Laegreid A, Thommesen L, Jahr T G, Sundan A, Espevik T
Institute of Cancer Research and Molecular Biology, University of Trondheim, Norway.
J Biol Chem. 1995 Oct 27;270(43):25418-25. doi: 10.1074/jbc.270.43.25418.
This study demonstrates that lipopolysaccharide (LPS) mediates induction of transcription factor NF kappa B and activation of the cytomegalovirus (CMV) promoter-enhancer in the SW480 cell line. These cells do not express a functional membrane CD14. The LPS response in SW480 cells was weaker and markedly slower than the tumor necrosis factor (TNF) response. Pretreatment with TNF for 72 h inhibited both TNF, tumor necrosis factor receptor (TNFR) p55, TNFR p75, and LPS-mediated activation of nuclear factor -kappa B (NF kappa B), whereas pretreatment with LPS only inhibited the LPS response. TNFR p55 antibody pretreatment resulted in marked inhibition of the LPS response, while pretreatment with TNFR p75 antiserum only had a weak inhibitory effect. Flowcytometric analysis showed that LPS binding as well as expression of TNFR p55 and TNFR p75 were not affected by LPS or TNF pretreatment, indicating that the observed inhibition is not due to reduction of specific binding sites at the cell surface. The results suggest that LPS signaling in SW480 cells involves intracellular components which may be depleted or inactivated via TNFR p55, indicating that the LPS and TNFR p55 pathways overlap. We propose that TNFR p55 can mediate activation of NF kappa B and cytomegalovirus promoter-enhancer in SW480 cells via two distinct mechanisms, one which is activated only via TNFR p55 and leads to rapid activation of NF kappa B, and another which is overlapping with the LPS pathway.
本研究表明，脂多糖（LPS）介导转录因子NF-κB的诱导以及SW480细胞系中巨细胞病毒（CMV）启动子-增强子的激活。这些细胞不表达功能性膜CD14。SW480细胞中的LPS反应比肿瘤坏死因子（TNF）反应弱且明显更慢。用TNF预处理72小时可抑制TNF、肿瘤坏死因子受体（TNFR）p55、TNFR p75以及LPS介导的核因子-κB（NF-κB）激活，而仅用LPS预处理则仅抑制LPS反应。TNFR p55抗体预处理导致LPS反应明显抑制，而用TNFR p75抗血清预处理仅有微弱的抑制作用。流式细胞术分析表明，LPS结合以及TNFR p55和TNFR p75的表达不受LPS或TNF预处理的影响，表明观察到的抑制不是由于细胞表面特异性结合位点的减少。结果表明，SW480细胞中的LPS信号传导涉及细胞内成分，这些成分可能通过TNFR p55被耗尽或失活，表明LPS和TNFR p55途径重叠。我们提出，TNFR p55可通过两种不同机制介导SW480细胞中NF-κB的激活和巨细胞病毒启动子-增强子的激活，一种仅通过TNFR p55激活并导致NF-κB的快速激活，另一种与LPS途径重叠。
