| Project/Area Number |
16590231
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General medical chemistry
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| Research Institution | The University of Tokushima |
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Principal Investigator |
NISHIMURA Noriyuki The University of Tokushima, Graduate School Institute of Health Biosciences, Associate Professor, 大学院・ヘルスバイオサイエンス研究部, 助教授 (00322719)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | cell polarity / cell adhesion / tight junction / Rab13 / JRAB / occludin / recycling / actin / カルシウムスイッチ |
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| Research Abstract |
Tight junctions (TJs) are continuous, circumferential belt-like structures located at the apical end of the intercellular space, where they delineate the boundaries between the apical and basolateral domains of the plasma membrane of epithelial cells. TJs are composed of integral TJ proteins and TJ plaque proteins. While integral TJ proteins including occludin and claudins mediate cell-cell adhesion and create physical intercellular barrier, TJ plaque proteins cluster integral TJ proteins and form an organizing platform for a variety of scaffolding, signaling, and vesicular transport proteins. Rab13 is identified as a TJ plaque protein in epithelial cells and is implicated in the assembly of functional TJs. We previously demonstrated that Rab13 specifically mediated the endocytic recycling of occludin. In the present study, we have identified MICAL-L2 (molecule interacting with CasL-like 2) as a novel Rab13-binding protein and renamed it as JRAB (junctional Rab13-binding protein). Immunoprecipitation and immunofluorescence microscopy showed that JRAB specifically bound to the GTP-bound form of Rab13 via its C-terminus, which contained a coiled-coil domain, and localized at TJs in epithelial MTD-1A cells. Recycling assay demonstrated that a JRAB mutant lacking the Rab13-binding domain (JRAB-N) specifically inhibited the endocytic recycling of occludin, but not transferrin receptor. Ca^<2+>-switch assay further revealed that JRAB-N as well as Rab13 Q67L inhibited the recruitment of occludin to the plasma membrane, the development of transepithelial electrical resistance, and the formation of a paracellular diffusion barrier. JRAB was displaced from TJs upon actin depolymerization in MTD-1A cells and was distributed along stress fibers in fibroblastic NIH3T3 cells. These results suggested that JRAB mediated the endocytic recycling of occludin and the formation of functional TJs by linking Rab13 to actin cytoskeleton.
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