A diacylglycerol-protein kinase C-RasGRP1 pathway directs Ras activation upon antigen receptor stimulation of T cells
A diacylglycerol-protein kinase C-RasGRP1 pathway directs Ras activation upon antigen receptor stimulation of T cells
复制标题
DOI：
10.1128/mcb.25.11.4426-4441.2005
复制
发表时间：
2005-06-01
影响因子：
5.3
通讯作者：
Weiss, A
中科院分区：
文献类型：
--
作者：
Roose, JP;Mollenauer, M;Weiss, A
Ras GTP酶是通过向各种效应分子发出信号来调节许多细胞应答的开/关开关。在T淋巴细胞中，Ras可以被两种Ras交换因子SOS和RasGRP 1激活，这两种因子分别通过衔接子Grb 2和LAT以及第二信使甘油二酯（DAG）募集。由活性Ras诱导的促分裂原活化蛋白（MAP）激酶磷酸化模式可以变化并有助于不同的细胞反应。由任一鸟嘌呤交换因子激活Ras的不同后果是未知的。DAG还募集并激活激酶蛋白激酶CO（PKCO），开启Erk MAP激酶途径，但负责的生化机制尚不清楚。我们产生的T细胞克隆缺乏佛波醇肉豆蔻酸酯乙酸酯（DAG的替代品）诱导的Ras激活。对RasGRP 1缺陷型Jurkat T细胞克隆和野生型细胞中RasGRP 1 RNA干扰的分析表明，RasGRP 1是最佳的抗原受体触发的Ras-Erk激活所必需的。RasGRP 1依赖于其DAG结合结构域选择性地激活Erk激酶。Erk的激活与RasGRP 1中苏氨酸残基184的磷酸化相关。这种磷酸化事件需要新的PKC激酶的活性。相反，活跃的PKCO依赖于RasGRP 1的充足性来有效地触发下游事件。最后，T细胞中DAG-PKC-RasGRP 1驱动的Ras-Erk激活是一种独特的信号传导事件，而不是简单地通过SOS活性进行补偿。
Ras GTPases are on/off switches regulating numerous cellular responses by signaling to various effector molecules. In T lymphocytes, Ras can be activated by two Ras exchange factors, SOS and RasGRP1, which are recruited through the adapters Grb2 and LAT and via the second-messenger diacylglycerol (DAG), respectively. Mitogen-activated protein (MAP) kinase phosphorylation patterns induced by active Ras can vary and contribute to distinct cellular responses. The different consequences of Ras activation by either guanine exchange factor are unknown. DAG also recruits and activates the kinase protein kinase CO (PKCO) turning on the Erk MAP kinase pathway, but the biochemical mechanism responsible is unclear. We generated T-cell clones deficient in phorbol myristate acetate (a surrogate for DAG)-induced Ras activation. Analysis of a RasGRP1-deficient Jurkat T-cell clone and RasGRP1 RNA interference in wild-type cells revealed that RasGRP1 is required for optimal, antigen receptor-triggered Ras-Erk activation. RasGRP1 relies on its DAG-binding domain to selectively activate Erk kinases. Activation of Erk correlates with the phosphorylation of threonine residue 184 in RasGRP1. This phosphorylation event requires the activities of novel PKC kinases. Conversely, active PKCO depends on RasGRP1 sufficiency to effectively trigger downstream events. Last, DAG-PKC-RasGRP1-driven Ras-Erk activation in T cells is a unique signaling event, not simply compensated for by SOS activity.