title: Effect of the pheromone-responsive G(alpha) and phosphatase proteins of Saccharomyces cerevisiae on the subcellular localization of the Fus3 mitogen-activated protein kinase.
abstract: The mating-specific G(alpha) protein of Saccharomyces cerevisiae, Gpa1, stimulates adaptation to pheromone by a mechanism independent of G(beta gamma) sequestration. Genetic evidence suggests that Gpa1 targets the Fus3 mitogen-activated protein kinase, and it has recently been shown that the two proteins interact in cells responding to pheromone. To test the possibility that Gpa1 downregulates the mating signal by affecting the localization of Fus3, we created a Fus3-green fluorescent protein (GFP) fusion protein. In vegetative cells, Fus3-GFP was found in both the cytoplasm and the nucleus. Pheromone stimulated a measurable increase in the ratio of nuclear to cytoplasmic Fus3-GFP. In contrast, the relative level of nuclear Fus3-GFP decreased as cells recovered from pheromone arrest and did not increase when cells adapted to chronic stimulus were challenged again. Accumulation of Fus3-GFP in the nuclei of stimulated cells was also inhibited by overexpression of either wild-type Gpa1, the E364K hyperadaptive mutant form of Gpa1, or the Msg5 dually specific phosphatase. The effects of Gpa1 and Msg5 on Fus3 are partially interdependent. In a genetic screen for adaptive defective mutants, a nonsense allele of the nucleocytoplasmic transport receptor, Kap104, was identified. Truncation of the Kap104 cargo-binding domain blocked the effect of both Gpa1(E364K) and Msg5 on Fus3-GFP localization. Based on these results, we propose that Gpa1 and Msg5 work in concert to downregulate the mating signal and that they do so by inhibiting the pheromone-induced increase of Fus3 in the nucleus. Kap104 is required for the G(alpha)/phosphatase-mediated effect on Fus3 localization.
authors.affiliation: Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
authors.forename: Ernest
authors.initials: E
authors.lastname: Blackwell
authors.forename: Izabel M
authors.initials: IM
authors.lastname: Halatek
authors.forename: Hye-Jin N
authors.initials: HJ
authors.lastname: Kim
authors.forename: Alexis T
authors.initials: AT
authors.lastname: Ellicott
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Obukhov
authors.forename: David E
authors.initials: DE
authors.lastname: Stone
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D001665:Binding Sites; D002455:Cell Division / Q000235:genetics; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D004843:Epistasis, Genetic; D044385:GTP-Binding Protein alpha Subunits; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D049452:Green Fluorescent Proteins; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D010675:Pheromones / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D028961:beta Karyopherins
chemical_list: D044385:GTP-Binding Protein alpha Subunits; C101820:KAP104 protein, S cerevisiae; D028884:Karyopherins; D008164:Luminescent Proteins; C080773:NAB2 protein, S cerevisiae; D029543:Nucleocytoplasmic Transport Proteins; D010675:Pheromones; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D028961:beta Karyopherins; D049452:Green Fluorescent Proteins; C075580:FUS3 protein, S cerevisiae; D020928:Mitogen-Activated Protein Kinases; C085791:MSG5 protein, S cerevisiae; D017027:Protein Tyrosine Phosphatases; C084293:GPA1 protein, S cerevisiae; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins