Kong S K, Suen Y K, Choy Y M, Fung K P, Lee C Y
Department of Biochemistry, Chinese University of Hong Kong, Shatin.
Immunopharmacol Immunotoxicol. 1991;13(3):329-39. doi: 10.3109/08923979109019708.
The role of membrane potential (Em) on the initiation of DNA synthesis in murine macrophage cell line PU5-1.8 was investigated with fluorescent probes bis-oxonol and diS-C3-(5). Incubation of PU5-1.8 cells in high K(+)-HEPES buffer or with gramicidin at 37 degrees C for 1h that depolarized the membrane induced [3H]-thymidine incorporation and expression of early response gene such as c-myc and c-fos. When PU5-1.8 cells were treated with a number of agents including fetal calf serum (FCS), lipopolysaccharide (LPS), epidermal growth factor (EGF), N-formyl-methionyl-leucyl-phenylalanine (FMLP) and bradykinin (BK), only FCS caused DNA synthesis and membrane depolarization. Other agents had no effect on these events. The FCS-mediated DNA synthesis in PU5-1.8 cells was inhibited by clamping the membrane potential with valinomycin. Moreover, intracellular alkalinization induced by nigericin at pH 7.9, which is believed to be a permissive signal for mitogenesis, caused membrane depolarization. On the other hand, challenge of cells with phorbol 12-myristate 13 acetate (PMA) suppressed the K(+)-mediated DNA synthesis. However, the treatment of cells with PMA did not change the membrane potential but suppressed the gramicidin-mediated membrane depolarization. These observations suggest that there is a correlation between membrane depolarization and initiation of DNA synthesis in PU5-1.8 cells. PKC may be acting as a modulator in this transducing pathway.
利用荧光探针双羟萘酚和二硫代辛可胺 - C3 - (5)研究了膜电位（Em）在小鼠巨噬细胞系PU5 - 1.8中启动DNA合成的作用。将PU5 - 1.8细胞在高钾 - HEPES缓冲液中或与短杆菌肽在37℃孵育1小时，使膜去极化，诱导了[3H] - 胸苷掺入以及早期反应基因如c - myc和c - fos的表达。当用多种试剂处理PU5 - 1.8细胞时，包括胎牛血清（FCS）、脂多糖（LPS）、表皮生长因子（EGF）、N - 甲酰 - 甲硫氨酰 - 亮氨酰 - 苯丙氨酸（FMLP）和缓激肽（BK），只有FCS引起了DNA合成和膜去极化。其他试剂对这些事件没有影响。通过缬氨霉素钳制膜电位可抑制PU5 - 1.8细胞中FCS介导的DNA合成。此外，尼日利亚菌素在pH 7.9时诱导的细胞内碱化，被认为是有丝分裂发生的允许信号，导致了膜去极化。另一方面，用佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）刺激细胞可抑制钾离子介导的DNA合成。然而，用PMA处理细胞并没有改变膜电位，但抑制了短杆菌肽介导的膜去极化。这些观察结果表明，PU5 - 1.8细胞中膜去极化与DNA合成的启动之间存在相关性。蛋白激酶C可能在这条转导途径中作为一种调节剂起作用。
