Neurotransmitter Transport

描述（由申请人提供）：血清素转运体（SERT）负责降低释放这种神经递质的突触附近的血清素（5-HT）水平。在这个过程中，5-羟色胺被运送到释放它的细胞中，在那里它可以被重新包装到突触囊泡中。抑制SERT的药物增加突触5-HT的水平，延长其作用的持续时间。这些药物包括可卡因等被滥用的物质，以及抗抑郁药等治疗药物。一些作为SERT底物的药物，如3,4-亚甲二氧基甲基苯丙胺（又名甲基安非他明）。“摇头丸”)通过SERT从神经元释放5-羟色胺。从这些药物对行为的深远影响来看，SERT活性的调节很可能是正常脑生理学中的一个关键事件。五年前，我们在强迫症患者身上发现了这种转运蛋白的突变形式。这种突变体显然是通过一种通常涉及环GMP （cGMP）的途径以构成方式激活的。我们已经发现，该缺陷代表了去除SERT分子中276位磷酸基的能力缺陷。该位置被cGMP依赖性酶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，本提案概述了研究SERT磷酸化和去磷酸化酶与cGMP信号通路其他组分的关联的计划。SERT构象受磷酸化影响的机制也将被研究。所有这些研究都是为了验证一个假设，即cGMP的产生激活了一个信号通路，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-HT转运对SERT与调节蛋白相互作用的影响的预测。公共卫生相关性：本建议涉及血清素转运体的调节机制，血清素转运体是滥用药物和抗抑郁药的靶点。在与精神疾病相关的这种转运体的突变形式中发现了调节缺陷。我们的目标是了解在分子水平上负责这种调节的结构和机制事件。

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.