MECHANISMS OF RESISTANCE TO FAS-INDUCED APOPTOSIS IN HUMAN THYMOCYTES

Fas（APO-1或CD 95）是一种细胞表面受体，与免疫系统细胞中凋亡细胞死亡的调节相关。Fas蛋白在人胸腺细胞发育过程中的表达和功能，但不参与细胞死亡信号的传递。人类物种的特定作用的Fas在胸腺细胞发育的理解不仅会阐明这些细胞如何逃避通过这种受体的凋亡死亡信号，但可能会建议潜在的免疫调节治疗的疾病，通过Fas凋亡信号失调。将在三种同时和重叠的方法中探索人胸腺细胞对Fas诱导的凋亡的抗性的机制。首先，通过测试与其他凋亡刺激物共享的远端Fas信号通路的能力，定位在人胸腺细胞中特异性缺陷的凋亡信号步骤。TNF α、TRAIL和FAS/FLICE嵌合体将用于在涉及或短路FADD的条件下触发人胸腺细胞的凋亡。第二，将测试从人胸腺细胞克隆的Fas受体结合Fas配体和多聚化FADD的内在能力，以及它们作为野生型Fas的显性负性抑制剂的能力。第三，将通过“死亡陷阱”方法筛选人胸腺细胞cDNA文库中具有抗凋亡功能的蛋白质。这些实验将补充本项目其他项目中其他信号功能的研究，以确定指导人类胸腺中免疫细胞发育的信号因子。

Fas (APO-1 or CD95) is a cell surface receptor associated with the regulation of apoptotic cell death in cells of the immune system. The expression and function of Fas protein in developing thymocytes in the human thymus, but is not function in signaling cell death. An understanding of the human species specific role of Fas in developing thymocytes would not only illuminate how these cells escape apoptotic death signaling through this receptor, but might suggest potential immunomodulating therapies for diseases in which apoptotic signaling through Fas is dysregulated. The mechanism(s) which are responsible for the resistance of human thymocytes to Fas-induced apoptosis will be explored in three concurrent and overlapping approaches. First, apoptotic signal steps which are specifically deficient in human thymocytes will be localized by testing for the competence of the distal Fas signal pathway which is shared with other apoptotic stimuli. TNFalpha, TRAIL, and FAS/FLICE chimeras will be employed to trigger apoptosis in human thymocytes under conditions which involve or short circuit FADD. Second, Fas receptors cloned from human thymocytes will be tested for their intrinsic competence to bind Fas ligand and to multimerize FADD, and for their ability to serve as dominant negative inhibitors of wild type Fas. Thirdly, a human thymocyte cDNA library will be screened for proteins with anti- apoptotic function through a "death trap" approach. These experiments will complement studies of other signal function in other projects of this program project to define the signaling factors which instructed the development of immune cells in the human thymus.