mGluR-Homer interactions in excessive drinking

描述（由申请人提供）：目前的酒精中毒理论认为，酒精诱导的大脑边缘系统结构（包括延髓核（NAC））内的神经适应有助于从娱乐性饮酒过渡到过度饮酒。最近，第1组代谢型谷氨酸受体（mGluR）相关的支架蛋白Homer 2被确定为酒精诱导的小鼠神经可塑性的活性和必要的细胞介质。组成型表达的Homer蛋白促进组1 mGluR刺激的细胞内信号传导，并在突触后密度内聚集组1 mGluR，使这些受体与涉及突触可塑性的其他蛋白质如PI 3 K（磷脂酰肌醇-3激酶）共定位。Homer 2缺失降低了NAC中第1组mGluRs的功能和表达，Homer 2敲除（KO）小鼠的酒精回避和不耐受行为表型类似于通过药理学阻断第1组mGluRs产生的表型。总的来说，这些观察结果表明，第1组mGluR-Homer信号是过度饮酒的重要细胞介质。为了直接检验这一假设，该提议将采用体内药理学和遗传学方法来表征NAC内第1组mGluR-Homer信号传导在预定高酒精消耗（SHAC）小鼠模型内调节过量酒精消耗中的作用（目的1）。将采用免疫组织化学和免疫印迹方法来确定Homer 2 n调节持续过量饮酒对NAC神经元突触结构的影响的作用，以及mGluR-Homer信号传导复合物的形成、亚细胞定位和功能（目的2）。最后，为了将过量饮酒中的遗传变异与NAC内的mGluR-Homer-PI 3 K表达和信号传导相关，将在针对高SHAC和SLAC（预定低酒精消耗）表型选择性繁殖的小鼠品系之间比较mGluR-Homer-PI 3 K信号传导级联的成员的总蛋白含量和膜定位的免疫印迹。这些研究的结果将进一步了解参与调节从娱乐性饮酒到过度饮酒的过渡的细胞机制，并对酒精中毒的病因及其治疗提供更深入的了解。

DESCRIPTION (provided by applicant): Current theories of alcoholism posit that alcohol-induced neuroadaptations within limbic structures in the brain, including the nucleus accumbens (NAC), contribute to the transition from recreational alcohol drinking to excessive alcohol consumption. Recently, the Group 1 metabotropic glutamate receptor (mGluR) associated scaffolding protein Homer2 was identified as an active and necessary cellular mediator of alcohol-induced neural plasticity in mice. Constitutively expressed Homer proteins facilitate Group 1 mGluRstimulated intracellular signaling and cluster Group 1 mGluRs within the postsynaptic density, co-localizing these receptors with other proteins implicated in synaptic plasticity, such as PI3K (phosphatiylionsitol-3 kinase). Homer2 deletion reduces the function and the expression of Group 1 mGluRs in the NAC in vivo and the alcohol-avoiding and -intolerant behavioral phenotype of Homer2 knock-out (KO) mice resembles that produced by the pharmacological blockade of Group 1 mGluRs. Collectively, these observations suggest that Group 1 mGluR-Homer signaling is an important cellular mediator of excessive alcohol consumption. To test this hypothesis directly, this proposal will employ in vivo pharmacological and genetic approaches to characterize the role for Group 1 mGluR-Homer signaling within the NAC in regulating excessive alcohol consumption within the scheduled high alcohol consumption (SHAC) murine model (Aim 1). Immunohistochemical and immunoblotting approaches will be employed to determine the role for Homer2 n regulating the effects of sustained, excessive alcohol consumption upon the synaptic architecture of NAC neurons, as well as the formation, subcellular localization and function of mGluR-Homer signaling complexes (Aim 2). Finally, to relate genetic variance in excessive alcohol drinking to mGluR-Homer-PI3K expression and signaling within the NAC, immunoblotting the total protein content and membrane localization of members of the mGluR-Homer-PI3K signaling cascade will be compared between mouse lines selectively bred for high SHAC and SLAC (Scheduled Low Alcohol Consumption) phenotypes. The results of these studies will further our understanding of the cellular mechanisms involved in regulating the transition from recreational to excessive alcohol drinking and provide greater insight into the etiology of alcoholism and its treatment.