Identification and characterization of RA-GEF-2, a Rap guanine nucleotide exchange factor that serves as a downstream target of M-Ras
Identification and characterization of RA-GEF-2, a Rap guanine nucleotide exchange factor that serves as a downstream target of M-Ras
复制标题
DOI：
10.1074/jbc.m105760200
复制
发表时间：
2001-11-09
影响因子：
4.8
通讯作者：
Kataoka, T
中科院分区：
文献类型：
--
作者：
Gao, XL;Satoh, T;Kataoka, T
Ras家族的小GTP酶Rap受一系列特定的鸟嘌呤核苷酸交换因子(GEF)的调控，以响应上游刺激。Ra-gef-1是一种新的Rap全环基金，具有RAS/RAP1结合(RA)结构域。在此，我们报道了一种与RA-gef-1密切相关的蛋白质，命名为RA-gef-2。与RA-gef-1一样，在RA-gef-2中还发现了一个假定的环核苷酸单磷酸结合结构域、一个RAS交换基序、一个PSD-95/D1gA/ZO-1结构域和一个RA结构域。然而，RA-gef-2表现出与RA-egf-1不同的组织分布特征。Ra-gef-2可刺激Rap1和Rap2的鸟核苷酸交换，但不能刺激Ha-RAs。RA-EF-2的RA结构域以GTP依赖的方式与M-RAS结合，但不与其他被测试的RAS家族GTP酶结合，包括Ha-RAS、N-RAS、Rap1A、Rap2A、R-RAS、Ra1A、Rin、Rit和Rheb，而RA-Global-1的RA结构域专门与Rap1结合。在COS-7细胞中，RA-gef-2与活化的M-RAS共定位于质膜上，提示RA-gef-2在调节Rap1和Rap2，特别是在质膜上发挥作用。事实上，当与RA-gef-2和活化的M-RAS共表达时，质膜上定位的Rap1的GTP结合型水平增加。因此，RA-Global-2在质膜中作为M-RAS下游的Rap1和Rap2的环境基金，而RA-gef-1在包括高尔基体在内的核周隔室发挥Rap Global功能。
The Ras family small GTPase Rap is regulated by an array of specific guanine nucleotide exchange factors (GEFs) in response to upstream stimuli. RA-GEF-1 was identified as a novel Rap GEF, which possesses a Ras/Rap1-associating (RA) domain. Here we report a protein closely related to RA-GEF-1, named RA-GEF-2. Like RA-GEF-1, a putative cyclic nucleotide monophosphate-binding domain, a Ras exchanger motif, a PSD-95/D1gA/ZO-1 domain, and an RA domain in addition to the GEF catalytic domain are found in RA-GEF-2. However, RA-GEF-2 displays a different tissue distribution profile from that of RA-GEF-1. RA-GEF-2 stimulates guanine nucleotide exchange of both Rap1 and Rap2, but not Ha-Ras. The RA domain of RA-GEF-2 binds to M-Ras in a GTP-dependent manner, but not to other Ras family GTPases tested, including Ha-Ras, N-Ras, Rap1A, Rap2A, R-Ras, Ra1A, Rin, Rit, and Rheb, in contrast to the RA domain of RA-GEF-1, which specifically binds to Rap1. In accordance with this, RA-GEF-2 colocalizes with activated M-Ras in the plasma membrane in COS-7 cells, suggesting a role of RA-GEF-2 in the regulation of Rap1 and Rap2, particularly in the plasma membrane. In fact, an increase in the level of the GTP-bound form of plasma membrane-located Rap1 was observed when coexpressed with RA-GEF-2 and activated M-Ras. Thus, RA-GEF-2 acts as a GEF for Rap1 and Rap2 downstream of M-Ras in the plasma membrane, whereas RA-GEF-1 exerts Rap GEF function in perinuclear compartments including the Golgi apparatus.