Antagonistic Functions of Dishevelleds Regulate Frizzled3 Endocytosis via Filopodia Tips in Wnt-Mediated Growth Cone Guidance
Antagonistic Functions of Dishevelleds Regulate Frizzled3 Endocytosis via Filopodia Tips in Wnt-Mediated Growth Cone Guidance
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DOI：
10.1523/jneurosci.2800-13.2013
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发表时间：
2013-12-04
影响因子：
5.3
通讯作者：
Zou, Yimin
中科院分区：
文献类型：
--
作者：
Onishi, Keisuke;Shafer, Beth;Zou, Yimin
生长锥体如何探测到引导信号的微小浓度差异，以进行正确的转向，仍然是一个长期存在的谜题。连合轴突与平面细胞极性(PCP)信号成分接触，在中线交叉后以Wnt梯度向前旋转。我们在这里发现，Wnt受体Frizzled3通过丝状足尖进行内吞作用。WNT5A增加Frizzled3的内吞作用，这与丝状孢子的伸长有关。我们发现了Dishevelled2之间意想不到的拮抗作用，这可能在PCP信号被激活的丝状足细胞中起到信号放大的作用：Dishevelled2阻止了Dishevelled1诱导的Frizzled3过度磷酸化和膜积累。心尖-基底极性(A-BP)信号的一个关键成分，aPKC，也抑制Dishevelled1诱导的Frizzled3过度磷酸化。另一种PCP成分Celsr3是连合神经元前转所必需的。Frizzled3过度磷酸化在Celsr3突变小鼠中增加，其中PCP信号受损，这表明Frizzled3过度磷酸化确实与体内PCP信号的丢失相关。此外，我们发现Frizzled3内吞所需的小GTPase Arf6对于Wnt促进的生长是必不可少的，这突显了Frizzled3循环在PCP信号在生长锥引导中的重要性。在Wnt5a梯度中，在面对较高Wnt5a浓度的生长锥一侧观察到更多的Frizzled3内吞作用和非典型蛋白激酶C的激活，这表明空间控制的Frizzled3内吞作用是生长锥转向的关键机制之一。
How growth cones detect small concentration differences of guidance cues for correct steering remains a long-standing puzzle. Commissural axons engage planar cell polarity (PCP) signaling components to turn anteriorly in a Wnt gradient after midline crossing. We found here that Frizzled3, a Wnt receptor, undergoes endocytosis via filopodia tips. Wnt5a increases Frizzled3 endocytosis, which correlates with filopodia elongation. We discovered an unexpected antagonism between Dishevelleds, which may function as a signal amplification mechanism in filopodia where PCP signaling is activated: Dishevelled2 blocks Dishevelled1-induced Frizzled3 hyperphosphorylation and membrane accumulation. Akey component of apical-basal polarity (A-BP) signaling, aPKC, also inhibits Dishevelled1-induced Frizzled3 hyperphosphorylation. Celsr3, another PCP component, is required in commissural neurons for anterior turning. Frizzled3 hyperphosphorylation is increased in Celsr3 mutant mice, where PCP signaling is impaired, suggesting Frizzled3 hyperphosphorylation does correlate with loss of PCP signaling in vivo. Furthermore, we found that the small GTPase, Arf6, which is required for Frizzled3 endocytosis, is essential for Wnt-promoted outgrowth, highlighting the importance of Frizzled3 recycling in PCP signaling in growth cone guidance. In a Wnt5a gradient, more Frizzled3 endocytosis and activation of atypical protein kinase C was observed on the side of growth cones facing higher Wnt5a concentration, suggesting that spatially controlled Frizzled3 endocytosis is part of the key mechanism for growth cone steering.