Ramsay Harrison J, Gookin Sara E, Ramsey Austin M, Kareemo Dean J, Crosby Kevin C, Stich Dominik G, Olah Samantha S, Actor-Engel Hannah S, Smith Katharine R, Kennedy Matthew J
Anschutz Medical Campus, Department of Pharmacology, University of Colorado, Aurora, CO, United States.
Anschutz Medical Campus, Advanced Light Microscopy Core, University of Colorado, Aurora, CO, United States.
Front Mol Neurosci. 2023 Aug 3;16:1232795. doi: 10.3389/fnmol.2023.1232795. eCollection 2023.
Postsynaptic neurotransmitter receptors and their associated scaffolding proteins assemble into discrete, nanometer-scale subsynaptic domains (SSDs) within the postsynaptic membrane at both excitatory and inhibitory synapses. Intriguingly, postsynaptic receptor SSDs are mirrored by closely apposed presynaptic active zones. These trans-synaptic molecular assemblies are thought to be important for efficient neurotransmission because they concentrate postsynaptic receptors near sites of presynaptic neurotransmitter release. While previous studies have characterized the role of synaptic activity in sculpting the number, size, and distribution of postsynaptic SSDs at established synapses, it remains unknown whether neurotransmitter signaling is required for their initial assembly during synapse development. Here, we evaluated synaptic nano-architecture under conditions where presynaptic neurotransmitter release was blocked prior to, and throughout synaptogenesis with tetanus neurotoxin (TeNT). In agreement with previous work, neurotransmitter release was not required for the formation of excitatory or inhibitory synapses. The overall size of the postsynaptic specialization at both excitatory and inhibitory synapses was reduced at chronically silenced synapses. However, both AMPARs and GABARs still coalesced into SSDs, along with their respective scaffold proteins. Presynaptic active zone assemblies, defined by RIM1, were smaller and more numerous at silenced synapses, but maintained alignment with postsynaptic AMPAR SSDs. Thus, basic features of synaptic nano-architecture, including assembly of receptors and scaffolds into trans-synaptically aligned structures, are intrinsic properties that can be further regulated by subsequent activity-dependent mechanisms.
在兴奋性和抑制性突触的突触后膜内，突触后神经递质受体及其相关的支架蛋白组装成离散的、纳米级的亚突触域（SSD）。有趣的是，突触后受体SSD与紧密相邻的突触前活性区相互对应。这些跨突触分子组装体被认为对高效神经传递很重要，因为它们将突触后受体集中在突触前神经递质释放部位附近。虽然先前的研究已经描述了突触活动在塑造成熟突触处突触后SSD的数量、大小和分布方面的作用，但在突触发育过程中其初始组装是否需要神经递质信号传导仍不清楚。在这里，我们评估了在突触形成之前和整个过程中用破伤风神经毒素（TeNT）阻断突触前神经递质释放的条件下的突触纳米结构。与先前的工作一致，兴奋性或抑制性突触的形成不需要神经递质释放。在长期沉默的突触处，兴奋性和抑制性突触的突触后特化的整体大小都减小了。然而，AMPA受体和GABA受体仍然与它们各自的支架蛋白一起聚集成SSD。由RIM1定义的突触前活性区组装体在沉默的突触处更小且更多，但与突触后AMPA受体SSD保持对齐。因此，突触纳米结构的基本特征，包括受体和支架组装成跨突触对齐的结构，是内在属性，可以通过随后的活动依赖机制进一步调节。
