title: Yeast pseudohyphal growth is regulated by GPA2, a G protein alpha homolog.
abstract: Pseudohyphal differentiation, a filamentous growth form of the budding yeast Saccharomyces cerevisiae, is induced by nitrogen starvation. The mechanisms by which nitrogen limitation regulates this process are currently unknown. We have found that GPA2, one of the two heterotrimeric G protein alpha subunit homologs in yeast, regulates pseudohyphal differentiation. Deltagpa2/Deltagpa2 mutant strains have a defect in pseudohyphal growth. In contrast, a constitutively active allele of GPA2 stimulates filamentation, even on nitrogen-rich media. Moreover, a dominant negative GPA2 allele inhibits filamentation of wild-type strains. Several findings, including epistasis analysis and reporter gene studies, indicate that GPA2 does not regulate the MAP kinase cascade known to regulate filamentous growth. Previous studies have implicated GPA2 in the control of intracellular cAMP levels; we find that expression of the dominant RAS2(Gly19Val) mutant or exogenous cAMP suppresses the Deltagpa2 pseudohyphal defect. cAMP also stimulates filamentation in strains lacking the cAMP phosphodiesterase PDE2, even in the absence of nitrogen starvation. Our findings suggest that GPA2 is an element of the nitrogen sensing machinery that regulates pseudohyphal differentiation by modulating cAMP levels.
authors.affiliation: Department of Genetics, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Lorenz
authors.forename: J
authors.initials: J
authors.lastname: Heitman
mesh_terms: D000483:Alleles; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation; D000242:Cyclic AMP / Q000378:metabolism; D004843:Epistasis, Genetic; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D044385:GTP-Binding Protein alpha Subunits; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005799:Genes, Dominant; D017930:Genes, Reporter; D020962:Heterotrimeric GTP-Binding Proteins; D008954:Models, Biological; D009024:Morphogenesis; D009584:Nitrogen / Q000172:deficiency*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D018631:ras Proteins / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; D029701:Saccharomyces cerevisiae Proteins; D000242:Cyclic AMP; D017871:Calcium-Calmodulin-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