Department of Biology, Brandeis University, Waltham, MA.
Department of Biology, University of Toronto Mississauga, Mississauga, Canada.
J Cell Biol. 2022 May 2;221(5). doi: 10.1083/jcb.202112094. Epub 2022 Mar 23.
Neuronal extracellular vesicles (EVs) are locally released from presynaptic terminals, carrying cargoes critical for intercellular signaling and disease. EVs are derived from endosomes, but it is unknown how these cargoes are directed to the EV pathway rather than for conventional endolysosomal degradation. Here, we find that endocytic machinery plays an unexpected role in maintaining a release-competent pool of EV cargoes at synapses. Endocytic mutants, including nervous wreck (nwk), shibire/dynamin, and AP-2, unexpectedly exhibit local presynaptic depletion specifically of EV cargoes. Accordingly, nwk mutants phenocopy synaptic plasticity defects associated with loss of the EV cargo synaptotagmin-4 (Syt4) and suppress lethality upon overexpression of the EV cargo amyloid precursor protein (APP). These EV defects are genetically separable from canonical endocytic functions in synaptic vesicle recycling and synaptic growth. Endocytic machinery opposes the endosomal retromer complex to regulate EV cargo levels and acts upstream of synaptic cargo removal by retrograde axonal transport. Our data suggest a novel molecular mechanism that locally promotes cargo loading into synaptic EVs.
神经元细胞外囊泡 (EVs) 从突触前末梢局部释放，携带对细胞间信号传递和疾病至关重要的货物。EVs 来源于内体，但尚不清楚这些货物是如何被定向到 EV 途径而不是进行常规的内溶酶体降解。在这里，我们发现内吞机制在维持突触处具有释放能力的 EV 货物库方面发挥了意想不到的作用。包括神经损伤（nwk）、shibire/dynamin 和 AP-2 在内的内吞突变体，出人意料地表现出局部突触前 EV 货物的耗竭。因此，nwk 突变体模拟了与 EV 货物突触结合蛋白-4（Syt4）缺失相关的突触可塑性缺陷，并在过表达 EV 货物淀粉样前体蛋白（APP）时抑制致死性。这些 EV 缺陷与突触小泡再循环和突触生长中的经典内吞功能在遗传上是可分离的。内吞机制与内体逆行转运体复合物（endosomal retromer complex）相对抗，以调节 EV 货物水平，并在上游作用于通过逆行轴突运输去除突触货物。我们的数据表明了一种新的分子机制，该机制可局部促进突触 EV 中的货物加载。
