Eps8 regulates axonal filopodia in hippocampal neurons in response to brain-derived neurotrophic factor (BDNF).
Eps8 regulates axonal filopodia in hippocampal neurons in response to brain-derived neurotrophic factor (BDNF).
复制标题
DOI：
10.1371/journal.pbio.1000138
复制
发表时间：
2009-06-30
期刊：
影响因子：
9.8
通讯作者：
Matteoli M
中科院分区：
文献类型：
--
作者：
Menna E;Disanza A;Cagnoli C;Schenk U;Gelsomino G;Frittoli E;Hertzog M;Offenhauser N;Sawallisch C;Kreienkamp HJ;Gertler FB;Di Fiore PP;Scita G;Matteoli M
一种新的信号级联控制肌动蛋白聚合反应的细胞外信号调节丝状伪足的形成，也可能是神经元突触的形成。丝状伪足的调节在神经元发育和突触发生中起着至关重要的作用。轴突丝状伪足，这是已知的起源突触前特化，调节响应神经营养因子。丝状伪足的结构成分是肌动蛋白丝，其动力学和组织由肌动蛋白结合蛋白控制。然而，神经营养因子如何调节这些后者的蛋白质仍然不清楚。在这里，使用小鼠遗传，生物化学和细胞生物学检测的组合，我们表明，遗传去除Eps 8，肌动蛋白结合和调节蛋白富集在生长锥和神经元的发育过程中，显着增加的数量和密度的血管扩张刺激磷蛋白（VASP）依赖性轴突丝状伪足。Eps 8野生型（WT），但不是Eps 8加帽缺陷突变体，重新引入原代海马神经元恢复轴突丝状伪足WT水平。我们进一步表明，肌动蛋白倒钩末端封端活性的Eps 8抑制脑源性神经营养因子（BDNF）治疗通过MAPK依赖性磷酸化的Eps 8残基S624和T628。此外，一个Eps 8突变体，在MAPK靶位点（S624 A/T628 A）受损，显示增加的关联肌动蛋白丰富的结构，是抗BDNF介导的释放从微丝，并抑制BDNF诱导的丝状伪足。对于磷酸化模拟Eps 8（S624 E/T628 E）突变体观察到相反的情况。因此，总的来说，我们的数据确定Eps 8作为一个关键的加帽蛋白在轴突丝状伪足的调节和描绘的分子途径，BDNF，通过MAPK依赖的磷酸化的Eps 8，刺激轴突丝状伪足的形成，一个过程与神经元发育和突触形成的关键影响。神经元通过称为突触的专门的细胞-细胞连接相互通信。突触的正确形成（“突触发生”）对神经系统的发育至关重要，但调节这一过程的分子途径尚未完全了解。外部信号，如脑源性神经营养因子（BDNF），通过促进轴突丝状伪足的形成来触发突触发生，丝状伪足是从生长的轴突向外伸出的细延伸。丝状伪足由肌动蛋白丝的伸长形成，这是一个由一组复杂的肌动蛋白结合蛋白调节的过程。在这里，我们揭示了一种新的分子电路的BDNF刺激丝状伪足的形成，通过调节抑制肌动蛋白加帽因子的活性。我们发现，肌动蛋白加帽蛋白Eps 8下调轴突丝状伪足的神经元中的神经营养因子的情况下形成。相反，在BDNF的存在下，激酶MAPK被激活并磷酸化Eps 8，导致其肌动蛋白加帽功能的抑制和丝状伪足形成的刺激。因此，我们的研究确定肌动蛋白帽因子抑制作为轴突丝状伪足形成的关键步骤，并可能在新的突触形成。
A novel signaling cascade controlling actin polymerization in response to extracellular signals regulates filopodia formation and likely also neuronal synapse formation. The regulation of filopodia plays a crucial role during neuronal development and synaptogenesis. Axonal filopodia, which are known to originate presynaptic specializations, are regulated in response to neurotrophic factors. The structural components of filopodia are actin filaments, whose dynamics and organization are controlled by ensembles of actin-binding proteins. How neurotrophic factors regulate these latter proteins remains, however, poorly defined. Here, using a combination of mouse genetic, biochemical, and cell biological assays, we show that genetic removal of Eps8, an actin-binding and regulatory protein enriched in the growth cones and developing processes of neurons, significantly augments the number and density of vasodilator-stimulated phosphoprotein (VASP)-dependent axonal filopodia. The reintroduction of Eps8 wild type (WT), but not an Eps8 capping-defective mutant, into primary hippocampal neurons restored axonal filopodia to WT levels. We further show that the actin barbed-end capping activity of Eps8 is inhibited by brain-derived neurotrophic factor (BDNF) treatment through MAPK-dependent phosphorylation of Eps8 residues S624 and T628. Additionally, an Eps8 mutant, impaired in the MAPK target sites (S624A/T628A), displays increased association to actin-rich structures, is resistant to BDNF-mediated release from microfilaments, and inhibits BDNF-induced filopodia. The opposite is observed for a phosphomimetic Eps8 (S624E/T628E) mutant. Thus, collectively, our data identify Eps8 as a critical capping protein in the regulation of axonal filopodia and delineate a molecular pathway by which BDNF, through MAPK-dependent phosphorylation of Eps8, stimulates axonal filopodia formation, a process with crucial impacts on neuronal development and synapse formation. Neurons communicate with each other via specialized cell–cell junctions called synapses. The proper formation of synapses (“synaptogenesis”) is crucial to the development of the nervous system, but the molecular pathways that regulate this process are not fully understood. External cues, such as brain-derived neurotrophic factor (BDNF), trigger synaptogenesis by promoting the formation of axonal filopodia, thin extensions projecting outward from a growing axon. Filopodia are formed by elongation of actin filaments, a process that is regulated by a complex set of actin-binding proteins. Here, we reveal a novel molecular circuit underlying BDNF-stimulated filopodia formation through the regulated inhibition of actin-capping factor activity. We show that the actin-capping protein Eps8 down-regulates axonal filopodia formation in neurons in the absence of neurotrophic factors. In contrast, in the presence of BDNF, the kinase MAPK becomes activated and phosphorylates Eps8, leading to inhibition of its actin-capping function and stimulation of filopodia formation. Our study, therefore, identifies actin-capping factor inhibition as a critical step in axonal filopodia formation and likely in new synapse formation.
登录
查看更多内容
影响因子：
4.8
作者：
Barzik, M;Kotova, TI;Schafer, DA
通讯作者：
Schafer, DA
影响因子：
5.3
作者：
Abbott, MA;Wells, DG;Fallon, JR
通讯作者：
Fallon, JR
影响因子：
64.8
作者：
JANMEY, PA;STOSSEL, TP
通讯作者：
STOSSEL, TP
影响因子：
64.8
作者：
Engert, F;Bonhoeffer, T
通讯作者：
Bonhoeffer, T
影响因子：
25
作者：
Chang, S;De Camilli, P
通讯作者：
De Camilli, P