Fit to remember? B cell metabolic 'fitness', AMPK & recall antibody responses

 描述（由申请人提供）：体液记忆是适应性免疫和一些自身免疫性疾病的关键特征，是疫苗抵抗微生物的能力的核心。这一过程的决定因素包括生发中心（GC）和滤泡外反应促进记忆B细胞分化和维持的程度，回忆反应源自这些细胞。关于B细胞激活后的潜在命运，包括BCR对Ag的亲和力的重要贡献，已经了解了很多，但关于B细胞内的信号传导如何影响记忆或回忆，却知之甚少。用体外操作以及小鼠模型系统积累的证据提供了局部生理学（例如，营养供应）与免疫系统细胞中的信号传导及其命运或功能特征。B细胞的独特生物学表明它们使用新的机制，但对B淋巴谱系的代谢调节知之甚少，尤其是对BclB细胞类别的持久性或足够浓度的Ab知之甚少。AMP激活激酶（AMPK）是二甲双胍等抗糖尿病药物的靶点，是调节生物合成中能量产生与利用之间平衡的关键。我们已经发现，在B细胞中AMPK的主要同种型AMPKa 1在B细胞内在作用中促进回忆Ab应答的能力。我们还发现了与AMPK平行的途径的证据，在该途径上，ADP-核糖基转移酶PARP 14促进糖酵解、葡萄糖氧化和B细胞存活的增加。此外，几种抗体同种型的回忆抗体应答依赖于PARP 14。这些和进一步的发现使我们假设AMPKa促进Ag特异性IgG+记忆B细胞的产生或维持，并且该功能至少部分地通过促进代谢适应性[脂肪酸氧化（FAO）、糖酵解和葡萄糖氧化]来发挥。该研究还将解决CTL记忆中心范式关键研究中一个尚未解决的悖论，其中（FAO）与记忆命运相关，而糖酵解与效应子样表型相关。难题是这种平衡作用归因于AMPK活性，但这种激酶促进FAO和糖酵解。我们将检验这样的假设，即这些形式的能量产生的差异调节是基于缺氧诱导因子（HIFs - 1，2）的活性，这些转录因子可以直接抑制FAO以及其糖酵解的激活。为了测试AMPK活性对体液回忆的影响，并阐明代谢途径可以平衡的机制，我们有三个具体的目的。第一个（目标1）是建立一个特定的B谱系-记忆中关键代谢调节因子AMPK的内在功能，并确定需要它的阶段。在目标2中，我们将测试其中HIF与AMPK整合以设置B细胞代谢平衡和回忆Ab应答的模型。最后，我们将评估mTOR是否是B细胞和体液记忆中AMPK的效应子（目的3）。这些研究的预期结果是，我们将发现AMPK和HIF- 1在决定B细胞代谢特征和体液免疫功能结果中的新作用。

 DESCRIPTION (provided by applicant): Humoral memory, a key feature of both adaptive immunity and some autoimmune diseases, is central to the capacity of vaccines to protect against microbes. Determinants of this process include the degrees to which germinal center (GC) and extrafollicular reactions foster the differentiation and maintenance of various classes of memory B (Bmem) cells from which recall responses are derived. Much has been learned about the potential fates of a B cell after its activation, including vital contributions of BCR affinity for Ag, but remarkably little is known about how signaling within the B cell impacts memory or recall. Accumulating evidence with in vitro manipulations as well as mouse model systems provides indications of a regulatory interplay of local physiology (e.g., nutrient supply) with signaling in cells of the immune system and their fate or functional characteristics. The unique biology of B cells suggests that they use novel mechanisms, but very little is known about metabolic regulation for the B lymphoid lineage and especially not for the persistence of classes of Bmem cells or adequate concentrations of Ab. AMP-activated kinase (AMPK), a target of anti-diabetic agents such as metformin, is central to regulation of the balance between energy generation versus utilization in bio-synthesis. We have found that the predominant isoform of AMPK in B cells, AMPKa1, promoted the capacity for a recall Ab response in a B cell- intrinsic role. We also developed evidence of a pathway parallel to AMPK, on which an ADP-ribosyl transferase, PARP14, promotes increases in glycolysis, glucose oxidation, and B cell survival. Moreover recall Ab responses of several Ab isotypes depended on PARP14. These and further findings lead us to hypothesize that AMPKa promotes the generation or maintenance of Ag-specific IgG+ memory B cells, and that this function is exerted at least in part through promotion of metabolic fitness [fatty acid oxidation (FAO), glycolysis, and glucose oxidation]. The research also will address an unresolved paradox from key studies of the central paradigm of CTL memory, in which (FAO) is associated with memory fate while glycolysis ties to effector-like phenotype. The conundrum is that the balancing act was attributed to AMPK activity, but this kinase promotes both FAO and glycolysis. We will test the hypothesis that differential regulation of these forms of energy generation is based on activity of hypoxia- induced factor(s) (HIFs - 1, 2), transcription factors that may directly repress FAO alongside its activation of glycolysis. To test the impact of AMPK activity on humoral recall, and elucidate a mechanism by which metabolic pathways can be balanced, we have three specific Aims. The first (Aim 1) is to establish a specific B lineage- intrinsic function for the key metabolic regulaor, AMPK, in memory and identify stages at which it is required. In Aim 2, we will test a model in which HIFs are integrated with AMPK in setting B cell metabolic balance and recall Ab responses. Finally, we will evaluate if mTOR is an effector of AMPK in B cells and humoral memory (Aim 3). The expected outcome of the proposed studies is that we will uncover novel roles for AMPK and HIF- 1 in determining the metabolic profile in B cells and functional outcomes in humoral immunity.