Regulation of neurotransmitter release by rab GTPases

描述(由申请人提供)： 神经末梢的神经递质的释放是通过融合 与突触前膜结合的膜小泡，以及 囊泡内容进入细胞外空间。我们正在迅速获得 基于囊泡研究的囊泡融合的分子理解 细胞内隔室之间的运输，如内质 网状结构和高尔基体。构成最低限度的蛋白质 已经确定了融合机制，以及这些蛋白的神经元亚型 对发射机的释放至关重要。他们是肉毒杆菌的靶子， 破伤风毒素，神经毒素，严重损害神经递质的释放 神经肌肉连接和AT抑制性突触分别在大脑中。 因此，突触囊泡融合是囊泡运输的一种形式，不再 不受监管--它需要一个信号：钙离子。钙离子越多， 进入神经末梢，递质释放量越大。 神经递质的释放可以通过活动来调节。取决于实验结果 条件和正在研究的突触，快速重复刺激可以 增加每个刺激释放的传递量(促进)，或 每一次连续的冲动(抑郁)都会减少释放。 我们还不知道基本的聚变机器是如何做出这样的反应的 不同于大水平和小水平的钙内流：需要调节 由先前的活动向上或向下。 Rab GTP酶是一个蛋白质家族，在每个步骤中都有特定的成员 沿着细胞内膜运输的途径。生化证据 提示Rab GTP酶促进基本融合机制的形成- 促进囊泡上的蛋白质与细胞上的蛋白质配对 靶膜。Rab3a是位于突触小泡上的Rab GTP酶，是一种 可能是突触小泡融合机制调节器的候选人，以及 因此，发射机释放。在本提案中，我们检查发射机的释放 神经肌肉接头和肾上腺嗜铬细胞表达的不同 Rab3a或构造激活的rab3a突变体Rab3a[Q81L]的水平 确定rab3a GTPase是否是递质释放的调节因子。这个 这些研究的结果将增加我们改变 神经疾病中的递质释放，其中递质释放 不正常。

DESCRIPTION (provided by applicant): The release of neurotransmitters from a nerve terminal occurs by fusion of membrane-bound vesicles with the presynaptic membrane, and dispersion of the vesicle contents into the extracellular space. We are rapidly gaining a molecular understanding of vesicle fusion, based on studies of vesicle trafficking between intracellular compartments, such as the endoplasmic reticulum and the golgi apparatus. The proteins that comprise the minimum fusion machinery have been identified, and neuronal isoforms of these proteins are essential for transmitter release. They are targets of the botulinum and tetanus toxins, neurotoxins that severely impair transmitter release at the neuromuscular junction and at inhibitory synapses in the brain, respectively. Thus synaptic vesicle fusion is a form of vesicle trafficking that is no longer unregulated - it requires a signal: calcium ions. The more calcium ions that enter the nerve terminal, the greater the amount of transmitter release. Transmitter release can be modulated by activity. Depending on experimental conditions and the synapse being studied, rapid repetitive stimulation can increase the amount of transmitter released by each stimulus (facilitation), or there can be a reduction in release with each successive impulse (depression). We do not yet understand how the basic fusion machinery is able to respond so differently to large vs. small levels of calcium influx: and to be modulated up, or down, by prior activity. Rab GTPases are a family of proteins with specific members located at each step along the pathway of intracellular membrane trafficking. Biochemical evidence suggests that rab GTPases promote the formation of the basic fusion machinery - facilitating the pairing between proteins on the vesicle and those on the target membrane. Rab3a, the rab GTPase located on synaptic vesicles, is a likely candidate for a regulator of the synaptic vesicle fusion machinery, and thus, transmitter release. In this proposal we examine transmitter release at the neuromuscular junction and in adrenal chromaffin cells expressing different levels of rab3a or a constituitively activated rab3a mutant, rab3a [Q81L], to determine if the rab3a GTPase is a modulator of transmitter release. The results of these studies will increase our ability to alter the amount of transmitter release in neurological diseases in which transmitter release is abnormal.