mGluR-Homer interactions in excessive drinking

描述(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结构(包括伏隔核(NAC))的神经适应有助于从娱乐饮酒向过度饮酒的转变。最近，第1组代谢性谷氨酸受体(MGluR)相关支架蛋白Hmer 2被确定为酒精诱导的小鼠神经可塑性的活跃和必要的细胞介质。组成性表达的荷马蛋白促进第1组mGluR刺激的细胞内信号转导，并在突触后密度内聚集第1组mGluR，将这些受体与其他与突触可塑性有关的蛋白共同定位，如PI3K(磷脂酰肌醇-3激酶)。在体内，Hmer 2基因缺失降低了NAC中第1组mGluRs的功能和表达，Hmer 2基因敲除(KO)小鼠避免酒精和不耐受的行为表型类似于第1组mGluRs的药物阻断所产生的行为表型。总而言之，这些观察表明，第1组mGluR-Hmer信号是过度饮酒的重要细胞介质。为了直接验证这一假说，这项提议将使用体内药理学和遗传学方法来表征NAC内第1组mGluR-Hmer信号在调节预定高酒精消耗量(SHAC)小鼠模型中过度饮酒中的作用(目标1)。免疫组织化学和免疫印迹方法将被用来确定Hmer 2对持续过量饮酒对NAC神经元突触结构的影响的调节作用，以及mGluR-Hmer信号复合体的形成、亚细胞定位和功能(目标2)。最后，为了将过量饮酒的遗传变异与mGluR-Hmer-PI3K在NAC内的表达和信号联系起来，我们将在选择性培育出高SHAC和SLAC(预定低酒精消耗量)表型的小鼠之间比较mGluR-Hmer-PI3K信号级联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加深我们对从娱乐性饮酒到过度饮酒的调控机制的理解，并为酒精中毒的病因及其治疗提供更多的见解。

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.