Li X, Multon M C, Henin Y, Schweighoffer F, Venot C, Josef J, Zhou C, LaVecchio J, Stuckert P, Raab M, Mhashilkar A, Tocque B, Marasco W A
Departments of Cancer Immunology and AIDS and Medicine, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Biol Chem. 2000 Oct 6;275(40):30925-33. doi: 10.1074/jbc.M005535200.
The MAPK pathway is required for T-cell activation; however, its role in modulating T-cell function following human immunodeficiency virus type 1 (HIV-1) infection is poorly understood. In this report, we investigated whether Grb3-3, an isoform of the Grb2 (growth factor receptor-bound protein-2) adaptor molecule that is associated with the MAPK pathway, could be involved. We found that Grb3-3, but not its isoform Grb2, is markedly up-regulated in CD4(+) peripheral blood mononuclear cells derived from either in vitro HIV-1-infected cultures or HIV-1-infected human subjects. Analysis of HIV-1 gene products indicated that Tat and Nef, both of which have been implicated in modulating T-cell function, can independently induce expression of Grb3-3. By using NFAT/AP-1, AP-1, or NFAT reporter assays, we found that Grb3-3 can potentiate NFAT (but not AP-1) promoter activity in Jurkat T-cells upon engagement of the T-cell receptor and CD28 co-receptor. In addition, potentiation of NFAT by Grb3-3 is substantially suppressed by MEKK1, a kinase that may play an important role in retaining NFAT in the cytoplasm, and by cyclosporin A. Finally, we also found that Grb3-3 potentiates HIV-1 long terminal (LTR) repeat promoter activity following T-cell receptor stimulation, an effect that can be largely suppressed by cyclosporin A. Taken together, this study indicates that Grb3-3 is a cellular factor that can be up-regulated by HIV-1. In addition, Grb3-3 can also function as a positive factor for T-cell activation and, in doing so, may aid in establishing an intracellular environment that can optimally support HIV-1 replication.
丝裂原活化蛋白激酶（MAPK）信号通路对于T细胞活化是必需的；然而，其在人类免疫缺陷病毒1型（HIV-1）感染后调节T细胞功能中的作用却知之甚少。在本报告中，我们研究了Grb3-3，一种与MAPK信号通路相关的Grb2（生长因子受体结合蛋白2）衔接分子的异构体，是否参与其中。我们发现，Grb3-3而非其异构体Grb2，在源自体外HIV-1感染培养物或HIV-1感染人类受试者的CD4(+)外周血单个核细胞中显著上调。对HIV-1基因产物的分析表明，Tat和Nef都与调节T细胞功能有关，它们能够独立诱导Grb3-3的表达。通过使用NFAT/AP-1、AP-1或NFAT报告基因检测，我们发现，在T细胞受体和CD28共受体结合后，Grb3-3能够增强Jurkat T细胞中NFAT（而非AP-1）启动子的活性。此外，MEKK1（一种可能在将NFAT保留在细胞质中起重要作用的激酶）和环孢素A可显著抑制Grb3-3对NFAT的增强作用。最后，我们还发现，T细胞受体刺激后，Grb3-3增强了HIV-1长末端（LTR）重复启动子的活性，环孢素A可在很大程度上抑制这一作用。综上所述，本研究表明Grb3-3是一种可被HIV-1上调的细胞因子。此外，Grb3-3还可作为T细胞活化的正向因子，在此过程中，可能有助于建立一个能够最佳支持HIV-1复制的细胞内环境。
