Wittenmayer Nina, Körber Christoph, Liu Huisheng, Kremer Thomas, Varoqueaux Frederique, Chapman Edwin R, Brose Nils, Kuner Thomas, Dresbach Thomas
Institute for Anatomy and Cell Biology, Ruprecht-Karls-University Heidelberg, Im Neuenheimer Feld 307, D-69120 Heidelberg, Germany.
Proc Natl Acad Sci U S A. 2009 Aug 11;106(32):13564-9. doi: 10.1073/pnas.0905819106. Epub 2009 Jul 23.
Presynaptic nerve terminals pass through distinct stages of maturation after their initial assembly. Here we show that the postsynaptic cell adhesion molecule Neuroligin1 regulates key steps of presynaptic maturation. Presynaptic terminals from Neuroligin1-knockout mice remain structurally and functionally immature with respect to active zone stability and synaptic vesicle pool size, as analyzed in cultured hippocampal neurons. Conversely, overexpression of Neuroligin1 in immature neurons, that is within the first 5 days after plating, induced the formation of presynaptic boutons that had hallmarks of mature boutons. In particular, Neuroligin1 enhanced the size of the pool of recycling synaptic vesicles, the rate of synaptic vesicle exocytosis, the fraction of boutons responding to depolarization, as well as the responsiveness of the presynaptic release machinery to phorbol ester stimulation. Moreover, Neuroligin1 induced the formation of active zones that remained stable in the absence of F-actin, another hallmark of advanced maturation. Acquisition of F-actin independence of the active zone marker Bassoon during culture development or induced via overexpression of Neuroligin1 was activity-dependent. The extracellular domain of Neuroligin1 was sufficient to induce assembly of functional presynaptic terminals, while the intracellular domain was required for terminal maturation. These data show that induction of presynaptic terminal assembly and maturation involve mechanistically distinct actions of Neuroligins, and that Neuroligin1 is essential for presynaptic terminal maturation.
突触前神经末梢在最初组装后会经历不同的成熟阶段。我们在此表明，突触后细胞粘附分子Neuroligin1调节突触前成熟的关键步骤。在培养的海马神经元中分析发现，来自Neuroligin1基因敲除小鼠的突触前末梢在活性区稳定性和突触小泡池大小方面在结构和功能上仍不成熟。相反，在未成熟神经元（即接种后的前5天内）中过表达Neuroligin1会诱导形成具有成熟突触小体特征的突触前终扣。具体而言，Neuroligin1增加了循环突触小泡池的大小、突触小泡胞吐速率、对去极化有反应的终扣比例，以及突触前释放机制对佛波酯刺激的反应性。此外，Neuroligin1诱导形成了在没有F-肌动蛋白的情况下仍保持稳定的活性区，这是高级成熟的另一个标志。在培养发育过程中或通过Neuroligin1过表达诱导活性区标记物巴松管获得F-肌动蛋白独立性是依赖于活性的。Neuroligin1的细胞外结构域足以诱导功能性突触前末梢的组装，而细胞内结构域是末梢成熟所必需的。这些数据表明，突触前末梢组装和成熟的诱导涉及Neuroligins在机制上不同的作用，并且Neuroligin1对突触前末梢成熟至关重要。
