Endoproteolytic Cleavage of TUG Protein Regulates GLUT4 Glucose Transporter Translocation
Endoproteolytic Cleavage of TUG Protein Regulates GLUT4 Glucose Transporter Translocation
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DOI：
10.1074/jbc.m112.339457
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发表时间：
2012-07-06
影响因子：
4.8
通讯作者：
Cresswell, James A.
中科院分区：
文献类型：
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作者：
Bogan, Jonathan S.;Rubin, Bradley R.;Cresswell, James A.
为了促进葡萄糖摄取到脂肪和肌肉细胞中，胰岛素导致GLUT 4葡萄糖转运蛋白从细胞内囊泡移位到细胞表面。先前的数据支持一种模型，其中TUG捕获含GLUT 4的囊泡并将其在未刺激的细胞中细胞内拴系，并且其中胰岛素通过释放该拴系来动员该囊泡池。在这里，我们表明，TUG进行位点特异性内切蛋白水解裂解，分离GLUT 4结合，N-末端区域的TUG从C-末端区域先前建议结合细胞内锚。3 T3-L1脂肪细胞中的胰岛素刺激加速了裂解，并且高度依赖于脂肪细胞分化。N-末端TUG切割产物具有一种新型18-kDa泛素样修饰剂的性质，我们称之为TUGUL。观察到C-末端产物的预期大小为42 kDa，也以54 kDa形式从膜释放到胞质溶胶中。在转染的细胞中，完整的TUG将GLUT 4连接到PIST，并且还通过其C-末端区域结合Golgin-160。PIST是TC 10 α的效应子，TC 10 α是一种先前显示传递GLUT 4易位所需的胰岛素信号的GT3，我们使用RNAi显示TC 10 α是TUG蛋白水解加工所需的。最后，我们证明了TUG的抗裂解形式不支持3 T3-L1脂肪细胞中的高胰岛素响应性GLUT 4易位或葡萄糖摄取。与先前的结果一起，这些数据支持胰岛素刺激TUG裂解以从高尔基体基质释放GLUT 4储存囊泡的模型，其促进GLUT 4易位到细胞表面并增强葡萄糖摄取。
To promote glucose uptake into fat and muscle cells, insulin causes the translocation of GLUT4 glucose transporters from intracellular vesicles to the cell surface. Previous data support a model in which TUG traps GLUT4-containing vesicles and tethers them intracellularly in unstimulated cells and in which insulin mobilizes this pool of vesicles by releasing this tether. Here we show that TUG undergoes site-specific endoproteolytic cleavage, which separates a GLUT4-binding, N-terminal region of TUG from a C-terminal region previously suggested to bind an intracellular anchor. Cleavage is accelerated by insulin stimulation in 3T3-L1 adipocytes and is highly dependent upon adipocyte differentiation. The N-terminal TUG cleavage product has properties of a novel 18-kDa ubiquitin-like modifier, which we call TUGUL. The C-terminal product is observed at the expected size of 42 kDa and also as a 54-kDa form that is released from membranes into the cytosol. In transfected cells, intact TUG links GLUT4 to PIST and also binds Golgin-160 through its C-terminal region. PIST is an effector of TC10 alpha, a GTPase previously shown to transmit an insulin signal required for GLUT4 translocation, and we show using RNAi that TC10 alpha is required for TUG proteolytic processing. Finally, we demonstrate that a cleavage-resistant form of TUG does not support highly insulin-responsive GLUT4 translocation or glucose uptake in 3T3-L1 adipocytes. Together with previous results, these data support a model whereby insulin stimulates TUG cleavage to liberate GLUT4 storage vesicles from the Golgi matrix, which promotes GLUT4 translocation to the cell surface and enhances glucose uptake.