Ephrin-A5 potentiates netrin-1 axon guidance by enhancing Neogenin availability
Ephrin-A5 potentiates netrin-1 axon guidance by enhancing Neogenin availability
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DOI：
10.1038/s41598-019-48519-0
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发表时间：
2019-08-19
影响因子：
4.6
通讯作者：
Kania, A.
中科院分区：
文献类型：
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作者：
Croteau, L. -P.;Kao, T. -J.;Kania, A.
轴突生长锥由细胞外环境中的分子线索引导。生长锥细胞膜上引导信号的组合整合机制仍待阐明。脊椎动物脊髓横向运动柱 (LMC) 神经元的肢体神经轴突通过其受体 Neogenin 被 netrin-1 吸引，并通过其受体 EphA4 被 ephrin-A5 排斥。两种信号的存在都会引发 LMC 轴突的协同引导，但这种效应的机制仍不清楚。使用荧光免疫组织化学，我们发现 ephrin-A5 增加了 LMC 生长锥 Neogenin 蛋白水平和 netrin-1 结合。过表达 EphA4 可以增强这种作用，而阻断 ephrin-A5-EphA4 结合则可以抑制这种作用。这些效应对 LMC 生长锥反应产生功能性影响，因为浴中添加 ephrin-A5 会增加 LMC 轴突对 netrin-1 的反应性。令人惊讶的是，缺乏细胞质尾部的 EphA4 的过度表达也提高了生长锥处的 Neogenin 水平，并增强了 LMC 轴突对 netrin-1 生长的偏好。由于 netrin 和 ephrins 参与多种生物过程，因此 ephrins 增强 netrin-1 信号传导可能具有广泛的影响。
Axonal growth cones are guided by molecular cues in the extracellular environment. The mechanisms of combinatorial integration of guidance signals at the growth cone cell membrane are still being unravelled. Limb-innervating axons of vertebrate spinal lateral motor column (LMC) neurons are attracted to netrin-1 via its receptor, Neogenin, and are repelled from ephrin-A5 through its receptor EphA4. The presence of both cues elicits synergistic guidance of LMC axons, but the mechanism of this effect remains unknown. Using fluorescence immunohistochemistry, we show that ephrin-A5 increases LMC growth cone Neogenin protein levels and netrin-1 binding. This effect is enhanced by overexpressing EphA4 and is inhibited by blocking ephrin-A5-EphA4 binding. These effects have a functional consequence on LMC growth cone responses since bath addition of ephrin-A5 increases the responsiveness of LMC axons to netrin-1. Surprisingly, the overexpression of EphA4 lacking its cytoplasmic tail, also enhances Neogenin levels at the growth cone and potentiates LMC axon preference for growth on netrin-1. Since netrins and ephrins participate in a wide variety of biological processes, the enhancement of netrin-1 signalling by ephrins may have broad implications.