Schaad N C, De Castro E, Nef S, Hegi S, Hinrichsen R, Martone M E, Ellisman M H, Sikkink R, Rusnak F, Sygush J, Nef P
Department of Biochemistry, University of Geneva, Switzerland.
Proc Natl Acad Sci U S A. 1996 Aug 20;93(17):9253-8. doi: 10.1073/pnas.93.17.9253.
Ca2+ and its ubiquitous intracellular receptor calmodulin (CaM) are required in the nervous system, among a host of cellular responses, for the modulation of several important enzymes and ion channels involved in synaptic efficacy and neuronal plasticity. Here, we report that CaM can be replaced by the neuronal calcium sensor NCS-1 both in vitro and in vivo. NCS-1 is a calcium binding protein with two Ca(2+)-binding domains that shares only 21% of homology with CaM. We observe that NCS-1 directly activates two Ca2+/CaM-dependent enzymes (3':5'-cyclic nucleotide phosphodiesterase and protein phosphatase calcineurin). Co-activation of nitric oxide synthase by NCS-1 and CaM results in a higher activity than with CaM alone. Moreover, NCS-1 is coexpressed with calcineurin and nitric oxide synthase in several neuron populations. Finally, injections of NCS-1 into calmodulin-defective cam1 Paramecium partially restore wildtype behavioral responses. With this highly purified preparation of NCS-1, we have obtained crystals suitable for crystallographic structure studies. NCS-1, despite its very different structure, distribution, and Ca(2+)-binding affinity as compared with CaM, can substitute for or potentiate CaM functions. Therefore, NCS-1 represents a novel protein capable of mediating multiple Ca(2+)-signaling pathways in the nervous system.
在神经系统中，众多细胞反应都需要Ca2+及其普遍存在的细胞内受体钙调蛋白（CaM）来调节与突触效能和神经元可塑性相关的几种重要酶和离子通道。在此，我们报告在体外和体内，神经元钙传感器NCS-1都可以替代CaM。NCS-1是一种具有两个Ca(2+)结合结构域的钙结合蛋白，与CaM的同源性仅为21%。我们观察到NCS-1直接激活两种Ca2+/CaM依赖性酶（3':5'-环核苷酸磷酸二酯酶和蛋白磷酸酶钙调神经磷酸酶）。NCS-1和CaM共同激活一氧化氮合酶所产生的活性高于单独使用CaM时。此外，在几个神经元群体中，NCS-1与钙调神经磷酸酶和一氧化氮合酶共同表达。最后，将NCS-1注射到钙调蛋白缺陷的cam1草履虫中可部分恢复野生型行为反应。利用这种高度纯化的NCS-1制剂，我们获得了适合晶体学结构研究的晶体。尽管NCS-1与CaM相比，其结构、分布和Ca(2+)结合亲和力有很大不同，但它可以替代或增强CaM的功能。因此，NCS-1代表了一种能够介导神经系统中多种Ca(2+)信号通路的新型蛋白质。
