Neurotransmitter Transport

描述(申请人提供)：5-羟色胺转运体(SERT)负责降低突触附近的5-羟色胺(5-HT)水平，释放这种神经递质。在这个过程中，5-羟色胺被运输到释放它的细胞中，在那里它可以重新包装成突触小泡。抑制SERT的药物会增加突触5-羟色胺的水平，并延长其作用时间。这些药物包括可卡因等滥用物质，以及抗抑郁药等治疗药物。作为SERT底物的一些药物，如3，4-亚甲基二氧基甲基苯丙胺(又名：“摇头丸”)通过SERT从神经元释放5-羟色胺。从这些药物的深远的行为后果来看，很明显，SERT活性的调节可能是正常大脑生理学中的一个关键事件。五年前，我们在强迫症患者中发现了一种转运蛋白的突变形式。这个突变体显然是通过一条通常涉及环状GMP(CGMP)的途径以结构性方式激活的。我们后来发现，该缺陷代表着去除SERT分子中第276位的磷酸基团的能力存在缺陷。这个位置被依赖于cGMP的酶PKG磷酸化。作为了解神经递质转运体结构和功能的长期目标的一部分，该提案概述了研究磷酸化和去磷酸化SERT的酶与cGMP信号通路的其他组成部分之间的关联的计划。此外，还将探讨磷酸化影响SERT构象的机制。所有这些研究都旨在验证一种假设，即cGMP的产生激活了一条信号通路，使SERT磷酸化和去磷酸化，从而导致周转率的增加和减少。我们还将测试构象变化对5-羟色胺运输对SERT与调节蛋白相互作用的影响的预测。与公共卫生相关：这项提案涉及一种调节5-羟色胺转运体的机制，该转运体是滥用药物和抗抑郁药的靶标。在与精神障碍相关的这种转运蛋白的突变形式中发现了调节上的缺陷。我们的目标是在分子水平上理解导致这种调控的结构和机制事件。

DESCRIPTION (provided by applicant): Serotonin transporter (SERT) is responsible for lowering serotonin (5-HT) levels in the vicinity of synapses that release this neurotransmitter. In this process, 5-HT is transported into the cell from which it was released, where it is available for repackaging into synaptic vesicles. Drugs that inhibit SERT increase the level of synaptic 5-HT and lengthen the duration of its action. These drugs include abused substances such as cocaine, and therapeutic drugs such as antidepressants. Some drugs that are substrates for SERT, such as 3,4-methylenedioxymethamphetamine (a.k.a. "ecstasy") act through SERT to release 5-HT from neurons. From the profound behavioral consequences of these drugs, it is clear that regulation of SERT activity is likely to be a key event in normal brain physiology. Five years ago we found a mutant form of the transporter in patients with obsessive compulsive disorder. This mutant is apparently activated in a constitutive fashion by a pathway normally involving cyclic GMP (cGMP). We have since discovered that the defect represents a defect in the ability to remove a phosphate group at position 276 in the SERT molecule. This position is phosphorylated by a cGMP-dependent enzyme, PKG. As part of the long term goal to understand the structure and function of neurotransmitter transporters, this proposal outlines plans to investigate the association of enzymes that phosphorylate and dephosphorylate SERT, along with other components of the cGMP signaling pathway. The mechanism by which SERT conformation is affected by phosphorylation will also be investigated. All of these studies are directed to testing the hypothesis that production of cGMP activates a signaling pathway that phosphorylates and dephosphorylates SERT with the consequent increase and decrease in turnover rate. We will also test the prediction that conformational changes underlie the effects that 5-HT transport has on SERT interaction with regulatory proteins. PUBLIC HEALTH RELEVANCE: This proposal concerns a mechanism for regulation of serotonin transporter, a target for drugs of abuse and antidepressants. Defects in regulation were found in a mutant form of this transporter associated with psychiatric disorders. We aim to understand the structural and mechanistic events that are responsible for this regulation at a molecular level.