Akt/GSK-3 Signaling Cascade and the Actions of Dopamine

描述(申请人提供)：多巴胺(DA)是一种单胺能神经递质，与中枢神经系统的多种神经和精神障碍有关。DA对靶神经元的各种作用是通过典型的7-跨膜G蛋白偶联受体介导的，这些受体通过G蛋白依赖的机制耦合到各种效应器。我们以前的工作已经证明，在纹状体中，DA D2受体(D2R)通过不依赖于G蛋白的Akt/GSK3信号通路，通过形成β-arrestin 2/Akt/PP2A信号复合体，抑制Akt，进而激活GSK3，从而介导其部分作用。最近对动物和人类的研究表明，Akt/GSK3信号通路在DA张力升高的行为表现以及精神分裂症或躁狂症等疾病中发挥着重要作用。临床上有效的抗精神病药物结合D2Rs显示出很高的倾向于参与β-arrestin 2介导的途径，而情绪稳定剂锂通过抑制？-arrestin 2/Akt/PP2A信号复合体的稳定性来干扰这一途径。尽管有这些令人兴奋的细胞结果，但这一途径在体内的功能后果还知之甚少。本研究的总体目标是建立一系列动物模型，在该模型中可以在β-arrestin 2下游的不同水平精确研究D2Rs下游通路的功能。和β-连环蛋白通过选择性地在纹状体传出通路突触后表达D1R和D2R的神经元中发挥作用。目的2：我们将通过选择性失活和挽救相同突触后神经元中的β-arrestin 2功能来确定其作用。目的3：最后，我们将设计有选择地表达野生型或D2Rs的小鼠品系，这些D2Rs可以在这些突触后神经元中通过G蛋白或α-arrestin 2依赖的机制选择性地耦合。我们期望通过对这些动物模型的生化、细胞生物学和行为学分析，能够对这种新的D2R信号机制如何在纹状体转导DA的作用提供独特的理解，我们的结果将为开发新的治疗药物提供新的见解。 公共卫生相关性：神经递质多巴胺与多种精神疾病有关，包括帕金森氏症和亨廷顿病、精神分裂症、注意力缺陷多动障碍、抽动症、躁狂症、成瘾和情感障碍。我们以前已经发现了一种新的信号机制，通过多巴胺D2样受体转导。由于这些受体是抗精神病药物的主要靶点，而且这些药物在精神病学中有广泛的应用，这种新的信号通路在这些疾病的病因和治疗管理中都可能是重要的。通过产生转基因小鼠来靶向这一途径中的组件，应该可以阐明这一途径在正常和病理生理作用下的作用，并为开发治疗各种精神疾病的新药物疗法提供独特的见解。

DESCRIPTION (provided by applicant): Dopamine (DA) is a monoaminergic neurotransmitter that has been implicated in multiple neurological and psychiatric disorders in the CNS. The various actions of DA on target neurons are mediated via prototypical 7-transmembrane G protein-coupled receptors that couple to various effectors through G protein-dependent mechanisms. Our previous work has demonstrated that in the striatum, DA D2 receptors (D2R) mediate some of their actions through the Akt/GSK3 signaling pathway in a G protein-independent fashion via formation of a ?-arrestin 2/Akt/PP2A signaling complex leading to inhibition of Akt and the consequent activation of GSK3. Recent investigations in animals and humans have suggested an important role for the Akt/GSK3 signaling pathway in behavioral manifestations of elevated DA tone and in conditions like schizophrenia or mania. Clinically effective antipsychotic drugs that bind D2Rs show a high propensity to engage the ?-arrestin 2-mediated pathway, and the mood stabilizer lithium interferes with this pathway by inhibiting the stability of the ?-arrestin 2/Akt/PP2A signaling complex. Despite these exciting cellular results, the functional consequences of this pathway in vivo are poorly understood. The overall objective of this research is to generate a series of animal models in which the functioning of the pathway downstream of D2Rs can be precisely investigated at different levels downstream of ?-arrestin 2. Aim 1: We will examine the role of GSK3? and ?-catenin in the actions of DA by selectively manipulating them in postsynaptic D1R- and D2R-expressing neurons of the striatal efferent pathways. Aim 2: We will determine the contribution of ?-arrestin 2 by selectively inactivating and rescuing its function in the same postsynaptic neurons. Aim 3: Finally, we will engineer mouse lines that selectively express either wild type or D2Rs that can selectively couple through either a G protein- or a ?-arrestin 2-dependent mechanism in these same postsynaptic neurons. We anticipate that the biochemical, cell biological and behavioral analyses of these animal models will provide a unique understanding of how this novel D2R signaling mechanism transduces the actions of DA in striatum and that our results will provide novel insights into the development of new therapeutic agents. PUBLIC HEALTH RELEVANCE: The neurotransmitter dopamine has been implicated in multiple psychiatric disorders including Parkinson's and Huntington's diseases, schizophrenia, attention deficit-hyperactivity disorder, Tourette syndrome, mania, addiction and affective disorders. We have previously identified a novel signaling mechanism transduced through dopamine D2-like receptors. Since these receptors are primary targets for antipsychotic drugs, and because these drugs have wide application in psychiatry, this new signaling pathway may be important both in the etiology of these conditions and in their therapeutic management. The targeting of components in this pathway through generation of genetically-modified mice should clarify the in vivo role of this pathway under normal and pathophysiological actions of dopamine transmission and provide unique insights into the development of novel pharmacotherapies to treat the various psychiatric conditions.