由胰岛素激活的Rab-GTP酶，并且在AS 160的下游，它们调节GLUT 4囊泡的交通，可能作用于不同的步骤和位点。这些发现接近于调节肌肉GLUT 4交通响应胰岛素的一系列事件，这对全身葡萄糖稳态至关重要。
Skeletal muscle is the primary site of dietary glucose disposal, a function that depends on insulin-mediated exocytosis of GLUT4 vesicles to its cell surface. In skeletal muscle and adipocytes, this response involves Akt signaling to the Rab-GAP (GTPase-activating protein) AS160/TBC1D4. Intriguingly, the AS160-targeted Rabs appear to differ, with Rab8A participating in GLUT4 exocytosis in muscle cells and Rab10 in adipocytes, and their activation by insulin is unknown. Rabs 8A, 10, and 13 belong to the same subfamily of Rab-GTPases. Here we show that insulin promotes GTP loading of Rab13 and Rab8A but not Rab10 in rat L6 muscle cells, Rab8A activation preceding that of Rab13. siRNA-mediated Rab13 knockdown blocked the insulin-induced increase of GLUT4 at the muscle cell surface that was rescued by a Rab13 ortholog but not by Rab8A. Constitutively active AS160 lowered basal and insulin-stimulated levels of surface GLUT4, effects that were reversed by overexpressing Rab8A or Rab13, suggesting that both Rabs are targets of AS160-GAP activity in the context of GLUT4 traffic. Rab13 had a broader intracellular distribution compared with the perinuclear restriction of Rab8A, and insulin promoted Rab13 colocalization with GLUT4 at the cell periphery. We conclude that Rab13 and Rab8A are Rab-GTPases activated by insulin, and that downstream of AS160 they regulate traffic of GLUT4 vesicles, possibly acting at distinct steps and sites. These findings close in on the series of events regulating muscle GLUT4 traffic in response to insulin, crucial for whole-body glucose homeostasis.