Intracellular phosphate serves as a signal for the regulation of the PHO pathway in Saccharomyces cerevisiae
Intracellular phosphate serves as a signal for the regulation of the PHO pathway in Saccharomyces cerevisiae
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DOI：
10.1074/jbc.m312202200
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发表时间：
2004-04-23
影响因子：
4.8
通讯作者：
Harashima, S
中科院分区：
文献类型：
--
作者：
Auesukaree, C;Homma, T;Harashima, S
在酿酒酵母中，磷酸盐信号转导通路（PHO通路）调节几种磷酸盐应答基因的表达，如PHO5和PHO84。然而，细胞是否感知细胞内或细胞外磷酸盐的基本问题仍未解决。为了解决这个问题，我们通过P-31核磁共振光谱直接测量了细胞内磷酸盐浓度。我们发现PHO5的表达与细胞内正磷酸盐和细胞内多磷酸盐的水平密切相关，并且Deltapho84菌株的信号缺陷可能是由于细胞内磷酸盐摄取缺陷导致的细胞内磷酸盐不足。此外，缺乏细胞内多磷酸盐的Deltaphm1Deltaphm2、Deltaphm3和Deltaphm4菌株的细胞内正磷酸盐水平高于野生型，PHO5表达量低于野生型。相比之下，与野生型菌株相比，细胞内正磷酸盐含量较低，多磷酸盐含量较高的deltapm5菌株PHO5表达受到抑制，与野生型菌株相似。这些观察结果表明，PHO5的表达受细胞内正磷酸盐的调控，尽管正磷酸盐不是唯一的信号分子。此外，在Deltapho84菌株中，PHM3、PHM4或PHM1和PHM2的破坏通过增加细胞内正磷酸盐来抑制PHO5组成型，尽管不是完全抑制，这表明Pho84p主要通过作为转运体影响磷酸盐信号传导。
In Saccharomyces cerevisiae, the phosphate signal transduction pathway (PHO pathway) is known to regulate the expression of several phosphate-responsive genes, such as PHO5 and PHO84. However, the fundamental issue of whether cells sense intracellular or extracellular phosphate remains unresolved. To address this issue, we have directly measured intracellular phosphate concentrations by P-31 NMR spectroscopy. We find that PHO5 expression is strongly correlated with the levels of both intracellular orthophosphate and intracellular polyphosphate and that the signaling defect in the Deltapho84 strain is likely to result from insufficient intracellular phosphate caused by a defect in phosphate uptake. Furthermore, the Deltaphm1Deltaphm2, Deltaphm3, and Deltaphm4 strains, which lack intracellular polyphosphate, have higher intracellular orthophosphate levels and lower expression of PHO5 than the wild-type strain. By contrast, the Deltaphm5 strain, which has lower intracellular orthophosphate and higher polyphosphate levels than the wild-type strain, shows repressed expression of PHO5, similar to the wildtype strain. These observations suggest that PHO5 expression is under the regulation of intracellular orthophosphate, although orthophosphate is not the sole signaling molecule. Moreover, the disruption of PHM3, PHM4, or of both PHM1 and PHM2 in the Deltapho84 strain suppresses, although not completely, the PHO5 constitutive phenotype by increasing intracellular orthophosphate, suggesting that Pho84p affects phosphate signaling largely by functioning as a transporter.