Regulation of neuronal morphology by Toca-1, an F-BAR/EFC protein that induces plasma membrane invagination
Regulation of neuronal morphology by Toca-1, an F-BAR/EFC protein that induces plasma membrane invagination
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DOI：
10.1074/jbc.m604025200
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发表时间：
2006-09-29
影响因子：
4.8
通讯作者：
Negishi, Manabu
中科院分区：
文献类型：
--
作者：
Kakimoto, Tetsuhiro;Katoh, Hironori;Negishi, Manabu
肌动蛋白重组对于神经元形态的调节很重要。神经维斯科特-奥尔德里奇综合征蛋白 (N-WASP) 是肌动蛋白聚合的重要调节因子，并且在大脑中强烈表达。最近，生化实验表明，Toca-1（Cdc42 依赖性肌动蛋白组装转导子）是 Cdc42 激活 N-WASP 所必需的。 Toca-1具有三个功能域：N端的F-BAR/EFC域、中心的HR1域和C端的SH3域。 F-BAR/EFC 结构域诱导管状质膜内陷，而 Toca-1 分别通过 SH3 结构域和 HR1 结合 N-WASP 和 Cdc42。然而，Toca-1的生理作用完全未知。在这里，我们研究了 Toca-1 的神经功能。 Toca-1在大脑发育早期的神经元中强烈表达，包括海马神经元。 PC12 细胞中 Toca-1 的敲低可显着增强神经突伸长。一致地，Toca-1 的过表达通过具有膜内陷特性的 F-BAR/EFC 结构域抑制神经突伸长，这表明膜运输对 Toca-1 神经功能的影响。此外，令我们惊讶的是，N-WASP的敲低还增强了PC12细胞中的神经突伸长，这与之前的报道形成鲜明对比，即N-WASP的显性失活突变体抑制PC12细胞中的神经突伸长。另一方面，在培养的大鼠海马神经元中敲低 Toca-1 会稍微增强轴突分支，但不会增强轴突伸长，而敲低 N-WASP 会增强轴突伸长和分支。这些结果表明，囊泡运输调节剂 Toca-1 调节 N-WASP 神经元形态的不同方面。
Actin reorganization is important for regulation of neuronal morphology. Neural Wiskott-Aldrich syndrome protein (N-WASP) is an important regulator of actin polymerization and also known to be strongly expressed in brain. Recently, Toca-1 (transducer of Cdc42-dependent actin assembly) has been shown to be required for Cdc42 to activate N-WASP from biochemical experiments. Toca-1 has three functional domains: an F-BAR/EFC domain at the N terminus, an HR1 at the center, and an SH3 domain at the C terminus. The F-BAR/EFC domain induces tubular invagination of plasma membrane, while Toca-1 binds both N-WASP and Cdc42 through the SH3 domain and the HR1, respectively. However, the physiological role of Toca-1 is completely unknown. Here we have investigated the neural function of Toca-1. Toca-1 is strongly expressed in neurons including hippocampal neurons in developing brain at early times. Knockdown of Toca-1 in PC12 cells significantly enhances neurite elongation. Consistently, overexpression of Toca-1 suppresses neurite elongation through the F-BAR/EFC domain with a membrane invaginating property, suggesting an implication of membrane trafficking in the neural function of Toca-1. In addition, knockdown of N-WASP, to our surprise, also enhances neurite elongation in PC12 cells, which is in clear contrast to the previous report that dominant negative mutants of N-WASP suppress neurite extension in PC12 cells. On the other hand, knockdown of Toca-1 in cultured rat hippocampal neurons enhances axon branching a little but not axon elongation, while knockdown of N-WASP enhances both axon elongation and branching. These results suggest that a vesicle trafficking regulator Toca-1 regulates different aspects of neuronal morphology from N-WASP.