Spatial control of Ca2+ signals in lymphocytes

描述(由申请人提供)：淋巴细胞激活包括多个细胞内信号传递过程。这种复杂性允许淋巴细胞以各种方式调节自己的功能，以便正确地进行分化和激活。这一复杂系统的损伤可能导致免疫系统功能障碍，如自身免疫、过敏和免疫缺陷。活化T细胞核因子(NF-AT)被认为是控制淋巴细胞活化的重要转录因子之一。核因子-AT由钙/钙调蛋白依赖的磷酸酶钙调神经磷酸酶(CN)激活。FK506和环孢菌素A可抑制NF-AT和CN之间的相互作用，这两种药物被广泛用于抑制免疫反应。最近，几种细胞蛋白和病毒蛋白也被确定为CN/NF-AT相互作用的抑制剂。在初步研究中，我们鉴定了一种蛋白Reps1，它与淋巴特异性的Src家族激酶Lck结合，并在淋巴细胞中的NF-AT激活中发挥关键作用。Reps1在胸腺细胞和其他淋巴器官中高表达。鸡B细胞系DT-40中Reps1基因敲除后，由于缺乏核因子-AT去磷酸化，导致核因子-AT活性丧失。即使在绕过近端信号转导事件的药物刺激下，核因子-AT的激活也不能恢复。此外，在T细胞中表达突变形式的Reps1的转基因小鼠显示，成熟T细胞产生的IL-2显著减少。综上所述，这些数据表明，Reps1在淋巴细胞激活中起着至关重要的作用。在本研究中，我们将详细分析Reps1在体外的作用机制及其在体内的生物学意义。

DESCRIPTION (provided by applicant): Lymphocyte activation consists of multiple intracellular signaling processes. This complexity allows lymphocytes to regulate their function in various ways so that their differentiation and activation are properly carried out. Impairment in this complex system could lead to malfunctioning of the immune system, such as autoimmunity, allergy, and immunodeficiency. Nuclear factor of activated T-cells (NF-AT) is regarded as one of the most important transcription factors that controls lymphocyte activation. NF-AT is activated by Ca2+/calmodulin-dependent phosphatase calcineurin (CN). The interaction between NF-AT and CN is inhibited by FK506 and Cyclosporin A, which are broadly utilized for suppression of the immune responses. Recently, several cellular and viral proteins were also determined as the inhibitors of CN/NF-AT interaction. In the preliminary study, we identify a protein Reps1 that binds the lymphoid specific Src family kinase Lck and plays a critical role in NF-AT activation in lymphocytes. Reps1 is highly expressed in thymocytes and other lymphoid organs. Gene knockout of Reps1 in a chicken B-cell line DT-40 resulted in abolishment of NF-AT activation due to lack of NF-AT dephosphorylation. NF-AT activation was not restored even when cells were stimulated by pharmacological agents that bypass proximal signaling events. Further, transgenic mice expressing a mutant form of Reps1 in T cells showed significantly reduced IL-2 production by mature T cells. Together, the data indicates that Reps1 plays an essential role in lymphocyte activation. In this study, we will analyze the detailed mechanism of Reps1 function in vitro and its biological significance in vivo.