Inserm, UMR-S 839, Institut du Fer à Moulin, 17 rue du Fer à Moulin, 75005, Paris, France.
Cell Mol Life Sci. 2013 Jan;70(1):137-52. doi: 10.1007/s00018-012-1075-5. Epub 2012 Jul 17.
Cytonuclear signaling is essential for long-term alterations of cellular properties. Several pathways involving regulated nuclear accumulation of Ser/Thr kinases have been described but little is known about cytonuclear trafficking of tyrosine kinases. Proline-rich tyrosine kinase 2 (Pyk2) is a cytoplasmic non-receptor tyrosine kinase enriched in neurons and involved in functions ranging from synaptic plasticity to bone resorption, as well as in cancer. We previously showed the Ca(2+)-induced, calcineurin-dependent, nuclear localization of Pyk2. Here, we characterize the molecular mechanisms of Pyk2 cytonuclear localization in transfected PC12 cells. The 700-841 linker region of Pyk2 recapitulates its depolarization-induced nuclear accumulation. This region includes a nuclear export motif regulated by phosphorylation at residue S778, a substrate of cAMP-dependent protein kinase and calcineurin. Nuclear import is controlled by a previously identified sequence in the N-terminal domain and by a novel nuclear targeting signal in the linker region. Regulation of cytonuclear trafficking is independent of Pyk2 activity. The region regulating nuclear localization is absent from the non-neuronal shorter splice isoform of Pyk2. Our results elucidate the mechanisms of Ca(2+)-induced nuclear accumulation of Pyk2. They also suggest that Pyk2 nuclear accumulation is a novel type of signaling response that may contribute to specific long-term adaptations in neurons.
细胞质-核信号对于细胞特性的长期改变是必不可少的。已经描述了几种涉及 Ser/Thr 激酶的调节性核积累的途径，但对于酪氨酸激酶的细胞质-核转运知之甚少。富含脯氨酸的酪氨酸激酶 2（Pyk2）是一种细胞质非受体酪氨酸激酶，在神经元中丰富，参与从突触可塑性到骨吸收以及癌症等功能。我们之前显示了 Pyk2 的 Ca(2+)-诱导、钙调神经磷酸酶依赖性核定位。在这里，我们描述了 Pyk2 在转染的 PC12 细胞中细胞质-核定位的分子机制。Pyk2 的 700-841 接头区域再现了其去极化诱导的核积累。该区域包含一个受 S778 残基磷酸化调节的核输出基序，是 cAMP 依赖性蛋白激酶和钙调神经磷酸酶的底物。核输入由 N 端结构域中先前鉴定的序列和接头区域中的新核靶向信号控制。细胞质-核转运的调节与 Pyk2 的活性无关。非神经元较短剪接异构体的 Pyk2 中不存在调节核定位的区域。我们的结果阐明了 Pyk2 钙诱导核积累的机制。它们还表明，Pyk2 核积累是一种新型的信号反应，可能有助于神经元的特定长期适应。
