Molecular Mechanisms Regulating BDNF Release

脑源性神经营养因子诱导中枢神经元结构和功能改变以调节突触效能；我们的目标是 是确定调控BDNF靶向和突触释放的分子机制 神经传递。BDNF被合成为前体proBDNF，分类为调节的分泌途径， 并以依赖活动的方式释放。在突触处，proBDNF可以选择性地与p75结合，从而 诱导LTD，并潜在地降低脊椎密度和树突复杂性。如果将proBDNF转换为 在分泌囊或突触裂隙中，TrkB被选择性地激活以增强突触 传导并促进轴突分支和树突生长。因此，监管机制 将proBDNF转化为成熟的BDNF，并调节运输到树突或轴突的关键调控 结构和功能神经元的可塑性。我们已经产生了表达HA标记的BDNF的敲入小鼠 显著提高内源性脑源性神经营养因子的检测水平。我们还鉴定了细胞内的伴侣， 包括山梨素和其他与proBDNF结合的山梨素家族成员。有了这些工具，三个相互关联的 目的是：(1)利用BDNF-HA小鼠的神经元，鉴定proBDNF是否转化为 成熟的脑源性神经营养因子发生在分选到分泌小泡的过程中，或在小泡融合和释放之后。我们 假设BDNF转化的位置可能因神经元亚型不同而不同。(2)我们会确定 山梨素家族成员认为，伴侣proBDNF到构成或调节的分泌途径，并到 树突或轴突。我们假设不同的sortilin成员将细胞内的运输引导到不同的 亚细胞室，递送到突触，并调节对成熟的BNDF的切割。使用BDNF-HA 小鼠和急性沉默的不同伴侣，我们将评估发育调节的变化 在前BDNF/成熟BDNF释放的比率以及BDNF逆行和顺行的情况下 异构体。(3)我们将产生有条件删除相关sortilin家族成员的敲入小鼠。这些 动物将允许我们剖析特定的BDNF伴侣在调节BDNF水平中的作用，目标是 轴突或树突，以及对完整的出生后大脑中神经元形态和连接的影响。 相关性(请参阅说明)： 该项目确定了调节BDNF释放的机制，并调节了形态和连通性 海马神经元和皮质神经元的；这些过程的失调有助于神经发育 疾病。一种减少BDNF释放的人类SNP会导致小鼠焦虑和抑郁症状，并且 与这些人类疾病相关。额缘连通性异常是焦虑症的原因 孤独症在本病中的治疗方法

BDNF induces structural and functional changes in central neurons to modulate synaptic efficacy; our goal is to identify molecular mechanisms that regulate BDNF targeting and release at synapses to modulate neurotransmission. BDNF is synthesized as a precursor, proBDNF, sorted to a regulated secretory pathway, and released in an activity-dependent manner. At the synapse, proBDNF can bind selectively to p75 to induce LTD, and potentially reduce spine density and dendritic complexity. If proBDNF is converted to mature BDNF in the secretory vesicle or synaptic cleft, TrkB is selectively activated to enhance synaptic transmission and promote axonal branching and dendritic growth. Thus, mechanisms that regulate conversion of proBDNF to mature BDNF, and regulate trafficking to dendrites or axons critically modulate structural and functional neuronal plasticity. We have generated knock-in mice expressing HA-tagged BDNF to markedly enhance detection of endogenous BDNF. We have also identified intracellular chaperones, including sortilin, and other sortilin family members that bind proBDNF. With these tools, three interrelated aims are proposed: (1) Using neurons from the BDNF-HA mouse, identify if conversion of proBDNF to mature BDNF occurs during sorting to secretory vesicles, or following vesicle fusion and release. We postulate that the location of BDNF conversion may differ among neuronal subtypes. (2) We will identify the sortilin family members that chaperone proBDNF to the constitutive or regulated secretory pathways, and to dendrites or axons. We posit that different sortilin members direct intracellular trafficking to different subcellular compartments, delivery to the synapse, and regulate cleavage to mature BNDF. Using BDNF-HA mouse, and acute silencing of different chaperones, we will assess the developmentally regulated changes in the ratio of proBDNF/mature BDNF release, and in retrograde and anterograde traffiking of BDNF isoforms. (3) We will generate knock-in mice to conditionally delete relevant sortilin family members. These animals will permit us to dissect the roles of select BDNF chaperones in regulating BDNF levels, targeting to axons or dendrites, and effects on neuronal morphology and connectively in the intact, postnatal brain. RELEVANCE (See instructions): This project identifies mechanisms that regulate BDNF release, and modulates morphology and connectivity of hippocampal and cortical neurons; disregulation of these processes contributes to neurodevelopmental disease. A human SNP that reduces BDNF release results in anxiety and depressive symptoms in mice, and correlates with these human diseases. Abnormal frontolimbic connectivity underiies conditions of anxiety anri autism Ths mfjchanlRms irifintifiert hfirR will vieiri npw tarnRt.¿; fnr fixaminatinn in thRSfi riiseases