Aktivitäts-abhängige Regulation von neuralen Zelloberflächenproteinen und ihre Funktion bei der Synaptogenese: Funktionelle Charakterisierung von CALEB

神经细胞表面蛋白的活性依赖性调节及其在突触发生中的功能：CALEB 的功能表征

• 批准号: 46813617
• 负责人: Professor Dr. Fritz G. Rathjen
• 金额: --
• 依托单位: Max-Delbrück-Centrum für Molekulare Medizin (MDC) in der Helmholtz-Gemeinschaft
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2007
• 资助国家: 德国
• 起止时间: 2006-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/46813617?language=en
• 关键词: Aktivit; ts; abh; ngige; Regulation

Neuronal activity is essential for the complex wiring of the brain. The links between electric activity and molecules that contribute to structural remodeling of neuronal circuits are not well understood. In past years we have therefore screened for cell surface proteins which establish a link between electric activity and which might play a role in circuit formation. We characterized two cell surface proteins: CAR (coxsackievirus adenovirus receptor) and CALEB. CAR is a cell adhesion protein of the Ig superfamily which modulates the frequency of action potentials and regulates the level of intracellular free calcium. It is primarily expressed in the developing nervous system and is almost undetectable in the mature nervous system. CALEB is a chondroitinsulfate-containing member of the EGF-family of differentiation factors that becomes proteolytically converted at the plasma membrane. This conversion is facilitated by electric activity. Its absence results in deficits of presynaptic differentiation in several brain structures at early developmental stages and in impairments in the elimination process of the climbing fiber synapse on Purkinje cells. CALEB is restricted to the central nervous system and is predominantly expressed in the somato-dendritic compartment. Aims of this follow-up application are investigations on these two proteins and two additional proteins of the Ig superfamily structurally related to CAR (termed BT-IgSF and clmp). On the basis of their structural similarity we assume that clmp and BT-IgSF subserve a similar function as CAR. For CAR and BT-IgSF we have generated transgenic mouse models and for clmp we are in the process in establishing a knockout. We intend to study the development of neuronal circuits in these mutant mice. By electrophysiological and histological tracing techniques we ask whether the formation of neuronal circuits is impaired in these mutant mice. Furthermore, we intend to characterize a signaling cascade implicated in the CAR-mediated release of calcium from intracellular stores. The same will be done for BT-IgSF and clmp. We speculate that CAR, BT-IgSF and clmp modulate the level of intracellular free calcium in neighboring neurons and thereby influence calcium waves in neural tissues. To characterize the role of CALEB in the process of presynaptic differentiation further we will screen for a pre-synaptic receptor protein of CALEB. In addition several electrophysiological characterizations in different brain structures in CALEB mutant mice as wells as investigations on the signaling function of CALEB are planned.

神经元活动对于大脑的复杂布线至关重要。电活动和分子之间的联系，有助于神经元电路的结构重塑还没有得到很好的理解。因此，在过去的几年里，我们筛选了细胞表面蛋白，这些蛋白在电活动之间建立了联系，并可能在电路形成中发挥作用。我们表征了两种细胞表面蛋白：CAR（柯萨奇病毒腺病毒受体）和CALEB。CAR是IG超家族的细胞粘附蛋白，其调节动作电位的频率并调节细胞内游离钙的水平。它主要在发育中的神经系统中表达，在成熟的神经系统中几乎检测不到。CALEB是EGF家族分化因子中含有硫酸软骨素的成员，其在质膜处被蛋白水解转化。这种转换是由电活动促进的。它的缺乏会导致在发育早期的几个脑结构中的突触前分化的缺陷和浦肯野细胞上的攀爬纤维突触的消除过程中的损伤。CALEB局限于中枢神经系统，主要在体细胞-树突隔室中表达。该后续申请的目的是研究这两种蛋白质和结构上与CAR相关的IG超家族的两种另外的蛋白质（称为BT-IgSF和clmp）。基于它们的结构相似性，我们假设clmp和BT-IgSF具有与CAR相似的功能。对于CAR和BT-IgSF，我们已经产生了转基因小鼠模型，对于clmp，我们正在建立敲除的过程中。我们打算研究这些突变小鼠神经元回路的发育。通过电生理学和组织学追踪技术，我们询问这些突变小鼠神经元回路的形成是否受损。此外，我们打算表征与CAR介导的钙从细胞内储存释放有关的信号级联。对于BT-IgSF和clmp也将进行同样的操作。我们推测CAR、BT-IgSF和clmp调节邻近神经元细胞内游离钙水平，从而影响神经组织中的钙波。为了进一步研究CALEB在突触前分化过程中的作用，我们将筛选CALEB的突触前受体蛋白。此外，还计划对CALEB突变小鼠不同脑结构的电生理特征以及CALEB的信号功能进行研究。