Raspé E, Reuse S, Roger P P, Dumont J E
IRIBHN, School of Medicine, Free University of Brussels, Belgium.
Exp Cell Res. 1992 Jan;198(1):17-26. doi: 10.1016/0014-4827(92)90143-v.
Changes in the [Ca2+]i and/or activation of phospholipase C are thought to participate in the control by several growth factors of the mammalian cell proliferation. It has even been claimed that activation of the Ca(2+)-phosphatidylinositol cascade is sufficient to elicit cell proliferation [Jackson et al. (1988) Nature 335, 437-440; Julius et al. (1989) Science 244, 1057-1062]. In this work, we have evaluated the control of DNA synthesis by this cascade in a differentiated epithelial cell model: the dog thyrocyte in primary culture. We first observed that potent activators of the dog thyrocyte (2+)-phosphatidylinositol cascade such as carbachol or bradykinin failed to promote the onset of DNA synthesis in these cells. Moreover, carbachol inhibited the mitogenic effect of thyroid stimulating hormone (TSH) and of epidermal growth factor (EGF). The mitogenic effect of EGF was also reduced by bradykinin. Nevertheless, carbachol enhanced the expression of the protooncogenes c-fos and c-myc mRNAs. The time course of this enhancement was identical to the time course for the induction of c-fos and c-myc mRNAs by phorbol esters or EGF. On the other hand, in most experiments, TSH and EGF were able to trigger the onset of dog thyrocyte DNA synthesis without affecting their intracellular free Ca2+ concentration [Ca2+]i, 45Ca2+ efflux, or inositol phosphate generation. In several experiments, TSH increased the dog thyrocyte 45Ca2+ release and promoted a rise in the [Ca2+]i or the inositol phosphate accumulation but these effects were weak. In contrast to the effect of carbachol, the TSH effects on the [Ca2+]i and the 45Ca2+ efflux appeared slowly, were sustained, and were extremely sensitive to extracellular Ca2+ depletion. They were observed at hormone concentrations higher than the concentration achieving maximal stimulation of DNA synthesis. Similarly, in a few experiments, a slight increase in the [Ca2+]i or in the inositol trisphosphate generation were provoked by EGF. However, these modifications were not associated with an increased mitogenic potency of EGF. Finally, in all experiments, fetal calf serum slightly accelerated the dog thyrocyte 45Ca2+ efflux and increased their inositol phosphate generation.(ABSTRACT TRUNCATED AT 400 WORDS)
细胞内钙离子浓度（[Ca2+]i）的变化和/或磷脂酶C的激活被认为参与了几种生长因子对哺乳动物细胞增殖的调控。甚至有人声称，钙-磷脂酰肌醇信号通路的激活足以引发细胞增殖[杰克逊等人（1988年）《自然》335卷，437 - 440页；朱利叶斯等人（1989年）《科学》244卷，1057 - 1062页]。在本研究中，我们在一种分化的上皮细胞模型——原代培养的犬甲状腺细胞中，评估了该信号通路对DNA合成的调控。我们首先观察到，犬甲状腺细胞钙-磷脂酰肌醇信号通路的强效激活剂，如卡巴胆碱或缓激肽，并不能促进这些细胞中DNA合成的起始。此外，卡巴胆碱抑制促甲状腺激素（TSH）和表皮生长因子（EGF）的促有丝分裂作用。缓激肽也降低了EGF的促有丝分裂作用。然而，卡巴胆碱增强了原癌基因c-fos和c-myc mRNA的表达。这种增强的时间进程与佛波酯或EGF诱导c-fos和c-myc mRNA的时间进程相同。另一方面，在大多数实验中，TSH和EGF能够触发犬甲状腺细胞DNA合成的起始，而不影响其细胞内游离钙离子浓度（[Ca2+]i）、45Ca2+外流或肌醇磷酸的生成。在一些实验中，TSH增加了犬甲状腺细胞45Ca2+的释放，并促进了[Ca2+]i的升高或肌醇磷酸的积累，但这些作用很微弱。与卡巴胆碱的作用相反，TSH对[Ca2+]i和45Ca2+外流的作用出现缓慢，持续存在，并且对细胞外钙离子耗竭极为敏感。这些作用在高于实现DNA合成最大刺激的激素浓度时才被观察到。同样，在少数实验中，EGF引起了[Ca2+]i或肌醇三磷酸生成的轻微增加。然而，这些变化与EGF促有丝分裂能力的增强无关。最后，在所有实验中，胎牛血清略微加速了犬甲状腺细胞45Ca2+外流，并增加了它们的肌醇磷酸生成。（摘要截断于400字）
