Tobler A, Miller C W, Norman A W, Koeffler H P
Department of Medicine, University of California, Los Angeles 90024.
J Clin Invest. 1988 Jun;81(6):1819-23. doi: 10.1172/JCI113525.
We recently showed that 1,25(OH)2D3 sensitively inhibited the expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in normal human mitogen-activated peripheral blood lymphocytes and in the human T lymphotropic virus I immortalized T cell line known as S-LB1 at the levels of both mRNA and protein. Using S-LB1 cells as a model system the present paper identifies at least in part the mechanisms by which 1,25(OH)2D3 regulates the expression of GM-CSF. Time-course studies demonstrated that by 6 and 48 h of exposure of S-LB1 cells to 1,25(OH)2D3 (10(-8) M) the GM-CSF mRNA levels were reduced by 50 and 90%, respectively. Studies using cycloheximide as a protein synthesis inhibitor showed that the inhibitory action of 1,25(OH)2D3 on GM-CSF expression was dependent on new protein synthesis. In vitro nuclear run-on assays demonstrated that 1,25(OH)2D3 (10(-8) M) did not change the rate of transcription of the GM-CSF gene. The t1/2 of GM-CSF mRNA, however, was profoundly reduced by 1,25(OH)2D3 when transcription was blocked by actinomycin D compared with the half-life of GM-CSF in the presence of actinomycin D alone (t1/2, less than 0.5 and 4 h, respectively). Taken together, these results demonstrate that 1,25(OH)2D3 regulates expression of the lymphokine GM-CSF posttranscriptionally by influencing the stability of GM-CSF mRNA.
我们最近发现，1,25(OH)₂D₃能灵敏地抑制正常人丝裂原激活的外周血淋巴细胞以及人嗜T淋巴细胞病毒I永生化T细胞系（称为S-LB1）中粒细胞-巨噬细胞集落刺激因子（GM-CSF）在mRNA和蛋白质水平的表达。本文以S-LB1细胞作为模型系统，至少部分地确定了1,25(OH)₂D₃调节GM-CSF表达的机制。时间进程研究表明，S-LB1细胞暴露于1,25(OH)₂D₃（10⁻⁸ M）6小时和48小时后，GM-CSF mRNA水平分别降低了50%和90%。使用环己酰亚胺作为蛋白质合成抑制剂的研究表明，1,25(OH)₂D₃对GM-CSF表达的抑制作用依赖于新的蛋白质合成。体外核转录分析表明，1,25(OH)₂D₃（10⁻⁸ M）不会改变GM-CSF基因的转录速率。然而，与单独存在放线菌素D时GM-CSF的半衰期（半衰期分别小于0.5小时和4小时）相比，当转录被放线菌素D阻断时，1,25(OH)₂D₃能显著降低GM-CSF mRNA的半衰期。综上所述，这些结果表明，1,25(OH)₂D₃通过影响GM-CSF mRNA的稳定性在转录后调节淋巴因子GM-CSF的表达。
