Calcium/Calmodulin-Dependent Protein Kinase Is Negatively and Positively Regulated by Calcium, Providing a Mechanism for Decoding Calcium Responses during Symbiosis Signaling
Calcium/Calmodulin-Dependent Protein Kinase Is Negatively and Positively Regulated by Calcium, Providing a Mechanism for Decoding Calcium Responses during Symbiosis Signaling
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DOI：
10.1105/tpc.113.116921
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发表时间：
2013-12-01
期刊：
影响因子：
11.6
通讯作者：
Oldroyd, Giles E. D.
中科院分区：
文献类型：
--
作者：
Miller, J. Benjamin;Pratap, Amitesh;Oldroyd, Giles E. D.
植物共生关系的建立需要钙离子振荡，而钙离子振荡必须被解码，才能启动下游的发育程序。在动物系统中，类似的钙振荡是由钙调素（CaM）依赖性蛋白激酶解码的，但共生信号涉及植物特有的钙/CaM依赖性蛋白激酶（CCaMK）。CCaMK与动物CaM激酶的不同之处在于它的双重能力，即通过蛋白质上的钙结合EF-hand结构域结合游离钙，或通过CaM结合结构域结合钙与CaM络合。在本研究中，我们剖析了钙对CCaMK的双重调控。我们发现，与EF-hand结构域结合的钙促进了自磷酸化，这通过稳定蛋白质的失活状态来负向调节CCaMK。相比之下，钙依赖性的CaM结合覆盖了自磷酸化的影响并激活了蛋白质。EF-hand结构域与CaM的钙结合亲和性差异表明，CCaMK在基础钙浓度下保持无活性状态，并在钙振荡期间通过CaM结合被激活。这项工作提供了一个解码钙振荡的模型，该模型使用不同的钙结合亲和力来创建一个强大的分子开关，该开关对与基态和振荡相关的钙浓度都有响应。
The establishment of symbiotic associations in plants requires calcium oscillations that must be decoded to invoke downstream developmental programs. In animal systems, comparable calcium oscillations are decoded by calmodulin (CaM)-dependent protein kinases, but symbiotic signaling involves a calcium/CaM-dependent protein kinase (CCaMK) that is unique to plants. CCaMK differs from the animal CaM kinases by its dual ability to bind free calcium, via calcium binding EF-hand domains on the protein, or to bind calcium complexed with CaM, via a CaM binding domain. In this study, we dissect this dual regulation of CCaMK by calcium. We find that calcium binding to the EF-hand domains promotes autophosphorylation, which negatively regulates CCaMK by stabilizing the inactive state of the protein. By contrast, calcium-dependent CaM binding overrides the effects of autophosphorylation and activates the protein. The differential calcium binding affinities of the EF-hand domains compared with those of CaM suggest that CCaMK is maintained in the inactive state at basal calcium concentrations and is activated via CaM binding during calcium oscillations. This work provides a model for decoding calcium oscillations that uses differential calcium binding affinities to create a robust molecular switch that is responsive to calcium concentrations associated with both the basal state and with oscillations.