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

 描述(由申请人提供)：体液记忆是获得性免疫和一些自身免疫性疾病的关键特征，是疫苗抵御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)和卵泡外反应促进各种记忆B细胞(Bmem)分化和维持的程度，回忆反应是从Bmem细胞产生的。关于B细胞激活后的潜在命运，包括对抗原的BCR亲和力的重要贡献，人们已经了解了很多，但关于B细胞内的信号如何影响记忆或回忆，人们知之甚少。通过体外操作和小鼠模型系统积累的证据表明，局部生理(例如，营养供应)与免疫系统细胞中的信号及其命运或功能特征之间存在调节相互作用。B细胞独特的生物学特性表明，它们使用新的机制，但对B淋巴系的代谢调节知之甚少，尤其是对不同类型的Bmem细胞或足够浓度的抗体的持久性。AMP激活的激酶(AMPK)是二甲双胍等抗糖尿病药物的靶标，在生物合成中调节能量产生与利用之间的平衡是关键。我们已经发现，B细胞中AMPK的主要亚型AMPKa1在B细胞内在作用中促进了召回抗体反应的能力。我们还发现了一条与AMPK平行的途径，在该途径上，ADP-核糖转移酶PARP14促进糖酵解、葡萄糖氧化和B细胞存活的增加。此外，几种抗体亚型的Recall抗体反应依赖于PARP14。这些和进一步的发现使我们假设AMPKA促进了抗原特异性的免疫球蛋白记忆B细胞的产生或维持，并且这一功能至少部分是通过促进代谢适宜[脂肪酸氧化、糖酵解和葡萄糖氧化]来发挥的。这项研究还将解决CTL记忆中心范式的关键研究中的一个尚未解决的悖论，其中(FAO)与记忆命运有关，而糖酵解与效应器样表型有关。难题是，这种平衡行为归因于AMPK活性，但这种激酶同时促进粮农组织和糖酵解。我们将检验这一假设，即这些形式的能量产生的不同调控是基于低氧诱导因子(S)(HIFS-1，2)的活性，低氧诱导因子是一种转录因子，可能在激活粮农组织糖酵解的同时直接抑制其活性。为了测试AMPK活性对体液回忆的影响，并阐明代谢途径可以被平衡的机制，我们有三个具体的目标。第一个(目标1)是为记忆中的关键代谢调节因子AMPK建立一个特定的B谱系固有功能，并确定需要它的阶段。在目标2中，我们将测试一个模型，在该模型中，HIFs与AMPK整合在设置B细胞代谢平衡和Recall Ab反应方面。最后，我们将评估mTOR是否在B细胞和体液记忆中是AMPK的效应者(目标3)。拟议研究的预期结果是，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角色。

 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.