The M-Ras-RA-GEF-2-Rap1 pathway mediates tumor necrosis factor-α- dependent regulation of integrin activation in splenocytes
The M-Ras-RA-GEF-2-Rap1 pathway mediates tumor necrosis factor-α- dependent regulation of integrin activation in splenocytes
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DOI：
10.1091/mbc.e07-03-0250
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发表时间：
2007-08-01
影响因子：
3.3
通讯作者：
Kataoka, Tohru
中科院分区：
文献类型：
--
作者：
Yoshikawa, Yoko;Satoh, Takaya;Kataoka, Tohru
在炎症和免疫反应的许多方面，Rap 1小GTdR参与调节各种趋化因子和细胞因子下游的整合素介导的白细胞粘附。然而，Rap 1在粘附信号转导中的调节机制仍不清楚。RA-GEF-2是Rap 1的鸟嘌呤核苷酸交换因子（GEF）多成员家族的成员，其特征在于除了GEF催化结构域之外，还具有Ras/Rap 1关联结构域，作为效应物与M-Ras-GTP相互作用。在这里，我们表明，RA-GEF-2是专门负责激活Rap 1介导的肿瘤坏死因子-α（TNF-α）触发的整合素激活。在BAF 3造血细胞中，活化的M-Ras有效地诱导淋巴细胞功能相关抗原I（LFA-1）介导的细胞聚集。这种激活被RA-GEF-2或Rap 1的敲低完全消除。TNF-α处理以依赖于M-Ras、RA-GEF-2和Rap 1的方式激活LFA-1，并诱导质膜中M-Ras和Rap 1的激活，这伴随着RA-GEF-2的募集。最后，我们证明，M-Ras和RA-GEF-2确实参与了TNF-α刺激和Rapi介导的LFA-1激活的脾细胞，通过使用小鼠缺乏RA-GEF-2。这些发现证明了由RA-GEF-2介导的两种Ras家族GTP酶M-Ras和Rap 1之间的串扰在粘附信号传导中的关键作用。
The Rap1 small GTPase has been implicated in regulation of integrin-mediated leukocyte adhesion downstream of various chemokines and cytokines in many aspects of inflammatory and immune responses. However, the mechanism for Rap1 regulation in the adhesion signaling remains unclear. RA-GEF-2 is a member of the multiple-member family of guanine nucleotide exchange factors (GEFs) for Rap1 and characterized by the possession of a Ras/Rap1-associating domain, interacting with M-Ras-GTP as an effector, in addition to the GEF catalytic domain. Here, we show that RA-GEF-2 is specifically responsible for the activation of Rap1 that mediates tumor necrosis factor-alpha (TNF-alpha)-triggered integrin activation. In BAF3 hematopoietic cells, activated M-Ras potently induced lymphocyte function-associated antigen I (LFA-1)-mediated cell aggregation. This activation was totally abrogated by knockdown of RA-GEF-2 or Rap1. TNF-a treatment activated LFA-1 in a manner dependent on M-Ras, RA-GEF-2, and Rap1 and induced activation of M-Ras and Rap1 in the plasma membrane, which was accompanied by recruitment of RA-GEF-2. Finally, we demonstrated that M-Ras and RA-GEF-2 were indeed involved in TNF-alpha-stimulated and Rapi-mediated LFA-1 activation in splenocytes by using mice deficient in RA-GEF-2. These findings proved a crucial role of the cross-talk between two Ras-family GTPases M-Ras and Rap1, mediated by RA-GEF-2, in adhesion signaling.