MAP Kinase Kinase Kinase ( MAPKKK)-dependent and -independent Activation of Sty1 Stress MAPK in Fission Yeast

作者：Zhou Xin; Ma Yan; Sugiura Reiko; Kobayashi Daiki; Suzuki Masahiro; Deng Lu; Kuno Takayoshi^*

来源：Journal of Biological Chemistry, 2010, 285(43): 32818-32823.

DOI：10.1074/jbc.M110.135764

In fission yeast, the Sty1/Spc1/Phh1 mitogen-activated protein kinase (MAPK) pathway is known to be involved in multiple-stress responses. It is currently thought that the Sty1 MAPK cascade is mediated by histidine kinases and phosphorelay proteins in response to oxidative stress signals. However, studies of the exact transduction mechanism of multiple-stress responses are lacking. Thus, in response to various stimuli, we monitored the Sty1 MAPK pathway through the downstream transcription factor Atf1 in living cells using a highly sensitive luciferase reporter gene. Surprisingly, in cadmium and low glucose (LG) medium, Atf1 activation was observed even in the absence of all of the four fission yeast MAPK kinase kinases (MAPKKKs); whereas in osmotic stress, Atf1 activation was abolished. Thus, the osmotic stress likely mediates the MAPK activation via MAPKKKs, whereas a cadmium or LG condition activates the MAPKin a MAPKKK-independent manner. On the other hand, knockout of tyrosine phosphatase gene pyp1(+) abolished the Atf1 response to cadmium and LG, but not to osmotic stress, suggesting that Pyp1 is a sensor for cadmium and LG.

• 出版日期2010-10-22