2005 Fiscal Year Final Research Report Summary
Molecular and cellular morphological analysis of sugar transporter dynamics between cell membrane and organelles
| Project/Area Number |
15390053
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General anatomy (including Histology/Embryology)
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| Research Institution | Gunma University |
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Principal Investigator |
TAKATA Kuniaki Gunma University, Graduate School of Medicine, Department of Anatomy and Cell Biology, Professor, 大学院・医学系研究科, 教授 (20129290)
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| Co-Investigator(Kenkyū-buntansha) |
HAGIWARA Haruo Gunma University, Graduate School of Medicine, Department of Anatomy and Cell Biology, Associate Professor, 大学院・医学系研究科, 助教授 (80189464)
AOKI Takeo Gunma University, Graduate School of Medicine, Department of Anatomy and Cell Biology, Associate Professor, 大学院・医学系研究科, 講師 (70150919)
MATSUZAKI Toshiyuki Gunma University, Graduate School of Medicine, Department of Anatomy and Cell Biology, Research Associate, 大学院・医学系研究科, 助手 (30334113)
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| Project Period (FY) |
2003 – 2005
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| Keywords | cell membrane / sugar transporter / water channel / microdomain / aquaporin-2 / endosome / compartment / organelle |
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| Research Abstract |
Sugar transporter GLUT4 is recruited from the intracellular compartments and is translocated to the cell membrane upon insulin stimulation, which increases the sugar transport activity at the cell surface. GLUT4, therefore, plays a pivotal role in the regulation of blood glucose level. I first examined the localization of GLUT4 in 3T3-L1 cultured adipocytes by immunofluorescence microscopy. Insulin-stimulation mobilized only a small portion of intracellular GLUT4. The paucity of translocation of GLUT4 was a serious drawback in analyzing the mechanism of transporter trafficking by morphological methods. Aquaporin 2 water channel is also translocated from the intracellular pool to the cell membrane upon anti-diuretic hormone-stimulation in principal cells of the kidney collecting ducts, which increases the water permeability at the apical cell membrane. This system provides a unique opportunity to study the translocation mechanism between intracellular compartments and cell membrane. I examined the immunolocalization and trafficking of aquaporin 2 with special reference to intracellular organelles and microdomains of the embrane such as rafts. Aquaporin 2 was recovered in Triton X100-insoluble fractions, suggesting the contribution of membrane rafts. Stimulation with forskolin induces the translocation of aquaporin 2 to the cell membrane, where it was colocalized with caveolin 1. Wash-out of forskolin initiated the retrieval of aquaporin 2 to the EEA1-positive early endosomes by endocytosis. Such trafficking was affected by drugs that perturb membrane microdomains, suggesting an important role of membrane microdomains in the trafficking of aquaporin 2.
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