The Active Zone Protein Family ELKS Supports Ca2+ Influx at Nerve Terminals of Inhibitory Hippocampal Neurons
The Active Zone Protein Family ELKS Supports Ca2+ Influx at Nerve Terminals of Inhibitory Hippocampal Neurons
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DOI：
10.1523/jneurosci.0999-14.2014
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发表时间：
2014-09-10
影响因子：
5.3
通讯作者：
Kaeser, Pascal S.
中科院分区：
文献类型：
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作者：
Liu, Changliang;Bickford, Lydia S.;Kaeser, Pascal S.
在突触前神经末梢，突触囊泡的胞吐作用仅限于称为活动区的特定部位。在这些部位，神经递质的释放取决于可释放囊泡的数量及其释放的可能性。活动区的蛋白质通过控制突触前Ca 2+信号以及突触囊泡的对接和启动来设置这些参数。脊椎动物ELKS蛋白在突触前活动区富集，但其功能尚不清楚。在脊椎动物中，ELKS蛋白由两个基因产生，每个基因占大脑ELKS总量的50%左右。我们产生了ELKS 1基因敲除小鼠，发现其组成性去除导致致死性。为了绕过致死性，并规避冗余之间的ELKS 1和ELKS 2在突触传递，我们使用了条件遗传学的方法来删除这两个基因在培养的海马神经元突触建立后。同时去除ELKS 1和ELKS 2导致抑制性突触的神经递质释放减少50%，释放概率降低。去除ELKS不影响突触数量或其电子显微镜外观。使用Ca 2+成像，我们发现ELKS的损失导致单一动作电位触发的抑制性神经末梢中的Ca 2+内流减少30%，这与突触传递和释放概率的缺陷一致。不像删除的活动区蛋白RIM，RIM-BP，或bruchpilot，ELKS去除并没有导致突触前钙离子通道水平的可测量的减少。我们的研究结果表明，ELKS是所需的抑制性海马神经元的神经末梢的正常Ca 2+内流。
In a presynaptic nerve terminal, synaptic vesicle exocytosis is restricted to specialized sites called active zones. At these sites, neurotransmitter release is determined by the number of releasable vesicles and their probability of release. Proteins at the active zone set these parameters by controlling the presynaptic Ca2+ signal, and through docking and priming of synaptic vesicles. Vertebrate ELKS proteins are enriched at presynaptic active zones, but their functions are not well understood. ELKS proteins are produced by two genes in vertebrates, and each gene contributes similar to 50% to total brain ELKS. We generated knock-out mice for ELKS1 and found that its constitutive removal causes lethality. To bypass lethality, and to circumvent redundancy between ELKS1 and ELKS2 in synaptic transmission, we used a conditional genetic approach to remove both genes in cultured hippocampal neurons after synapses are established. Simultaneous removal of ELKS1 and ELKS2 resulted in a 50% decrease of neurotransmitter release at inhibitory synapses, paralleled by a reduction in release probability. Removal of ELKS did not affect synapse numbers or their electron microscopic appearance. Using Ca2+ imaging, we found that loss of ELKS caused a 30% reduction in single action potential-triggered Ca2+ influx in inhibitory nerve terminals, consistent with the deficits in synaptic transmission and release probability. Unlike deletion of the active zone proteins RIM, RIM-BP, or bruchpilot, ELKS removal did not lead to a measurable reduction in presynaptic Ca2+ channel levels. Our results reveal that ELKS is required for normal Ca2+ influx at nerve terminals of inhibitory hippocampal neurons.