Amino acid transporter ATA2 is stored at the trans-Golgi network and released by insulin stimulus in adipocytes
Amino acid transporter ATA2 is stored at the trans-Golgi network and released by insulin stimulus in adipocytes
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DOI：
10.1074/jbc.m604534200
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发表时间：
2006-12-22
影响因子：
4.8
通讯作者：
Setou, Mitsutoshi
中科院分区：
文献类型：
--
作者：
Hatanaka, Takahiro;Hatanaka, Yasue;Setou, Mitsutoshi
最近，我们克隆了负责氨基酸转运系统A的ATA/SNAT转运体。A系统是以丙氨酸为代表的小分子中性和生糖氨基酸的主要转运系统之一，参与葡萄糖和脂肪的代谢。在这里，我们描述了在3T3-L1脂肪细胞中通过胰岛素刺激参与ATA2急性移位的细胞机制。我们使用增强型绿色荧光蛋白标记的ATA2表达系统来监测这种胰岛素刺激的ATA2易位。在活细胞中的研究表明，ATA2储存在一个离散的核周部位，转运蛋白以小泡的形式从这个部位释放到质膜。在免疫荧光分析中，ATA2的存储位置与反式高尔基体网络(TGN)的标志物Synaxin 6的位置重叠，而与早期内体的标志物EEA1的位置不重叠。质膜上或靠近质膜的含ATA2的囊泡与含GLUT4的囊泡不同。囊泡退出TGN的抑制剂Brefeldin A引起ATA2存储部位的形态变化，TGN也发生了类似的变化。在未转基因的脂肪细胞中，灯盏花素A比胰岛素刺激的2-脱氧-D-葡萄糖的摄取更能抑制胰岛素刺激的α-甲氨基异丁酸的摄取。这些数据表明，ATA2的储存位置与TGN特异性相关，而不是与一般的内体循环系统相关。因此，胰岛素刺激的ATA2和GLUT4在脂肪细胞中的易位途径是不同的，涉及不同的存储位置。
Recently, we cloned the ATA/SNAT transporters responsible for amino acid transport system A. System A is one of the major transport systems for small neutral and glucogenic amino acids represented by alanine and is involved in the metabolism of glucose and fat. Here, we describe the cellular mechanisms that participate in the acute translocation of ATA2 by insulin stimulus in 3T3-L1 adipocytes. We monitored this insulin-stimulated translocation of ATA2 using an expression system of enhanced green fluorescent protein-tagged ATA2. Studies in living cells revealed that ATA2 is stored in a discrete perinuclear site and that the transporter is released in vesicles from this site toward the plasma membrane. In immunofluorescent analysis, the storage site of ATA2 overlapped with the location of syntaxin 6, a marker of the trans-Golgi network (TGN), but not with that of EEA1, a marker of the early endosomes. The ATA2-containing vesicles on or near the plasma membrane were distinct from GLUT4-containing vesicles. Brefeldin A, an inhibitor of vesicular exit from the TGN, caused morphological changes in the ATA2 storage site along with the similar changes in the TGN. In non-transfected adipocytes, brefeldin A inhibited insulin-stimulated uptake of alpha-(methylamino) isobutyric acid more profoundly than insulin-stimulated uptake of 2-deoxy-D-glucose. These data demonstrate that the ATA2 storage site is specifically associated with the TGN and not with the general endosomal recycling system. Thus, the insulin-stimulated translocation pathways for ATA2 and GLUT4 in adipocytes are distinct, involving different storage sites.