Molecular Mechanisms Controlling Postsynaptic Secretion

控制突触后分泌的分子机制

• 批准号: 8223314
• 负责人: Anton Maximov
• 金额: $ 47万
• 依托单位: SCRIPPS RESEARCH INSTITUTE, THE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-07 至 2014-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8223314
• 关键词: Acute; Address; Adult; Binding; Biochemical Genetics; Brain; Brain-Derived Neurotrophic Factor; C2 Domain; Calcium; Cell Fractionation; Cognition Disorders; Cognitive; Development; Exocytosis; Family; Genes; Genetic; Genetic Polymorphism; Goals; Health; Homologous Gene; Human; Image; Imaging Techniques; Impaired cognition; Knockout Mice; Laboratories; Lead; Learning; Life; Link; Mediating; Membrane; Membrane Protein Traffic; Memory; Molecular; Mus; Neurons; Neurotransmitters; Organelles; Pathway interactions; Phenotype; Physiological; Play; Process; Prosencephalon; Proteins; Resolution; Role; Schizophrenia; Secretory Vesicles; Signal Transduction; Site; Slice; Staging; Synapses; Synaptic Receptors; Synaptic Transmission; Synaptic plasticity; Testing; Transport Vesicles; Vertebral column; Vesicle; base; cellular imaging; cognitive function; insight; loss of function; member; mutant; nervous system development; neural circuit; neurotrophic factor; novel; postnatal; postsynaptic; relating to nervous system; research study; secretory protein; sensor; synaptic function; synaptotagmin; trafficking

DESCRIPTION (provided by applicant): Brain-derived neurotrophic factor (BDNF) is a small secreted protein that plays a fundamental role in nervous system development and in regulating the strength of existing synapses throughout the adult life. Imbalances in BDNF signaling impair several forms of synaptic plasticity and lead to a wide range of cognitive abnormalities. Unlike the classical neurotransmitters, BDNF is secreted by membrane-trafficking vesicular organelles that undergo exocytosis in neuronal processes and postsynaptic spines. The polymorphism in human BDNF gene which selectively abolishes activity-dependent synaptic release of BDNF has been associated with deficits in learning and memory. Remarkably, despite the importance of BDNF in brain development and plasticity, the molecular mechanisms underlying BDNF secretion have not been elucidated. Syt-11 is a member of synaptotagmin family of secretory proteins that are known to regulate exocytosis of various trafficking organelles. Recent genetic studies linked Syt-11 to familiar schizophrenia. The new observations in this proposal implicate Syt-11 to BDNF secretion. Specifically, we show that: i) Syt-11 is exclusively expressed in neurons and is localized on vesicular organelles that undergo activity-dependent exocytosis; ii) Syt-11 co-localizes with BDNF; iii) mouse Syt-11 gene is essential for survival during postnatal development; and iv) genetic deletion of Syt-11 impairs activity- dependent secretion of BDNF and homeostatic synaptic plasticity. Based on these observations we hypothesize that Syt-11 resides on and regulates exocytosis of trafficking vesicles that transport and release BDNF in neurons. This central hypothesis will be tested by several approaches. By using the subcellular fractionations and high-resolution live cell imaging, we will determine whether Syt-11 and BDNF co-traffic in the same secretory vesicles. Importantly, we will identify the sites of vesicle exocytosis and determine how exocytosis correlates with neural activity. As the next step, we will determine the extent to which transport and secretion of BDNF depends on Syt-11, and on interactions of Syt-11 with its effectors. This goal will be accomplished by analyses of subcellular distribution and secretion of BDNF in Syt-11 deficient neurons. Finally, we will perform electrophysiological analyses of cultured neurons and acute slices to test whether genetic deletion of Syt-11 impairs synaptic transmission and BDNF-dependent synaptic plasticity. These studies will provide new significant insights into cellular and molecular mechanisms underlying neurotrophin signaling in brain. Importantly, these studies will elucidate a secretory pathway that when defective causes abnormalities in synaptic and cognitive functions PUBLIC HEALTH RELEVANCE: Secreted brain-derived neurotrophic factor (BDNF) plays a fundamental role in nervous system development and in regulating the strength of existing synapses throughout the adult life. Imbalances in BDNF signaling have been implicated to a wide range of cognitive dysfunctions in humans. In this proposal, we will combine the biochemical, genetic, imaging and electrophysiological approaches to elucidate the mechanisms controlling transport and secretion of BDNF in neurons. These novel studies will provide significant insights into molecular and cellular mechanisms that regulate activity of neural circuitry in brain and link the abnormalities in BDNF secretion to cognitive diseases.

描述（由申请人提供）：脑衍生的神经营养因子（BDNF）是一种小型分泌蛋白，在神经系统发育以及调节整个成人生活中现有突触的强度方面起着基本作用。 BDNF信号传导的失衡会损害几种形式的突触可塑性，并导致广泛的认知异常。与经典的神经递质不同，BDNF是通过膜贩运的囊泡细胞器分泌的，这些细胞器在神经元过程和突触后刺中会胞吞作用。人类BDNF基因的多态性有选择地废除活性依赖性BDNF的突触释放与学习和记忆中的缺陷有关。值得注意的是，尽管BDNF在脑发育和可塑性中的重要性，但尚未阐明BDNF分泌的分子机制。 SYT-11是分泌蛋白的突触毒素家族的成员，该家族蛋白质是调节各种运输细胞器的胞吐作用。最近的遗传研究将SYT-11与熟悉的精神分裂症联系起来。该提案中的新观察结果暗示SYT-11向BDNF分泌。具体而言，我们表明：i）SYT-11仅在神经元中表达，并局部在经历活性依赖性胞吐作用的水泡细胞器上； ii）SYT-11与BDNF共定位； iii）小鼠SYT-11基因对于产后发育过程中的生存至关重要； IV）SYT-11的遗传缺失会损害BDNF和稳态突触可塑性的活性依赖性分泌。基于这些观察结果，我们假设SYT-11驻留在和调节贩运囊泡的胞吞作用，这些囊泡在神经元中运输和释放BDNF。该中心假设将通过几种方法进行检验。通过使用亚细胞分馏和高分辨率的活细胞成像，我们将确定在同一分泌囊泡中SYT-11和BDNF是否会共同流量。重要的是，我们将确定囊泡胞吐作用的部位，并确定胞吐作用与神经活性的相关性。作为下一步，我们将确定BDNF的运输和分泌取决于SYT-11的程度，以及SYT-11及其效应子的相互作用。该目标将通过分析SYT-11缺乏神经元中BDNF的亚细胞分布和分泌来实现。最后，我们将对培养的神经元和急性切片进行电生理分析，以测试SYT-11的遗传缺失是否会损害突触传播和BDNF依赖性突触可塑性。这些研究将为大脑中神经营养蛋白信号传导下的细胞和分子机制提供新的重要见解。重要的是，这些研究将阐明分泌途径，当缺陷引起突触和认知功能的异常时，公共卫生相关性：分泌的脑衍生的神经营养因子（BDNF）在神经系统发展中起着基本作用，在整个成人生活中调节现有突触的强度。 BDNF信号的失衡已与人类的多种认知功能障碍有关。在此提案中，我们将结合生化，遗传，成像和电生理方法，以阐明控制神经元中BDNF转运和分泌的机制。这些新的研究将提供对调节大脑神经回路活性的分子和细胞机制的重要见解，并将BDNF分泌异常与认知疾病联系起来。