| Summary: | 博士 === 國立陽明大學 === 生命科學暨基因體科學研究所 === 96 === Neurons are highly polarized cells comprised single axon, multiple dendrites, and numerous dendritic spines. This unique morphology is important for neural functions. Neurofibromin, a tumor suppressor protein down regulating Ras activity and activating adenylate cyclase, regulates neurite outgrowth implying a potential role of neurofibromin in neuronal morphogenesis. By investigating the roles of neurofibromin-interacting proteins syndecan-2, VCP, and CRMP-2, the involvement of neurofibromin in neuronal morphogenesis was revealed.
Syndecan-2 induces morphological change in various cell types. In neurons, syndecan-2 promotes spine formation via inducing filopodia formation. Here, a novel signaling pathway was revealed. Neurofibromin acted down stream of syndecan-2 to activate adenylate cyclase-PKA-Ena/VASP pathway and thus promotes filopodia formation. VCP, a molecule with multiple functions, mediates membrane fusion. It was shown that the interaction between neurofibromin and VCP is also required for spinogenesis by probably regulating membrane fusion. In addition to spinogenesis, neurofibromin is also involved in dendrite formation. Under the control of syndecan-2, neurofibromin regulated dendrite outgrowth by both PKA and VCP pathways. Finally, CRMP-2, a highly phosphorylated protein, is involved in axon outgrowth. CDK5 phosphorylated CRMP-2 leads to growth cone collapse. Neurofibromin interacted with CRMP-2 in a CDK5-dependent manner, suggesting that neurofibromin also plays a role in axonal outgrowth.
In conclusion, neurofibromin regulates neuronal morphogenesis, which may account for neurological defects of NF1 patients.
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