Kalirin-7 is essential in cocaine signaling: focus on nucleus accumbens

描述(申请人提供)：吸毒成瘾是当今社会对公众健康的一大危害，对使用非法药物的人及其家人会产生终身影响。滥用药物最令人恼火的问题之一是，即使经过适当的治疗，成瘾者也有极大的复发倾向。在动物模型中，长期给药后最一致的发现之一是大脑特定区域的树突棘数量增加。即使在长期撤军之后，这些结构性变化仍然存在。在我们的实验室里，我们研究了一种名为Kalirin-7的蛋白质，它与树突棘的形成和维护有关。我们的假设是，这种树突棘的增加在药物滥用的长期影响中发挥了作用，并且Kalirin-7在结构变化中发挥了重要作用。我们将使用一组Kalirin-7基因缺陷的小鼠(Kal7KO)来确定它们对可卡因的行为或生化反应是否与野生型小鼠不同。初步研究表明，Kal7KO小鼠对可卡因的运动敏感度高，但对可卡因的位置偏好降低。我们现在正试图阐明Kalirin-7通过结合对可卡因的位置偏好和受体拮抗剂的共同给药来调节的特定途径(目标1)。有趣的是，当使用可卡因剂量方案增加Wt动物伏隔核中的树突棘时，Kal7KO动物并没有表现出树突棘的增加。下一步，我们将使用由多巴胺1受体启动子驱动的表达GFP的小鼠来检测KAL7在特定纹状体神经元亚群中的表达和形态效应(目标2)。纹状体中不同种类的神经元在成瘾过程中扮演着不同的角色，了解它们的功能对于了解成瘾至关重要。此外，我们最近发现，Kal7KO动物改变了NMDA受体NR2B亚单位的表面运输。NMDA受体的正常功能对于学习和记忆的正常可塑性是必不可少的，而NMDA受体功能的改变在药物成瘾的形成中起着重要作用。利用细胞培养模型和可卡因处理动物的组织，我们现在正在研究Kalirin-7和NR2B之间的特定相互作用，以及Kalirin-7如何改变这一关键受体的定位和运输(目标3)。当这些研究完成后，我们希望极大地扩大对神经元形态和受体运输变化在药物成瘾病理生理学中所起作用的认识。

DESCRIPTION (provided by applicant): Drug addiction is a major detriment to public health in today's society, with lifelong effects on people who use illicit drugs and their families. One of the most vexing problems with drugs of abuse is that addicts have a tremendous propensity to relapse, even with proper treatment. In animal models, one of the most consistent findings after prolonged drug administration is an increase in the number of dendritic spines in specific regions of the brain. These structural changes remain even after long periods of withdrawal. In our lab, we work on a protein, Kalirin-7, that has been implicated in the formation and maintenance of dendritic spines. It is our hypothesis that this increase in dendritic spines plays a role in the long-term effects of drug abuse, and that Kalirin-7 is an essential player in the structural changes. We will be using a line of mice genetically deficient in Kalirin-7 (Kal7KO) to determine if their behavioral or biochemical response to cocaine is different from that of wildtype mice. Initial studies have shown that the Kal7KO mice are hypersensitive to the locomotor sensitization effects of cocaine, yet show decreased place preference for cocaine. We are now trying to clarify the specific pathways that Kalirin-7 modulates by combining place preference for cocaine with co-administration of receptor antagonists (Aim 1). Interestingly, when using a cocaine dosing regimen that increases dendritic spines in the nucleus accumbens of Wt animals, Kal7KO animals do not show an increase in dendritic spines. Moving forward, we will be using mice expressing GFP driven by the dopamine 1 receptor promoter to examine the expression and morphological effect of Kal7 in specific subsets of striatal neurons (Aim 2). The different populations of neurons in the striatum play different roles in the addiction process, and understanding of their function is critical for the understanding of addiction. Additionally, we have recently discovered that Kal7KO animals have altered surface trafficking of the NR2B subunit of NMDA receptors. Proper function of NMDA receptors is essential for the normal plasticity underlying learning and memory, and altered NMDA receptor function has been shown to play a role in the development of drug addiction. Using both cell culture models and tissue from cocaine treated animals we are now investigating the specific interaction between Kalirin-7 and NR2B, and how Kalirin-7 alters the localization and trafficking of this critical receptor (Aim 3). When these studies are finished, we hope to have greatly expanded the knowledge of the roles that alterations in neuronal morphology and receptor trafficking play in the pathophysiology of drug addiction.