Regulation of Synapse Formation and Function by Neurexin-1 Proteolysis

描述（由申请人提供）：突触的形成、成熟和功能需要跨突触粘附复合物的精密协调，从而能够集中和控制突触前和突触后信号传导机制。特别是，突触前神经毒素（Nrxns）与它们的突触后配体（例如神经配素、LRRTM等）的结合，介导突触功能的几个方面，如突触传递和功能性突触后位点的组装。越来越多的遗传学证据表明，编码Nrxn-1的基因的杂合缺失与特发性自闭症谱系障碍和精神分裂症的病因有关。关于Nrxn-1在发育和成年突触中的功能和调节仍然知之甚少，了解这一点可能会提高我们对神经发育障碍的认识，并揭示新的药理学靶点。我在这里提出的初步数据，验证使用两个新的小鼠模型研究Nrxn-1，包括Nrxn-1-HA敲入小鼠，这将允许改善检测内源性Nrxn-1，以及Nrxn-1？/？条件性敲除小鼠（cKO）用于功能研究。使用Nrxn-1-HA敲入，我进一步表明，突触活动影响Nrxn-1的处理中的金属蛋白酶依赖的方式，这可能是一个重要的调节机制的Nrxn-含粘附复合物。为了更好地理解Nrxn-1在突触中的基本功能和调节，我建议鉴定负责活性依赖性Nrxn-1加工的特异性金属蛋白酶和切割位点。然后，我将确定，在平行，Nrxn-1的基本功能，在调节海马突触的形成和生理功能。最后，通过一系列的救援实验，通过慢病毒重新表达野生型，切割抗性，切割诱导Nrxn-1 β/β cKO神经元，我将评估Nrxn-1加工在其正常功能中的作用。预计拟议的研究将为Nrxn-1缺失如何引起人类神经发育障碍提供基本见解，并将首次对细胞外蛋白水解作为调节机制进行功能分析 含有neurexin的粘附复合物。

DESCRIPTION (provided by applicant): The formation, maturation, and function of synapses requires the exquisite coordination of transynaptic adhesion complexes, enabling the concentration and control of pre- and postsynaptic signaling machinery. In particular, the association of presynaptic neurexins (Nrxns) with their postsynaptic ligands (e.g. neuroligins, LRRTMs, etc.), mediates several aspects of synaptic function, such as synaptic transmission and the assembly of functional postsynaptic sites. A growing body of genetic evidence implicates heterozygous deletions of the gene encoding Nrxn-1 in the pathoetiology of idiopathic autism spectrum disorders and schizophrenia. Still very little is known regarding the function and regulation of Nrxn-1 at developing and adult synapses, an understanding of which may improve our knowledge of neurodevelopmental disorders and reveal novel pharmacological targets. I present here preliminary data that validates the use of two new mouse models for studying Nrxn-1, including a Nrxn-1-HA knockin mouse which will allow improved detection of endogenous Nrxn-1, as well as a Nrxn-1?/? conditional knockout mouse (cKO) mouse for functional studies. Using the Nrxn-1-HA knockin, I further show that synaptic activity influences the processing of Nrxn-1 in a metalloproteinase-dependent fashion, which may represent an important regulatory mechanism of Nrxn- containing adhesion complexes. In order to better understand the basic function and regulation of Nrxn-1 at synapses, I propose to identify the specific metalloproteinase and cleavage site responsible for activity- dependent Nrxn-1 processing. Then I will determine, in parallel, the basic function of Nrxn-1 in regulating the formation and physiological function of hippocampal synapses. Finally, through a series of rescue experiments achieved through lentiviral re-expression of wild-type, cleavage-resistant, and cleavage-inducible Nrxn-1� in Nrxn-1�/� cKO neurons, I will assess the role of Nrxn-1 processing in its normal function. It is anticipated that the proposed research will provide fundamental insight into how Nrxn-1 deletions give rise to human neurodevelopmental disorders and will offer the first functional analysis of extracellular proteolysis as a regulatory mechanism of neurexin-containing adhesion complexes.