Cell-contact mediated mechanisms assembling synapses

描述（由申请人提供）：功能性神经系统依赖于特定目标神经元之间精确突触连接的形成。兴奋性突触形成的两个关键因素是成熟的蘑菇状树突棘的形成和突触蛋白的募集，如NMDARs和PSD-95。许多粘附分子，包括EphB/ephrinB、synCAM、SALM2、NGL2、neurexin/ neuroigin和cadherins，都被证明可以调节突触发生的各个方面。然而，突触形成的分子机制以及发育中的动物如何协调突触形成的因素仍有待确定。为了解决这些问题，我们将重点放在EphB受体酪氨酸激酶家族及其ephrinB配体的作用上，因为EphB敲除小鼠在突触形成方面表现出严重的缺陷，而其他突触粘附分子的敲除似乎没有兴奋性突触形成表型。此外，由于可卡因改变皮层和纹状体中EphB和ephrinB的表达，我们对突触发生机制的研究将为皮层发育提供见解，并影响我们对疾病和成瘾的理解。我们提出，跨突触EphB- ephrinB信号传导诱导突触前和突触后多种成分的组织：突触前ephrinB通过与树突EphB的相互作用刺激突触后发育，而突触后EphB的相互作用诱导轴突ephrinB依赖性突触前蛋白聚集。我提出了三个具体的目标来解决EphB和ephrinB在突触发育中的作用。具体目标1：确定ephb依赖性诱导突触前特化的信号机制。专项目的2：检测EphB是否启动突触形成。特异性目的3：确定EphB蛋白在体内皮质突触接触的树突位置中的作用。我们从更简化的模型系统转移到完整动物的方法是创新的，将导致重大的新发现。此外，鉴于EphB/ephrinB在突触和结构可塑性中的作用，以及EphB和ephrinB对滥用药物的敏感性，我们的研究将为控制突触发育的机制提供基础见解，并且随着细胞治疗的出现，将促进对人类发育疾病和成瘾的理解。

DESCRIPTION (provided by applicant): A functional nervous system relies on the formation of precise synaptic connections between specific target neurons. Two key elements of excitatory synapse formation are the formation of mature, mushroom-shaped dendritic spines and the recruitment of synaptic proteins, like NMDARs and PSD-95. A number of adhesion molecules, including EphB/ephrinB, synCAM, SALM2, NGL2, neurexin/neuroligin and cadherins, have each been shown to regulate aspects of synaptogenesis. However, the molecular mechanisms that underlie synapse formation as well as how factors act to coordinate synapse formation in the developing animal remain to be determined. To begin to address these issues, we have focused on the role of the EphB family of receptor tyrosine kinases and their ephrinB ligands because EphB knockout mice show serious deficits in synapse formation, while available knockouts for other synaptic adhesion molecules appear not to have an excitatory synapse formation phenotype. Moreover, because cocaine alters expression of EphB and ephrinB in cortex and striatum, our work on mechanisms of synaptogenesis will provide insights into cortical development and impact our understanding of disease and addiction. We propose that trans-synaptic EphB- ephrinB signaling induces both pre- and post-synaptic organization of multiple components of synapses: presynaptic ephrinB, through interactions with dendritic EphB, stimulates postsynaptic development while the reciprocal interaction of postsynaptic EphB induces axonal ephrinB dependent clustering of presynaptic proteins. I propose three specific aims to address the role of EphB and ephrinB in synapse development. Specific aim 1: Determine the signaling mechanisms responsible for EphB-dependent induction of presynaptic specializations. Specific aim 2: Test whether EphB acts to initiate synapse formation. Specific aim 3: Determine the role of EphB proteins in specifying dendritic locations of cortical synaptic contacts in vivo. Our approach of moving from more reduced model systems to the intact animal is innovative and will lead to significant new findings. Moreover, given the role of EphB/ephrinB in synaptic and structural plasticity, and the sensitivity of EphBs and ephrinBs to drugs of abuse, our studies will provide fundamental insights into mechanisms controlling synapse development and with the advent of cell based therapies will advance understanding of human developmental diseases and addiction.