2006 Fiscal Year Final Research Report Summary
Analyses of Rho small GTPase-dependent regulation of septin structure and functions
| Project/Area Number |
17590259
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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 | Institute for Developmental Research, Aichi Human Service Center |
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Principal Investigator |
NAGATA Koh-ichi Institute for Developmental Research, Aichi Human Service Center, Department of Molecular Neurobiology, Section Head, 神経制御学部, 室長 (50252143)
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| Project Period (FY) |
2005 – 2006
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| Keywords | signal transduction / biomolecules / septin / cytoskeleton / Rho |
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| Research Abstract |
We showed that active Rho disrupts septin filament structures in REF52 cells. Among Rho effector molecules tested, Rhotekin induced morphological changes similar to those by activated Rho. In neuroblastoma cells, Rhotekin and Sept9b were enriched in the tip of neurites, a location where cortical actin reorganization is induced. We proposed that Rhotekin is a novel regulator organizing septin structures and provide a new link between the septin and Rho-signaling. We then identified PIST as a binding partner for Rhotekin. Rhotekin associated with PIST in vitro and in MDCK cells. The C-terminal SPV motif of Rhotekine xhibited binding to the PDZ domain of PIST. The binding was markedly inhibited by an activated Rho in COS7 cells. PIST and Rhotekin was co-localized at the Golgi-apparatus in non-polarized fibroblast-like MDCK cells and adherens junctions (AJs) in the fully polarized cells. PIST and Rhotekin were recruited from the cytosol to AJs as the cell becomes polarized. Expression of active Rho or prevention of Rhotekin-PIST interaction induced diffuse cytoplasmic distribution of Rhotekin in MDCK cells. We also identified a PDZ protein, Lin-7B, as a binding partner for Rhotekin. We found that Rhotekin interacts with Lin-7B in in vitro pull-down assays, and forms an immunocomplex in the rat brain. Their binding affinity became increased in the presence of active Rho in the COS7 cells. In addition, immunohistochemical analyses demonstrated that Lin-7 as well as Rhotekin is enriched in neurons. These results suggest that Lin-7 plays some role in neuronal functions in concert with Rho/Rhotekin signals.
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