EGR1 and the MAPKinase pathway provide a focus for signal integration in antibody secreting cells (STC data set)

Antibody secreting cells (ASCs) survive in niche microenvironments as mature plasma cells, but how niche signals are integrated is poorly understood. Here we dissect such a response in human ASCs using an in vitro model, time course expression data, and a parsimonious gene correlation networking approach (PGCNA), we map expression changes that occur during the maturation to quiescent PCs. We demonstrate that TGF-beta, a niche factor, drives a focused effect on gene expression, including up-regulation of CXCR4, while progression to secretory optimization is completed. Heightened expression of CXCR4 in the presence of TGF-beta is in turn associated with enhanced ERK activation in response to SDF1. Mapping expression changes following SDF1/TGF-beta signaling we identify a module of immediate early genes including EGR1 as a primary nexus, upstream of subsequent waves of gene expression including genes encoding membrane proteins, such as solute channels and surface receptors. We conclude that niche signals delivered from SDF1 and TGFB integrate at the level of MAPkinase pathway and link downstream to changes in potential capacity for further niche sensing.proteases (MBTPS2/S2P) and release of the cytoplasmic domain as an active transcription factor. Such regulation is shared with a family of CREB3-related transcription factors and sterol regulatory element-binding proteins (SREBPs). Of these, we identify that the CREB3 family member CREB3L2 is strongly induced and activated during the transition from B-cell to plasma cell state. Inhibition of site-1 protease leads to a profound reduction in plasmablast number linked to induction of autophagy. Plasmablasts generated in the presence of site-1 protease inhibitor segregated into CD38high and CD38low populations, the latter characterized by a marked reduction in the capacity to secrete IgG. Site-1 protease inhibition is accompanied by a distinctive change in gene expression associated with amino acid synthesis, steroid and fatty acid synthesis pathways. These result demonstrate that transcriptional control of metabolic programs necessary for secretory activity can be targeted via site-1 protease inhibition during ASC differentiation. B-cells were isolated from the peripheral blood of 3 adult donors and differentiated in vitro until day 7 (see individual samples for culture conditions)

抗体分泌细胞（Antibody secreting cells, ASCs）作为成熟浆细胞存活于微环境龛中，但目前学界对微环境龛信号的整合机制仍知之甚少。本研究借助体外模型、时序表达谱数据以及简约基因关联网络分析方法（PGCNA），解析人类抗体分泌细胞中的此类应答，并绘制了其向静息浆细胞（quiescent PCs）成熟过程中的表达变化图谱。本研究证实，作为微环境龛因子的转化生长因子-β（TGF-beta）可对基因表达产生靶向调控作用，包括在分泌功能优化完成过程中上调C-X-C趋化因子受体4（CXCR4）的表达。在转化生长因子-β存在的情况下，C-X-C趋化因子受体4的高表达又可增强基质细胞衍生因子1（SDF1）诱导的细胞外调节蛋白激酶（ERK）激活。通过绘制基质细胞衍生因子1/转化生长因子-β信号通路激活后的表达变化，本研究鉴定出以早期生长应答蛋白1（EGR1）为核心枢纽的即刻早期基因模块，该模块位于后续多波基因表达调控的上游，其中包含编码溶质通道、表面受体等膜蛋白的基因。本研究认为，基质细胞衍生因子1与转化生长因子-β所传递的微环境龛信号可在丝裂原活化蛋白激酶通路层面实现整合，并将下游信号与细胞进一步感知微环境的潜能变化相关联；位点1蛋白酶（MBTPS2/S2P）可将胞质结构域切割为活性转录因子并释放。此类调控机制与CREB3相关转录因子家族及固醇调节元件结合蛋白（SREBPs）的调控模式一致。在该家族中，本研究鉴定出CREB3家族成员CREB3L2在B细胞向浆细胞状态转变的过程中被显著诱导并激活。抑制位点1蛋白酶可导致浆母细胞数量大幅减少，这一现象与自噬的诱导相关。在位点1蛋白酶抑制剂存在的情况下生成的浆母细胞可分为CD38高表达与CD38低表达两个群体，其中CD38低表达群体的免疫球蛋白G（IgG）分泌能力显著下降。抑制位点1蛋白酶会伴随出现与氨基酸合成、类固醇及脂肪酸合成通路相关的独特基因表达变化。本研究结果表明，在抗体分泌细胞分化过程中，可通过抑制位点1蛋白酶，对分泌活性所需代谢程序的转录调控进行靶向干预。本研究从3名健康成人供者的外周血中分离B细胞，并在体外进行分化培养至第7天（具体培养条件详见各样本信息）。