Regulation of thymocyte maturation and mature T lymphocyte homeostasis by c-FLIP

描述(申请人提供)：细胞caspase-8(FLICE)样抑制蛋白(c-flip)是死亡受体诱导的细胞凋亡的重要调节因子，在胸腺细胞成熟过程中起重要作用。C-flip的两种主要亚型c-flipl和c-flips在小鼠T淋巴细胞中已被鉴定。我们以前的研究表明，T淋巴细胞中两种c-flip亚型的条件性缺失会导致几乎完全缺乏成熟的T细胞，并增加单个阳性(SP)胸腺细胞的凋亡率。为了进一步确定c-FLIPL和c-flps亚型在胸腺细胞成熟和外周T细胞功能中所起的作用，我们培育了专门缺乏c-flipl(c-flipl-/-)或c-flps(c-flps-/-)亚型的小鼠。令人惊讶的是，我们发现在c-flip条件基因敲除小鼠中，c-flp的表达而不是c-flipl的表达拯救了胸腺细胞的发育。我们的研究进一步证明，c-Flipl对成熟T细胞的增殖是必不可少的，因为c-flipl-/-小鼠的T细胞在感染单核细胞增多性李斯特菌后不能发育为效应器。尽管越来越多的证据表明c-FLIP具有抗凋亡和细胞信号转导功能，但c-FLIP调节胸腺细胞成熟和成熟T细胞稳态的机制尚不清楚。根据我们的初步结果，我们假设c-flip1和c-flips在T细胞室具有三个主要功能：1.c-flips保护成熟的SP胸腺细胞免受TCR诱导的胸腺髓质细胞的凋亡。2.这两种c-flip异构体在维持成熟T细胞的动态平衡方面都是必不可少的，促进了T细胞的存活和增殖。3.c-Flipl通过其裂解形式c-Flipp43调控T细胞的增殖。在这个提案中，我们将使用我们生成的几个c-flip遗传模型来测试这三个假设。这些结果不仅将为c-flip调节胸腺细胞成熟和T细胞稳态的机制提供重要的见解，也将为更好地理解一般T淋巴细胞生物学提供依据。此外，确定c-FLIP在调节效应器T细胞存活中的作用可能会改进免疫和疫苗设计的策略。 简介：C-FLIP是一种重要的蛋白质，可以保护T淋巴细胞免于死亡，对T淋巴细胞的发育至关重要。我们提出的研究将提供关于c-flip如何保护T细胞以及何时它将保护T细胞免于死亡的重要信息。这项研究的结果将提高我们对免疫缺陷的理解，以及对微生物病原体感染的免疫反应的调节。

DESCRIPTION (provided by applicant): Cellular caspase-8 (FLICE)-like inhibitory protein (c-FLIP) is an important regulator of death receptor-induced apoptosis and plays an essential role in thymocyte maturation. Two major isoforms of c-FLIP derived from alternative mRNA splicing, c-FLIPL and c-FLIPS, have been identified in mouse T lymphocytes. Our previous studies have demonstrated that conditional deletion of both c-FLIP isoforms in T lymphocytes results in an almost complete lack of mature T cells and increased apoptosis of single positive (SP) thymocytes. To further define the roles played by the c-FLIPL and c-FLIPS isoforms in thymocyte maturation and peripheral T cell function, we have generated mice specifically lacking the c-FLIPL (c-FLIPL-/-) or c-FLIPS (c-FLIPS-/-) isoform. Surprisingly, we found that expression of c-FLIPS but not c-FLIPL in c-FLIP conditional knockout mice rescued thymocyte development. Our studies further demonstrate that c-FLIPL is essential for mature T cell proliferation, as T cells from c-FLIPL-/- mice fail to develop into effectors after Listeria monocytogenes infection. Although accumulating evidence suggests that c-FLIP has both anti-apoptotic and cell signaling functions, the mechanisms by which c-FLIP regulates thymocyte maturation and mature T cell homeostasis remain unknown. Based on our preliminary results, we hypothesize that c-FLIP has three major functions mediated through c-FLIPL and c-FLIPS in the T cell compartment: 1. c-FLIPS protects mature SP thymocytes from TCR-induced apoptosis in the thymic medulla. 2. Both c-FLIP isoforms are essential in maintaining mature T cell homeostasis by promoting survival and proliferation. 3. c-FLIPL regulates T cell proliferation through its cleaved form c-FLIPp43. In this proposal, we will test these three hypotheses using several c-FLIP genetic models we have generated. The results will not only provide important insights into the mechanisms by which c-FLIP regulates thymocyte maturation and T cell homeostasis but also provide a better understanding of general T lymphocyte biology. Furthermore, determining the role of c-FLIP in regulating effector T cell survival may improve strategies for immunization and vaccine design. Narrative: c-FLIP is an important protein that protects T lymphocytes from death and is essential for T lymphocyte to develop. Our proposed studies will provide important information on how c-FLIP protects T cells and when it will protect T cells from death. Results from this study will improve our understanding of immunodeficiency and the regulation of immune response to microbial pathogen infections.