Differential roles for the low-affinity phosphate transporters Pho87 and Pho90 in Saccharomyces cerevisiae
Differential roles for the low-affinity phosphate transporters Pho87 and Pho90 in Saccharomyces cerevisiae
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DOI：
10.1042/bj20101118
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发表时间：
2011-03-01
影响因子：
4.1
通讯作者：
Winderickx, Joris
中科院分区：
文献类型：
--
作者：
Ghillebert, Ruben;Swinnen, Erwin;Winderickx, Joris
当缺乏Pi时，酵母细胞激活PHO信号传导途径，其中Pho 4转录因子介导参与Pi获得的基因的表达，例如编码高亲和力H+/Pi同向转运体的PHO 84。相反，编码低亲和力H+/P-i转运系统的PHO 87和PHO 90的转录不依赖于磷酸盐状态。在目前的工作中，我们发现，在P-1饥饿，这些低亲和力的P-1转运蛋白被内吞和有针对性的液泡。对于Pho 87，这个过程严格依赖于SPL 2，SPL 2是另一个Pho 4依赖性基因，编码一种已知与转运蛋白的N-末端SPX结构域相互作用的蛋白质。相比之下，Pi饥饿时Pho 90的液泡靶向不依赖于Pho 4和Spl 2，尽管它仍然需要其SPX结构域。此外，Pho 87和Pho 90也靶向液泡后，碳源饥饿或用雷帕霉素，模拟氮饥饿的治疗，但尽管这些反应是独立的PHO途径信号，他们再次需要的N-末端SPX结构域的转运。这些观察结果表明，其他SPX相互作用的蛋白质必须参与。此外，我们表明，Pho 90是最重要的P-i转运蛋白在高P-i条件下，在没有一个高亲和力的P-i-运输系统。两者合计，我们的研究结果表明，Pho 87和Pho 90代表非冗余的P-I转运蛋白，这是调谐的多个营养信号传导机制的整合，以调整P-I运输能力的一般营养状况的环境。
When starved of P-i, yeast cells activate the PHO signalling pathway, wherein the Pho4 transcription factor mediates expression of genes involved in P-i acquisition, such as PHO84, encoding the high-affinity H+/P-i symporter. In contrast, transcription of PHO87 and PHO90, encoding the low-affinity H+/P-i transport system, is independent of phosphate status. In the present work, we reveal that, upon P-i starvation, these low-affinity P-i transporters are endocytosed and targeted to the vacuole. For Pho87, this process strictly depends on SPL2, another Pho4-dependent gene that encodes a protein known to interact with the N-terminal SPX domain of the transporter. In contrast, the vacuolar targeting of Pho90 upon P-i starvation is independent of both Pho4 and Spl2, although it still requires its SPX domain. Furthermore, both Pho87 and Pho90 are also targeted to the vacuole upon carbon-source starvation or upon treatment with rapamycin, which mimics nitrogen starvation, but although these responses are independent of PHO pathway signalling, they again require the N-terminal SPX domain of the transporters. These observations suggest that other SPX-interacting proteins must be involved. In addition, we show that Pho90 is the most important P-i transporter under high P-i conditions in the absence of a high-affinity P-i-transport system. Taken together, our results illustrate that Pho87 and Pho90 represent non-redundant P-i transporters, which are tuned by the integration of multiple nutrient signalling mechanisms in order to adjust P-i-transport capacity to the general nutritional status of the environment.