Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, California 94304-5543, USA.
J Neurosci. 2010 Mar 17;30(11):4132-42. doi: 10.1523/JNEUROSCI.3129-09.2010.
Calmodulin regulates multifarious cellular processes via a panoply of target interactions. However, the central role, multiple isoforms, and complex target interactions of calmodulin make it difficult to examine its precise functions. Here, we analyzed calmodulin function in neurons using lentivirally delivered short-hairpin RNAs that suppressed expression of all calmodulin isoforms by approximately 70%. Calmodulin knockdown did not significantly alter neuronal survival or synapse formation but depressed spontaneous neuronal network activity. Strikingly, calmodulin knockdown decreased the presynaptic release probability almost twofold, without altering the presynaptic readily-releasable vesicle pool or postsynaptic neurotransmitter reception. In calmodulin knockdown neurons, presynaptic release was restored to wild-type levels by expression of constitutively active calmodulin-dependent kinase-IIalpha (CaMKIIalpha); in contrast, in control neurons, expression of constitutively active CaMKIIalpha had no effect on presynaptic release. Viewed together, these data suggest that calmodulin performs a major function in boosting synaptic strength via direct activation of presynaptic calmodulin-dependent kinase II.
钙调蛋白通过多种靶标相互作用调节多种细胞过程。然而，钙调蛋白的核心作用、多种同工型和复杂的靶标相互作用使其难以精确研究其功能。在这里，我们使用慢病毒传递的短发夹 RNA 分析了神经元中的钙调蛋白功能，该短发夹 RNA 可使所有钙调蛋白同工型的表达降低约 70%。钙调蛋白敲低不会显著改变神经元的存活或突触形成，但会抑制自发性神经元网络活动。引人注目的是，钙调蛋白敲低使突触前释放概率降低近两倍，而不改变突触前易释放囊泡池或突触后神经递质接收。在钙调蛋白敲低神经元中，表达组成型激活的钙调蛋白依赖性激酶 IIalpha（CaMKIIalpha）可将突触前释放恢复至野生型水平；相比之下，在对照神经元中，表达组成型激活的 CaMKIIalpha 对突触前释放没有影响。综合来看，这些数据表明钙调蛋白通过直接激活突触前钙调蛋白依赖性激酶 II 来增强突触强度发挥主要功能。
