The role of NG2-LNS-domain-mediated glia-to-neuron signaling in neuronal synapse formation and function

目前的建议是基于我们最近发现的一种新的和功能上重要的机制，通过这种机制，神经胶质细胞调节突触和神经网络特性。我们发现，胶质蛋白NG2的层粘连蛋白G/Neurexin/性激素结合球蛋白（LNS）结构域通过调节谷氨酸受体动力学和LTP，在体感觉皮层中充当谷氨酸能神经元突触的有效调节剂。鉴于这一发现以及LNS结构域是突触细胞粘附蛋白的典型组成部分，我们建议结合两个实验室（Trotter -细胞生物学、胶质细胞、NG2生物学；Brose -生物化学、电生理学、突触发生和突触功能）的专业知识，研究NG2 LNS结构域改变突触形成和突触信号传导的确切机制。我们计划描述NG2 LNS结构域对定义的突触亚型和神经元亚群的形态和功能的影响。重要的是，我们计划确定NG2 LNS结构域的神经元相互作用伙伴，介导其对神经元的调节作用。在这方面，我们将首先关注CD166，这是我们共同通过亲和层析鉴定的NG2 LNS候选受体。我们将研究NG2 LNS与CD166之间相互作用的功能相关性，这将包括产生CD166功能改变或消除的突变小鼠模型。最后，我们将使用生化和质谱方法扩展我们对NG2 LNS受体的系统搜索。我们期望我们的研究将为NG2 LNS结构域调节突触和神经元微电路的分子和细胞机制提供详细的见解。这不仅将揭示大脑发育和功能中一个新的、功能上高度相关的调控过程的机制、分子和细胞复杂性，而且可能最终揭示NG2 LNS作用的这一新的调控原理与脑部疾病之间的关键联系。

The present proposal is based in our recent discovery of a novel and functionally important mechanism by which glia cells modulate synapse and neuronal network properties. We found that Laminin G/Neurexin/Sex hormone-binding Globulin (LNS) domains of the glial protein NG2 act as potent modulators of glutamatergic neuronal synapses in the somatosensory cortex by regulating glutamate receptor kinetics and LTP. In view on this finding and the fact that LNS-domains are typical components of synaptic cell adhesion proteins, we propose here to combine the expertise of two laboratories (Trotter - cell biology, glial cells, NG2 biology; Brose - biochemistry, electrophysiology, synaptogenesis and synapse function) to study the exact mechanisms by which the NG2 LNS domains alter synapse formation and synaptic signaling. We plan to characterize the effect of NG2 LNS domains on the morphology and function of defined synapse subtypes and neuronal subpopulations. Importantly, we plan to identify the neuronal interaction partner(s) of the NG2 LNS domains that mediate their modulatory effect on neurons. In this regard, we will initially focus on CD166, a candidate NG2 LNS receptor that we jointly identified by affinity chromatography. We will study the functional relevance of the interaction between NG2 LNS and CD166, which will include the generation of mutant mouse models with altered or eliminated CD166 function. Finally, we will expand our systematic search for NG2 LNS receptors using biochemical and mass spectrometric approaches. We expect that our study will provide detailed insights into the molecular and cellular mechanisms by which NG2 LNS domains regulate synapses and neuronal microcircuits. This will not only reveal the mechanistic molecular and cellular intricacies of a novel and functionally highly relevant regulatory process in brain development and function, but may ultimately also reveal key links between this novel regulatory principle of NG2 LNS action and brain disease.