Regulation of Leukocyte Migration by WD40 Repeat Proteins

描述(申请人提供)：细胞迁移是胚胎发生、血管生成、伤口愈合和免疫反应所必需的基本过程，而在这一过程中的异常与包括自身免疫性疾病、关节硬化和肿瘤转移在内的大量病理条件有关。细胞迁移受作用于细胞表面受体的趋化物质的调节，这些受体属于G蛋白偶联受体大家族。这些受体通常与Gi/o类G蛋白偶联，并通过GBG二聚体调节其功能。尽管GBG在细胞迁移中的重要作用已经得到了很好的证实，但GBG如何激活下游效应器以产生高度极化的细胞内信号，作为驱动细胞定向迁移的内部“罗盘”，仍不清楚。我们最近发现了GBG与WD40重复蛋白RACK1(活化C激酶1的受体)和WDR26之间的新的相互作用。根据RACK1和WDR26分别位于极化白细胞前沿并对GBG信号进行负向和正向调节的研究结果，我们推测GBG与WDR26和RACK1的相互作用是驱动白细胞极化和定向迁移的前沿协调GBG信号的重要正负反馈调节。在目标1中，我们将探索WDR26与GBG及其效应分子(包括PI3Ks和PLCB)相互作用的分子机制，以促进GBG信号转导，并在白细胞迁移的前沿产生高度极化的细胞内反应。在目标2中，我们将确定RACK1如何限制GBG信号，以便在前沿产生本地放大的信号，并用于信号适应和定向检测。最后，我们将剖析控制WDR26和RACK1与GBG相互作用的分子信号，并确定这些相互作用的平衡对白细胞迁移的影响。这些研究有可能填补我们在了解趋化物质如何通过GBG传递的关键空白，在前沿产生一个空间定位的细胞信号来驱动白细胞迁移，并揭示一种在G蛋白水平上调节趋化作用的新机制，这些G蛋白上游是所有对细胞迁移至关重要的已知信号通路。鉴于白细胞异常迁移在许多病理条件下的参与，这项拟议的研究将对识别新的靶点以实现与疾病发展相关的信号通路的选择性干扰至关重要。因此，这项工作具有很高的生物学意义和对人类健康的潜在影响。 公共卫生相关性：这项申请建议研究白细胞迁移的潜在机制。这项研究有望为开发治疗与白细胞异常迁移相关的疾病的新疗法做出重大贡献，包括自身免疫性疾病、心血管疾病和肿瘤转移。

DESCRIPTION (provided by applicant): Cell migration is a fundamental process required for embryogenesis, angiogenesis, wound healing and immune responses, and abnormalities in this process are associated with a plethora of pathological conditions including autoimmune diseases, arthrosclerosis and tumor metastasis. Cell migration is regulated by chemoattractants acting on cell-surface receptors belonging to the large family of G protein-coupled receptors. These receptors typically couple to G proteins of the Gi/o class, and mediate their functions through Gbg dimers. Although the essential role of Gbg in cell migration has been well established, it is still unclear how Gbg activate downstream effectors to generate a highly polarized intracellular signal that acts as an internal "compass" to drive directional cell migration. We have recently identified novel interactions between Gbg and the WD40 repeat proteins RACK1 (receptor for activated C kinase 1) and WDR26. Based on the findings that RACK1 and WDR26 are localized at the leading edge of a polarized leukocyte and negatively and positively regulate Gbg signaling, respectively, we hypothesize that reciprocal interactions of Gbg with WDR26 and RACK1 are important positive and negative feedback regulations for the coordinated Gbg signaling at the leading edge that drives leukocyte polarization and directed migration. In Aim 1, we will explore the molecular mechanism by which WDR26 interacts with Gbg and its effectors including PI3Ks and PLCb to promote Gbg signaling and generate a highly polarized intracellular response at the leading edge for leukocyte migration. In Aim 2, we will determine how RACK1 restricts Gbg signaling for the generation of a locally amplified signal at the leading edge and for signal adaptation and directional sensing. Finally, we will dissect the molecular signals that control the reciprocal interactions of WDR26 and RACK1 with Gbg and determine the impact of the balance of these interactions on leukocyte migration. These studies have the potential to close a critical gap in our understanding of how chemoattractants transmit through Gbg to generate a spatially localized cellular signal at the leading edge that drives leukocyte migration, and to unveil a novel mechanism of regulating chemotaxis at the level of G proteins upstream to all known signaling pathways essential for cell migration. Given the involvement of abnormal leukocyte migration in many pathological conditions, the proposed research will be vital for identifying novel targets to enable selective interference of the signaling pathways related to disease development. Thus, this work has high biological significance and potential impact on human health. PUBLIC HEALTH RELEVANCE: This application proposes to study the mechanisms underlying leukocyte migration. The study is expected to contribute significantly to the development of new therapies for the treatment of diseases related to abnormal leukocyte migration including autoimmune diseases, cardiovascular diseases and tumor metastasis.