Unmasking a Role for Cortical Dopamine D4 Receptors in Controlling Circuit Dynamics and Behavior

摘要 前额叶皮质(PFC)是皮质-纹状体-丘脑-皮质(CSTC)环路的一部分，是认知/执行功能和社会过程的重要调节器。这一回路和这些行为区域的中断通常与几种神经精神障碍有关。尽管这些损伤的本质是虚弱的，但开发有效管理这无数缺陷的疗法的挑战仍然没有得到满足。虽然目前治疗神经精神疾病的药物主要针对多巴胺受体(DAR)，特别是D2R，但它们也与DAR的其他D2亚类(D3R、D4R)相互作用。D4R尤其令人感兴趣，因为它在关键的PFC神经元群体中的表达水平高于D2R。此外，一些临床上更有效的药物也显示出高D4R亲和力。然而，之前针对D4R开发临床有效疗法的尝试被证明是不成功的。有趣的是，这些努力发生在我们最近对gpr偏向信号概念的理解取得进展之前，即通过G蛋白或β-arrestins的信号，这引起了不同的细胞和生理结果。这一点，再加上设计细胞特异性遗传操作的能力，以及实时询问大脑神经网络功能和响应药物或行为操作的能力，都为我们提供了一个应对这一重要挑战的令人兴奋的机会。我们的合作者最近开发了一种纯D4R选择性部分激动剂(UCSF924)，我们发现它在药理和遗传动物模型中显示出显著的抗精神病药物样特性。这项建议的目的是提供概念证明，功能选择性靶向D4R是必要的，以减轻在神经精神障碍中观察到的认知/执行功能和社会损害。这是通过以下具体目标实现的。目的1：系统测定PFC神经元亚型中D4R介导的信号转导。目的2：阐明选择性D4R信号在神经网络调控中的作用。在目标1中，我们将利用我们验证的CRISPR/CAS9交叉系统选择性和系统地删除PFC锥体神经元或中间神经元中的D4R或β-arrestin2，并评估UCSF924如何调节选定的行为域。这将在AIM 2中得到扩展，我们的合作研究员的实验室将利用体内的电生理集合记录来评估UCSF924如何与神经网络接触并调节行为结果。解决这些目标将检验我们的中心假设，即在关键的PFC神经元中选择性靶向D4R介导的信号具有治疗潜力。我们提议的工作应该为制定一种策略来纠正目前对现有疗法难以解决的行为领域提供一个概念验证。

ABSTRACT The prefrontal cortex (PFC), part of the cortico-striato-thalamo-cortical (CSTC) circuit, is a critical regulator of cognition/executive function and social processes. Disruptions to this circuit and these behavioral domains are often associated with several neuropsychiatric disorders. Despite the debilitating nature of these impairments, the challenge to develop therapies that effectively manage this myriad of deficits remains unmet. Although current therapeutics to treat neuropsychiatric conditions primarily target dopamine receptors (DARs), specifically the D2R, they also interact with other D2 subclass of DARs (D3R, D4R). The D4R is of particular interest as it is expressed at higher levels than the D2R in key PFC neuronal populations. Additionally, some of the more clinically effective agents also exhibit high D4R affinity. However, previous attempts to develop clinically effective therapies targeting the D4R have proved unsuccessful. Intriguingly, these efforts occurred prior to recent advances in our understanding of the concepts of GPCR biased signaling i.e. signaling through G proteins or β-arrestins, which elicit different cellular and physiological outcomes. This, coupled with the ability to engineer cell specific genetic manipulations and the capacity to interrogate brain neural network function in real time and in response to pharmacological or behavioral manipulations, all provide us with an exciting opportunity to address this important challenge. Our collaborators have recently developed a purely D4R-selective partial agonist (UCSF924), and we have discovered that it exhibits remarkable antipsychotic-like properties in pharmacological and genetic animal models. The objective of this proposal is to provide proof-of-concept that functionally-selective targeting of the D4R is necessary to mitigate both the cognitive/executive function and social impairments observed in neuropsychiatric disorders. This is accomplished in the following Specific Aims. Aim 1: Systematic determination of D4R-mediated signaling in PFC neuronal subtypes. Aim 2: Elucidating the effect of selective D4R signaling in the regulation of neuronal networks. In Aim 1, we will utilize our validated CRISPR/Cas9 intersectional system to selectively and systematically delete D4R or β-arrestin2 in PFC pyramidal neurons or interneurons, and assess how UCSF924 modulates select behavioral domains. This will be expanded in Aim 2, where our co-investigator’s laboratory will utilize in vivo electrophysiological ensemble recordings to assess how UCSF924 engages neural networks and modulates behavioral outcomes. Addressing these aims will test our central hypothesis that selective targeting of D4R-mediated signaling in key PFC neurons has therapeutic potential. Our proposed work should provide a proof-of-concept for the development of a strategy to correct behavioral domains that are currently refractory to existing therapies.