Department of Physiology and Medical Physics, Innsbruck Medical University, Innsbruck, Austria.
Neuroscience. 2010 May 19;167(3):786-98. doi: 10.1016/j.neuroscience.2010.02.037. Epub 2010 Feb 24.
The importance and diversity of calcium signaling in the brain is mirrored by the expression of a multitude of voltage-activated calcium channel (Ca(V)) isoforms. Whereas the overall distributions of alpha(1) subunits are well established, the expression patterns of distinct channel isoforms in specific brain regions and neurons, as well as those of the auxiliary beta and alpha(2)delta subunits are still incompletely characterized. Further it is unknown whether neuronal differentiation and activity induce changes of Ca(V) subunit composition. Here we combined absolute and relative quantitative TaqMan reverse transcription PCR (RT-PCR) to analyze mRNA expression of all high voltage-activated Ca(V) alpha(1) subunits and all beta and alpha(2)delta subunits. This allowed for the first time the direct comparison of complete Ca(V) expression profiles of mouse cortex, hippocampus, cerebellum, and cultured hippocampal neurons. All brain regions expressed characteristic profiles of the full set of isoforms, except Ca(V)1.1 and Ca(V)1.4. In cortex development was accompanied by a general down regulation of alpha(1) and alpha(2)delta subunits and a shift from beta(1)/beta(3) to beta(2)/beta(4). The most abundant Ca(V) isoforms in cerebellum were Ca(V)2.1, beta(4), and alpha(2)delta-2, and in hippocampus Ca(V)2.3, beta(2), and alpha(2)delta-1. Interestingly, cultured hippocampal neurons also expressed the same Ca(V) complement as adult hippocampus. During differentiation specific Ca(V) isoforms experienced up- or down-regulation; however blocking electrical activity did not affect Ca(V) expression patterns. Correlation analysis of alpha(1), beta and alpha(2)delta subunit expression throughout all examined preparations revealed a strong preference of Ca(V)2.1 for beta(4) and alpha(2)delta-2 and vice versa, whereas the other alpha(1) isoforms were non-selectively expressed together with each of the other beta and alpha(2)delta isoforms. Together our results revealed a remarkably stable overall Ca(2+) channel complement as well as tissue specific differences in expression levels. Developmental changes are likely determined by an intrinsic program and not regulated by changes in neuronal activity.
钙信号在大脑中的重要性和多样性反映在大量电压激活钙通道（Ca(V)）同工型的表达上。虽然α(1)亚基的总体分布已经确定，但特定脑区和神经元中不同通道同工型的表达模式，以及辅助β和α(2)δ亚基的表达模式仍不完全清楚。此外，尚不清楚神经元分化和活动是否会引起 Ca(V)亚基组成的变化。在这里，我们结合绝对和相对定量 TaqMan 逆转录 PCR（RT-PCR）分析了所有高电压激活 Ca(V)α(1)亚基和所有β和α(2)δ亚基的 mRNA 表达。这使得首次能够直接比较小鼠皮层、海马体、小脑和培养的海马神经元的完整 Ca(V)表达谱。除了 Ca(V)1.1 和 Ca(V)1.4 之外，所有脑区都表达了完整的同工型特征谱。在皮层发育过程中，α(1)和α(2)δ亚基普遍下调，β(1)/β(3)向β(2)/β(4)转变。小脑最丰富的 Ca(V)同工型是 Ca(V)2.1、β(4)和α(2)δ-2，而海马体中则是 Ca(V)2.3、β(2)和α(2)δ-1。有趣的是，培养的海马神经元也表达了与成年海马体相同的 Ca(V)补体。在分化过程中，特定的 Ca(V)同工型经历了上调或下调；然而，阻断电活动不会影响 Ca(V)表达模式。对所有检查制剂中α(1)、β和α(2)δ亚基表达的相关性分析表明，Ca(V)2.1 与β(4)和α(2)δ-2强烈偏好，反之亦然，而其他α(1)同工型则与其他β和α(2)δ同工型非选择性地表达在一起。总的来说，我们的结果揭示了一个非常稳定的整体 Ca(2+)通道补充，以及组织特异性的表达水平差异。发育变化可能由内在程序决定，而不是由神经元活动变化调节。
