Molecular studies of neural histone monoaminylation in normal and aberrant brain plasticity

严重抑郁障碍(MDD)，在其他情绪障碍中，是一种高度异质性的、使人衰弱的疾病 这影响了全球数百万人；然而，引发MDD的大脑功能障碍是 人们知之甚少，目前的治疗方法疗效有限。尽管被偶然发现 60多年前，单胺类相关抗抑郁药(ADS；例如SSRI)仍然是 对许多MDD患者进行治疗，但在开始治疗和症状缓解之间存在很长的延迟， 以及较低的缓解率，这鼓励了进一步的调查，试图发现更多 直接治疗靶点。特别是5-羟色胺，被认为在神经元可塑性中起着关键作用， 其信号的改变与MDD的发生和治疗有关。虽有水泡 5-羟色胺的包装对于神经传递是必不可少的，最近的数据，包括我们自己的实验室，已经 证明囊泡外单胺类物质存在于两种单胺类神经元核中 神经元，以及来自单胺能投射区域的神经元；然而，它仍然不清楚， 核5-羟色胺是否可能发挥不依赖神经传递的作用。5-羟色胺此前已被 通过组织转谷氨酰胺酶2的转酰胺化与某些蛋白质形成共价键 酶，这一过程被称为5羟色胺基化。我们实验室最近发现了组蛋白，并对其进行了全面表征。 蛋白质(特别是组蛋白H3谷氨酰胺5结合赖氨酸4三甲基化；H3K4me3Q5ser)作为 体内5-羟色胺基化的新底物。此外，我们最近发现，H3K4me3Q5ser显著 人死后中缝背核(DRN)中的表达变化 MDD，以及在人类抑郁(慢性社会失败应激)的病因学相关啮齿动物模型中- 通过有效的慢性阿尔茨海默病治疗完全逆转的现象。因此，我们 假设组蛋白5-羟色胺基化可能建立了神经元基因表达的重要模式 正常转录所必需的大脑，这是一种分子机制，如果受到慢性应激的干扰(或 改变5-羟色胺动态的其他操作)可能会导致异常的可塑性和易感性 类似抑郁和/或焦虑的行为。这种机制也可以解释SSRI的延迟疗效 广告。因此，我们计划在以下目标中评估这些可能性：1)执行性别和细胞类型特定 H3K4me3Q5ser在正常大脑和应激大脑中的表观基因组分析，包括基础和SSRIs的背景； 2)评估组蛋白H3的细胞类型特异性操作对转录和行为的影响 5羟色胺在应激诱导行为中的作用；以及3)探索组蛋白之间新的机制联系 慢性应激后脆弱神经元中5-羟色胺和预启动复合体的形成。这部作品 承诺提供关于5-羟色胺(独立于神经传递)如何有助于 成年期神经元可塑性，以及它可能如何影响MDD/应激相关表型的发生。

Major depressive disorder (MDD), among other mood disorders, is a highly heterogeneous, debilitating illness that affects millions of individuals worldwide; however, disruptions in brain function that precipitate MDD are poorly understood, and current treatments have limited efficacy. Despite being serendipitously discovered more than 60 years ago, monoamine associated antidepressants (ADs; e.g., SSRIs) remain the first line of therapy for many with MDD, yet long delays between initiation of treatment and symptomatic alleviation, as well as low remission rates, have encouraged further investigations in an attempt to identify more direct therapeutic targets. Serotonin, in particular, is thought to play a critical role in neuronal plasticity, with alterations in its signaling implicated in both the development and treatment of MDD. Although vesicular packaging of serotonin is essential for neurotransmission, recent data, including from our own laboratory, have demonstrated the additional presence of extravesicular monoamines in the nucleus of both monoaminergic neurons, as well as in neurons from monoaminergic projection regions; it has remained unclear, however, whether nuclear serotonin may play roles independent of neurotransmission. Serotonin has previously been shown to form covalent bonds with certain proteins via transamidation by the tissue Transglutaminase 2 enzyme, a process known as serotonylation. Our laboratory recently identified and fully characterized histone proteins (specifically histone H3 glutamine 5 in combination with lysine 4 tri-methylation; H3K4me3Q5ser) as novel substrates for serotonylation in vivo. Furthermore, we recently found that H3K4me3Q5ser is significantly altered in its expression in both postmortem dorsal raphe nucleus (DRN) of human subjects diagnosed with MDD, and in an etiologically relevant rodent model of human depression (chronic social defeat stress)– phenomena that are completely reversed by therapeutically effective chronic AD treatments. Thus, we hypothesize that histone serotonylation likely establishes important patterns of neuronal gene expression in brain that are necessary for normal transcription, a molecular mechanism that if perturbed by chronic stress (or other manipulations that alter serotonin dynamics) may lead to aberrant plasticity and vulnerability to depressive- and/or anxiety-like behaviors. Such a mechanism may also explain the delayed efficacy of SSRI ADs. We therefore plan to assess these possibilities in the following Aims: 1) perform sex and cell-type specific epigenomic analyses of H3K4me3Q5ser in normal vs. stressed brain, both basally and in the context of SSRIs; 2) assess the transcriptional and behavioral impacts of cell-type specific manipulations of histone H3 serotonylation on stress-induced behaviors; and 3) explore novel mechanistic links between histone serotonylation and pre-initiation complex formation in vulnerable neurons following chronic stress. This work promises to provide critical insights into how serotonin, independently from neurotransmission, contributes to adulthood neuronal plasticity, as well as how it may influence on the onset of MDD/stress related phenotypes.