Sustained Activation of the Tyrosine Kinase Syk by Antigen in Mast Cells Requires Local Ca2+ Influx through Ca2+ Release-activated Ca2+ Channels
Sustained Activation of the Tyrosine Kinase Syk by Antigen in Mast Cells Requires Local Ca2+ Influx through Ca2+ Release-activated Ca2+ Channels
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DOI：
10.1074/jbc.m804942200
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发表时间：
2008-11-14
影响因子：
4.8
通讯作者：
Parekh, Anant B.
中科院分区：
文献类型：
--
作者：
Ng, Siaw Wei;Di Capite, Joseph;Parekh, Anant B.
肥大细胞活化涉及IgE受体的交联，随后是非受体酪氨酸激酶Syk的磷酸化。这导致质膜结合酶磷脂酶C γ 1的活化，其水解次要膜磷脂磷脂酰肌醇4，5-二磷酸以产生二酰基甘油和三磷酸肌醇。三磷酸肌醇通过从细胞内储存的Ca 2+释放而提高细胞质Ca 2+浓度。该Ca 2+释放阶段伴随着通过钙库操作的Ca 2+释放激活的Ca 2+（CRAC）通道的持续Ca 2+内流。在这里，我们发现IgE受体的参与激活Syk，这导致Ca 2+从商店释放，然后是Ca 2+流入。Ca 2+内流期则维持Syk活性。这些受体激活的Ca 2+内流途径被鉴定为CRAC通道，因为用低浓度的Gd 3+或暴露于新型CRAC通道阻断剂3-氟吡啶-4-羧酸可以药理学阻断该通道（2 '，5'-二甲氧基联苯-4-基）酰胺或RNA干扰敲低编码CRAC通道孔的Orai 1，所有这些都阻止了由Ca 2+进入引发的Syk活性的增加。CRAC通道和Syk在空间上靠近在一起，因为用快速Ca 2+螯合剂1，2-双（2-氨基苯氧基）乙烷-N，N，N '，N'-四乙酸四倍体增加细胞质Ca 2+缓冲未能阻止Ca 2+进入激活Syk。我们的研究结果揭示了肥大细胞激活中的正反馈步骤，其中受体触发的Syk激活和随后的Ca 2+释放打开CRAC通道，随后的局部Ca 2+进入然后维持Syk活性。因此，通过CRAC通道的Ca 2+进入提供了Ca 2+和酪氨酸激酶信号传导途径可以彼此相互作用的手段。
Mast cell activation involves cross-linking of IgE receptors followed by phosphorylation of the non-receptor tyrosine kinase Syk. This results in activation of the plasma membrane-bound enzyme phospholipase C gamma 1, which hydrolyzes the minor membrane phospholipid phosphatidylinositol 4,5-bisphosphate to generate diacylglycerol and inositol trisphosphate. Inositol trisphosphate raises cytoplasmic Ca2+ concentration by releasing Ca2+ from intracellular stores. This Ca2+ release phase is accompanied by sustained Ca2+ influx through store-operated Ca2+ release-activated Ca2+ (CRAC) channels. Here, we find that engagement of IgE receptors activates Syk, and this leads to Ca2+ release from stores followed by Ca2+ influx. The Ca2+ influx phase then sustains Syk activity. The Ca2+ influx pathway activated by these receptors was identified as the CRAC channel, because pharmacological block of the channels with either a low concentration of Gd3+ or exposure to the novel CRAC channel blocker 3-fluoropyridine-4-carboxylic acid (2', 5'-dimethoxybiphenyl-4-yl) amide or RNA interference knockdown of Orai1, which encodes the CRAC channel pore, all prevented the increase in Syk activity triggered by Ca2+ entry. CRAC channels and Syk are spatially close together, because increasing cytoplasmic Ca2+ buffering with the fast Ca2+ chelator 1,2-bis(2-aminophenoxy) ethane-N, N, N', N'-tetraacetic acid tetrakis failed to prevent activation of Syk by Ca2+ entry. Our results reveal a positive feedback step in mast cell activation where receptor-triggered Syk activation and subsequent Ca2+ release opens CRAC channels, and the ensuing local Ca2+ entry then maintains Syk activity. Ca2+ entry through CRAC channels therefore provides a means whereby the Ca2+ and tyrosine kinase signaling pathways can interact with one another.