Amplification of receptor signalling by Ca2+ entry-mediated translocation and activation of PLCγ2 in B lymphocytes
Amplification of receptor signalling by Ca2+ entry-mediated translocation and activation of PLCγ2 in B lymphocytes
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DOI：
10.1093/emboj/cdg457
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发表时间：
2003-09-15
期刊：
影响因子：
11.4
通讯作者：
Mori, Y
中科院分区：
文献类型：
--
作者：
Nishida, M;Sugimoto, K;Mori, Y
在不可兴奋的细胞中，受体激活的钙信号包括最初的瞬时反应，随后是钙离子依赖的持续和/或振荡阶段。在这里，我们描述了与信号放大有关的第二阶段的分子机制。体内1，4，5-三磷酸肌醇(IP3)传感器显示，在B淋巴细胞中，受体激活和存储操作的钙离子进入极大地促进了IP3的产生，并终止于磷脂酶CGamma2(PLCGamma2)缺陷的细胞。免疫共沉淀法证实了受体激活的TRPC3钙通道和PLCGamma2之间的联系，它们共同增强了钙离子的反应。PLCGamma2基因缺陷的细胞表现出钙离子进入诱导的钙反应减弱。然而，这一缺陷可通过抑制IP3诱导的钙释放而被消除，这意味着IP3和IP3受体介导了第二钙相。此外，对突变体PLCGamma2的共聚焦显示表明，钙离子进入诱导了C2结构域介导的PLCGamma2以非脂肪酶依赖的方式向质膜移位，从而激活了PLCGamma2。值得注意的是，钙离子内流激活的PLCGamma2维持着蛋白激酶C下游的钙振荡和细胞外信号调节的激酶激活。我们认为，钙离子内流与PLCGamma2移位和激活的偶联控制着受体信号的放大和协调。
In non-excitable cells, receptor-activated Ca2+ signalling comprises initial transient responses followed by a Ca2+ entry-dependent sustained and/or oscillatory phase. Here, we describe the molecular mechanism underlying the second phase linked to signal amplification. An in vivo inositol 1,4,5-trisphosphate (IP3) sensor revealed that in B lymphocytes, receptor-activated and store-operated Ca2+ entry greatly enhanced IP3 production, which terminated in phospholipase Cgamma2 (PLCgamma2)-deficient cells. Association between receptor-activated TRPC3 Ca2+ channels and PLCgamma2, which cooperate in potentiating Ca2+ responses, was demonstrated by co-immunoprecipitation. PLCgamma2-deficient cells displayed diminished Ca2+ entry-induced Ca2+ responses. However, this defect was canceled by suppressing IP3-induced Ca2+ release, implying that IP3 and IP3 receptors mediate the second Ca2+ phase. Furthermore, confocal visualization of PLCgamma2 mutants demonstrated that Ca2+ entry evoked a C2 domain-mediated PLCgamma2 translocation towards the plasma membrane in a lipase-independent manner to activate PLCgamma2. Strikingly, Ca2+ entry-activated PLCgamma2 maintained Ca2+ oscillation and extracellular signal-regulated kinase activation downstream of protein kinase C. We suggest that coupling of Ca2+ entry with PLCgamma2 translocation and activation controls the amplification and co-ordination of receptor signalling.