Faculty of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany.
Department of Molecular Pharmacology and Cell Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, 13125 Berlin, Germany.
Proc Natl Acad Sci U S A. 2017 Nov 7;114(45):12057-12062. doi: 10.1073/pnas.1715341114. Epub 2017 Oct 23.
Neurotransmission is mediated by the exocytic release of neurotransmitters from readily releasable synaptic vesicles (SVs) at the active zone. To sustain neurotransmission during periods of elevated activity, release-ready vesicles need to be replenished from the reserve pool of SVs. The SV-associated synapsins are crucial for maintaining this reserve pool and regulate the mobilization of reserve pool SVs. How replenishment of release-ready SVs from the reserve pool is regulated and which other factors cooperate with synapsins in this process is unknown. Here we identify the endocytic multidomain scaffold protein intersectin as an important regulator of SV replenishment at hippocampal synapses. We found that intersectin directly associates with synapsin I through its Src-homology 3 A domain, and this association is regulated by an intramolecular switch within intersectin 1. Deletion of intersectin 1/2 in mice alters the presynaptic nanoscale distribution of synapsin I and causes defects in sustained neurotransmission due to defective SV replenishment. These phenotypes were rescued by wild-type intersectin 1 but not by a locked mutant of intersectin 1. Our data reveal intersectin as an autoinhibited scaffold that serves as a molecular linker between the synapsin-dependent reserve pool and the presynaptic endocytosis machinery.
神经递质的释放是通过在活性区中从可释放的突触小泡（SVs）中胞吐释放神经递质来介导的。为了在活性升高的时期维持神经递质的传递，释放准备好的囊泡需要从 SV 的储备池中补充。SV 相关的突触结合蛋白对于维持这种储备池至关重要，并调节储备池 SV 的动员。SV 从储备池释放的过程中，储备池的补充是如何被调节的，以及其他哪些因素与突触结合蛋白在这个过程中合作，目前尚不清楚。在这里，我们确定了内吞多域支架蛋白 intersectin 作为海马突触 SV 补充的重要调节因子。我们发现 intersectin 通过其 Src 同源性 3 A 结构域直接与突触结合蛋白 I 结合，并且这种结合受 intersectin 1 内的分子内开关调节。在小鼠中删除 intersectin 1/2 会改变突触结合蛋白 I 的突触前纳米尺度分布，并由于 SV 补充缺陷而导致持续神经传递缺陷。这些表型可以通过野生型 intersectin 1 挽救，但不能通过 intersectin 1 的锁定突变体挽救。我们的数据揭示了 intersectin 作为一种自动抑制的支架，作为突触结合蛋白依赖性储备池和突触前内吞作用机制之间的分子连接物。
