Yoshimura T, Kobayashi T, Goda S, Goto I
Department of Neurology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Neurochem Res. 1994 Jun;19(6):735-41. doi: 10.1007/BF00967714.
The repetitive passages of a Schwann cell culture results in the appearance of immortalized cells. In order to investigate the direct effects of cyclic AMP (cAMP) on Schwann cell proliferation, we used the immortalized Schwann cells because the responses of a short-term Schwann cell culture to agents increasing the intracellular cAMP are more complicated and it does not seem that all of them are due to the direct effects of cAMP. By adding up to 200 microM of forskolin, an adenylate cyclase activator, to the culture medium, Schwann cell proliferation was inhibited and the intracellular 1,2-diacylglycerol (DG) level was decreased in a dose-dependent manner to 44 and 53% of the control values, respectively. The protein phosphorylation activity in the cytosol from the cell treated with 100 microM forskolin, assayed with myelin basic protein as the acceptor, decreased to 78% and this inhibition was then reversed by the addition of 1-oleoyl-2-acetyl-sn-glycerol (OAG), a membrane-permeable DG, to the assay mixture. The cell proliferation inhibited by forskolin was also restored by the addition of OAG. These data suggest that cAMP inhibits both the activity of protein kinase C (PKC) and consequently cell proliferation through suppression of intracellular DG level, an activator of PKC. Since the inositol 1,4,5-triphosphate level and the hydrolysis of phosphatidylcholine to DG and phosphorylcholine were not affected, forskolin therefore appears to suppress the de novo synthesis of DG.
雪旺细胞培养的重复传代导致永生化细胞的出现。为了研究环磷酸腺苷（cAMP）对雪旺细胞增殖的直接影响，我们使用了永生化雪旺细胞，因为短期雪旺细胞培养物对增加细胞内cAMP的试剂的反应更为复杂，而且似乎并非所有反应都是由cAMP的直接作用引起的。通过向培养基中添加高达200微摩尔的毛喉素（一种腺苷酸环化酶激活剂），雪旺细胞增殖受到抑制，细胞内1,2 - 二酰甘油（DG）水平分别以剂量依赖的方式降至对照值的44%和53%。以髓鞘碱性蛋白为受体，对用100微摩尔毛喉素处理的细胞的胞质溶胶中的蛋白质磷酸化活性进行测定，其活性降至78%，然后通过向测定混合物中添加1 - 油酰基 - 2 - 乙酰 - sn - 甘油（OAG，一种可透过膜的DG）来逆转这种抑制作用。添加OAG也能恢复被毛喉素抑制的细胞增殖。这些数据表明，cAMP通过抑制细胞内DG水平（PKC的一种激活剂）来抑制蛋白激酶C（PKC）的活性，进而抑制细胞增殖。由于肌醇1,4,5 - 三磷酸水平以及磷脂酰胆碱水解为DG和磷酸胆碱不受影响，因此毛喉素似乎抑制了DG的从头合成。
