REGULATION OF NMDA RECEPTOR CLUSTERING BY EPH KINASES

该项目的目标是描述发育中大脑中调节突触发生的信号通路。以往的研究表明，突触的分化经历了一系列的步骤，其中之一就是突触后神经递质受体的聚集。 在神经肌肉接头中，胆碱能受体的聚集由蛋白聚糖（聚集蛋白）诱导，其激活受体酪氨酸激酶（MuSK）。 在中枢神经系统中，尚不清楚是什么调节兴奋性突触处的突触后受体如NMDA受体的聚集。 申办方实验室的初步数据表明，培养的海马神经元上Eph受体酪氨酸激酶的激活诱导NMDA受体亚基NR 1的聚集。 此外，Eph受体配体（ephrin）诱导Eph和NMDA受体之间的生物化学相互作用。 本研究将通过三个特定的目的来研究介导ephrin诱导的NMDA受体聚集的蛋白质-蛋白质相互作用。 首先，我们将确定的Eph和NR 1受体的领域是肝配蛋白诱导的受体聚集的关键。 然后，我们将研究酪氨酸磷酸化的作用，NMDA受体的聚集Eph酪氨酸激酶。 最后，NMDA受体聚集的细胞机制将通过两组实验进行检查。 我们将在细胞膜上呈现肝配蛋白配体，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的发育障碍，如精神发育迟滞和癫痫的基础。 通过在Michael Greenberg博士的监督下进行基础科学的强化培训以及在波士顿儿童医院进行儿科神经病学的临床实践，候选人有望成为一名医生-科学家，配备分子和细胞工具来研究儿童神经元发育不良。

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.