Capzb2 Interacts with β-Tubulin to Regulate Growth Cone Morphology and Neurite Outgrowth
Capzb2 Interacts with β-Tubulin to Regulate Growth Cone Morphology and Neurite Outgrowth
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DOI：
10.1371/journal.pbio.1000208
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发表时间：
2009-10-01
期刊：
影响因子：
9.8
通讯作者：
Delalle, Ivana
中科院分区：
文献类型：
--
作者：
Davis, David A.;Wilson, Meredith H.;Delalle, Ivana
封盖蛋白（CP）是一种异源二聚体，通过结合f -肌动蛋白的倒钩端来调节肌动蛋白的组装。在培养的非神经元细胞中，每个CP亚基在板足和丝足的组织和动力学中起着关键作用。α或β CP亚基突变可导致果蝇视网膜变性。然而，CP亚基在哺乳动物神经元中的功能尚不清楚。在这里，我们研究了大脑中表达的β - CP亚基Capzb2在生长锥形态和神经突生长中的作用。我们发现，在海马神经元中沉默Capzb2会导致短的神经突和畸形的生长锥，其中微管过度生长到周围并与f -肌动蛋白完全重叠。为了寻找这些细胞骨架异常的机制，我们确定了β -微管蛋白是Capzb2的一个新的结合伙伴，并证明了Capzb2在体外降低了微管蛋白聚合的速率和程度。我们绘制了Capzb2亚基与β -微管蛋白相互作用并抑制微管聚合所需的区域。缺少该区域的突变体Capzb2能够与F-actin结合并形成具有α 2亚基的CP异二聚体。然而，该突变体无法挽救由Capzb2敲低引起的生长锥体和神经突生长表型。综上所述，这些数据表明Capzb2在生长锥形成和神经突生长中起重要作用，其潜在机制可能涉及Capzb2和微管之间的直接相互作用。
Capping protein (CP) is a heterodimer that regulates actin assembly by binding to the barbed end of F-actin. In cultured nonneuronal cells, each CP subunit plays a critical role in the organization and dynamics of lamellipodia and filopodia. Mutations in either alpha or beta CP subunit result in retinal degeneration in Drosophila. However, the function of CP subunits in mammalian neurons remains unclear. Here, we investigate the role of the beta CP subunit expressed in the brain, Capzb2, in growth cone morphology and neurite outgrowth. We found that silencing Capzb2 in hippocampal neurons resulted in short neurites and misshapen growth cones in which microtubules overgrew into the periphery and completely overlapped with F-actin. In searching for the mechanisms underlying these cytoskeletal abnormalities, we identified beta-tubulin as a novel binding partner of Capzb2 and demonstrated that Capzb2 decreases the rate and the extent of tubulin polymerization in vitro. We mapped the region of Capzb2 that was required for the subunit to interact with beta-tubulin and inhibit microtubule polymerization. A mutant Capzb2 lacking this region was able to bind F-actin and form a CP heterodimer with alpha 2-subunit. However, this mutant was unable to rescue the growth cone and neurite outgrowth phenotypes caused by Capzb2 knockdown. Together, these data suggest that Capzb2 plays an important role in growth cone formation and neurite outgrowth and that the underlying mechanism may involve direct interaction between Capzb2 and microtubules.