Dopamine receptor trafficking in drug sensitization and behavioral flexibility

 描述（由申请人提供）：D2多巴胺受体（D2 R）在所有类型的药物滥用者中均显著下调。然而，D2 R下调药物滥用的功能后果，以及介导药物诱导的D2 R在体内损失的分子机制仍然没有得到解决。多巴胺受体介导的信号传导受许多过程调节。一种方式是通过内吞作用，由此受体在活化后从细胞表面移除。在胞吞作用之后，不同的多巴胺受体被不同地分类：D1 R被再循环，而D2 R被降解。我们已经鉴定了一种蛋白质GASP 1，其负责靶向D2 R以在胞吞作用后降解。我们继续提出，在对药物滥用很重要的回路中，D1 R-Gs信号与D2 R-Gi信号的平衡由于在高多巴胺张力条件下D2 R的下调而被破坏，从而促进可塑性和行为的变化。为了支持这一假设，GASP 1的遗传破坏阻止了可卡因诱导的D2 R下调，并减弱了小鼠对可卡因的运动敏感性的发展。在这里，我们将研究如何改变D2 R和D1 R信号的平衡影响敏感性的运动（目标1）和奖励（目标2）可卡因的影响。然后，我们将评估是否多巴胺受体信号的平衡的变化，在选定的神经元的脑桥，腹侧被盖区，基底外侧杏仁核，或内侧前额叶皮层是必要的或足以影响这些行为（目的3）。我们将在一定程度上通过我们已经产生的新型转基因工具来实现这一目标，包括条件性和非条件性GASP 1敲除（KO）小鼠，以及表达不结合GASP 1的D2 R的敲入小鼠。我们还将探讨D2 R下调在改变行为中的作用，使用商业上可获得的和治疗上重要的多巴胺能配体。虽然这些配体的“药理学”已经研究了一段时间，在我们的方法的创新在于我们的考试不仅经典的药理学性质，如配体的亲和力和选择性，但也对这些配体的影响内吞和后内吞受体贩运。

 DESCRIPTION (provided by applicant): D2 dopamine receptors (D2R) are significantly downregulated in drug abusers of all types. However, both the functional consequences of D2R downregulation for drug abuse, and the molecular mechanisms that mediate drug-induced loss of D2R in vivo remain unresolved. Dopamine receptor-mediated signaling is regulated by numerous processes. One way is by endocytosis, whereby receptors are removed from the cell surface after activation. Following endocytosis, distinct dopamine receptors are sorted differentially: the D1Rs are recycled, while the D2Rs, are degraded. We have identified a protein, GASP1, that is responsible for the targeting of the D2R for degradation after endocytosis. We went on to propose that the balance of D1R-Gs signaling versus D2R-Gi signaling in circuits important to drug abuse becomes disrupted due to downregulation of D2R under conditions of high dopamine tone, and thereby promotes changes in plasticity and behavior. In support of this hypothesis, genetic disruption of GASP1, prevents cocaine induced downregulation of D2Rs and attenuates the development of locomotor sensitization to cocaine in mice. Here, we will examine how altering the balance of D2R and D1R signaling impacts sensitivity to both the locomotor (Aim 1) and rewarding (Aim 2) effects of cocaine. We will then assess whether changes in the balance of dopamine receptor signaling in selected neurons of the nucleus accumbens, ventral tegmental area, basolateral amygdala, or medial pre-frontal cortex are either necessary or sufficient to affect these behaviors (Aim 3). We will accomplish this, in part, with novel transgenic tools we have generated, including conditional and non-conditional GASP1 knock out (KO) mice, and a knock-in mouse expressing a D2R that does not bind GASP1. We will also approach the question of the role of D2R downregulation in altering behavior using commercially available, and therapeutically important, dopaminergic ligands. Although the "pharmacology" of these ligands have been studied for some time, the innovation in our approach lies in our examination of not only classical pharmacological properties, such as ligand affinity and selectivity, but also the effects of these ligands on both endocytic and post-endocytic receptor trafficking.