GABAergic Neuron Differentiation in C. elegans

描述(由申请人提供)： 化学突触是超微结构上不同的亚细胞实体，介导从神经元到其靶点的信息流。在突触前终末，突触小泡在电子致密活动区周围排列整齐。最近的研究揭示了控制突触前分化的多条途径。这个实验室的一个重点是在线虫中采用遗传学方法来识别调节突触形成的基因。Rpm-1基因(用于突触前形态的调节)编码一个进化上保守的大蛋白，它包含包括Ring-inger E3泛素连接酶结构域在内的多个功能结构域。Rpm-1功能的丧失会导致各种突触缺陷，从无法形成稳定的突触到突触前终末的紊乱。通过遗传筛选，我们已经确定了一个被rpm-1抑制其活性的MAP激酶模块。该MAP激酶模块由DLK-1、MKK-4和PMK-3组成，DLK-1是MAP激酶，MAP-4是MAP激酶，PMK-3是p38样MAP激酶。在rpm-1突变体中，任何一种激酶功能的丧失都会抑制突触缺陷，而在野生型动物中，上调MAP激酶信号会导致类似于rpm-1突变体的异常突触。DLK-1定位于突触前区域，其丰度在rpm-1突变体中似乎升高。基于这些数据，我们假设在突触形成过程中，RPM-1可能通过靶向DLK-1的降解而下调MAP激酶途径。这一更新应用的主要目的是确定MAP激酶(特别是DLK-1)和RPM-1之间的生化相互作用，并确定该MAP激酶途径的其他组件和其他可能与RPM-1相互作用的基因。RPM-1定位于一个不同的突触亚结构域。还提出了更多的实验来研究它的突触定位是如何调节的。这一应用的结果将促进我们对突触形成中的调控网络的理解。突触的完整性会损害大脑的功能，从而影响人类的健康。这项研究将有助于理解维持健康突触的基本机制，也可能为突触功能障碍的发病机制提供见解。

DESCRIPTION (provided by applicant): Chemical synapses are ultrastructurally distinct subcellular entities that mediate the information flow from neurons to their targets. In the presynaptic terminals, synaptic vesicles are arranged orderly around the electron-dense active zones. Recent studies have revealed multiple pathways controlling presynaptic differentiation. A focus of this lab is to take a genetic approach in the nematode C. elegans to identify genes that regulate synapse formation. The rpm-1 gene (for regulator of presynaptic morphology) encodes a large evolutionarily conserved protein that contains multiple functional domains including a Ring-finger E3 ubiquitin ligase domain. Loss of function in rpm-1 results in diverse synaptic defects, ranging from failure to form stable synapses to disorganized presynaptic terminals. Through genetic screens, we have identified a MAP kinase module whose activity is inhibited by rpm-1. This MAP kinase module is composed of DLK-1, a MAP kinase kinase kinase; MKK-4, a MAP kinase kinase; and PMK-3, a p38-like MAP kinase. Loss of function in any one of the kinases suppresses the synaptic defects in rpm-1 mutants, whereas elevating the MAP kinase signaling in wild type animals causes abnormal synapses resembling those of rpm-1 mutants. DLK-1 is localized to presynaptic regions, and its abundance appears to be elevated in rpm-1 mutants. Based on these data, we hypothesize that during synapse formation RPM-1 functions to down-regulate the MAP kinase pathway, possibly by targeting DLK-1 for degradation. The main goals of this renewal application are to define the biochemical interactions between the MAP kinases (in particular DLK-1) and RPM-1, and to identify additional components of this MAP kinase pathway and other genes that may interact with RPM- 1. RPM-1 is localized to a distinct subsynaptic domain. Additional experiments are proposed to examine how its synaptic localization is regulated. The outcome of this application will advance our understanding of the regulatory network in synapse formation. Synapse integrity is detrimental to the function of the brain, hence the health of a human being. This study will contribute to the understanding of the basic mechanisms that maintain healthy synapses, and may also provide insights into the pathogenesis of synapse dysfunction.