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

描述（由申请人提供）：多巴胺（DA）是一种单胺能神经递质，与CNS中的多种神经和精神疾病有关。DA对靶神经元的各种作用是通过原型7跨膜G蛋白偶联受体介导的，这些受体通过G蛋白依赖性机制与各种效应器偶联。我们以前的工作已经证明，在纹状体，DA D2受体（D2 R）介导的一些行动，通过Akt/GSK 3信号通路在G蛋白不依赖的方式，通过形成？抑制蛋白2/Akt/PP 2A信号传导复合物导致Akt的抑制和随后的GSK 3的活化。最近在动物和人类中的研究表明Akt/GSK 3信号通路在DA张力升高的行为表现和精神分裂症或躁狂症等疾病中起重要作用。临床有效的抗精神病药物，结合D2 R显示出高倾向于从事？-抑制蛋白2介导的通路，而情绪稳定剂锂通过抑制？arrestin 2/Akt/PP 2A信号复合物。尽管这些令人兴奋的细胞结果，该途径在体内的功能后果知之甚少。本研究的总体目标是产生一系列动物模型，其中D2 R下游通路的功能可以在？抑制蛋白2.目的1：我们将研究GSK 3的作用？然后呢？通过选择性地在纹状体传出通路的突触后D1 R和D2 R表达神经元中操纵它们，从而在DA的作用中调节连环蛋白。目标2：我们将确定？arrestin 2通过选择性失活和挽救其在相同突触后神经元中的功能。目标3：最后，我们将设计小鼠品系，选择性表达野生型或D2 R，可以选择性地通过G蛋白或？抑制蛋白2依赖的机制在这些相同的突触后神经元。我们预计，这些动物模型的生物化学，细胞生物学和行为分析将提供一个独特的理解，这种新的D2 R信号转导机制如何在纹状体DA的行动，我们的研究结果将提供新的见解，新的治疗药物的发展。 公共卫生相关性：神经递质多巴胺与多种精神障碍有关，包括帕金森病和亨廷顿病、精神分裂症、注意力缺陷多动障碍、图雷特综合征、躁狂症、成瘾和情感障碍。我们以前已经确定了一种新的信号转导机制，通过多巴胺D2样受体。由于这些受体是抗精神病药物的主要靶点，并且由于这些药物在精神病学中具有广泛的应用，因此这种新的信号通路在这些疾病的病因学和治疗管理中可能都很重要。通过产生基因修饰小鼠来靶向该途径中的组分，应该澄清该途径在多巴胺传递的正常和病理生理作用下的体内作用，并为开发治疗各种精神疾病的新型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.