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A Truncated Tropo-Myosine-Related Kinase B Receptor, T1, Regulates Glial Cell Morphology via Rho GDP Dissociation Inhibitor 1
Koichi J. Homma,3
Shun Nakamura,1 , and
1Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo 187-8502, Japan, 2Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan, and 3Department of Molecular Pathology, Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa 199-0195, Japan
Through tropo-myosine-related kinase B (TrkB) receptors, brain-derivedneurotrophic factor (BDNF) performs many biological functionssuch as neural survival, differentiation, and plasticity. T1,an isoform of TrkB receptors that lacks a tyrosine kinase, predominatesin the adult mammalian CNS, yet its role remains controversial.In this study, to examine whether T1 transduces a signal andto determine its function, we first performed an affinity purificationof T1-binding protein with the T1-specific C-terminal peptideand identified Rho GDP dissociation inhibitor 1 (GDI1), a GDPdissociation inhibitor of Rho small G-proteins, as a signalingprotein directly associated with T1. The binding of BDNF toT1 caused Rho GDI1 to dissociate from the C-terminal tail ofT1. Astrocytes cultured for 30 d expressed only endogenous T1among the BDNF receptors. In 30 d cultured astrocytes, Rho GDI1,when dissociated in a BDNF-dependent manner, controlled theactivities of the Rho GTPases, which resulted in rapid changesin astrocytic morphology. Furthermore, using 2 d cultured astrocytesthat were transfected with T1, a T1 deletion mutant, or cyanfluorescent protein fusion protein of the T1-specific C-terminalsequence, we demonstrated that T1-Rho GDI1 signaling was indispensablefor regulating the activities of Rho GTPases and for the subsequentmorphological changes among astrocytes. Therefore, these findingsindicate that the T1 signaling cascade can alter astrocyticmorphology via regulation of Rho GTPase activity.
Proteomics study of neuropathic and nonneuropathic dorsal root ganglia: altered protein regulation following segmental spinal nerve ligation injury.
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A kinase-deficient TrkC receptor isoform activates Arf6-Rac1 signaling through the scaffold protein tamalin.
P. F. Esteban, H.-Y. Yoon, J. Becker, S. G. Dorsey, P. Caprari, M. E. Palko, V. Coppola, H. U. Saragovi, P. A. Randazzo, and L. Tessarollo (2006)
J. Cell Biol.
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