Calcineurin inhibits Na+/Ca2+ exchange in phenylephrine-treated hypertrophic cardiomyocytes
Calcineurin inhibits Na+/Ca2+ exchange in phenylephrine-treated hypertrophic cardiomyocytes
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DOI：
10.1074/jbc.m410240200
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发表时间：
2005-02-18
影响因子：
4.8
通讯作者：
Shigekawa, M
中科院分区：
文献类型：
--
作者：
Katanosaka, Y;Iwata, Y;Shigekawa, M
心肌Na+/Ca 2+交换器（NCX 1）是搏动心肌细胞Ca 2+排出的主要机制。蛋白磷酸化在正常和病变心脏中调节NCX 1功能的作用尚不清楚。在我们使用酵母双杂交筛选与NCX 1相互作用的蛋白质的搜索中，我们发现钙调磷酸酶Abeta的C末端，含有自抑制结构域，结合到NCX 1的中央胞质环的β 1重复序列，推测其构成了别构Ca 2+调控位点的一部分。与正常对照相比，在BI014.6心肌病仓鼠心脏中NCX 1与钙调神经磷酸酶的关联显著增加。在肥大的新生大鼠心肌细胞中，我们观察到慢性苯肾上腺素处理对NCX活性的显著抑制，测量为Na+ i依赖性Ca-45（2+）摄取速率或Na+ o依赖性Ca-45（2+）流出速率。抑制的NCX活性被钙调神经磷酸酶和蛋白激酶C活性的急性抑制部分和独立逆转，对肌细胞肥大表型的影响很小。在CCL 39细胞中表达的NCX 1缺失突变体的研究与β 1.重复是内源性钙调磷酸酶的作用所必需的，并且可能需要大的细胞质环来维持酶与其底物的相互作用。我们的数据表明，NCX 1是一种新的钙调神经磷酸酶的调节靶点，抑制NCX活性可能有助于在钙调神经磷酸酶和蛋白激酶C慢性激活的条件下发生的体内心脏肥大和功能障碍的病因。
The cardiac Na+/Ca2+ exchanger (NCX1) is the predominant mechanism for the extrusion of Ca2+ from beating cardiomyocytes. The role of protein phosphorylation in the regulation of NCX1 function in normal and diseased hearts remains unclear. In our search for proteins that interact with NCX1 using a yeast two-hybrid screen, we found that the C terminus of calcineurin Abeta, containing the autoinhibitory domain, binds to the beta1 repeat of the central cytoplasmic loop of NCX1 that presumably constitutes part of the allosterie Ca2+ regulatory site. The association of NCX1 with calcineurin was significantly increased in the BI014.6 cardiomyopathic hamster heart compared with that in the normal control. In hypertrophic neonatal rat cardiomyocytes subjected to chronic phenylephrine treatment, we observed a marked depression of NCX activity measured as the rate of Na+ i-dependent Ca-45(2+) uptake or the rate of Na+ o-dependent Ca-45(2+) efflux. Depressed NCX activity was partially and independently reversed by the acute inhibition of calcineurin and protein kinase C activities with little effect on myocyte hypertrophic phenotypes. Studies of NCX1 deletion mutants expressed in CCL39 cells were consistent with the view that the beta1. repeat is required for the action of endogenous calcineurin and that the large cytoplasmic loop may be required to maintain the interaction of the enzyme with its substrate. Our data suggest that NCX1 is a novel regulatory target for calcineurin and that depressed NCX activity might contribute to the etiology of in vivo cardiac hypertrophy and dysfunction occurring under conditions in which both calcineurin and protein kinase C are chronically activated.