Adrenergic Receptor Mechanisms in Antidepressant Therapy

肾上腺素能受体(ARs)是中枢神经系统(CNS)介导的行为和多种神经功能的重要调节因子，包括情绪、记忆、神经内分泌控制和自主神经功能的刺激。肾上腺素能受体数目的改变与包括抑郁症在内的情感性精神障碍的病理生理学有关。β-肾上腺素能受体(β-AR)在慢性药物治疗期间发生下调 抗抑郁药物的研究表明，大脑中主要的β-AR亚型--β-肾上腺素受体(Beta1-AR)亚型的失调可能与抑郁症有关。我们建议在抗抑郁治疗过程中发展对转录和转录后β1-AR基因调控的机械性理解。我们研究了激动剂诱导后β1-AR mRNA下调的分子机制，并确定了潜在的转录和转录后调控机制。首先，我们最近确定RNA结合因子Hur、hnRNP A1和AUF-1都与大鼠61-AR mRNAs的3‘非翻译区(UTR)相互作用，并且Hur在β-AR激动剂异丙肾上腺素的存在下被诱导，导致_I-AR转录本的加速降解。其次，我们研究了异丙肾上腺素对C6细胞的作用，发现异丙肾上腺素可在刺激后2小时内迅速诱导cAMP早期抑制因子(ICER)和其他相关的CREM(cAMP反应元件(CRE)调节剂)mRNA的表达，从而抑制β1-AR基因的转录。第三，我们已经在Beta1-AR基因中发现了另一个转录抑制区，包括-396到-367位，并确定该抑制物分子是一个新的bZlP样转录因子。我们将长期向大鼠和恒河猴体内注入不同的抗抑郁药物，并回收皮质标本，以确定β1-AR基因下调的特定分子机制。这些信息可能为肾上腺素受体在抑郁症中的分子作用提供线索，并对抗抑郁药物的疗效有更好的了解。因此，这份R21赠款申请是对PA-00-073的目标4，“为建立有意义的未来研究而进行的初步研究和开发”做出的回应。特定目的1的主要实验目标是验证RNA结合蛋白HUR、hnRNP A1和/或AUF-1是参与抗抑郁剂诱导的β1-AR mRNA下调的降解分子，并确定抗抑郁剂是否通过与HUR和其他选择性HUR配体相互作用而触发β1-AR mRNAs的核质输出。特异性目标2的主要实验目标是验证ICER和新的bZlP样转录因子在抗抑郁治疗过程中作为β1-AR基因表达的潜在抑制因子。

Adrenergic receptors (ARs) serve as important regulators of central nervous system- (CNS-) mediated behavior and several neural functions, including mood, memory, neuroendocrine control, and stimulation of autonomic function. Alterations in adrenergic receptor number have been implicated in the pathophysiology of affective psychiatric disorders, including depression. Beta-adrenergic receptor (beta-AR) down-regulation occurs during chronic treatment with antidepressants, suggesting that the dysregulation of the betal-adrenerqic receptor (beta1-AR) subtype, the predominant beta- AR subtype in the brain, may be associated with depressive illness. We propose to develop a mechanistic understanding of transcriptional and post-transcriptional beta1-AR mRNA control during antidepressant therapy. We have examined the molecular mechanisms underlying beta1-AR mRNA down-regulation following agonist induction, and have identified potential transcriptional and post-transcriptional control mechanisms. Firstly, we have recently determined that the RNA binding factors HuR, hnRNP A1, and AUF-1 all interact with the 3' untranslated region (UTR) of the rat 61- AR mRNAs, and that HuR becomes induced in the presence of beta-AR agonist isoproterenol, resulting in the acceleration of _I-AR transcript degradation. Secondly, we have determined that exposure of C6 cells to isoproterenol results in a rapid induction of inducible cyclic AMP early repressor (ICER) and other related CREM (cyclic AMP response element (CRE) modulator) mRNA within two hours of stimulation, and serves to repress beta1-AR gene transcription. And thirdly, we have identified another transcriptional repressor region in the beta1-AR gene, encompassing positions -396 to -367, and have identified the repressor molecule as a novel bZlP-like transcription factor. We will chronically-infuse various antidepressants into rats and rhesus macaques, and recover cortical specimens to identify the specific molecular mechanisms underlying beta1-AR mRNA down-regulation. This information may provide insiahts in the molecular role of the adrenerqic receptors in depression, and develop a better understandinq of the efficacy of antidepressant treatment. Thus, this R21 grant submission is responsive to objective 4 of PA-00-073, "initial research and development for building significant future research". The primary experimental objectives of Specific Aim 1 are to verify that the RNA binding proteins HuR, hnRNP A1, and/or AUF-1 are the degradative molecules involved in antidepressant-induced beta1-AR mRNA down-regulation, and to determine whether antidepressants trigger the nucleocytoplasmic export of beta1-AR mRNAs, via interaction with HuR and other selective HuR ligands. The primary experimental objectives of Specific Aim 2 are to validate ICER and the novel bZlP-like transcription factor as potential repressors of beta1-AR gene expression during antidepressant therapy.