Nerve growth factor promotes reorganization of the axonal microtubule array at sites of axon collateral branching.
Nerve growth factor promotes reorganization of the axonal microtubule array at sites of axon collateral branching.
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DOI：
10.1002/dneu.22294
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发表时间：
2015-12
影响因子：
3
通讯作者：
Gallo G
中科院分区：
文献类型：
--
作者：
Ketschek A;Jones S;Spillane M;Korobova F;Svitkina T;Gallo G
轴突微管阵列的局部解束和微管进入轴突丝状伪足是侧枝分支的两个定义特征。神经生长因子（NGF）是一种分支诱导信号，可增加鸡胚感觉神经元轴突沿着微管解聚的频率。解开的位点与微管进入丝状伪足的局部靶向密切相关。铂复型电子显微镜表明解开微管和轴突肌动蛋白丝之间的物理相互作用。然而，肌动蛋白丝的解聚和肌球蛋白II的抑制证明，肌动球蛋白力的产生并不促进解开。相反，肌动蛋白丝的损失或肌球蛋白II活性的抑制促进解开，表明轴突肌动球蛋白力抑制解开。MAP 1B是一种微管相关蛋白，抑制轴突分支。用NGF处理后，微管在分支的早期阶段穿透丝状伪足表现出较低水平的相关MAP 1B。NGF分别增加和降低轴突轴沿着和轴突丝状伪足内GSK-3β位点（pMAP 1B）磷酸化的MAP 1B水平。MAP 1B和pMAP 1B的水平没有改变在网站的解开，相对于其余的轴突。与先前确定的神经生长因子对轴突肌动蛋白细胞骨架的影响不同，神经生长因子对微管解束的影响不受蛋白质合成抑制的影响。总的来说，这些数据表明，神经生长因子促进局部轴突微管解束，肌动球蛋白部队拮抗微管解束和神经生长因子调节pMAP 1B在轴突丝状伪足在侧枝分支形成的早期阶段。
The localized debundling of the axonal microtubule array and the entry of microtubules into axonal filopodia are two defining features of collateral branching. We report that nerve growth factor (NGF), a branch inducing signal, increases the frequency of microtubule debundling along the axon shaft of chicken embryonic sensory neurons. Sites of debundling correlate strongly with the localized targeting of microtubules into filopodia. Platinum replica electron microscopy suggests physical interactions between debundled microtubules and axonal actin filaments. However, as evidenced by depolymerization of actin filaments and inhibition of myosin II, actomyosin force generation does not promote debundling. In contrast, loss of actin filaments or inhibition of myosin II activity promotes debundling, indicating that axonal actomyosin forces suppress debundling. MAP1B is a microtubule associated protein that represses axon branching. Following treatment with NGF, microtubules penetrating filopodia during the early stages of branching exhibited lower levels of associated MAP1B. NGF increased and decreased the levels of MAP1B phosphorylated at a GSK-3β site (pMAP1B) along the axon shaft and within axonal filopodia, respectively. The levels of MAP1B and pMAP1B were not altered at sites of debundling, relative to the rest of the axon. Unlike the previously determined effects of NGF on the axonal actin cytoskeleton, the effects of NGF on microtubule debundling were not affected by inhibition of protein synthesis. Collectively, these data indicate that NGF promotes localized axonal microtubule debundling, that actomyosin forces antagonize microtubule debundling and that NGF regulates pMAP1B in axonal filopodia during the early stages of collateral branch formation.