Osmostress enhances activating phosphorylation of Hog1 MAP kinase by mono‐phosphorylated Pbs2 MAP2K

• Kazuo Tatebayashi ^[4] ; Katsuyoshi Yamamoto ^[1] ; Taichiro Tomida ^[2] ; Akiko Nishimura ^[5] ; Tomomi Takayama ^[5] ; Masaaki Oyama ^[1] ; Hiroko Kozuka‐Hata ^[1] ; Satomi Adachi‐Akahane ^[2] ; Yuji Tokunaga ^[3] ; Haruo Saito ^[1]
  1. [1] University of Tokyo

     University of Tokyo

     Japón

     
  2. [2] Toho University

     Toho University

     Japón

     
  3. [3] National Institute of Advanced Industrial Science and Technology

     National Institute of Advanced Industrial Science and Technology

     Japón

     
  4. [4] 1 Laboratory of Molecular Genetics Frontier Research Unit Institute of Medical Science The University of Tokyo Tokyo Japan; 2 Division of Molecular Cell Signaling Institute of Medical Science The University of Tokyo Tokyo Japan; 3 Department of Biological Sciences Graduate School of Science The University of Tokyo Tokyo Japan
  5. [5] 2 Division of Molecular Cell Signaling Institute of Medical Science The University of Tokyo Tokyo Japan; 3 Department of Biological Sciences Graduate School of Science The University of Tokyo Tokyo Japan

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• Localización: EMBO journal: European Molecular Biology Organization, ISSN 0261-4189, Vol. 39, Nº. 5, 2020
• Idioma: inglés
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• Resumen

  • 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 (MAP3K) activates a MAPK kinase (MAP2K) by phosphorylating two conserved Ser/Thr residues in the activation loop. Here, we report that the MAP3K Ste11 phosphorylates only one activating phosphorylation site (Thr‐518) in Pbs2, whereas the MAP3Ks 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 MAP3K 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.