Leibniz Institut für Molekulare Pharmakologie (FMP) & Freie Universität Berlin, Robert-Roessle-Straße 10, 13125 Berlin, Germany; Charite Universitätsmedizin, NeuroCure Cluster of Excellence, Virchowweg 6, 10117 Berlin, Germany.
Leibniz Institut für Molekulare Pharmakologie (FMP) & Freie Universität Berlin, Robert-Roessle-Straße 10, 13125 Berlin, Germany.
Neuron. 2014 Jun 4;82(5):981-8. doi: 10.1016/j.neuron.2014.05.007.
Neurotransmission depends on presynaptic membrane retrieval and local reformation of synaptic vesicles (SVs) at nerve terminals. The mechanisms involved in these processes are highly controversial with evidence being presented for SV membranes being retrieved exclusively via clathrin-mediated endocytosis (CME) from the plasma membrane or via ultrafast endocytosis independent of clathrin. Here we show that clathrin and its major adaptor protein 2 (AP-2) in addition to the plasma membrane operate at internal endosome-like vacuoles to regenerate SVs but are not essential for membrane retrieval. Depletion of clathrin or conditional knockout of AP-2 result in defects in SV reformation and an accumulation of endosome-like vacuoles generated by clathrin-independent endocytosis (CIE) via dynamin 1/3 and endophilin. These results together with theoretical modeling provide a conceptual framework for how synapses capitalize on clathrin-independent membrane retrieval and clathrin/AP-2-mediated SV reformation from endosome-like vacuoles to maintain excitability over a broad range of stimulation frequencies.
神经传递依赖于突触前膜的回收和神经末梢突触小泡（SVs）的局部重构。这些过程中涉及的机制存在很大争议，有证据表明 SV 膜是通过网格蛋白介导的内吞作用（CME）从质膜上专门回收的，或者通过与网格蛋白无关的超快内吞作用回收的。在这里，我们表明，网格蛋白及其主要衔接蛋白 2（AP-2）除了质膜外，还在类似于内体的内部空泡中运作，以重新形成 SV，但对于膜的回收不是必需的。网格蛋白的耗竭或 AP-2 的条件敲除导致 SV 形成缺陷，并积累由网格蛋白非依赖性内吞作用（CIE）通过 dynamin 1/3 和 endophilin 产生的类似于内体的空泡。这些结果与理论模型一起，为突触如何利用网格蛋白非依赖性膜回收和网格蛋白/AP-2 介导的 SV 从类似于内体的空泡中重新形成提供了一个概念框架，以在广泛的刺激频率范围内维持兴奋性。
