Tuning Local Calcium Availability: Cell-Type-Specific Immobile Calcium Buffer Capacity in Hippocampal Neurons
Tuning Local Calcium Availability: Cell-Type-Specific Immobile Calcium Buffer Capacity in Hippocampal Neurons
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DOI：
10.1523/jneurosci.4118-12.2013
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发表时间：
2013-09-04
影响因子：
5.3
通讯作者：
Dietrich, Dirk
中科院分区：
文献类型：
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作者：
Matthews, Elizabeth A.;Schoch, Susanne;Dietrich, Dirk
它仍然很难归因于一个特定的功能作用，以固定或固定的细胞内钙缓冲中枢神经元，因为这些缓冲的量是未知的。在这里，我们明确地分离固定缓冲液馏分延长全细胞膜片钳透析和量化其缓冲能力在小鼠海马切片使用共聚焦钙成像和“添加缓冲液”的方法。在齿状颗粒细胞中，钙结合蛋白D-28 k（Cb）完全洗脱后的钙结合率（kappa），kappa（固定）显示出类似于100的实质性值。相比之下，在CA 1 oriens lacunosum moleculare（OLM）中间神经元中，不含任何已知的钙结合蛋白，kappa（固定）仅相当于30。基于这些值，局部进入后钙的树突状扩散的理论分析表明，固定的缓冲液，在没有移动的物种，降低细胞内钙流动性100-和30倍，分别在颗粒细胞和OLM细胞，从而大大减缓钙信号。尽管大κ（固定的）单独强烈延迟颗粒细胞中钙的扩散，但该值优化了额外表达移动的钙结合蛋白Cb的益处。在如此高的kappa值（固定）下，Cb有效地将传播速度增加到OLM细胞中所见的水平，并且与预期相反，不影响接近源的峰值钙浓度，但使空间和时间钙梯度变陡。这些数据表明，固定缓冲液的量决定了钙结合伴侣的钙的时间可用性，并在设定细胞钙信号方案的库中起着关键作用。
It has remained difficult to ascribe a specific functional role to immobile or fixed intracellular calcium buffers in central neurons because the amount of these buffers is unknown. Here, we explicitly isolated the fixed buffer fraction by prolonged whole-cell patch-clamp dialysis and quantified its buffering capacity in murine hippocampal slices using confocal calcium imaging and the "added-buffer" approach. In dentate granule cells, the calcium binding ratio (kappa) after complete washout of calbindin D-28k (Cb), kappa(fixed), displayed a substantial value of similar to 100. In contrast, in CA1 oriens lacunosum moleculare (OLM) interneurons, which do not contain any known calcium-binding protein(s), kappa(fixed) amounted to only similar to 30. Based on these values, a theoretical analysis of dendritic spread of calcium after local entry showed that fixed buffers, in the absence of mobile species, decrease intracellular calcium mobility 100- and 30-fold in granule cells and OLM cells, respectively, and thereby strongly slow calcium signals. Although the large kappa(fixed) alone strongly delays the spread of calcium in granule cells, this value optimizes the benefits of additionally expressing the mobile calcium binding protein Cb. With such high kappa(fixed), Cb effectively increases the propagation velocity to levels seen in OLM cells and, contrary to expectation, does not affect the peak calcium concentration close to the source but sharpens the spatial and temporal calcium gradients. The data suggest that the amount of fixed buffers determines the temporal availability of calcium for calcium-binding partners and plays a pivotal role in setting the repertoire of cellular calcium signaling regimens.