Chang J H, Pratt J C, Sawasdikosol S, Kapeller R, Burakoff S J
Division of Pediatric Oncology, Dana-Farber Cancer Institute, and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Mol Cell Biol. 1998 Sep;18(9):4986-93. doi: 10.1128/MCB.18.9.4986.
The Rho family of small GTP-binding proteins is involved in the regulation of cytoskeletal structure, gene transcription, specific cell fate development, and transformation. We demonstrate in this report that overexpression of an activated form of Rho enhances AP-1 activity in Jurkat T cells in the presence of phorbol myristate acetate (PMA), but activated Rho (V14Rho) has little or no effect on NFAT, Oct-1, and NF-kappaB enhancer element activities under similar conditions. Overexpression of a V14Rho construct incapable of membrane localization (CAAX deleted) abolishes PMA-induced AP-1 transcriptional activation. The effect of Rho on AP-1 is independent of the mitogen-activated protein kinase pathway, as a dominant-negative MEK and a MEK inhibitor (PD98059) did not affect Rho-induced AP-1 activity. V14Rho binds strongly to protein kinase Calpha (PKCalpha) in vivo; however, deletion of the CAAX site on V14Rho severely diminished this association. Evidence for a role for PKCalpha as an effector of Rho was obtained by the observation that coexpression of the N-terminal domain of PKCalpha blocked the effects of activated Rho plus PMA on AP-1 transcriptional activity. These data suggest that Rho potentiates AP-1 transcription during T-cell activation.
小GTP结合蛋白的Rho家族参与细胞骨架结构、基因转录、特定细胞命运发育和转化的调控。我们在本报告中证明，在佛波酯肉豆蔻酸乙酸酯（PMA）存在的情况下，Rho活化形式的过表达增强了Jurkat T细胞中的AP-1活性，但在类似条件下，活化的Rho（V14Rho）对NFAT、Oct-1和NF-κB增强子元件活性几乎没有影响。无法进行膜定位的V14Rho构建体（CAAX缺失）的过表达消除了PMA诱导的AP-1转录激活。Rho对AP-1的作用独立于丝裂原活化蛋白激酶途径，因为显性负性MEK和MEK抑制剂（PD98059）不影响Rho诱导的AP-1活性。V14Rho在体内与蛋白激酶Cα（PKCα）强烈结合；然而，V14Rho上CAAX位点的缺失严重削弱了这种结合。通过观察PKCαN端结构域的共表达阻断了活化的Rho加PMA对AP-1转录活性的影响，获得了PKCα作为Rho效应器作用的证据。这些数据表明，Rho在T细胞活化过程中增强AP-1转录。
