The high-osmolarity glycerol- and cell wall integrity-MAP kinase pathways of Saccharomyces cerevisiae are involved in adaptation to the action of killer toxin HM-1.
Fps1p is an aquaglyceroporin important for turgor regulation of Saccharomyces cerevisiae. Previously we reported the involvement of Fps1p in the yeast-killing action of killer toxin HM-1. The fps1 cells showed a high HM-1-resistant phenotype in hypotonic medium and an HM-1-susceptible phenotype in hypertonic medium. This osmotic dependency in HM-1 susceptibility was similar to those observed in Congo red, but different from those observed in other cell wall-disturbing agents. These results indicate that HM-1 exerts fungicidal activity mainly by binding and inserting into the yeast cell wall structure, rather than by inhibiting 1,3-β-glucan synthase. We next determined HM-1-susceptibility and diphospho-MAP kinase inductions in S. cerevisiae. In the wild-type cell, expressions of diphospho-Hog1p and -Slt2p, and mRNA transcription of CWP1 and HOR2, were induced within 1 h after an addition of HM-1. ssk1 and pbs2 cells, but not sho1 and hkr1 cells, showed HM-1-sensitive phenotypes and lacked inductions of phospho-Hog1p in response to HM-1. mid2, rom2 and bck1 cells showed HM-1-sensitive phenotypes and decreased inductions of phospho-Slt2p in response to HM-1. From these results, we postulated that the Sln1-Ypd1-Ssk1 branch of the high-osmolality glycerol (HOG) pathway and plasma membrane sensors of the cell wall integrity (CWI) pathway detect cell wall stresses caused by HM-1. We further suggested that activations of both HOG and CWI pathways have an important role in the adaptive response to HM-1 toxicity.
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, Niigata, Japan. miyamoto@nupals.ac.jp
Masahiko
M
Miyamoto
Yasuhiro
Y
Furuichi
Tadazumi
T
Komiyama
D002473:Cell Wall / Q000187:drug effects; D003470:Culture Media / Q000737:chemistry; D005990:Glycerol / Q000378:metabolism; D055646:Killer Factors, Yeast / Q000633:toxicity*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009997:Osmotic Pressure; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological
D003470:Culture Media; D055646:Killer Factors, Yeast; D029701:Saccharomyces cerevisiae Proteins; D020928:Mitogen-Activated Protein Kinases; D005990:Glycerol