Autophagy in T lymphocyte function

描述(申请人提供)：巨自噬(以下简称“自噬”)是真核细胞中一种保守的分解代谢过程。它的定义是形成双膜自噬小泡，并在细胞内降解胞浆和细胞器中发挥作用。虽然自噬很早就被认识到了，但它在各种生理和病理过程中的作用才刚刚开始阐明。我们最近的工作表明，原代T淋巴细胞具有进行自噬的能力，自噬基因ATG5对T细胞的生存和增殖是必不可少的，这表明自噬是调节成熟T细胞稳态的一种新机制。然而，自噬促进T淋巴细胞存活和增殖的潜在分子机制仍不清楚。具体地说，目前尚不清楚ATG5-/-T细胞的缺陷是由于不能形成自噬小体还是ATG5的自噬非依赖性功能所致？更重要的是，如果自噬受损损害了T细胞的存活，自噬通过什么机制抑制T淋巴细胞的死亡？通过有条件地删除T淋巴细胞中的第二个自噬基因ATG7，我们已经确立了自噬在幼稚T淋巴细胞存活中的重要作用。我们发现，在缺乏ATG5或ATG7的T细胞中，线粒体的动态平衡被破坏。这些结果表明，自噬通过维持细胞内细胞器的动态平衡，在T细胞功能中起着关键作用。我们的总体假设是，成熟的初级T淋巴细胞的自噬功能是细胞生存和TCR介导的增殖所必需的，它通过维持细胞质物质的周转，特别是线粒体等基本细胞器结构的周转。我们提出了三个具体目标来检验这一假设。在目标1中，我们将确定自噬是如何在原代T淋巴细胞中调节的，以及自噬诱导有助于细胞存活的发育阶段。在目标2中，我们将研究细胞器稳态的解除如何导致自噬缺陷的初级T淋巴细胞的细胞死亡。在目标3中，我们将建立自噬基因缺失在T细胞增殖过程中抑制细胞周期进展的机制。这项研究的结果将为调节成熟T细胞功能的分子机制提供重要的见解。更好地了解这一过程无疑将有助于未来设计增强T细胞对病原体的免疫反应的策略。公共卫生相关性：我们建议研究一种称为自噬的基本细胞内过程在调节T淋巴细胞存活和增殖中的作用。这项研究的结果如果得到资助，将为T淋巴细胞相关疾病的治疗和预防提供重要信息，包括设计疫苗以增强T细胞对微生物病原体的免疫反应、肿瘤发生和自身免疫性疾病的发展。

DESCRIPTION (provided by applicant): Macroautophagy (hereafter referred to as "autophagy") is a well-conserved catabolic process in eukaryotic cells. It is defined by the formation of double membrane autophagosome vesicles and functions in the intracellular degradation of cytosol and organelles. Although autophagy has long been recognized, its functions in various physiological and pathological processes have only begun to be elucidated. Our recent work has demonstrated that primary T lymphocytes have the capacity to undergo autophagy and that the autophagy gene Atg5 is essential for T cell survival and proliferation, suggesting that autophagy is a novel mechanism regulating mature T cell homeostasis. However, the underlying molecular mechanisms by which autophagy promotes T lymphocyte survival and proliferation remain unknown. Specifically, it is not clear whether the defect in Atg5-/- T cells is caused by an inability to form autophagosomes or an autophagy-independent function of Atg5? More importantly, if impaired autophagy compromises T cell survival, by what mechanism does autophagy inhibit death in T lymphocytes? Using conditional deletion of a second autophagy gene, Atg7, in T lymphocytes, we have established an essential role for autophagy in the survival of naive T lymphocytes. We have found that mitochondrial homeostasis is disrupted in T cells lacking Atg5 or Atg7. These results suggest that autophagy plays a key role in T cell function through maintaining the homeostasis of intracellular organelles. Our overall hypothesis is that autophagic function in mature primary T lymphocytes is required for cell survival and TCR-mediated proliferation through maintaining turnover of cytoplasmic material, in particular the essential organelle structures such as mitochondria. We proposed three specific aims to test this hypothesis. In aim 1, we will determine how autophagy is regulated in primary T lymphocytes and the developmental stages at which the induction of autophagy contributes to cell survival. In aim 2, we will examine how deregulation of organelle homeostasis contributes to cell death in autophagy-deficient primary T lymphocytes. In aim 3, we will establish the mechanisms by which loss of autophagy genes inhibits cell cycle progression during T cell proliferation. Results from this study will shed important insights to the molecular mechanisms by which mature T cell function is regulated. Better understanding this process will undoubtedly help future design of strategies boosting T cell immune responses to pathogens. PUBLIC HEALTH RELEVANCE: We propose to study the roles of an essential intracellular process termed autophagy in regulating T lymphocyte survival and proliferation. The results from this study, if funded, will provide important information for the treatment and prevention of diseases related to T lymphocytes including designing vaccines to boost T cell immune response to microbial pathogens, tumor genesis and autoimmune disease development.