Regulation of Vesicular Glutamate Transport

描述（由申请人提供）：突触强度的变化是学习、记忆和成瘾等行为现象的基础，通常归因于受体敏感性的突触后变化，但它们也可能反映突触前对递质释放量的调节。每个囊泡可用于胞外释放的谷氨酸的量取决于其通过一个囊泡谷氨酸转运蛋白家族（VGLUTs）从细胞质转运到囊泡中。VGLUT1和vglut2在成人大脑中表现出一种互斥的表达模式，与递质释放的概率和可塑性的潜力相关，它是所有成熟的兴奋性神经元胞外释放谷氨酸的原因。VGLUT1还含有几个在VGLUT2中没有发现的蛋白相互作用结构域。这项K08指导临床科学家发展奖提案的长期目标是了解VGLUT同种异构体的运输差异如何导致不同突触中观察到的谷氨酸释放差异。该策略是研究c端序列在不同VGLUT亚型的活性和转运中的作用。我们发现在VGLUT1的c端有一个聚脯氨酸基序与参与突触囊泡循环的蛋白相互作用。我们将描述这些相互作用，并确定它们是否通过影响囊泡填充、运输或囊泡周期的其他方面来调节谷氨酸运输。此外，我们将表征和鉴定蛋白质与VGLUT1中其他两个内化基序的相互作用。总之，这些基序可能导致谷氨酸信号中囊泡填充、胞吐和内吞速度的差异。越来越多的证据表明，谷氨酸功能低下与精神分裂症的病理生理有关，可能涉及谷氨酸释放的变化。因此，了解谷氨酸储存和释放的调控可能对精神分裂症治疗药物的靶向性很重要

DESCRIPTION (provided by applicant): The changes in synaptic strength that underlie behavioral phenomena such as learning, memory and addiction, are usually attributed to postsynaptic changes in receptor sensitivity, but they may also reflect presynaptic regulation of the amount of transmitter released. The amount of glutamate per vesicle available for exocytotic release depends on its transport from the cytoplasm into vesicles by a family of vesicular glutamate transporter proteins, VGLUTs. VGLUT1 and 2, which account for the exocytotic release of glutamate by essentially all well-established excitatory neurons, exhibit a mutually exclusive pattern of expression in adult brain that correlates with the probability of transmitter release and the potential for plasticity. VGLUT1 also contains several protein-protein interaction domains not found in VGLUT2. The long-term goal of this K08 Mentored Clinical Scientist Development Award proposal is to understand how differences in the trafficking of VGLUT isoforms contribute to the differences in glutamate release observed at different synapses. The strategy is to study the role of C-terminal sequences in activity and trafficking of the different VGLUT isoforms. We have found that one of the polyproline motifs in the C-terminus of VGLUT1 interacts with proteins involved in synaptic vesicle recycling. We will characterize these interactions and determine whether they regulate glutamate transport by influencing vesicle filling, trafficking, or other aspects of the vesicle cycle. In addition, we will characterize and identify protein interactions with two other internalization motifs in VGLUT1. Together, these motifs may contribute to differences in the speed of vesicle filling, exocytosis and endocytosis in glutamate signaling. Increasing evidence implicates glutamate hypofunction in the pathophysiology of schizophrenia, which may involve changes in glutamate release. Thus, an understanding of the regulation of glutamate storage and release may be important in the targeting of therapeutic agents for schizophrenia