The two Isoforms of the Na+/Ca2+ exchanger, NCX1 and NCX3, constitute novel additional targets for the prosurvival action of Akt/protein kinase B pathway
The two Isoforms of the Na+/Ca2+ exchanger, NCX1 and NCX3, constitute novel additional targets for the prosurvival action of Akt/protein kinase B pathway
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DOI：
10.1124/mol.107.042549
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发表时间：
2008-03-01
影响因子：
3.6
通讯作者：
Annunziato, Lucio
中科院分区：
文献类型：
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作者：
Formisano, Luigi;Saggese, Mariangela;Annunziato, Lucio
在神经元质膜上表达的蛋白质NCX 1、NCX 2和NCX 3在离子调节中起关键作用，因为它们是促进Na+和Ca 2+离子流出和流入的主要双向系统。在这里，我们证明了NCX 1和NCX 3蛋白是磷脂酰肌醇3-激酶（PI 3-K）/Akt通路的存活作用的新的额外靶点。事实上，四环素（泰特）-Off PC-12阳性突变体中组成型活性Akt 1的强力霉素依赖性过表达以及Tet-Off PC-12野生型暴露于神经生长因子诱导了NCX 1和NCX 3蛋白的上调。Akt 1激活诱导的NCX 1表达上调发生在转录水平，这是因为NCX 1 mRNA的表达增加，并且通过小干扰RNA策略抑制cAMP反应元件结合蛋白1（cAMP response element-binding protein 1，cAMP R1）的表达而抵消了这一上调。相比之下，Akt 1诱导的NCX 3上调认识到在蛋白酶体水平发生的转录后机制，因为1）NCX 3转录物没有增加，2）蛋白酶体抑制剂N-苄氧羰基（Z）-Leu-Leu-亮氨酸（MG-132）没有进一步增强Akt 1活性突变体中的NCX 3蛋白水平，这是预期的，如果泛素-蛋白酶体复合物没有被Akt 1途径阻断的话。正如预期的那样，在PC-12 Tet-Off野生型细胞中，MG-132增强了NCX 3蛋白水平。这种上调产生了NCX功能活性的增加。此外，NCX 1和NCX 3的上调有助于Akt 1在化学缺氧过程中的存活作用，因为NCX 1或NCX 3的沉默和NCX亚型的药理学泛抑制都降低了Akt 1的促存活特性。总之，这些结果表明，NCX 1和NCX 3代表了PI 3-K/Akt通路的促存活作用的新的额外分子靶标。
The proteins NCX1, NCX2, and NCX3 expressed on the plasma membrane of neurons play a crucial role in ionic regulation because they are the major bidirectional system promoting the efflux and influx of Na+ and Ca2+ ions. Here, we demonstrate that NCX1 and NCX3 proteins are novel additional targets for the survival action of the phosphatidylinositol 3-kinase (PI3-K)/Akt pathway. Indeed, the doxycycline-dependent overexpression of constitutively active Akt1 in tetracycline (Tet)-Off PC-12 positive mutants and the exposure of Tet-Off PC-12 wild type to nerve growth factor induced an up-regulation of NCX1 and NCX3 proteins. NCX1 up-regulation induced by Akt1 activation occurred at the transcriptional level because NCX1 mRNA increased, and it was counteracted by cAMP response element-binding protein 1 inhibition through small interfering RNA strategy. In contrast, Akt1-induced NCX3 up-regulation recognized a post-transcriptional mechanism occurring at the proteasome level because 1) NCX3 transcript did not increase and 2) the proteasome inhibitor N-benzyloxycarbonyl (Z)-Leu-Leu-leucinal (MG-132) did not further enhance NCX3 protein levels in Akt1 active mutants as it would be expected if the ubiquitin-proteasome complex was not already blocked by Akt1 pathway. As expected, in PC-12 Tet-Off wild-type cells MG-132 enhanced NCX3 protein levels. This up-regulation produced an increased activity of NCX function. Furthermore, NCX1 and NCX3 up-regulation contributed to the survival action of Akt1 during chemical hypoxia because both the silencing of NCX1 or NCX3 and the pharmacological paninhibition of NCX isoforms reduced the prosurvival property of Akt1. Together, these results indicated that NCX1 and NCX3 represent novel additional molecular targets for the prosurvival action of PI3-K/Akt pathway.