G protein signaling in the C. elegans nervous system

描述(申请人提供)：我们试图了解神经递质如何通过异源三聚体G蛋白来调节神经元的活动。我们将专注于5-羟色胺的信号传递机制，其中的缺陷被认为是人类严重抑郁症的基础。我们的目标是了解许多G蛋白偶联的5-羟色胺受体是如何共同作用的，以介导对这种神经递质的适当反应，并找出受体激活的下游发生了什么。线虫使用5-羟色胺作为神经递质，我们将使用这个模型系统来研究三个不同的5-羟色胺信号事件的机制。在我们的第一个目标中，我们将描述一个信号复合体，它将5-羟色胺信号传递到线虫的产卵肌肉上。我们将测试一个模型，在该模型中，多个5-羟色胺受体和一个ERG钾通道共定位于突触后结构，以便由5-羟色胺受体信号产生的局部信号可以抑制ERG通道，从而促进肌肉收缩。在第二个目标中，我们将研究释放到产蛋肌的5-羟色胺也通过自身受体反馈抑制5-羟色胺进一步释放的机制。我们将结合遗传和生化研究来分析两种新型的信号调节因子，我们的初步结果表明它们增强了这种反馈信号：一种是与G1亚基结合的GPR/GoLoco蛋白，另一种是作为G蛋白核苷酸交换因子的RIC-8蛋白。在第三个目标中，我们将研究5-羟色胺信号减缓线虫运动行为的机制。我们已经使用基因筛查来确定这个5-羟色胺信号事件所需的基因。我们发现，5-羟色胺对运动的影响需要两个不同的5-羟色胺受体：单独敲除或同时敲除其中一个受体会导致同样强烈的5-羟色胺反应缺陷。我们将研究这两种不同的5-羟色胺受体如何协同工作。我们还将全面分析我们筛选出的一种新的蛋白质，它是5-羟色胺信号转导所必需的，但它与之前已知的任何参与5-羟色胺信号转导的蛋白质不同。5-羟色胺信号的机制在线虫和人类之间是高度保守的，线虫模型系统的力量所带来的洞察力应该会揭示人类5-羟色胺信号的新细节。这最终将有助于了解抑郁症的原因以及可以用来治疗它的干预措施。

DESCRIPTION (provided by applicant): We seek to understand how neurotransmitters signal through heterotrimeric G proteins to modulate the activities of neurons. We will focus on the mechanism of signaling by serotonin, defects in which are thought to underlie major depression in humans. Our goal is to understand how the many G protein coupled serotonin receptors function together to mediate appropriate responses to this neurotransmitter, and to find out what happens downstream of receptor activation. C. elegans uses serotonin as a neurotransmitter, and we will use this model system to investigate the mechanism of three different serotonin signaling events. In our first aim, we will characterize a signaling complex that mediates serotonin signaling onto the C. elegans egg-laying muscles. We will test a model in which multiple serotonin receptors and an ERG potassium channel are co-localized to postsynaptic structures so that localized signals produced by serotonin receptor signaling can inhibit the ERG channel to promote muscle contraction. In the second aim, we will study the mechanism by which serotonin released onto the egg-laying muscles also signals back onto the neurons that release it via autoreceptors to feedback inhibit further serotonin release. We will use a combination of genetic and biochemical studies to analyze two new types of signaling regulators that our preliminary results show enhance such feedback signaling: a GPR/GoLoco protein which binds G1 subunits, and the RIC-8 protein which acts as a G protein nucleotide exchange factor. In the third aim, we will study the mechanism by which serotonin signals to slow down C. elegans locomotion behavior. We have used a genetic screen to identify genes required for this serotonin signaling event. We found that two different serotonin receptors are each required for the effect of serotonin on locomotion: knocking out either receptor alone or both together leads to the same strong defect in serotonin response. We will study how these two different serotonin receptors work together. We will also comprehensively analyze a new protein identified by our screen that is required specifically for serotonin signaling, but that is not similar to any protein previously known to be involved in serotonin signaling. The mechanisms of serotonin signaling are highly conserved between C. elegans and humans and the insights made possible by the power of the C. elegans model system should shed light on new details of human serotonin signaling. This will ultimately help to understand the causes of depression and the interventions that can be used to treat it.