Department of Physiology, Anatomy and Genetics; University of Oxford; Oxford, UK.
Channels (Austin). 2013 Sep-Oct;7(5):374-8. doi: 10.4161/chan.25298. Epub 2013 Jun 13.
Cytoplasmic Ca(2+) is an universal intracellular messenger that activates cellular responses over a broad temporal range, from neurotransmitter release to cell growth and proliferation. Inherent to the use of the multifarious Ca(2+) signal is the question of specificity: how can some Ca(2+)-dependent responses be activated in a cell and not others? A rise in cytoplasmic Ca(2+) can evoke a response either by binding directly to the target (as occurs with certain Ca(2+)-activated K(+) and Cl(-) channels, for example) or through recruitment of intermediary proteins, such as calmodulin and troponin C. A substantial body of evidence has now established that Ca(2+)-binding proteins differ both in their affinities for Ca(2+) and in their on- and off-rates for Ca(2+) binding/unbinding. Furthermore, different Ca(2+)-binding proteins often occupy distinct locations within the cell. Therefore, the size, kinetics and spatial profile of a cytoplasmic Ca(2+) signal are all important in determining which Ca(2+)-dependent response will be activated, when and for how long.
细胞质 Ca(2+) 是一种普遍的细胞内信使，可在广泛的时间范围内激活细胞反应，从神经递质释放到细胞生长和增殖。由于 Ca(2+) 信号的多样性，就产生了一个问题：如何在细胞中激活某些 Ca(2+) 依赖性反应而不激活其他反应？细胞质 Ca(2+) 的增加可以通过直接与靶标结合（例如，某些 Ca(2+) 激活的 K(+) 和 Cl(-) 通道就是如此）或通过募集中介蛋白（如钙调蛋白和肌钙蛋白 C）来引发反应。大量证据表明，Ca(2+) 结合蛋白在 Ca(2+) 亲和力和 Ca(2+) 结合/解吸的 ON 和 OFF 速率方面存在差异。此外，不同的 Ca(2+) 结合蛋白通常在细胞内占据不同的位置。因此，细胞质 Ca(2+) 信号的大小、动力学和空间分布对于确定将激活哪种 Ca(2+) 依赖性反应、何时以及持续多长时间都非常重要。
