Aspergillus nidulans HOG pathway is activated only by two-component signalling pathway in response to osmotic stress
Aspergillus nidulans HOG pathway is activated only by two-component signalling pathway in response to osmotic stress
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DOI：
10.1111/j.1365-2958.2005.04605.x
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发表时间：
2005-06-01
影响因子：
3.6
通讯作者：
Abe, K
中科院分区：
文献类型：
--
作者：
Furukawa, K;Hoshi, Y;Abe, K
基因组测序分析表明构巢曲霉与酿酒酵母的高渗透压甘油（HOG）反应丝裂原活化蛋白激酶（MAPK）途径的所有基因都具有同源性。A.缺少sskA、sskB、pbsB或hogA的构巢菌突变株，分别编码与酵母Ssk 1 p反应调节因子Ssk 2 p/Ssk 22 p MAPKKK、Pbs 2 p MAPKK和Hog 1 p MAPK的蛋白质，在高渗透压下表现出生长抑制，并且这些突变株中的HogA MAPK在渗透压或氧化胁迫下不被磷酸化。因此，A.构巢菌HOG（AnHOG）途径仅依赖于双组分信号系统，并且AnHOG途径中的MAPKK活化机制不同于酵母HOG途径中的MAPKK活化机制，其中Pbs 2 p由两个分支Sln 1 p和Sho 1 p活化。pbsB的表达弥补了酵母pbs 2 Delta的高渗透压敏感性，并且互补依赖于Ssk 2 p/Ssk 22 p，而不是Sho 1 p。Pbs 2 p需要其富含Pro的基序来结合Sho 1 p的Src同源3（SH 3）结构域，但PbsB缺乏典型的富含Pro的基序。然而，具有酵母Pro富集基序的PbsB突变体（PbsB（Pro））被酵母中的Sho 1 p分支激活。相反，在表达PbsB（Pro）的sskA Delta中，HogA在渗透胁迫下不被磷酸化，表明A.构巢菌ShoA与酵母Sho 1 p同源，不参与AnHOG通路的转录应答激活。我们还发现，除了HogA，PbsB可以激活另一个Hog 1 p MAPK的同源物，MpkC，在A。nidulans，虽然mpkC是不适应的。在这项研究中，我们讨论了AnHOG和酵母HOG途径之间的差异。
Genome sequencing analyses revealed that Aspergillus nidulans has orthologous genes to all those of the high-osmolarity glycerol (HOG) response mitogen-activated protein kinase (MAPK) pathway of Saccharomyces cerevisiae. A. nidulans mutant strains lacking sskA, sskB, pbsB, or hogA, encoding proteins orthologous to the yeast Ssk1p response regulator, Ssk2p/Ssk22p MAPKKKs, Pbs2p MAPKK and Hog1p MAPK, respectively, showed growth inhibition under high osmolarity, and HogA MAPK in these mutants was not phosphorylated under osmotic or oxidative stress. Thus, activation of the A. nidulans HOG (AnHOG) pathway depends solely on the two-component signalling system, and MAPKK activation mechanisms in the AnHOG pathway differ from those in the yeast HOG pathway, where Pbs2p is activated by two branches, Sln1p and Sho1p. Expression of pbsB complemented the high-osmolarity sensitivity of yeast pbs2 Delta, and the complementation depended on Ssk2p/Ssk22p, but not on Sho1p. Pbs2p requires its Pro-rich motif for binding to the Src-homology3 (SH3) domain of Sho1p, but PbsB lacks a typical Pro-rich motif. However, a PbsB mutant (PbsB(Pro)) with the yeast Pro-rich motif was activated by the Sho1p branch in yeast. In contrast, HogA in sskA Delta expressing PbsB(Pro) was not phosphorylated under osmotic stress, suggesting that A. nidulans ShoA, orthologous to yeast Sho1p, is not involved in osmoresponsive activation of the AnHOG pathway. We also found that besides HogA, PbsB can activate another Hog1p MAPK orthologue, MpkC, in A. nidulans, although mpkC is dispensable in osmoadaptation. In this study, we discuss the differences between the AnHOG and the yeast HOG pathways.