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Osmostress enhances activating phosphorylation of Hog1 MAP kinase by mono‐phosphorylated Pbs2 MAP 2K
Author(s) -
Tatebayashi Kazuo,
Yamamoto Katsuyoshi,
Tomida Taichiro,
Nishimura Akiko,
Takayama Tomomi,
Oyama Masaaki,
KozukaHata Hiroko,
AdachiAkahane Satomi,
Tokunaga Yuji,
Saito Haruo
Publication year - 2020
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.15252/embj.2019103444
Subject(s) - phosphorylation , biology , kinase , microbiology and biotechnology
Abstract The MAP kinase ( MAPK ) Hog1 is the central regulator of osmoadaptation in yeast. When cells are exposed to high osmolarity, the functionally redundant Sho1 and Sln1 osmosensors, respectively, activate the Ste11‐Pbs2‐Hog1 MAPK cascade and the Ssk2/Ssk22‐Pbs2‐Hog1 MAPK cascade. In a canonical MAPK cascade, a MAPK kinase kinase ( MAP 3K) activates a MAPK kinase ( MAP 2K) by phosphorylating two conserved Ser/Thr residues in the activation loop. Here, we report that the MAP 3K Ste11 phosphorylates only one activating phosphorylation site (Thr‐518) in Pbs2, whereas the MAP 3Ks Ssk2/Ssk22 can phosphorylate both Ser‐514 and Thr‐518 under optimal osmostress conditions. Mono‐phosphorylated Pbs2 cannot phosphorylate Hog1 unless the reaction between Pbs2 and Hog1 is enhanced by osmostress. The lack of the osmotic enhancement of the Pbs2‐Hog1 reaction suppresses Hog1 activation by basal MAP 3K activities and prevents pheromone‐to‐Hog1 crosstalk in the absence of osmostress. We also report that the rapid‐and‐transient Hog1 activation kinetics at mildly high osmolarities and the slow and prolonged activation kinetics at severely high osmolarities are both caused by a common feedback mechanism.