title: Complementation and characterization of the Pneumocystis carinii MAPK, PCM.
abstract: Mitogen-activated protein kinase (MAPK) pathways transfer environmental signals into intracellular events such as proliferation and differentiation. Fungi utilize a specific pheromone-induced MAPK pathway to regulate conjugation, formation of an ascus, and entry into meiosis. We have previously identified a MAPK, PCM, from the fungal opportunist Pneumocystis, responsible for causing severe pneumonia in patients with AIDS. In order to gain insight into the function of PCM, we expressed it in Saccharomyces cerevisiae deficient in pheromone signaling and tested activation and inhibition of this MAPK pathway. PCM restored pheromone signaling in S. cerevisiae fus3Delta kss1Delta mutants with alpha-factor pheromone (six-fold increase) and was not activated by osmotic stress. Signaling through this pathway decreased 2.5-fold with 10 microM U0126, and was unaffected with SB203580. We evaluated the conditions for native PCM kinase activity isolated from Pneumocystis carinii organisms and found that 0.1 mM MgCl2, pH 6.5, temperature 30-35 degrees C, and 10 microM ATP were optimal. The activity of PCM is significantly elevated in P. carinii trophic forms compared to cysts, implicating a role for PCM in the life cycle transition of P. carinii from trophic forms to cysts.
authors.affiliation: Department of Medicine, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
authors.forename: Pawan K
authors.initials: PK
authors.lastname: Vohra
authors.forename: Veenu
authors.initials: V
authors.lastname: Puri
authors.forename: Charles F
authors.initials: CF
authors.lastname: Thomas
mesh_terms: D002070:Butadienes / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005816:Genetic Complementation Test; D020935:MAP Kinase Signaling System; D000072235:Mating Factor; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D011010:Pneumocystis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D012331:RNA, Fungal / Q000378:metabolism
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D009570:Nitriles; D010455:Peptides; D012331:RNA, Fungal; C113580:U 0126; D000072235:Mating Factor; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases