title: Cyclic AMP-dependent protein kinase regulates pseudohyphal differentiation in Saccharomyces cerevisiae.
abstract: In response to nitrogen starvation, diploid cells of the yeast Saccharomyces cerevisiae differentiate to a filamentous growth form known as pseudohyphal differentiation. Filamentous growth is regulated by elements of the pheromone mitogen-activated protein (MAP) kinase cascade and a second signaling cascade involving the receptor Gpr1, the Galpha protein Gpa2, Ras2, and cyclic AMP (cAMP). We show here that the Gpr1-Gpa2-cAMP pathway signals via the cAMP-dependent protein kinase, protein kinase A (PKA), to regulate pseudohyphal differentiation. Activation of PKA by mutation of the regulatory subunit Bcy1 enhances filamentous growth. Mutation and overexpression of the PKA catalytic subunits reveal that the Tpk2 catalytic subunit activates filamentous growth, whereas the Tpk1 and Tpk3 catalytic subunits inhibit filamentous growth. The PKA pathway regulates unipolar budding and agar invasion, whereas the MAP kinase cascade regulates cell elongation and invasion. Epistasis analysis supports a model in which PKA functions downstream of the Gpr1 receptor and the Gpa2 and Ras2 G proteins. Activation of filamentous growth by PKA does not require the transcription factors Ste12 and Tec1 of the MAP kinase cascade, Phd1, or the PKA targets Msn2 and Msn4. PKA signals pseudohyphal growth, in part, by regulating Flo8-dependent expression of the cell surface flocculin Flo11. In summary, the cAMP-dependent protein kinase plays an intimate positive and negative role in regulating filamentous growth, and these findings may provide insight into the roles of PKA in mating, morphogenesis, and virulence in other yeasts and pathogenic fungi.
authors.affiliation: Departments of Genetics, Pharmacology and Cancer Biology, Microbiology, and Medicine, the Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: X
authors.initials: X
authors.lastname: Pan
authors.forename: J
authors.initials: J
authors.lastname: Heitman
mesh_terms: D020134:Catalytic Domain; D002454:Cell Differentiation; D002455:Cell Division; D003470:Culture Media; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits; D019204:GTP-Binding Proteins / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism; D009584:Nitrogen; D009687:Nuclear Proteins; D011956:Receptors, Cell Surface / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
chemical_list: D003470:Culture Media; D004268:DNA-Binding Proteins; C110690:FLO11 protein, S cerevisiae; C100940:FLO8 protein, S cerevisaie; D005656:Fungal Proteins; C109334:GPR1 protein, S cerevisiae; D044385:GTP-Binding Protein alpha Subunits; C081935:MSN2 protein, S cerevisiae; C081937:MSN4 protein, S cerevisiae; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C489241:STE12 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C069926:TEC1 protein, S cerevisiae; D015534:Trans-Activators; D014157:Transcription Factors; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; C083907:Gpa2 protein, S cerevisiae; D020962:Heterotrimeric GTP-Binding Proteins; C489015:RAS2 protein, S cerevisiae; D018631:ras Proteins; D009584:Nitrogen