title: Stress-induced response, localization, and regulation of the Pmk1 cell integrity pathway in Schizosaccharomyces pombe.
abstract: Mitogen-activated protein kinase (MAPK) signaling pathways are critical for the sensing and response of eukaryotic cells to extracellular changes. In Schizosaccharomyces pombe, MAPK Pmk1/Spm1 has been involved in cell wall construction, morphogenesis, cytokinesis, and ion homeostasis, as part of the so-called cell integrity pathway together with MAPK kinase kinase Mkh1 and MAPK kinase Pek1. We show that Pmk1 is activated in multiple stress situations, including hyper- or hypotonic stress, glucose deprivation, presence of cell wall-damaging compounds, and oxidative stress induced by hydrogen peroxide or pro-oxidants. The stress-induced activation of Pmk1 was completely dependent on Mkh1 and Pek1 function, supporting a nonbranched pathway in the regulation of MAPK activation. Fluorescence microscopy revealed that Mkh1, Pek1, and Pmp1 (a protein phosphatase that inactivates Pmk1) are cytoplasmic proteins. Mkh1 and Pek1 were also found at the septum, whereas Pmk1 localized in both cytoplasm and nucleus as well as in the mitotic spindle and septum during cytokinesis. Interestingly, Pmk1 subcellular localization was unaffected by stress or the absence of Mkh1 and Pek1, suggesting that its activation by the Mkh1-Pek1 cascade takes place at the cytoplasm and/or septum and that the active and inactive forms of this kinase cross the nuclear membrane. Cdc42 GTPase and its effectors, p21-activated kinases Pak2 and Pak1, are not upstream elements controlling the basal level or the stress-induced activation of Pmk1. However, Sty1 MAPK was essential for proper Pmk1 deactivation after hypertonic stress in a process regulated by Atf1 transcription factor. These results provide the first evidence for the existence of cross-talk between two MAPK cascades during the stress response in fission yeast.
authors.affiliation: Departamento de Genética y Microbiología, Facultad de Biología, University of Murcia, Camous Universitario de Espinardo, Murcia 30071, Spain.
authors.forename: Marisa
authors.initials: M
authors.lastname: Madrid
authors.forename: Teresa
authors.initials: T
authors.lastname: Soto
authors.forename: Hou Keat
authors.initials: HK
authors.lastname: Khong
authors.forename: Alejandro
authors.initials: A
authors.lastname: Franco
authors.forename: Jero
authors.initials: J
authors.lastname: Vicente
authors.forename: Pilar
authors.initials: P
authors.lastname: Pérez
authors.forename: Mariano
authors.initials: M
authors.lastname: Gacto
authors.forename: José
authors.initials: J
authors.lastname: Cansado
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D048749:Cytokinesis; D003593:Cytoplasm / Q000378:metabolism; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation; D000939:Epitopes / Q000737:chemistry; D005656:Fungal Proteins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D047468:Immunoprecipitation; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism / Q000502:physiology*; D020935:MAP Kinase Signaling System; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009995:Osmosis; D018384:Oxidative Stress; D010957:Plasmids / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism / Q000502:physiology*; D013696:Temperature; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D000939:Epitopes; D005656:Fungal Proteins; D011506:Proteins; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; C079238:alcohol O-acetyltransferase; C119549:Mek1 protein, S pombe; D020928:Mitogen-Activated Protein Kinases; C102726:Pmk1 protein, Magnaporthe grisea; D020930:MAP Kinase Kinase Kinases; C106762:Mkh1 protein, S pombe; D048369:MAP Kinase Kinase 1; C110459:Pmp1 protein, S pombe; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases; D020764:cdc42 GTP-Binding Protein; D005947:Glucose