An intersection of the cAMP/PKA and two-component signal transduction systems in Dictyostelium
An intersection of the cAMP/PKA and two-component signal transduction systems in Dictyostelium
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DOI：
10.1093/emboj/17.10.2838
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发表时间：
1998-05-15
期刊：
影响因子：
11.4
通讯作者：
Kay, RR
中科院分区：
文献类型：
--
作者：
Thomason, PA;Traynor, D;Kay, RR
环腺苷酸依赖的蛋白激酶（PKA）的激活可以触发网骨藻柄细胞和孢子细胞的终末分化。通过筛选柄细胞和孢子细胞独立成熟的突变体，获得了3个可能作为PKA负调控因子的基因：rdeC（编码PKA调节亚基）、regA和rdeA。一个结构域是cAMP磷酸二酯酶（K-m类似于5 μ M）;另一个是同源的双组分信号转导系统的反应调节剂（RRs）。它可以在RR的典型反应中从乙酰磷酸接受磷酸，转移依赖于Asp 212，预测的磷酸受体RegA磷酸二酯酶活性被磷酸供体氨基磷酸酯刺激高达8倍，刺激再次依赖于Asp 212，这表明RR结构域的磷酸化激活磷酸二酯酶结构域。RR结构域在野生型细胞中的过表达表型模仿regA无效。我们解释这种显性负效应是由于从RegA转移了磷酸盐的正常流动，从而阻止了其激活。已知rdeA突变会产生升高的cAMP水平。我们认为cAMP的分解是由一个磷酸化系统控制的，该系统激活RegA，可能包括RdeA，当该系统被抑制时，细胞成熟应该被触发。
Terminal differentiation of both stalk and spore cells in Dictyostelium can be triggered by activation of cAMP-dependent protein kinase (PKA), A screen for mutants where stalk and spore cells mature in isolation produced three genes which may act as negative regulators of PKA: rdeC (encoding the PKA regulatory subunit), regA and rdeA, The biochemical properties of RegA were studied in detail. One domain is a cAMP phosphodiesterase (K-m similar to 5 mu M); the other is homologous to response regulators (RRs) of two-component signal transduction systems. It can accept phosphate from acetyl phosphate in a reaction typical of RRs, with transfer dependent on Asp212, the predicted phosphoacceptor, RegA phosphodiesterase activity is stimulated up to 8-fold by the phosphodonor phosphoramidate, with stimulation again dependent on Asp212, This indicates that phosphorylation of the RR domain activates the phosphodiesterase domain. Overexpression of the RR domain in wild-type cells phenocopies a regA null. We interpret this dominant-negative effect as due to a diversion of the normal flow of phosphates from RegA, thus preventing its activation. Mutation of rdeA is known to produce elevated cAMP levels. We propose that cAMP breakdown is controlled by a phosphorelay system which activates RegA, and may include RdeA, Cell maturation should be triggered when this system is inhibited.