title: MAP kinases have different functions in Dictyostelium G protein-mediated signaling.
abstract: Extracellular signal regulated kinases (ERKs) are a class of MAP kinases that function in many signaling pathways in eukaryotic cells and in some cases, a single stimulus can activate more than one ERK suggesting functional redundancy or divergence from a common pathway. Dictyostelium discoideum encodes only two MAP kinases, ERK1 and ERK2, that both function during the developmental life cycle. To determine if ERK1 and ERK2 have overlapping functions, chemotactic and developmental phenotypes of erk1(-) and erk2(-) mutants were assessed with respect to G protein-mediated signal transduction pathways. ERK1 was specifically required for Galpha5-mediated tip morphogenesis and inhibition of folate chemotaxis but not for cAMP-stimulated chemotaxis or cGMP accumulation. ERK2 was the primary MAPK phosphorylated in response to folate or cAMP stimulation. Cell growth was not altered in erk1(-), erk2(-) or erk1(-)erk2(-) mutants but each mutant displayed a different pattern of cell sorting in chimeric aggregates. The distribution of GFP-ERK1 or GFP-ERK2 fusion proteins in the cytoplasm and nucleus was not grossly altered in cells stimulated with cAMP or folate. These results suggest ERK1 and ERK2 have different roles in G protein-mediated signaling during growth and development.
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, 74078-3020, USA.
authors.forename: Hoai-Nghia
authors.initials: HN
authors.lastname: Nguyen
authors.forename: Brent
authors.initials: B
authors.lastname: Raisley
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hadwiger
mesh_terms: D000818:Animals; D002449:Cell Aggregation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002633:Chemotaxis / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology; D004023:Dictyostelium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D004789:Enzyme Activation / Q000187:drug effects; D005492:Folic Acid / Q000494:pharmacology; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009024:Morphogenesis / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology; D014170:Transformation, Genetic / Q000187:drug effects
chemical_list: D044385:GTP-Binding Protein alpha Subunits; D005492:Folic Acid; D000242:Cyclic AMP; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019204:GTP-Binding Proteins