Uechi Yukiko, Bayarjargal Maitsetseg, Umikawa Masato, Oshiro Minoru, Takei Kimiko, Yamashiro Yoshito, Asato Tsuyoshi, Endo Shogo, Misaki Ryo, Taguchi Tomohiko, Kariya Ken-ichi
Division of Cell Biology, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan.
Biochem Biophys Res Commun. 2009 Jan 23;378(4):732-7. doi: 10.1016/j.bbrc.2008.11.107. Epub 2008 Dec 4.
Rap2A, Rap2B, and Rap2C are Ras-like small G proteins. The role of their post-translational processing has not been investigated due to the lack of information on their downstream signaling. We have recently identified the Traf2- and Nck-interacting kinase (TNIK), a member of the STE20 group of mitogen-activated protein kinase kinase kinase kinases, as a specific Rap2 effector. Here we report that, in HEK293T cells, Rap2A (farnesylated) and Rap2C (likely farnesylated), but not Rap2B (geranylgeranylated), require palmitoylation for membrane-association and TNIK activation, whereas all Rap2 proteins, including Rap2B, require palmitoylation for induction of TNIK-mediated phenotype, the suppression of cell spreading. Furthermore, we report for the first time that, in COS-1 cells, Rap2 proteins localize, and recruit TNIK, to the recycling endosomes, but not the Golgi nor the endoplasmic reticulum, in a palmitoylation-dependent manner. These observations implicate the involvement of palmitoylation and recycling endosome localization in cellular functions of Rap2 proteins.
Rap2A、Rap2B和Rap2C是类Ras小G蛋白。由于缺乏其下游信号传导的相关信息，它们翻译后加工的作用尚未得到研究。我们最近鉴定出Traf2和Nck相互作用激酶（TNIK），它是丝裂原活化蛋白激酶激酶激酶激酶的STE20家族成员，作为Rap2的特异性效应蛋白。在此我们报告，在HEK293T细胞中，Rap2A（法尼基化）和Rap2C（可能法尼基化），而非Rap2B（香叶基香叶基化），需要棕榈酰化才能进行膜结合和激活TNIK，而所有Rap2蛋白，包括Rap2B，需要棕榈酰化才能诱导TNIK介导的表型，即抑制细胞铺展。此外，我们首次报告，在COS-1细胞中，Rap2蛋白以棕榈酰化依赖的方式定位于再循环内体并募集TNIK，而非高尔基体或内质网。这些观察结果表明棕榈酰化和再循环内体定位参与了Rap2蛋白的细胞功能。
