Regulation of neurotransmitter release by rab GTPases

描述（由申请人提供）： 神经递质从神经末梢的释放是通过以下方式发生的： 膜结合囊泡与突触前膜，和分散的 囊泡内容物进入细胞外空间。我们正在迅速获得一个 基于对囊泡的研究，对囊泡融合的分子理解 细胞内区室之间的运输，如内质网 网织膜和高尔基体。这些蛋白质构成了 已经鉴定出融合机制，并且这些蛋白质的神经元同种型 是释放发射器的关键它们是肉毒杆菌的目标， 破伤风毒素，神经毒素，严重损害递质释放在 神经肌肉接头和抑制性突触。 因此，突触囊泡融合是囊泡运输的一种形式， 它需要一个信号：钙离子。钙离子越多， 进入神经末梢，释放的递质量越大。 发射器的释放可以通过活动来调节。取决于实验 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递质量（促进作用），或 随着每个连续的脉冲（按压），释放会减少。 我们还不知道基本的核聚变机器是如何能够做出如此反应的。 不同的大与小水平的钙内流：并被调制 上或下，由先前的活动。 Rab GTP酶是一个蛋白质家族，每个步骤都有特定的成员 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囊泡上的蛋白质之间的配对， 靶膜。Rab 3a是位于突触囊泡上的RabGT酶，是一种 可能是突触囊泡融合机制调节剂的候选者，以及 从而释放发射器。在本提案中，我们检查变送器的释放， 神经肌肉接头和肾上腺嗜铬细胞表达不同的 rab 3a或组成型激活的rab 3a突变体rab 3a [Q81 L]的水平， 确定rab 3a GTvalve是否是发射器释放的调节器。的 这些研究的结果将提高我们改变 神经系统疾病中的递质释放，其中递质释放是 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.