Integrated Program in Cellular, Molecular and Biomedical Studies, Columbia University Medical Center, New York, NY, USA.
Autophagy. 2012 Oct;8(10):1540-1. doi: 10.4161/auto.21330. Epub 2012 Jul 6.
The mechanistic target of rapamycin (MTOR) has been implicated in regulating synaptic plasticity and neurodegeneration, but MTOR's role in modulating presynaptic function through autophagy is unexplored. We studied presynaptic function in ventral dopamine neurons, a system from which neurotransmitter release can be measured directly by cyclic voltammetry. We generated mutant mice that were specifically deficient for macroautophagy in dopaminergic neurons by deleting the Atg7 gene in cells that express the dopamine uptake transporter. Dopamine axonal profiles in the mutant dorsal striatum were ~one third larger in the mutant mice, released ~50% more stimulus-evoked dopamine release, and exhibited more rapid presynaptic recovery than controls. Rapamycin reduced dopamine neuron axon profile size by ~30% in control mice, but had no effect on macroautophagy deficient axons. Acute rapamycin decreased dopaminergic synaptic vesicle density by ~25% and inhibited evoked dopamine release by ~25% in control mice, but not in the Atg7 deficient mutants. Thus, both basal and induced macroautophagy can provide a brake on presynaptic activity in vivo, perhaps by regulating the turnover of synaptic vesicles, and further regulates terminal volume and the kinetics of transmitter release.
雷帕霉素的作用靶点（mTOR）已被证实参与调节突触可塑性和神经退行性变，但 mTOR 通过自噬调节突触前功能的作用尚未得到探索。我们研究了腹侧多巴胺神经元的突触前功能，这是一个可以通过循环伏安法直接测量神经递质释放的系统。我们通过在表达多巴胺摄取转运体的细胞中敲除 Atg7 基因，生成了多巴胺能神经元中巨自噬特异性缺失的突变小鼠。与对照组相比，突变小鼠的突变背侧纹状体中的多巴胺轴突形态大约大三分之一，刺激诱发的多巴胺释放增加约 50%，并且表现出更快的突触前恢复。雷帕霉素使对照组中小鼠的多巴胺神经元轴突形态缩小了约 30%，但对巨自噬缺失的轴突没有影响。急性雷帕霉素使对照组中小鼠的多巴胺囊泡密度降低约 25%，并抑制约 25%的诱发多巴胺释放，但在 Atg7 缺失突变体中没有影响。因此，基础和诱导的巨自噬都可以在体内对突触前活性起到制动作用，可能通过调节突触囊泡的周转率，进一步调节末梢体积和递质释放的动力学。
