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

 描述(申请人提供)：体液记忆，适应性免疫的一个关键特征，对疫苗保护微生物至关重要，但也可能促进一些自身免疫性疾病的持久性。长寿的浆细胞在第一次与抗原(Ag)相遇后会分泌表位特异性抗体(Ab)，但在较长时间后，这一群体可能需要通过重新激活Ag特异性记忆B(Bmem)细胞来实现补充。T细胞帮助和生发中心(GC)反应培养IgM+和类转换的Bmem细胞，并促进高亲和力抗体的回忆反应。在B细胞激活后的潜在命运中，人们对B细胞内的信号如何调节记忆的形成、持久性或重新激活知之甚少。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相互作用。B细胞记忆的独特生物学特性表明，Bmem可能使用与T细胞不同的机制，但对B细胞系记忆调节知之甚少。雷帕霉素(TOR)的靶点是一种被免疫调节药物雷帕霉素抑制的丝氨酸苏氨酸激酶，它是调节生物合成能量使用的主要纽带。本研究的目的是阐明mTOR如何调节淋巴细胞功能。Tor激酶参与了两个不同功能的接头复合体，因此其酶活性在mTORC1中受到严重损害，而变构抑制剂(如雷帕霉素)对mTORC2的影响是时间和细胞类型相关的。在一个明显的悖论中，雷帕霉素可能会阻止B细胞的增殖和类别转换抗体的产生，但接受雷帕霉素治疗的患者的再次接种反应似乎完全完好无损。我们已经发现B系细胞需要表达Rictor，它是B细胞中mTOR复合体2的核心成分，以维持对Recall Ab的应答能力。这些和进一步的发现使我们假设Rictor，部分是因为它是mTORC2的支架，促进Ag特异性记忆B细胞的产生或维持，并且这一功能至少部分是通过抑制FoxO1发挥的。为了检验mTOR对体液记忆的影响，我们有三个具体的目标。第一个是阐明Rictor通过T和B系促进保护性抗体和体液记忆的阶段(AIM 1)。我们还旨在确定Rictor在B谱系回忆中发挥作用的内在分子机制(AIM 2)。同时，我们将使用遗传学方法来确定mTORC1对初级抗体和Recall Ab反应的影响(AIM 3)。我们将确定mTORC1在免疫中调节Ig类光谱的机制，并测试一个模型，即AID的表达由mTORC1增强但不完全依赖于mTORC1，并且在Bmem细胞中对雷帕霉素相对耐药。这些研究的预期结果是，我们将揭示mTORC1和2在决定B细胞系和体液免疫的功能结果中的新的但不同的作用。特别是，我们期望发现mTOR通过mTORC1&2依赖的机制促进Bmem细胞的生长，并且mTORC1不仅调节B细胞的增殖和克隆性增殖，而且调节免疫后切换的Ig类的谱。

 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.