Soler Concepció, Felipe Antonio, García-Manteiga José, Serra Maria, Guillén-Gómez Elena, Casado F Javier, MacLeod Carol, Modolell Manuel, Pastor-Anglada Marçal, Celada Antonio
Macrophage Biology Group, Institute of Biomedical Research of Barcelona, Barcelona Science Park, Josep Samitier 1-5, Barcelona E-08028, Spain.
Biochem J. 2003 Nov 1;375(Pt 3):777-83. doi: 10.1042/BJ20030260.
The expressions of CNT and ENT (concentrative and equilibrative nucleoside transporters) in macrophages are differentially regulated by IFN-gamma (interferon-gamma). This cytokine controls gene expression through STAT1-dependent and/or -independent pathways (where STAT1 stands for signal transduction and activator of transcription 1). In the present study, the role of STAT1 in the response of nucleoside transporters to IFN-gamma was studied using macrophages from STAT1 knockout mice. IFN-gamma triggered an inhibition of ENT1-related nucleoside transport activity through STAT1-dependent mechanisms. Such inhibition of macrophage growth and ENT1 activity by IFN-gamma is required for DNA synthesis. Interestingly, IFN-gamma led to an induction of the CNT1- and CNT2-related nucleoside transport activities independent of STAT1, thus ensuring the supply of extracellular nucleosides for the STAT1-independent RNA synthesis. IFN-gamma up-regulated CNT2 mRNA and CNT1 protein levels and down-regulated ENT1 mRNA in both wild-type and STAT1 knockout macrophages. This is consistent with a STAT1-independent, long-term-mediated, probably transcription-dependent, regulation of nucleoside transporter genes. Moreover, STAT1-dependent post-transcriptional mechanisms are implicated in the regulation of ENT1 activity. Although nitric oxide is involved in the regulation of ENT1 activity in B-cells at a post-transcriptional level, our results show that STAT1-dependent induction of nitric oxide by IFN-gamma is not implicated in the regulation of ENT1 activity in macrophages. Our results indicate that both STAT1-dependent and -independent pathways are involved in the regulation of nucleoside transporters by IFN-gamma in macrophages.
巨噬细胞中CNT和ENT（集中性和平衡性核苷转运体）的表达受到干扰素-γ（IFN-γ）的差异性调控。这种细胞因子通过STAT1依赖性和/或非依赖性途径控制基因表达（其中STAT1代表信号转导和转录激活因子1）。在本研究中，利用STAT1基因敲除小鼠的巨噬细胞研究了STAT1在核苷转运体对IFN-γ反应中的作用。IFN-γ通过STAT1依赖性机制触发ENT1相关核苷转运活性的抑制。IFN-γ对巨噬细胞生长和ENT1活性的这种抑制是DNA合成所必需的。有趣的是，IFN-γ导致CNT1和CNT2相关核苷转运活性的诱导，且不依赖于STAT1，从而确保为不依赖于STAT1的RNA合成提供细胞外核苷。IFN-γ在野生型和STAT1基因敲除巨噬细胞中均上调CNT2 mRNA和CNT1蛋白水平，并下调ENT1 mRNA。这与核苷转运体基因不依赖于STAT1的长期介导、可能是转录依赖性的调控一致。此外，STAT1依赖性的转录后机制参与了ENT1活性的调控。尽管一氧化氮在转录后水平参与B细胞中ENT1活性的调控，但我们的结果表明，IFN-γ通过STAT1依赖性诱导一氧化氮并不参与巨噬细胞中ENT1活性的调控。我们的结果表明，STAT1依赖性和非依赖性途径均参与IFN-γ对巨噬细胞中核苷转运体的调控。
