Role of circHomer1 in synaptic plasticity and cocaine-seeking behavior

与物质使用障碍(Suds)相关的大脑异常涉及到长期的变化。 在基因表达中，使寻求和吸毒的动机电路脱轨 负面后果。而转录因子在基因表达变化中的作用 已经得到很好的证实，随后的转录后事件导致功能 人们对变化的理解还远远不够。最近的突破表明，环状RNA(CircRNAs) 在调控转录后事件中起着关键作用。这类新的非编码RNA发挥着 作为隔离的海绵，在脑发育和突触功能中发挥关键作用 调节基因表达的microRNAs(MiRNAs)和RNA结合蛋白(RBPs)通常 以竞争的方式。例如，我们的实验室已经表明，RBP，HUD，竞争 用miR-495调节成瘾相关基因的表达。我们新的初步结果 证明HUD也结合并调节HUD的表达和突触定位 14个大脑特异的CircRNA，包括CircHmer 1。CircHmer 1是由相同的基因产生的 (Hmer 1)产生线性Hmer 1b mRNA，这也是HUD的靶标。重要的是 Hmer-1蛋白通过其作用参与可卡因诱导的可塑性和药物寻找 调节I型代谢型谷氨酸受体信号与动态型突触 在神经元活动增加后缩小比例。我们发现CircHmer 1水平的击倒 增加突触活性和突触Hmer 1b基因水平。使用HUD过度表达 在小鼠的实验中，我们确定这个过程需要将CircRNA与HUD结合。此外，我们 发现小鼠伏隔核(NAC)的CircHmer 1水平降低 条件性地点偏好模型中寻求可卡因行为的增加。相比之下， 生活在丰富环境中的大鼠不同程度的可卡因寻找行为(低 在有可卡因自我吸毒史的强制戒断期间)与隔离(高水平) 给药与肿瘤细胞CircHmer 1/Hmer 1b mRNA水平的比值呈负相关 南汽壳牌。根据这些结果，我们假设突触CircHmer 1在脑内的表达 NAC壳通过与Hmer 1b mRNA竞争HUD结合来调节突触活动， 导致Hmer 1b功能的下游效应，从而减弱药物寻找行为。至 检验这一假设，我们将首先检查CircHmer 1和Hmer 1b mRNA是否竞争 HUD结合，转运到突触，以及培养神经元中神经元活动的控制。 然后，我们将评估慢病毒介导的CircHmer 1水平操纵对 Hmer 1b基因突触水平与可卡因寻找行为的调节。这 研究将通过阐明CircHmer 1在机制中的作用来影响该领域 可卡因诱导的神经可塑性和成瘾相关行为的潜在变化。 最终，获得对大脑变化背后的分子机制的理解 SODS将有助于开发针对可卡因使用障碍的新治疗策略。

Brain abnormalities associated with substance use disorders (SUDs) involve long-term changes in gene expression that derail motivational circuits toward drug seeking and taking despite negative consequences. While the role of transcription factors in gene expression changes has been well established, the subsequent post-transcriptional events that result in functional change are far from understood. Recent breakthroughs suggest that circular RNAs (circRNAs) are critical in regulating post-transcriptional events. This new class of non-coding RNAs plays a critical role in brain development and synaptic function by acting as sponges for sequestering microRNAs (miRNAs) and RNA-binding proteins (RBPs), which regulate gene expression, often in a competitive manner. For instance, our laboratory has shown that the RBP, HuD, competes with miR-495 to regulate expression of addiction-related genes. Our new preliminary results demonstrate that HuD also binds to, and regulates, the expression and synaptic localization of 14 brain-specific circRNAs, including circHomer1. circHomer1 is generated from the same gene (Homer1) that generates linear Homer1b mRNA, which is also a HuD target. Importantly, Homer1 protein is involved in cocaine–induced plasticity and drug seeking via its role in regulating type I metabotropic glutamate receptor signaling and homeostatic synaptic downscaling after increased neuronal activity. We found that knockdown of circHomer1 levels increases synaptic activity and synaptic Homer1b mRNA levels. Using HuD overexpressing mice, we determined that this process requires binding of the circRNA to HuD. Furthermore, we found that circHomer1 levels in the nucleus accumbens (NAc) are decreased in mice displaying increased cocaine-seeking behavior in the conditioned place preference model. In contrast, the varying levels of operant cocaine-seeking behavior in rats living in an enriched environment (low levels) versus isolation (high levels) during forced abstinence after a history of cocaine self- administration inversely correlate with the ratios of circHomer1 to Homer1b mRNA levels in the NAc shell. Based on these results, we hypothesize that synaptic circHomer1 expression in the NAc shell regulates synaptic activity by competing with Homer1b mRNA for HuD binding, leading to downstream effects in Homer1b function that attenuate drug-seeking behavior. To test this hypothesis, we will first examine whether circHomer1 and Homer1b mRNA compete for HuD binding, transport to synapses, and the control of neuronal activity in neurons in culture. We will then evaluate the effects of lentiviral-mediated manipulations of circHomer1 levels on Homer1b mRNA synaptic levels and the modulation of operant cocaine-seeking behavior. This research will impact the field by elucidating the role of circHomer1 in the mechanisms underlying changes in cocaine-induced neuroplasticity and addiction-related behaviors. Ultimately, gaining an understanding of the molecular mechanisms underlying brain changes in SUDs will aid in developing novel treatment strategies for cocaine use disorders.