The tyrosine kinase Syk is required for light chain isotype exclusion but dispensable for the negative selection of B cells
The tyrosine kinase Syk is required for light chain isotype exclusion but dispensable for the negative selection of B cells
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DOI：
10.1002/eji.200324309
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发表时间：
2004-04-01
影响因子：
5.4
通讯作者：
Turner, M
中科院分区：
文献类型：
--
作者：
Meade, J;Tybulewicz, VLJ;Turner, M
在这项研究中，我们着手测试Syk是否是不成熟B细胞阴性选择所必需的。表达B细胞抗原受体（BCR）转基因（3-83，抗H-2K（k））的B细胞在胎肝器官培养和辐射嵌合体模型中均经历了与Syk无关的阴性选择。此外，Syk非依赖性负选择并不能通过Bcl-2的转基因过表达而逆转。受体编辑在Syk缺陷的B细胞中不明显，推测是由于成熟的编辑的B细胞在Syk不存在的情况下不能发育的结果。有趣的是，BCR转基因的轻链同种型排除在Syk不存在的情况下失败。我们观察到在Syk缺陷的未成熟B细胞中，BCR介导的细胞蛋白酪氨酸磷酸化的总体水平显著降低。然而，包括磷脂酶Cgamma 2在内的许多底物的酪氨酸磷酸化虽然减少，但并未完全消除。BCR连接在Syk不存在的情况下触发钙通量的增加。因此，在Syk不存在的情况下，介导负选择的信号传导事件仍然可以发生。这可能是由于zeta相关蛋白70（ZAP-70）的冗余，我们证明它在未成熟的B细胞中表达。
In this study we set out to test whether Syk was required for negative selection of immature B cells. B cells expressing a B cell antigen receptor (BCR) transgene (3-83, anti-H-2K(k)) underwent negative selection independently of Syk in both fetal liver organ culture and radiation chimera models. Furthermore, Syk-independent negative selection was not reversed by transgenic overexpression of Bcl-2. Receptor editing was not apparent in Syk-deficient B cells, presumably as a consequence of the failure of mature edited B cells to develop in the absence of Syk. Interestingly, light chain isotype exclusion by the BCR transgene failed in the absence of Syk. We observed a dramatic reduction in the overall BCR-mediated tyrosine phosphorylation of cellular proteins in Syk-deficient immature B cells. However, the tyrosine phosphorylation of a number of substrates including phospholipase Cgamma2, although reduced, was not completely abrogated. BCR ligation triggered an increase in calcium flux in the absence of Syk. Thus signaling events that mediate negative selection can still occur in the absence of Syk. This may be due to redundancy with zeta-associated protein 70 (ZAP-70), which we demonstrate to be expressed in immature B cells.