Insulin Regulates Fusion of GLUT4 Vesicles Independent of Exo70-mediated Tethering
| Autor: | Vladimir A. Lizunov, Samuel W. Cushman, Ivonne Lisinski, Karin G. Stenkula, Joshua Zimmerberg |
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| Rok vydání: | 2009 |
| Předmět: |
Male
Vesicle fusion endocrine system diseases Glucose uptake Vesicular Transport Proteins Exocyst Biology Membrane Fusion Biochemistry Exocytosis Cell membrane Mice 3T3-L1 Cells Adipocytes medicine Animals Hypoglycemic Agents Insulin Molecular Biology Cells Cultured Glucose Transporter Type 4 Secretory Vesicles Vesicle Cell Membrane nutritional and metabolic diseases Lipid bilayer fusion Biological Transport Cell Biology musculoskeletal system Rats Cell biology Membrane Transport Structure Function and Biogenesis medicine.anatomical_structure Mutation biology.protein hormones hormone substitutes and hormone antagonists GLUT4 |
| Zdroj: | Journal of Biological Chemistry. 284:7914-7919 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m806460200 |
| Popis: | Insulin regulates cellular glucose uptake by changing the amount of glucose transporter-4 (GLUT4) in the plasma membrane through stimulation of GLUT4 exocytosis. However, how the particular trafficking, tethering, and fusion steps are regulated by insulin is still debated. In a 3T3-L1 adipocyte cell line, the Exocyst complex and its Exo70 subunit were shown to critically affect GLUT4 exocytosis. Here we investigated the effects of Exo70 on tethering and fusion of GLUT4 vesicles in primary isolated rat adipose cells. We found that Exo70 wild type was sequestered away from the plasma membrane in non-stimulated cells, and its overexpression had no effect on GLUT4 trafficking. The addition of insulin increased the amount of Exo70 in the vicinity of the plasma membrane and stimulated the tethering and fusion of GLUT4 vesicles, but the rates of fusion and GLUT4 exposure were not affected by overexpression of Exo70. Surprisingly, the Exo70-N mutant induced insulin-independent tethering of GLUT4 vesicles, which, however, did not lead to fusion and exposure of GLUT4 at the plasma membrane. Upon insulin stimulation, the stationary pretethered GLUT4 vesicles in Exo70-N mutant cells underwent fusion without relocation. Taken together, our data suggest that fusion of GLUT4 vesicles is the rate-limiting step regulated by insulin downstream of Exo70-mediated tethering. |
| Databáze: | OpenAIRE |
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