Kaptein J S, Yang C L, Lin C K, Nguyen T T, Chen F S, Lad P M
Regional Research Laboratory, Kaiser Permanente Medical Center, Los Angeles, CA, USA.
Immunobiology. 1995 Aug;193(5):465-85. doi: 10.1016/S0171-2985(11)80431-6.
Expression of the protooncogene c-fos is controlled by three main regulatory pathways involving kinase C, cAMP, and calcium. Kinase C mediates its effects via phosphorylation of serum response factor (SRF) which interacts with the serum response element (SRE); cAMP and calcium mediate their effects via phosphorylation of CREB (cAMP regulatory element binding protein) presumably by activation of a protein kinase A or calmodulin-regulated kinase. We have examined the function of these elements in Burkitt's lymphoma cells (Ramos and Daudi) as well as a T lymphocytic cell line (Jurkat). We have found that stimulation of any one of these pathways alone has little or no effect on c-fos induction. However, kinase C activation (PMA stimulation) combined with either cAMP (forskolin plus MIX) or calcium stimulation (ionophore) leads to greatly enhanced c-fos induction. By contrast, cAMP in the presence of calcium shows no synergy in c-fos induction. Okadaic acid augments PMA- as well as calcium-mediated activation of c-fos, and has little or no effect when combined with cAMP. The main difference between Ramos (B cells) and Jurkat (T cells) in the regulation of c-fos is that cAMP plus calcium is strongly synergistic in Jurkat and is without effect in Ramos. Analysis of AP-1 activity using gel mobility shift assays confirms that the requirements for synergy in c-fos mRNA induction are paralleled by requirements for synergy in induction of AP-1 activity. Signaling in B cells due to anti-Ig stimulation involves both kinase C activation and release of intracellular calcium, and results in c-fos mRNA induction. Our results indicate that synergy between the kinase C activation and calcium is needed for efficient c-fos induction since neither of these two alone induces c-fos well. That synergy of signaling pathways is relevant for the anti-Ig induction of c-fos is supported by the fact that cAMP-inducing agents and okadaic acid further enhance anti-Ig induction of c-fos. These results suggest that cell-specific patterns of synergy are an essential feature for c-fos induction and may be relevant for c-fos control through B and T cell antigen receptors.
原癌基因c-fos的表达受三条主要调控途径控制，这些途径涉及蛋白激酶C、环磷酸腺苷（cAMP）和钙。蛋白激酶C通过血清反应因子（SRF）的磷酸化介导其效应，血清反应因子与血清反应元件（SRE）相互作用；cAMP和钙可能通过蛋白激酶A或钙调蛋白调节激酶的激活，使cAMP反应元件结合蛋白（CREB）磷酸化来介导它们的效应。我们已经研究了这些元件在伯基特淋巴瘤细胞（拉莫斯细胞和道迪细胞）以及一种T淋巴细胞系（ Jurkat细胞）中的功能。我们发现，单独刺激这些途径中的任何一条对c-fos的诱导几乎没有或没有影响。然而，蛋白激酶C激活（佛波酯刺激）与cAMP（福斯高林加MIX）或钙刺激（离子载体）相结合会导致c-fos诱导大大增强。相比之下，在有钙存在的情况下，cAMP在c-fos诱导中没有协同作用。冈田酸增强了蛋白激酶C以及钙介导的c-fos激活，与cAMP联合使用时几乎没有影响。拉莫斯细胞（B细胞）和Jurkat细胞（T细胞）在c-fos调控方面的主要区别在于，cAMP加钙在Jurkat细胞中具有强烈的协同作用，而在拉莫斯细胞中没有作用。使用凝胶迁移率变动分析对活化蛋白-1（AP-1）活性进行分析证实，c-fos mRNA诱导中的协同作用需求与AP-1活性诱导中的协同作用需求是平行的。抗免疫球蛋白刺激引起的B细胞信号传导涉及蛋白激酶C激活和细胞内钙释放，并导致c-fos mRNA诱导。我们的结果表明，蛋白激酶C激活和钙之间的协同作用是有效诱导c-fos所必需的，因为这两者单独都不能很好地诱导c-fos。cAMP诱导剂和冈田酸进一步增强抗免疫球蛋白对c-fos的诱导，这一事实支持了信号通路的协同作用与抗免疫球蛋白诱导c-fos相关。这些结果表明，细胞特异性的协同模式是c-fos诱导的一个基本特征，可能与通过B细胞和T细胞抗原受体对c-fos的控制有关。
