Research Group Molecular Mechanisms of Synaptic Function, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA; Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou 646000, China.
Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242, USA.
Cell Rep. 2018 Jul 10;24(2):284-293.e6. doi: 10.1016/j.celrep.2018.06.024.
In the presynaptic terminal, the magnitude and location of Ca entry through voltage-gated Ca channels (VGCCs) regulate the efficacy of neurotransmitter release. However, how presynaptic active zone proteins control mammalian VGCC levels and organization is unclear. To address this, we deleted the CAST/ELKS protein family at the calyx of Held, a Ca2.1 channel-exclusive presynaptic terminal. We found that loss of CAST/ELKS reduces the Ca2.1 current density with concomitant reductions in Ca2.1 channel numbers and clusters. Surprisingly, deletion of CAST/ELKS increases release probability while decreasing the readily releasable pool, with no change in active zone ultrastructure. In addition, Ca channel coupling is unchanged, but spontaneous release rates are elevated. Thus, our data identify distinct roles for CAST/ELKS as positive regulators of Ca2.1 channel density and suggest that they regulate release probability through a post-priming step that controls synaptic vesicle fusogenicity.
在突触前末梢，通过电压门控钙通道 (VGCC) 的 Ca 内流幅度和位置调节神经递质释放的效率。然而，突触前活性区蛋白如何控制哺乳动物 VGCC 的水平和组织尚不清楚。为了解决这个问题，我们在钙通道-递质释放偶联的专属突触前末梢——膨大终扣处敲除了 CAST/ELKS 蛋白家族。我们发现 CAST/ELKS 的缺失降低了 Ca2.1 电流密度，同时减少了 Ca2.1 通道数量和簇。令人惊讶的是，CAST/ELKS 的缺失增加了释放概率，同时减少了易释放池，而活性区超微结构没有变化。此外，钙通道偶联没有改变，但自发释放速率升高。因此，我们的数据确定了 CAST/ELKS 作为 Ca2.1 通道密度的正调节剂的独特作用，并表明它们通过控制突触囊泡融合性的引发后步骤来调节释放概率。
