REGULATION OF NMDA RECEPTOR CLUSTERING BY EPH KINASES

该项目的目的是表征信号通路调节突触发生在发育中的大脑。先前的研究表明，突触的分化有一系列步骤，其中一个步骤是突触后神经递质受体的聚集。在神经肌肉连接处，胆碱能受体的聚集是由一种蛋白聚糖（agrin）诱导的，它可以激活受体酪氨酸激酶（MuSK）。在中枢神经系统中，是什么调控突触后受体如兴奋性突触的NMDA受体的聚集尚不清楚。赞助商实验室的初步数据表明，在培养的海马神经元上激活Eph受体酪氨酸激酶可诱导NMDA受体亚基NR1聚集。此外，Eph受体配体（ephrins）诱导了Eph和NMDA受体之间的生化相互作用。本研究将通过三个特定的目的来研究介导ephrin诱导的NMDA受体聚集的蛋白-蛋白相互作用。首先，我们将确定Eph和NR1受体的结构域，它们对ephrin诱导的受体聚类至关重要。然后，我们将研究酪氨酸磷酸化对Eph酪氨酸激酶聚集NMDA受体的作用。最后，NMDA受体聚类的细胞机制将通过两组实验进行检验。我们将介绍细胞膜上的ephrin配体，并确定它们对邻近神经元上的NMDA受体的影响。突触形成的机制是儿科神经学家特别感兴趣的，因为异常的突触形成可能是常见发育障碍如智力迟钝和癫痫的基础。在Michael Greenberg博士的指导下接受基础科学的强化训练，并在波士顿儿童医院进行儿科神经病学的临床实践，该候选人希望成为一名具备分子和细胞工具的医生-科学家，研究儿童神经发育不良。

The goal of this project is to characterize the signaling pathways that regulate synaptogenesis in the developing brain. Previous studies have demonstrated that synapses differentiate in a series of steps, one of which is the clustering of postsynaptic neurotransmitter receptors. In the neuromuscular junction, clustering of the cholinergic receptors is induced by a proteoglycan (agrin), which activates a receptor tyrosine kinase (MuSK). In the central nervous system, it is not clear what regulates the clustering of postsynaptic receptors such as the NMDA receptors at excitatory synapses. Preliminary data from the Sponsor's laboratory indicate that activation of Eph receptor tyrosine kinases on cultured hippocampal neurons induces the clustering of a NMDA receptor subunit, NR1. Furthermore, Eph receptor ligands (ephrins) induce a biochemical interaction between the Eph and NMDA receptors. This study will examine the protein-protein interactions that mediate ephrin-induced NMDA receptor clustering through three specific aims. First, we will identify the domains of Eph and NR1 receptors that are critical for ephrin-induced receptor clustering. Then, we will investigate the role of tyrosine phosphorylation on the clustering of NMDA receptors by Eph tyrosine kinases. Finally, the cellular mechanisms of NMDA receptor clustering will be examined through two sets of experiments. We will present the ephrin ligands on the cell membrane and determine their effect on the NMDA receptors on neighboring neurons. Mechanisms of synapse formation are of particular interest to pediatric neurologists because aberrant synapse formation is likely to underlie common developmental disorders such as mental retardation and epilepsy. Through intensive training in basic science under the supervision of Dr. Michael Greenberg and clinical practice in pediatric neurology at the Children's Hospital in Boston, the candidate expects to become a physician- scientist equipped with the molecular and cellular tools to study neuronal dysgenesis in children.