Graded Ca²⁺/calmodulin-dependent coupling of voltage-gated CaV1.2 channels.
Graded Ca²⁺/calmodulin-dependent coupling of voltage-gated CaV1.2 channels.
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DOI：
10.7554/elife.05608
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发表时间：
2015-02-25
期刊：
影响因子：
7.7
通讯作者：
Santana LF
中科院分区：
文献类型：
--
作者：
Dixon RE;Moreno CM;Yuan C;Opitz-Araya X;Binder MD;Navedo MF;Santana LF
在心脏中，在心室动作电位的平台期间，可靠地激活从肌浆网释放的Ca 2+需要同步打开多个CaV1.2通道。然而，在每次心跳期间协调这种同时开放的机制尚不清楚。在这里，我们证明了CaV1.2通道形成集群，进行动态的，相互的，变构的相互作用。这种“功能性偶联”通过增加相邻通道的激活促进Ca 2+内流，并通过C-末端至C-末端相互作用发生。这些相互作用是由进入的Ca 2+与钙调蛋白（CaM）结合引发的，并通过Ca 2 +/CaM与CaV1.2前IQ结构域结合进行。耦合随着[Ca 2 +]i的降低而减弱，但比诱发它的电流持续时间更长，为“分子记忆”提供了证据。我们的研究结果提出了CaV1.2通道门控和Ca 2+内流放大的模型，该模型统一了关于心脏中Ca 2+信号传导的不同观察结果，并挑战了长期以来认为电压门控通道独立打开和关闭的观点。http://dx.doi.org/10.7554/eLife.05608.001为了将血液泵送到全身，心脏内的肌肉细胞必须以有规律的节奏收缩和放松。当嵌入心脏细胞膜中的CaV1.2通道蛋白打开，允许钙离子进入细胞时，收缩开始。通过这些CaV1.2通道进入的钙离子触发细胞内储存室的钙离子释放，导致心脏收缩。然而，为了触发钙离子的释放，许多CaV1.2通道必须同时打开，我们还不知道这是如何协调的。狄克逊等人研究了小鼠心肌细胞中的CaV 1.2通道。实验表明，这些蛋白质在细胞膜上平均排列成8个簇。当钙离子进入细胞时，它们与一种称为钙调蛋白的蛋白质结合，钙调蛋白又与CaV1.2通道结合。这允许簇内的CaV1.2通道彼此交互。簇内CaV1.2通道之间的物理关联使它们能够协同工作;它们同时打开以允许更多的钙离子进入，然后关闭以允许细胞放松。狄克逊等人发现，即使当细胞中的钙离子水平下降时，簇内的CaV 1.2通道在关闭之前仍保持打开一段时间。这表明CaV1.2通道之间的相互作用作为一种“分子记忆”，可能会改变细胞对未来活动的反应。这些结果挑战了先前持有的观点，即CaV1.2通道彼此独立地打开和关闭。未来的研究将试图了解这些通道如何聚集在一起的分子细节，以及这种聚集如何影响心率和心脏异常（如长QT综合征）的变化。DOI：http://dx.doi.org/10.7554/eLife.05608.002网站
In the heart, reliable activation of Ca2+ release from the sarcoplasmic reticulum during the plateau of the ventricular action potential requires synchronous opening of multiple CaV1.2 channels. Yet the mechanisms that coordinate this simultaneous opening during every heartbeat are unclear. Here, we demonstrate that CaV1.2 channels form clusters that undergo dynamic, reciprocal, allosteric interactions. This ‘functional coupling’ facilitates Ca2+ influx by increasing activation of adjoined channels and occurs through C-terminal-to-C-terminal interactions. These interactions are initiated by binding of incoming Ca2+ to calmodulin (CaM) and proceed through Ca2+/CaM binding to the CaV1.2 pre-IQ domain. Coupling fades as [Ca2+]i decreases, but persists longer than the current that evoked it, providing evidence for ‘molecular memory’. Our findings suggest a model for CaV1.2 channel gating and Ca2+-influx amplification that unifies diverse observations about Ca2+ signaling in the heart, and challenges the long-held view that voltage-gated channels open and close independently. DOI: http://dx.doi.org/10.7554/eLife.05608.001 To pump blood around the body, the muscle cells within the heart must contract and relax together with a regular rhythm. A contraction begins when proteins called CaV1.2 channels embedded in the cell membranes of heart cells open to allow calcium ions to enter the cells. The calcium ions that enter through these CaV1.2 channels trigger the release of calcium ions from storage compartments within the cells, which leads to the heart contracting. However, to trigger this release of calcium ions, many CaV1.2 channels have to open at the same time and we do not yet know how this is co-ordinated. Dixon et al. studied CaV1.2 channels in heart muscle cells from mice. The experiments show that these proteins are arranged in clusters of eight, on average, in the cell membrane. When calcium ions enter the cell they bind to a protein called calmodulin, which in turn binds to a CaV1.2 channel. This allows the CaV1.2 channels within a cluster to interact with each other. The physical association between CaV1.2 channels within clusters enables them to work cooperatively; they open at the same time to allow more calcium ions to enter and then close together to allow the cell to relax. Dixon et al. found that even when levels of calcium ions in the cells declined, the CaV1.2 channels within clusters remained open for a little while longer before they closed. This suggests that the interactions between the CaV1.2 channels act as a type of ‘molecular memory’ that may alter how the cells respond to future activity. These results challenge the previously held view that the CaV1.2 channels open and close independently of one another. Future studies will seek to understand the molecular details of how these channels cluster together, and how this clustering affects changes in heart rate and heart abnormalities like long QT syndrome. DOI: http://dx.doi.org/10.7554/eLife.05608.002