LUPUS GENES AND B-CELL SIGNALING

描述(申请人提供)：在NZM2410小鼠模型中，位于小鼠1号染色体上的Sle1和位于小鼠7号染色体上的Sle3代表了狼疮最强的2个基因座。为了了解这些基因座在狼疮发病中的作用，我们将这些疾病基因座作为同源基因间隔回交到相对正常的C57BL/6背景上。而B6小鼠健康，B6.Sle1小鼠发展为轻度狼疮，B6.Sle1双基因小鼠发展为严重狼疮性肾炎。我们最近发现，在这些基因中，成熟的B细胞表现出多种信号通路的渐进激活，包括AKT/mTOR轴、各种MAPK通路、NFkB、STAT3、STAT5和各种Bcl-2家族成员，其激活程度与疾病严重程度和易感基因剂量密切相关。重要的是，其中一些轴的激活，特别是NFkB和STAT3，在患有严重狼疮的双基因小鼠中特别明显，但在B6.Sle1小鼠中不明显。目前尚不清楚这些信号通路中的任何一个的激活对疾病是必要的还是充分的。我们推测NFkB和STAT3的激活在狼疮的发病机制中起着至关重要的作用。这一点将在AIM 2中使用遗传学方法进行测试，在AIM 3中使用药理学方法进行测试。尽管Sle3的罪魁祸首基因仍然未知，但我们已经了解到Sle1中最强大的亚位点的候选基因，即SLAMF6/Ly108，以B细胞固有的方式发挥功能，打破早期的B细胞耐受。目前，LY108可能突破耐受性的分子机制尚不清楚。我们推测，Ly108的多态变异可能通过在未成熟的B细胞内参与不同的信号通路而打破B细胞的耐受性。这一假设将在目标1中得到检验。总的来说，这些研究对系统性红斑狼疮的机制起源以及如何通过治疗进行管理具有重要的意义。

DESCRIPTION (provided by applicant): Sle1 on murine chromosome 1 and Sle3 on murine chromosome 7 represent 2 of the strongest loci for lupus in the NZM2410 mouse model. To understand how these loci contribute to lupus, these disease loci have been backcrossed onto the relatively normal C57BL/6 background as congenic intervals. Whereas B6 mice are healthy, B6.Sle1 mice develop mild lupus, and B6.Sle1.Sle3 bicongenic mice develop severe lupus nephritis. We have recently documented that mature B-cells in these congenics exhibit progressive activation of multiple signaling pathways, including the AKT/mTOR axis, various MAPK pathways, NFkB, STAT3, STAT5, and various Bcl-2 family members, with the levels of activation correlating well with disease severity and susceptibility gene dosage. Importantly, the activation of some of these axes, notably NFkB and STAT3, were particularly pronounced in bicongenic mice with severe lupus, but not in B6.Sle1 mice. Whether the activation of any of these signaling pathways is necessary or sufficient for disease is not known. We hypothesize that NFkB and STAT3 activation is essential for the pathogenesis of lupus. This will be tested using a genetic approach in Aim 2 and a pharmacological approach in Aim 3. Though the culprit gene for Sle3 remains unknown, we have learned that the candidate gene for the strongest sub-locus within Sle1, namely SLAMF6/Ly108, functions in a B-cell intrinsic fashion to breach early B-cell tolerance. Presently, the molecular mechanisms through which Ly108 might breach tolerance remain unclear. We hypothesize that polymorphic variants of Ly108 may breach B- cell tolerance by engaging different signaling pathways within immature B-cells. This hypothesis will be tested in Aim 1. Collectively, these studies have important implications towards the mechanistic origins o systemi lupus erythematosus and how it is managed therapeutically.