Distinct contributions of mTOR complexes 1 and 2 to antibody responses and memory

 描述（由申请人提供）：体液记忆是适应性免疫的一个关键特征，对于疫苗抵抗微生物至关重要，但也可能促进某些自身免疫性疾病的持续存在。长寿命的浆细胞在第一次遇到抗原（Ag）后组成性地分泌表位特异性抗体（Ab），但在较长的时间后，该群体可能需要通过Ag特异性记忆B（BclB）细胞的再活化来实现的补充。T细胞帮助和生发中心（GC）反应促进IgM+和类别转换的Bmem细胞，并促进高亲和力Ab的回忆反应。在B细胞激活后的潜在命运中，关于B细胞内的信号传导如何调节记忆的形成、持续或再激活，我们知之甚少。在T细胞中，越来越多的证据表明细胞代谢与信号及其功能和命运的相互作用。B细胞记忆的独特生物学特性表明，BclA可能使用与T细胞不同的机制，但对B谱系记忆调节知之甚少。雷帕霉素靶蛋白（TOR）是一种丝氨酸-苏氨酸激酶，可被免疫调节药物雷帕霉素抑制，是生物合成中调节能量利用的主要联系。本研究的目的是阐明mTOR如何调节淋巴细胞功能。TOR激酶参与两种功能不同的衔接子复合物，使得其酶活性在mTORC 1中急性受损，而变构抑制剂（例如，雷帕霉素）对mT 0 RC 2的作用是时间和细胞类型依赖性的。在一个明显的矛盾，雷帕霉素可能会阻止B细胞增殖和类转换抗体的产生，但雷帕霉素治疗的患者再次接种疫苗的反应似乎总体上完好无损。我们已经发现，B谱系细胞需要表达Rictor（B细胞中mTOR复合物2的核心组分）以维持回忆Ab应答的能力。这些和进一步的发现使我们假设，Rictor，部分是因为它支架mTORC 2，促进Ag特异性记忆B细胞的产生或维持，并且这种功能至少部分是通过抑制FoxO 1来发挥的。为了测试mTOR对体液记忆的影响，我们有三个具体的目的。第一是阐明Rictor通过T和B谱系促进保护性Ab和体液记忆的阶段（AIM 1）。我们还旨在确定B谱系内在的分子机制，从而Rictor的行为在B谱系回忆（AIM 2）。同时，我们将使用遗传学方法来确定mTORC 1对初次和回忆性抗体应答（AIM 3）的影响。我们将确定mTORC 1调节免疫中IG类谱的机制，并测试AID表达通过mTORC 1增强但不完全依赖于mTORC 1的模型，并且在Bcells细胞中相对具有雷帕霉素抗性。这些研究的预期结果是，我们将发现mTORC 1和2在决定B谱系细胞和体液免疫的功能结果方面的新的但不同的作用。特别地，我们期望发现mTOR通过mTORC 1和2依赖性机制促进B细胞增殖，并且mTORC 1不仅调节B细胞增殖和克隆扩增，而且调节免疫后转换的IG类谱。

 DESCRIPTION (provided by applicant): Humoral memory, a key feature of adaptive immunity, is vital for vaccine protection against microbes but may also foster persistence of some auto-immune diseases. Long-lived plasma cells constitutively secrete epitope-specific antibody (Ab) after a first encounter with antigen (Ag), but after longer periods this population can need replenishment that is achieved by re-activation of Ag-specific memory B (Bmem) cells. T cell help and the germinal center (GC) reaction foster IgM+ and class-switched Bmem cells, and promote recall responses with high-affinity Ab. Among the potential fates of a B cell after its activation, remarkably little is known about how signaling within B cells regulates the formation, persistence, or reactivation of memory. In T cells, accumulating evidence suggests an interplay of cell metabolism with signaling and their functions and fates. The distinct biology of B cells an memory suggests that Bmem may use mechanisms different from T cells, yet very little is known about B lineage memory regulation. Target of Rapamycin (TOR), a major nexus for regulation of energy use in biosynthesis, is a serine-threonine kinase inhibited by the immune modulatory drug rapamycin. The goal of this research is to elucidate how mTOR regulates lymphocyte functions. TOR kinase participates in two functionally distinct adapter complexes, so that its enzymatic activity is acutely impaired in mTORC1 whereas the impact of allosteric inhibitors (e.g., rapamycin) on mTORC2 is time- and cell type-dependent. In an apparent paradox, rapamycin may block B cell proliferation and the generation of class-switched Ab, and yet re-vaccination responses in rapamycin-treated patients appear grossly intact. We have found that B lineage cells require expression of Rictor, a core component of mTOR complex 2 in B cells, to maintain the capacity for a recall Ab response. These and further findings lead us to hypothesize that Rictor, in part because it scaffolds mTORC2, promotes the generation or maintenance of Ag-specific memory B cells, and that this function is exerted at least in part through inhibition of FoxO1. To test the impact of mTOR on humoral memory, we have three specific Aims. The first is to elucidate the stages at which Rictor promotes protective Ab and humoral memory via T and B lineages (AIM 1). We also aim to determine B lineage-intrinsic molecular mechanisms whereby Rictor acts in B lineage recall (AIM 2). In parallel, we will use genetic approaches to determine what is the impact of mTORC1 on primary and recall Ab responses (AIM 3). We will identify mechanisms by which mTORC1 regulates the spectrum of Ig classes in immunity, and test a model that AID expression is enhanced by but not absolutely dependent on mTORC1, and is relatively rapamycin-resistant in Bmem cells. The expected outcome of the studies is that we will uncover novel but divergent roles for mTORC1 and 2 in determining the functional outcomes for B lineage cells and humoral immunity. In particular, we expect to find that mTOR acts to promote Bmem cells by mTORC1 & 2-dependent mechanisms, and that mTORC1 regulates not only B cell proliferation and clonal expansion, but the spectrum of switched Ig classes after immunization.