Identification of nuclear import mechanisms for the neuronal Cdk5 activator
Identification of nuclear import mechanisms for the neuronal Cdk5 activator
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DOI：
10.1074/jbc.m512663200
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发表时间：
2006-12-22
影响因子：
4.8
通讯作者：
Qi, Robert Z.
中科院分区：
文献类型：
--
作者：
Fu, Xinrong;Choi, Yuk-Kwan;Qi, Robert Z.
p35 激活 Cdk5 在从神经元分化到退化的多种神经系统活动中发挥着关键作用。 Cdk5 和 p35 的一部分定位于细胞核，其中 Cdk5-p35 通过蛋白质磷酸化发挥其功能，并且 p35 在细胞质和细胞核之间显示出动态定位。在这里，我们检查了 p35 的核输入特性。在核输入测定中，p35 通过细胞质载体介导的机制主动转运至洋地黄皂苷透化的 HeLa 细胞和皮质神经元的细胞核中。 importin-beta、importin-5 和 importin-7 经鉴定可通过与 p35 直接相互作用将 p35 输入到细胞核中。 p35 的 N 末端区域被定义为与上述输入蛋白相互作用，充当核定位信号。最后，我们证明p35的核定位不需要Cdk5的关联。此外，Cdk5 和 importin-beta/5/7 在与 p35 的结合方面是相互排斥的。这些结果表明 p35 采用与 Cdk5 不同的途径转运至细胞核。
The activation of Cdk5 by p35 plays a pivotal role in a multitude of nervous system activities ranging from neuronal differentiation to degeneration. A fraction of Cdk5 and p35 localizes in the nucleus where Cdk5-p35 exerts its functions via protein phosphorylation, and p35 displays a dynamic localization between the cytoplasm and the nucleus. Here, we examined the nuclear import properties of p35. In nuclear import assays, p35 was actively transported into the nuclei of digitonin-permeabilized HeLa cells and cortical neurons by cytoplasmic carrier-mediated mechanisms. Importin-beta, importin-5, and importin-7 were identified to import p35 into the nuclei via a direct interaction with it. An N-terminal region of p35 was defined to interact with the above importins, serving as a nuclear localization signal. Finally, we show that the nuclear localization of p35 does not require the association of Cdk5. Furthermore, Cdk5 and importin-beta/5/7 are mutually exclusive in binding to p35. These results suggest that p35 employs pathways distinct from that used by Cdk5 for transport to the nucleus.