Laboratory of Neurobiology, Bellvitge Biomedical Research Institute (IDIBELL), and Department of Pathology and Experimental Therapeutics, Faculty of Medicine, University of Barcelona, 08907 L'Hospitalet de Llobregat, Spain, and.
Division of Biomedical Cell Biology, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom
J Neurosci. 2014 Jun 18;34(25):8618-29. doi: 10.1523/JNEUROSCI.5081-13.2014.
To maintain communication, neurons must recycle their synaptic vesicles with high efficiency. This process places a huge burden on the clathrin-mediated endocytic machinery, but the consequences of this are poorly understood. We found that the amount of clathrin in a presynaptic terminal is not fixed. During stimulation, clathrin moves out of synapses as a function of stimulus strength and neurotransmitter release probability, which, together with membrane coat formation, transiently reduces the available pool of free clathrin triskelia. Correlative functional and morphological experiments in cholinergic autapses established by superior cervical ganglion neurons in culture show that presynaptic terminal function is compromised if clathrin levels fall by 20% after clathrin heavy chain knock down using RNAi. Synaptic transmission is depressed due to a reduction of cytoplasmic and readily releasable pools of vesicles. However, synaptic depression reverts after dialysis of exogenous clathrin, thus compensating RNAi-induced depletion. Lowering clathrin levels also reduces quantal size, which occurs concomitantly with a decrease in the size of synaptic vesicles. Large dense-core vesicles are unaffected by clathrin knock down. Together, our results show that clathrin levels are a dynamic property of presynaptic terminals that can influence short-term plasticity in a stimulus-dependent manner.
为了维持通讯，神经元必须高效地回收其突触小泡。这个过程给网格蛋白介导的胞吞作用机器带来了巨大的负担，但人们对其后果知之甚少。我们发现，突触前末梢中的网格蛋白数量不是固定的。在刺激过程中，网格蛋白会根据刺激强度和神经递质释放概率从突触中移出，这与膜衣形成一起，会暂时减少游离网格蛋白三聚体的可用池。通过培养的颈上交感神经节神经元建立的胆碱能自体突触的相关功能和形态学实验表明，如果在 RNAi 敲低网格蛋白重链后，网格蛋白水平下降 20%，则突触前末梢功能受损。由于细胞质和易于释放的囊泡池减少，突触传递被抑制。然而，在用外源性网格蛋白透析后，突触抑制会恢复，从而补偿 RNAi 诱导的耗竭。降低网格蛋白水平也会减小量子大小，这与突触小泡的减小同时发生。大致密核心囊泡不受网格蛋白敲低的影响。总之，我们的结果表明，网格蛋白水平是突触前末梢的一个动态特性，它可以以刺激依赖的方式影响短期可塑性。
