Scapinin-induced Inhibition of Axon Elongation Is Attenuated by Phosphorylation and Translocation to the Cytoplasm
Scapinin-induced Inhibition of Axon Elongation Is Attenuated by Phosphorylation and Translocation to the Cytoplasm
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DOI：
10.1074/jbc.m110.205781
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发表时间：
2011-06-03
影响因子：
4.8
通讯作者：
Cole, Adam R.
中科院分区：
文献类型：
--
作者：
Farghaian, Hovik;Chen, Yu;Cole, Adam R.
Scapinin 是一种肌动蛋白和 PP1 结合蛋白，仅在大脑中表达；然而，其在神经元中的功能尚未得到研究。在这里，我们发现原代大鼠皮质神经元中斯卡皮宁的表达抑制轴突伸长，而不影响轴突分支、树突生长或极性。这种抑制作用取决于其结合肌动蛋白的能力，因为不结合肌动蛋白的突变形式对轴突伸长没有影响。免疫荧光分析表明，斯卡皮宁主要位于神经元的远端轴突轴、细胞体和细胞核中，并显示出与鬼笔环肽相反的染色模式，这与之前的报道一致，即它结合肌动蛋白单体以抑制聚合。我们发现 scapinin 在体外被 Cdk5 在蛋白质中心区域 (Ser-277) 的高度保守位点磷酸化。斯卡皮宁磷酸模拟突变体（S277D）的表达恢复了正常的轴突伸长而不影响肌动蛋白结合。相反，磷酸化的斯卡皮宁被隔离在神经元的细胞质中并远离轴突。由于其表达在成人大脑的相对可塑性区域（皮质、海马体）中最高，因此 scapinin 是大脑中神经突生长和神经可塑性的新调节剂。
Scapinin is an actin-and PP1-binding protein that is exclusively expressed in the brain; however, its function in neurons has not been investigated. Here we show that expression of scapinin in primary rat cortical neurons inhibits axon elongation without affecting axon branching, dendritic outgrowth, or polarity. This inhibitory effect was dependent on its ability to bind actin because a mutant form that does not bind actin had no effect on axon elongation. Immunofluorescence analysis showed that scapinin is predominantly located in the distal axon shaft, cell body, and nucleus of neurons and displays a reciprocal staining pattern to phalloidin, consistent with previous reports that it binds actin monomers to inhibit polymerization. We show that scapinin is phosphorylated at a highly conserved site in the central region of the protein (Ser-277) by Cdk5 in vitro. Expression of a scapinin phospho-mimetic mutant (S277D) restored normal axon elongation without affecting actin binding. Instead, phosphorylated scapinin was sequestered in the cytoplasm of neurons and away from the axon. Because its expression is highest in relatively plastic regions of the adult brain (cortex, hippocampus), scapinin is a new regulator of neurite outgrowth and neuroplasticity in the brain.