Myo1c binding to submembrane actin mediates insulin-induced tethering of GLUT4 vesicles.
Myo1c binding to submembrane actin mediates insulin-induced tethering of GLUT4 vesicles.
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DOI：
10.1091/mbc.e12-04-0263
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发表时间：
2012-10
影响因子：
3.3
通讯作者：
Klip A
中科院分区：
文献类型：
--
作者：
Boguslavsky S;Chiu T;Foley KP;Osorio-Fuentealba C;Antonescu CN;Bayer KU;Bilan PJ;Klip A
通过全内反射荧光显微镜观察，胰岛素降低了肌细胞膜下myo1c阳性GLUT4囊泡的移动速度。囊泡结合的Myo1c与肌动蛋白丝的结合是Myo1c参与GLUT4囊泡系结的基础，从而使GLUT4囊泡随后与质膜进行有效对接和融合。含glut4的囊泡在质膜和细胞内隔室之间循环。胰岛素通过调节GLUT4囊泡到达细胞外周并随后与质膜系结、对接和融合来促进GLUT4胞吐。参与GLUT4囊泡系锁的分子机制尚不清楚。我们在这里展示了Myo1c，一种肌动蛋白为基础的运动蛋白，与膜和肌动蛋白丝相关，是胰岛素诱导的肌细胞囊泡系固所必需的。研究发现，Myo1c与移动和系住的GLUT4囊泡有关，并且是质膜下全内反射荧光（TIRF）区囊泡捕获所必需的。Myo1c敲低或过表达肌动蛋白结合缺陷Myo1c突变体可消除胰岛素诱导的囊泡固定化，增加TIRF区GLUT4囊泡速度，并阻止其外化。相反，Myo1c过表达将GLUT4囊泡固定在TIRF区，并促进胰岛素诱导的GLUT4暴露于细胞外环境。Myo1c也有助于胰岛素依赖性肌动蛋白丝重塑。因此，我们提出，在胰岛素介导的GLUT4囊泡拴系和GLUT4在肌肉细胞中的有效表面递送中，泡状Myo1c与皮质肌动蛋白丝的相互作用是必需的。
Insulin reduces the velocity of mobile Myo1c-positive GLUT4 vesicles beneath the muscle cell plasma membrane as visualized by total internal reflection fluorescence microscopy. Binding of vesicle-bound Myo1c to actin filaments underlies Myo1c's participation in GLUT4 vesicle tethering for subsequent productive docking and fusion of GLUT4 vesicles with the plasma membrane. GLUT4-containing vesicles cycle between the plasma membrane and intracellular compartments. Insulin promotes GLUT4 exocytosis by regulating GLUT4 vesicle arrival at the cell periphery and its subsequent tethering, docking, and fusion with the plasma membrane. The molecular machinery involved in GLUT4 vesicle tethering is unknown. We show here that Myo1c, an actin-based motor protein that associates with membranes and actin filaments, is required for insulin-induced vesicle tethering in muscle cells. Myo1c was found to associate with both mobile and tethered GLUT4 vesicles and to be required for vesicle capture in the total internal reflection fluorescence (TIRF) zone beneath the plasma membrane. Myo1c knockdown or overexpression of an actin binding–deficient Myo1c mutant abolished insulin-induced vesicle immobilization, increased GLUT4 vesicle velocity in the TIRF zone, and prevented their externalization. Conversely, Myo1c overexpression immobilized GLUT4 vesicles in the TIRF zone and promoted insulin-induced GLUT4 exposure to the extracellular milieu. Myo1c also contributed to insulin-dependent actin filament remodeling. Thus we propose that interaction of vesicular Myo1c with cortical actin filaments is required for insulin-mediated tethering of GLUT4 vesicles and for efficient GLUT4 surface delivery in muscle cells.