Trans-synaptic mechanism of retinal synapse formation and function

我们最佳的视觉表现始于视网膜中正确的平行视觉信息处理 这取决于精确的视网膜神经回路形成。为了实现这一点，视网膜神经元必须准确地设置 突触前神经递质释放位点之间需要精确对齐的功能性突触 和突触后受体。越来越多的证据表明，细胞粘附分子（CAM）介导的 跨突触复合物对突触的形成和功能至关重要，然而， 突触释放机制与视网膜带处的突触后受体信号复合体协调 突触在很大程度上是未知的。我们最近报道，细胞外钙通道辅助亚基α2δ4 是视杆细胞轴突发育和突触形成所必需的，并证明α2δ4确实 因此，通过控制ELFN 1的突触靶向，一种特异性表达的富含亮氨酸重复序列（LRR）蛋白， 在杆突触处，并与突触后mGluR 6受体跨突触相互作用。我们还发现， α2δ4通过LRR结构域与ELFN 1相互作用，LRR结构域是许多LRR蛋白共有的保守结构域。 有趣的是，我们和其他实验室发现了另一种LRR蛋白，称为LRIT 1，它特异性影响视锥细胞， 突触功能拟议工作的目标是确定它是否是一个一般性机制， 突触前钙通道复合体利用α2δ4通过突触后膜与突触后受体协同作用， 不同LRR蛋白的促进作用。在目标1中，我们将确定α2δ4-ELFN 1相互作用在 使用体内电穿孔结合缺失诱变形成杆突触。在目标2中，我们将研究 LRIT 1如何通过测试LRIT 1是否影响突触前Cav1.4通道来调节锥体突触功能 通过电生理记录的α2δ4活性。在目标3中，我将研究是否突触在 通过研究α2δ4和LRIT 1如何影响内丛状层（IPL），发现内丛状层（IPL）也采取类似的跨突触机制 RBC-AII无长突突触的形成和功能，使用在指导阶段获得的技术。这 该建议是创新的，因为尽管α2δ4蛋白明显具有生物学活性，但尚未对α2δ4蛋白进行机制研究。 在光感受器突触形成和功能中起重要作用。拟议的工作是重要的，因为结果 这项研究将使我们更好地了解视网膜神经元如何建立和维持突触联系。

Our optimal visual performance starts with the correct parallel visual information processing in the retina which depends on precise retinal neural circuit formation. To achieve this, retinal neurons must accurately set up functional synapses which require precise alignment between the pre-synaptic neurotransmitter releasing site and the post-synaptic receptor. Increasing evidence suggests that cell adhesion molecules (CAMs)-mediated trans-synaptic complexes are critical for synapse formation and function, however, the mechanism how pre- synaptic releasing machinery coordinates with the post-synaptic receptor signaling complex at retinal ribbon synapses is largely unknown. We recently reported that the extracellular calcium channel auxiliary subunit α2δ4 is necessary for rod photoreceptor axonal elaboration and synapse formation and demonstrated that α2δ4 does so through controlling the synaptic targeting of ELFN1, a leucine-rich repeat (LRR) protein specifically expressed at rod synapse and interacts trans-synaptically with the post-synaptic mGluR6 receptor. We also showed that α2δ4 interacts with ELFN1 through the LRR domain, a conserved domain shared across many LRR proteins. Interestingly, we and other lab identified another LRR protein termed LRIT1, which specifically affects cone synaptic function. The objective of the proposed work is to determine whether it is a general mechanism that pre-synaptic calcium channel complex utilizes α2δ4 to coordinate with post-synaptic receptor through the facilitation of different LRR proteins. In Aim 1, we will determine the functional role of α2δ4-ELFN1 interaction in rod synapse formation using in vivo electroporation combined with deletion mutagenesis. In Aim 2, we will study how LRIT1 regulates cone synaptic function by testing whether LRIT1 affects pre-synaptic Cav1.4 channel activity through α2δ4 using electrophysiological recording. In Aim 3, I will investigate whether synapses in the inner plexiform layer (IPL) also adopt similar trans-synaptic mechanism by studying how α2δ4 and LRIT1 affect RBC-AII amacrine synapse formation and function using the technique gained during the mentored phase. This proposal is innovative because no mechanistic studies has been done on α2δ4 protein despite its clearly important role in photoreceptor synapse formation and function. The proposed work is significant since results from this study will enable better understanding of how retinal neurons establish and maintain synaptic contact.