Decoding and functional characterization of the tonic B cell Antigen receptor signaling Network in human B cells

除了B细胞的发育、活化和分化外，B细胞抗原受体（BCR）还控制着B细胞的生存。BCR介导的生存信号被称为强直BCR信号，因为它们发生在没有抗原结合的情况下。尽管有大量证据表明磷脂酰3-激酶信号通路的重要性，但强直性BCR信号转导的分子细节仍然知之甚少。然而，潜在信号过程的功能表征对于提高我们对B细胞生存信号及其在B细胞肿瘤中的失调的理解是重要的。因此，本项目的总体目标是阐明原代人B细胞中的补性BCR信号转导，以识别和功能表征关键过程，并特别关注细胞骨架相关过程和BCR信号转导事件的功能相互作用，我们将以正常人B细胞和淋巴瘤细胞之间的比较方式进行研究。我们将通过三个子项目来实现这一目标，这些子项目将在我们在Göttingen大学和法兰克福大学的实验室密切合作下进行。基于我们之前对BL细胞强直性BCR信号的研究，我们的第一个子项目将利用磷蛋白组学研究正常人B细胞强直性BCR信号。通过使用特定的小分子抑制剂，我们将讨论BCR-近端效应物以及细胞骨架在强直BCR信号传导中的作用。我们将系统地将这些结果与我们在淋巴瘤细胞中获得的补性BCR信号的磷酸化蛋白质组数据进行比较。在第二个子项目中，我们将基于我们的初步数据，在分子水平上机械地表征进行性BCR信号传导过程。我们将产生缺乏表达某些信号效应器的B细胞系。由于肌动蛋白细胞骨架在控制BCR信号中的关键作用，我们将主要关注被认为是细胞骨架调节因子的候选蛋白。这些细胞系将使我们能够分析某些细胞骨架调节剂在强直性BCR信号转导中的作用，并将用于在原代人B细胞中进行比较分析。在第三个子项目中，我们将研究强直性BCR信号的空间方面。在这里，我们将重点关注稳定预先形成的信号复合物以控制强直性BCR信号的过程，并特别关注基于肌动蛋白的细胞骨架的作用。

Beyond the development, activation, and differentiation of B cells the B cell antigen receptor (BCR) controls their survival. The BCR-mediated survival signals are referred to as tonic BCR signals because they occur in the absence of antigen binding. Despite substantial evidence for an importance of the phosphatidyl-3-kinase signaling pathway the molecular details of the tonic BCR signal transduction remain poorly understood. A functional characterization of the underlying signaling processes is, however, important to improve our understanding of survival signals in B cells and their dysregulation in B cell neoplasia. Hence, the overall aim of this project is the elucidation of tonic BCR signal transduction in primary human B cells to identify and functionally characterize key processes with a particular focus on the functional interplay of cytoskeleton-related processes and BCR signaling events that we will study in a comparative manner between normal human B cells and lymphoma cells. We will address this aim with three subprojects that will be carried out in close collaboration between our laboratories at the Universities of Göttingen and Frankfurt.Based on our previous studies of tonic BCR signaling in BL cells, our first subproject will aim at investigating tonic BCR signaling in normal human B cells by phosphoproteomics. By using specific small molecule inhibitors, we will address the role of the BCR-proximal effectors as well as the cytoskeleton in the context of tonic BCR signaling. We will systematically compare these results with the phosphoproteome data that we have obtained for tonic BCR signaling in lymphoma cells.In the second subproject, we will, based on our preliminary data, mechanistically characterize tonic BCR signaling processes on a molecular level. We will generate B cell lines that are deficient for expression of certain signal effectors. Because of the pivotal role of the actin cytoskeleton in controlling BCR signals, we will mainly focus on candidate proteins that are putative regulators of the cytoskeleton. The cell lines will allow us to analyze the role of certain cytoskeletal regulators in tonic BCR signal transduction and will be used to perform comparative analyses in primary human B cells.In the third subproject we will study spacial aspects of tonic BCR signaling. Here, we will focus on the processes that stabilize preformed signaling complexes to control tonic BCR signaling with a particular focus on the role of the actin-based cytoskeleton.