Cheatham B, Volchuk A, Kahn C R, Wang L, Rhodes C J, Klip A
Research Division, Joslin Diabetes Center, Boston, MA 02215, USA.
Proc Natl Acad Sci U S A. 1996 Dec 24;93(26):15169-73. doi: 10.1073/pnas.93.26.15169.
A major physiological role of insulin is the regulation of glucose uptake into skeletal and cardiac muscle and adipose tissue, mediated by an insulin-stimulated translocation of GLUT4 glucose transporters from an intracellular vesicular pool to the plasma membrane. This process is similar to the regulated docking and fusion of vesicles in neuroendocrine cells, a process that involves SNARE-complex proteins. Recently, several SNARE proteins were found in adipocytes: vesicle-associated membrane protein (VAMP-2), its related homologue cellubrevin, and syntaxin-4. In this report we show that treatment of permeabilized 3T3-L1 adipocytes with botulinum neurotoxin D, which selectively cleaves VAMP-2 and cellubrevin, inhibited the ability of insulin to stimulate translocation of GLUT4 vesicles to the plasma membrane. Furthermore, treatment of the permeabilized adipocytes with glutathione S-transferase fusion proteins encoding soluble forms of VAMP-2 or syntaxin-4 also effectively blocked insulin-regulated GLUT4 translocation. These results provide evidence of a functional role for SNARE-complex proteins in insulin-stimulated glucose uptake and suggest that adipocytes utilize a mechanism of regulating vesicle docking and fusion analogous to that found in neuroendocrine tissues.
胰岛素的一个主要生理作用是调节葡萄糖摄取到骨骼肌、心肌和脂肪组织中，这一过程由胰岛素刺激的GLUT4葡萄糖转运体从细胞内囊泡池转运至质膜介导。该过程类似于神经内分泌细胞中囊泡的调节性对接和融合，这一过程涉及SNARE复合蛋白。最近，在脂肪细胞中发现了几种SNARE蛋白：囊泡相关膜蛋白（VAMP-2）、其相关同源物细胞ubrevin和 syntaxin-4。在本报告中，我们表明，用肉毒杆菌神经毒素D处理通透的3T3-L1脂肪细胞，该毒素可选择性切割VAMP-2和细胞ubrevin，抑制了胰岛素刺激GLUT4囊泡转运至质膜的能力。此外，用编码VAMP-2或syntaxin-4可溶性形式的谷胱甘肽S-转移酶融合蛋白处理通透的脂肪细胞，也有效阻断了胰岛素调节的GLUT4转运。这些结果为SNARE复合蛋白在胰岛素刺激的葡萄糖摄取中的功能作用提供了证据，并表明脂肪细胞利用了一种类似于神经内分泌组织中发现的调节囊泡对接和融合的机制。
