N-wasp is essential for the negative regulation of B cell receptor signaling.
N-wasp is essential for the negative regulation of B cell receptor signaling.
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DOI：
10.1371/journal.pbio.1001704
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发表时间：
2013-11
期刊：
影响因子：
9.8
通讯作者：
Song W
中科院分区：
文献类型：
--
作者：
Liu C;Bai X;Wu J;Sharma S;Upadhyaya A;Dahlberg CI;Westerberg LS;Snapper SB;Zhao X;Song W
使用条件基因敲除小鼠模型的细胞生物学研究揭示了肌动蛋白细胞骨架负调节B细胞抗原受体的信号转导的新机制。受体信号传导的负调节对于控制细胞活化和分化是必不可少的。在B淋巴细胞中，B细胞抗原受体（BCR）信号传导的下调对于抑制自身反应性B细胞的活化是至关重要的;然而，信号传导的负调节的潜在机制仍然难以捉摸。使用基因操作的小鼠模型和全内反射荧光显微镜，我们证明了神经元Wiskott-Aldrich综合征蛋白（N-WASP），这是与WASP在所有免疫细胞共表达，是一个关键的负调节B细胞信号。B细胞特异性N-WASP基因缺失导致小鼠血清中BCR信号传导增强和延长以及自身抗体水平升高。N-WASP敲除B细胞中信号传导的增加与B细胞表面F-肌动蛋白积累的增加、抗原呈递膜上B细胞铺展的增强、B细胞收缩的延迟、信号传导活性BCR微簇合并成信号传导非活性中心簇的抑制以及BCR内化的阻断同时发生。在小鼠和人原代B细胞中，BCR激活后，WASP首先被激活，然后是N-WASP。N-WASP的激活被布鲁顿酪氨酸激酶诱导的WASP激活抑制，并通过抑制WASP激活的含有SH 2结构域的肌醇5-磷酸酶的激活恢复。我们的研究结果揭示了BCR信号负调控的新机制，并广泛地表明肌动蛋白介导的信号下调机制。关闭B细胞活化的机制是必要的，以确保在感染被清除时终止免疫反应。当这种负调节出错时，也会导致自身免疫。为了理解这种抑制过程是如何调节的，在这里，我们利用含有B细胞的敲除小鼠，这些细胞缺乏可能参与其负调节的蛋白质。我们专注于Wiskott-Aldrich综合征蛋白（WASP），造血细胞的关键细胞骨架调节因子，和神经WASP（N-WASP），它与WASP有50%的同源性，并且广泛表达。我们的研究表明，缺乏N-WASP蛋白的小鼠B细胞比表达这种蛋白的B细胞被激活到更高的水平和更长的时间。此外，在B细胞不产生N-WASP的小鼠中，自身反应性B细胞的数量升高。我们继续鉴定促进或抑制N-WASP活化的分子，并研究N-WASP抑制B细胞活化的细胞机制。基于这些发现，我们提出N-WASP是B细胞活化的关键抑制剂，并用于抑制自身反应性B细胞。
A cell biology study using conditional gene knockout mouse models reveals a novel mechanism by which the actin cytoskeleton negatively regulates the signal transduction of the B cell antigen receptor. Negative regulation of receptor signaling is essential for controlling cell activation and differentiation. In B-lymphocytes, the down-regulation of B-cell antigen receptor (BCR) signaling is critical for suppressing the activation of self-reactive B cells; however, the mechanism underlying the negative regulation of signaling remains elusive. Using genetically manipulated mouse models and total internal reflection fluorescence microscopy, we demonstrate that neuronal Wiskott–Aldrich syndrome protein (N-WASP), which is coexpressed with WASP in all immune cells, is a critical negative regulator of B-cell signaling. B-cell–specific N-WASP gene deletion causes enhanced and prolonged BCR signaling and elevated levels of autoantibodies in the mouse serum. The increased signaling in N-WASP knockout B cells is concurrent with increased accumulation of F-actin at the B-cell surface, enhanced B-cell spreading on the antigen-presenting membrane, delayed B-cell contraction, inhibition in the merger of signaling active BCR microclusters into signaling inactive central clusters, and a blockage of BCR internalization. Upon BCR activation, WASP is activated first, followed by N-WASP in mouse and human primary B cells. The activation of N-WASP is suppressed by Bruton's tyrosine kinase-induced WASP activation, and is restored by the activation of SH2 domain-containing inositol 5-phosphatase that inhibits WASP activation. Our results reveal a new mechanism for the negative regulation of BCR signaling and broadly suggest an actin-mediated mechanism for signaling down-regulation. Mechanisms to shut down B-cell activation are necessary to ensure termination of an immune response when an infection has been cleared. When this negative regulation goes wrong, it can also lead to autoimmunity. To understand how this inhibitory process is regulated, here we utilized knockout mice containing B cells that are deficient for proteins potentially involved in their negative regulation. We focus on Wiskott–Aldrich syndrome protein (WASP), a key cytoskeletal regulator of hematopoietic cells, and neural WASP (N-WASP), which shares 50% homology with WASP and is ubiquitously expressed. Our study shows that mouse B cells that lack N-WASP protein are activated to a greater level and for longer periods than B cells that express this protein. Furthermore, in mice where B cells do not make N-WASP, the numbers of self-reactive B cells are elevated. We went on to identify molecules that promote or inhibit N-WASP activation and to examine the cellular mechanisms by which N-WASP inhibits B-cell activation. Based on these findings we propose that N-WASP is a critical inhibitor of B-cell activation and serves to suppress self-reactive B cells.
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