Regulation of plasma cell differentiation by PI3-kinase

描述（由申请方提供）：T依赖性免疫应答的特征在于分泌IgM的浆细胞快速出现，随后出现滤泡生发中心和同种型转换的高亲和力IgG、伊加或IgE分泌浆细胞。最近相当多的注意力已经给予了参与指定浆细胞发育（BLIMP 1）和生发中心发育（BCL 6和AID，激活诱导的胞苷脱氨酶）的基因。此外，使用模型T依赖性抗原的研究提供了对免疫应答期间B细胞中的定性和定量变化的了解。然而，在我们对活化的B细胞分化的理解中仍然缺乏的是对促进终末分化为分泌抗体的浆细胞的信号传导要求的理解，或者相反地，对促进进入生发中心导致类别转换重组（CSR）和体细胞超变（SHM）的信号传导要求的理解。这项工作提出了磷脂酰肌醇-3激酶（PI 3 K）在指导活化的B细胞的命运决定向浆细胞生成或生发中心的作用。我们的初步数据支持这一假设，即强PI 3 K活性促进浆细胞形成，而弱PI 3 K活性促进CSR。我们已经表明，通过化学或遗传方式降低PI 3 K活性，我们可以促进CSR; CSR与浆细胞生成呈负相关，但与增殖无关。我们的数据表明，这种调节在控制AID的表达和功能的水平上起作用，并强烈暗示Akt是控制CSR的PI 3 K激活的下游靶点。此外，我们发现Akt介导的CSR抑制通过Foxo家族转录因子的失活而发生。该提议的具体目的被设计为通过i）表征B细胞特异性PTEN缺陷动物、PTEN/CD 19双缺陷动物和PTEN/BLIMP 1双缺陷动物中的体内浆细胞和生发中心发育，ii）评估调节PI 3 K信号传导对参与浆细胞分化的基因的影响，和iii）鉴定调节AID表达和/或功能的PI 3 K应答元件。相关性：形成浆细胞和进行CSR的能力对于抗体介导的免疫应答至关重要。高IgM综合征是一种人类免疫缺陷，其中经历CSR的能力有缺陷，导致抗感染能力严重受损，而浆细胞形成失调最终可导致骨髓瘤。因此，了解调节这些过程的途径是我们了解这些疾病病因的必要步骤。

DESCRIPTION (provided by applicant): T-dependent immune responses are characterized by the rapid appearance of IgM secreting plasma cells followed by the appearance of follicular germinal centers and isotype class switched, high affinity IgG, IgA, or IgE secreting plasma cells. Considerable recent attention has been given to the genes involved in specifying plasma cell development (BLIMP1) and germinal center development (BCL6 and AID, activation induced cytidine deaminase). Additionally, studies using model T-dependent antigens have provided insight into the qualitative and quantitative changes in B cells during an immune response. However, what continues to be lacking in our appreciation of activated B cell differentiation is an understanding of the signaling requirements that promote terminal differentiation into antibody secreting plasma cells or conversely, the signals that promote entry into the germinal center resulting in class switch recombination (CSR) and somatic hypermutation (SHM). The proposed work addresses the role of phosphatidyl inositol-3 kinase (PI3K) in directing the activated B cell fate decision toward plasma cell generation or the germinal center. Our preliminary data support the hypothesis that strong PI3K activity promotes plasma cell formation, whereas weak PI3K activity promotes CSR. We have shown that by reducing PI3K activity, chemically or genetically, we can promote CSR; which is inversely correlated with plasma cell generation but not proliferation. Our data suggest that this regulation operates at the level of controlling the expression and function of AID, and strongly implicate the Akt as the downstream target of PI3K activation that controls CSR. Further, we show that Akt-mediated inhibition of CSR occurs through the inactivation of the Foxo family of transcription factors. The specific aims of this proposal are designed to define the role of PI3K signaling in activated B cell fate decisions by i) characterizing in vivo plasma cell and germinal center development in B cell-specific PTEN-deficient animals, PTEN/CD19 double-deficient animals, and PTEN/BLIMP1 double-deficient animals, ii) assessing the impact of modulating PI3K signaling on genes involved in plasma cell differentiation, and iii) identifying PI3K responsive elements regulating AID expression and/or function. Relevance: The ability to form plasma cells and to undergo CSR is critical for antibody mediated immune responses. Hyper-IgM syndrome is a human immunodeficiency in which the ability to undergo CSR is defective resulting in a severe impairment in the ability to fight infections, whereas dysregulated plasma cell formation can ultimately lead to myeloma. Hence, understanding the pathways regulating these processes is a requisite step towards our ability to understand the etiology of these diseases.