RC3/neurogranin and Ca2+/calmodulin-dependent protein kinase II produce opposing effects on the affinity of calmodulin for calcium
RC3/neurogranin and Ca2+/calmodulin-dependent protein kinase II produce opposing effects on the affinity of calmodulin for calcium
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DOI：
10.1074/jbc.m405352200
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发表时间：
2004-09-17
影响因子：
4.8
通讯作者：
Waxham, MN
中科院分区：
文献类型：
--
作者：
Gaertner, TR;Putkey, JA;Waxham, MN
已知钙调蛋白与其靶蛋白的相互作用会影响钙离子与钙调蛋白结合的动力学和亲和力。根据热力学原理，与钙离子-钙调蛋白结合的蛋白质应该增加钙调素对钙的亲和力，而与脱脂蛋白结合的蛋白质应该降低对钙的亲和力。我们量化了两个神经元钙调蛋白靶标RC3和αCaM激酶II对钙-钙调蛋白相互作用的影响，RC3既能结合钙离子，又能结合脱辅基-钙调蛋白，而α-CaM激酶II能选择性地结合钙-钙调蛋白。RC3降低了钙调蛋白对钙离子的亲和力，而CaM激酶II则增加了钙调蛋白对钙离子的亲和力。具体地说，RC3使钙调蛋白C末端的钙解离速率提高了60倍，而对钙结合速率几乎没有影响。相反，CaM激酶II降低了钙调蛋白两叶钙离子的解离速率，而在Thr(286)处，CaM激酶II的自动磷酸化导致了钙解离速率的进一步降低。RC3通过增加钙调蛋白C-端叶的解离速率来抑制CaM-K II对钙离子解离的影响。这种作用在磷酸化的CaM-KK II中看不到。这一结果是根据一个动力学方案解释的，在该动力学方案中，存在着竞争的钙-钙调蛋白复合体的解离途径。这项工作表明，钙调蛋白的钙结合特性受到高度调控，并揭示了RC3在钙信号结束时加速钙-钙调蛋白靶标复合体解离的作用。
The interaction of calmodulin with its target proteins is known to affect the kinetics and affinity of Ca2+ binding to calmodulin. Based on thermodynamic principles, proteins that bind to Ca2+-calmodulin should increase the affinity of calmodulin for Ca2+, while proteins that bind to apo-calmodulin should decrease its affinity for Ca2+. We quantified the effects on Ca2+-calmodulin interaction of two neuronal calmodulin targets: RC3, which binds both Ca2+- and apo-calmodulin, and alphaCaM kinase II, which binds selectively to Ca2+-calmodulin. RC3 was found to decrease the affinity of calmodulin for Ca2+, whereas CaM kinase II increases the calmodulin affinity for Ca2+. Specifically, RC3 increases the rate of Ca2+ dissociation from the C-terminal sites of calmodulin up to 60-fold while having little effect on the rate of Ca2+ association. Conversely, CaM kinase II decreases the rates of dissociation of Ca2+ from both lobes of calmodulin and autophosphorylation of CaM kinase II at Thr(286) induces a further decrease in the rates of Ca2+ dissociation. RC3 dampens the effects of CaM kinase II on Ca2+ dissociation by increasing the rate of dissociation from the C-terminal lobe of calmodulin when in the presence of CaM kinase II. This effect is not seen with phosphorylated CaM kinase II. The results are interpreted according to a kinetic scheme in which there are competing pathways for dissociation of the Ca2+-calmodulin target complex. This work indicates that the Ca2+ binding properties of calmodulin are highly regulated and reveals a role for RC3 in accelerating the dissociation of Ca2+-calmodulin target complexes at the end of a Ca2+ signal.