Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, Göttingen, Germany.
EMBO J. 2018 Aug 1;37(15). doi: 10.15252/embj.201798044. Epub 2018 Jun 27.
Aged proteins can become hazardous to cellular function, by accumulating molecular damage. This implies that cells should preferentially rely on newly produced ones. We tested this hypothesis in cultured hippocampal neurons, focusing on synaptic transmission. We found that newly synthesized vesicle proteins were incorporated in the actively recycling pool of vesicles responsible for all neurotransmitter release during physiological activity. We observed this for the calcium sensor Synaptotagmin 1, for the neurotransmitter transporter VGAT, and for the fusion protein VAMP2 (Synaptobrevin 2). Metabolic labeling of proteins and visualization by secondary ion mass spectrometry enabled us to query the entire protein makeup of the actively recycling vesicles, which we found to be younger than that of non-recycling vesicles. The young vesicle proteins remained in use for up to ~ 24 h, during which they participated in recycling a few hundred times. They were afterward reluctant to release and were degraded after an additional ~ 24-48 h. We suggest that the recycling pool of synaptic vesicles relies on newly synthesized proteins, while the inactive reserve pool contains older proteins.
衰老的蛋白质会通过积累分子损伤而对细胞功能造成危害。这意味着细胞应该优先依赖新合成的蛋白质。我们在培养的海马神经元中检验了这一假说，重点关注突触传递。我们发现，新合成的囊泡蛋白被整合到负责生理活动期间所有神经递质释放的活跃再循环囊泡池中。我们观察到钙传感器突触结合蛋白 1、神经递质转运蛋白 VGAT 和融合蛋白 VAMP2（突触融合蛋白 2）都是如此。通过对蛋白质进行代谢标记并通过二次离子质谱进行可视化，我们能够查询活跃再循环囊泡中的整个蛋白质组成，发现它们比非再循环囊泡年轻。年轻的囊泡蛋白在长达24 小时的时间内持续使用，在此期间它们参与了几百次的循环。之后，它们不愿意释放，并在额外的24-48 小时后被降解。我们认为，突触囊泡的再循环池依赖于新合成的蛋白质，而不活跃的储备池则包含较老的蛋白质。
