Molecular Mechanisms Regulating BDNF Research

BDNF诱导中枢神经元的结构和功能变化，以调节突触功效;我们的目标是 是为了确定调节BDNF靶向和在突触释放的分子机制， 神经传递BDNF作为前体proBDNF被合成，被分类到受调节的分泌途径， 并以活性依赖的方式释放。在突触处，proBDNF可以选择性地与p75结合， 诱导LTD，并可能降低棘密度和树突复杂性。如果proBDNF被转化为 在分泌囊泡或突触间隙中的成熟BDNF中，TrkB被选择性地激活以增强突触连接。 传递并促进轴突分支和树突生长。因此，调控机制 原BDNF向成熟BDNF的转化，并调节向树突或轴突的运输， 结构和功能神经元可塑性。我们已经产生了表达HA标记的BDNF的敲入小鼠， 显著增强内源性BDNF的检测。我们还鉴定了细胞内的伴侣， 包括分拣蛋白和其它结合proBDNF的分拣蛋白家族成员。有了这些工具，三个相互关联的 目的：（1）使用BDNF-HA小鼠的神经元，鉴定proBDNF是否转化为 成熟的BDNF在分选成分泌囊泡期间或囊泡融合和释放之后出现。我们 假设BDNF转换的位置在神经元亚型之间可能不同。(2)我们将确定 分拣蛋白家族成员陪伴proBDNF进入组成性或调节性分泌途径， 树突或轴突。我们证实，不同的分拣蛋白成员指导细胞内运输到不同的目的地。 BNDF在神经元中起重要作用，它通过调节亚细胞区室，递送到突触，并调节分裂成成熟的BNDF。使用BDNF-HA 小鼠和不同分子伴侣的急性沉默，我们将评估发育调节的变化 在原BDNF/成熟BDNF的释放比例，以及BDNF的逆行和顺行运输中， 同种型。(3)我们将产生敲入小鼠以有条件地删除相关分拣蛋白家族成员。这些 动物将使我们能够解剖选择BDNF伴侣在调节BDNF水平中的作用， 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。

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.