ERK2-Mediated Phosphorylation of Par3 Regulates Neuronal Polarization
ERK2-Mediated Phosphorylation of Par3 Regulates Neuronal Polarization
复制标题
DOI：
10.1523/jneurosci.4210-12.2013
复制
发表时间：
2013-08-14
影响因子：
5.3
通讯作者：
Kaibuchi, Kozo
中科院分区：
文献类型：
--
作者：
Funahashi, Yasuhiro;Namba, Takashi;Kaibuchi, Kozo
轴突形成是神经元极化中最重要的事件之一，并受到参与细胞骨架重排和蛋白质运输的信号分子的调节。我们之前发现分区缺陷 3 (Par3) 与 KIF3A (驱动蛋白-2) 相关，并以 KIF3A 依赖性方式转运到新生轴突中。 Par3 与 Rac 特异性鸟嘌呤核苷酸交换因子 (GEF) Tiam1/2 相互作用，后者激活 Rac1，并参与培养的海马神经元的轴突形成。然而，人们对 Par3-KIF3A 相互作用的调节机制知之甚少，并且 Par3 在体内神经元极化中的作用仍然难以捉摸。在这里，我们发现细胞外信号调节激酶 2 (ERK2) 直接与 Par3 相互作用，ERK2 在 Ser-1116 位点磷酸化 Par3，并且磷酸化的 Par3 以依赖于 ERK2 活性的方式在轴突尖端积累。 ERK2 对 Par3 的磷酸化抑制了 Par3 与 KIF3A 的相互作用，但不抑制与其他 Par3 伴侣（包括 Par6 和 aPKC）的相互作用。 Par3 的拟磷突变体 (Par3-S1116D) 显示出与 KIF3 的结合活性较低，并且轴突中的运输较慢。在体内培养的大鼠海马神经元和小鼠皮层投射神经元中，RNA 干扰敲低 Par3 会损害神经元极化，而抗 RNAi 的 Par3 可以恢复这种极化，但拟磷化 Par3 突变体则不能恢复这种极化。这些结果表明，ERK2 磷酸化 Par3 并抑制其与 KIF3A 的结合，从而控制 Par3 转运和神经元极性。
Axon formation is one of the most important events in neuronal polarization and is regulated by signaling molecules involved in cytoskeletal rearrangement and protein transport. We previously found that Partition-defective 3 (Par3) is associated with KIF3A (kinesin-2) and is transported into the nascent axon in a KIF3A-dependent fashion. Par3 interacts with the Rac-specific guanine nucleotide-exchange factors (GEFs) Tiam1/2, which activate Rac1, and participates in axon formation in cultured hippocampal neurons. However, the regulatory mechanism of the Par3-KIF3A interaction is poorly understood, and the role of Par3 in neuronal polarization in vivo remains elusive. Here, we found that extracellular signal-regulated kinase 2 (ERK2) directly interacts with Par3, that ERK2 phosphorylates Par3 at Ser-1116, and that the phosphorylated Par3 accumulates at the axonal tips in a manner dependent upon ERK2 activity. The phosphorylation of Par3 by ERK2 inhibited the interaction of Par3 with KIF3A but not with the other Par3 partners, including Par6 and aPKC. The phosphomimic mutant of Par3 (Par3-S1116D) showed less binding activity with the KIF3s and slower transport in the axons. The knockdown of Par3 by RNA interference impaired neuronal polarization, which was rescued with RNAi-resistant Par3, but not with the phosphomimic Par3 mutant, in cultured rat hippocampal neurons and mouse cortical projection neurons in vivo. These results suggest that ERK2 phosphorylates Par3 and inhibits its binding with KIF3A, thereby controlling Par3 transport and neuronal polarity.