Protein kinases involved in mating and osmotic stress in the yeast Kluyveromyces lactis.
Systematic disruption of genes encoding kinases and mitogen-activated protein kinases (MAPKs) was performed in Kluyveromyces lactis haploid cells. The mutated strains were assayed by their capacity to mate and to respond to hyperosmotic stress. The K. lactis Ste11p (KlSte11p) MAPK kinase kinase (MAPKKK) was found to act in both mating and osmoresponse pathways while the scaffold KlSte5p and the MAPK KlFus3p appeared to be specific for mating. The p21-activated kinase KlSte20p and the kinase KlSte50p participated in both pathways. Protein association experiments showed interaction of KlSte50p and KlSte20p with Galpha and Gbeta, respectively, the G protein subunits involved in the mating pathway. Both KlSte50p and KlSte20p also showed interaction with KlSte11p. Disruption mutants of the K. lactis PBS2 (KlPBS2) and KlHOG1 genes of the canonical osmotic response pathway resulted in mutations sensitive to high salt and high sorbitol but dispensable for mating. Mutations that eliminate the MAPKK KlSte7p activity had a strong effect on mating and also showed sensitivity to osmotic stress. Finally, we found evidence of physical interaction between KlSte7p and KlHog1p, in addition to diminished Hog1p phosphorylation after a hyperosmotic shock in cells lacking KlSte7p. This study reveals novel roles for components of transduction systems in yeast.
Kawasaki
Laura
L
Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-242, 04510 México, D. F. México.
Castañeda-Bueno
María
M
Sánchez-Paredes
Edith
E
Velázquez-Zavala
Nancy
N
Torres-Quiroz
Francisco
F
Ongay-Larios
Laura
L
Coria
Roberto
R
D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D049770:Genes, Mating Type, Fungal; D007716:Kluyveromyces / Q000201:enzymology* / Q000235:genetics; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009994:Osmolar Concentration; D009995:Osmosis; D009997:Osmotic Pressure; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
D005656:Fungal Proteins; D011494:Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases