Paxillin nuclear-cytoplasmic localization is regulated by phosphorylation of the LD4 motif: evidence that nuclear paxillin promotes cell proliferation
Paxillin nuclear-cytoplasmic localization is regulated by phosphorylation of the LD4 motif: evidence that nuclear paxillin promotes cell proliferation
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DOI：
10.1042/bj20080170
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发表时间：
2009-02-15
影响因子：
4.1
通讯作者：
Manser, Ed
中科院分区：
文献类型：
--
作者：
Dong, Jing-Ming;Lau, Lei-Shong;Manser, Ed
桩蛋白属于LIM结构域蛋白亚家族，是黏着斑复合物的主要成分，参与细胞黏附介导的信号转导。它与细胞表面受体活化后的细胞运动性反应有关，并且可以募集GIT 1 [GRK（G蛋白偶联受体激酶）相互作用ARF（ADP核糖基化因子）GAP（GTP酶活化蛋白）] PIX [PAK（p21活化激酶）相互作用交换因子] PAK 1复合物。一些粘附蛋白包括zyxin，Hic 5和Trip 6也是核的，并且可以发挥转录作用。在本研究中，我们表明，内源性桩蛋白穿梭于细胞质和细胞核之间，我们已经使用了各种标记桩蛋白构建映射的核输出信号。该区域与结合GIT 1和FAK 1（局灶性粘附激酶1）的重要LD 4基序重叠。我们提供的证据表明，LD 4内Ser（272）的磷酸化阻断了核输出，我们表明，这种修饰也减少了GIT 1，但不是FAK 1，结合;然而，Ser（272）磷酸化似乎并不像以前建议的那样由PAK 1介导。核定位桩蛋白LIM结构域的表达刺激DNA合成和细胞增殖。通过实时PCR分析，我们已经确定，无论是全长桩蛋白或截短的核形式的过表达抑制父母的印记基因H19的表达，和调制这个位点可能会影响NIH-3 T3细胞增殖的速度。
Paxillin, a major focal-adhesion complex component belongs to the subfamily of LIM domain proteins and participates in cell adhesion-mediated signal transduction. It is implicated in cell-motility responses upon activation of cell-surface receptors and can recruit, among others, the GIT1 [GRK (G-protein-coupled-receptor kinase)-interacting ARF (ADP-ribosylation factor) GAP (GTPase-activating protein)] PIX [PAK (p21-activated kinase)interacting exchange factor] PAK1 complex. Several adhesion proteins including zyxin, Hic5 and Trip6 are also nuclear and can exert transcriptional effects. In the present study we show that endogenous paxillin shuttles between the cytoplasm and nucleus, and we have used a variety of tagged paxillin constructs to map the nuclear export signal. This region overlaps an important LD4 motif that binds GIT1 and FAK1 (focal-adhesion kinase 1). We provide evidence that phosphorylation of Ser(272) within LD4 blocks nuclear export, and we show that this modification also reduces GIT1, but not FAK1, binding; however, Ser(272) phosphorylation does not appear to be mediated by PAK1 as previously suggested. Expression of nuclear-localized paxillin LIM domains stimulate DNA synthesis and cell proliferation. By real-time PCR analysis we have established that overexpression of either full-length paxillin or a truncated nuclear form suppresses expression of the parental imprinted gene H19, and modulation of this locus probably affects the rate of NIH-3T3 cell proliferation.