title: Molecular crosstalk between p70S6k and MAPK cell signaling pathways.
abstract: We report here for the first time that the specific MAPK kinase (MEK) inhibitor, PD-98059, completely knocked out granulocyte-macrophage colony-stimulating factor (GM-CSF)-stimulated MAPK activity but also partially inactivated the ribosomal kinase p70S6K. Since a connection between the two major signaling pathways, Ras/MEK/MAPK and PI3-K/p70S6K was suspected, experiments were designed to prove a molecular crosstalk between those. First, p70S6K protein could be co-immunoprecipitated with anti-MAPK antibodies, MAPK protein was similarly present in anti-p70S6K immunoprecipitates, indicating close spatial proximity of both signaling molecules. Second, p70S6K enzymatic activity was found in anti-MAPK immunoprecipitates and MAPK in anti-p70S6K immunoprecipitates, being the latter activity higher in samples derived from GM-CSF-treated cells. Since an upstream activator of p70S6K, phosphatidylinositol (PI)3-kinase, has been associated to cell movement in phagocytic cells, we studied a possible participation of p70S6K in chemotaxis and whether MAPK had an input. Our data show that functional chemotaxis was inhibited by rapamycin, a specific p70S6K inhibitor, as well as by PD-98059. Thus, a connection between these two kinases extends from the molecular level to cell migration, a key functionality in non-proliferative, mature phagocytes such as neutrophils.
authors.affiliation: Department of Physiology and Biophysics, Wright State University School of Medicine, Dayton, OH 45435, USA.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Lehman
authors.forename: Julian
authors.initials: J
authors.lastname: Gomez-Cambronero
mesh_terms: D000595:Amino Acid Sequence; D002455:Cell Division / Q000187:drug effects; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation; D020239:Receptor Cross-Talk / Q000502:physiology; D011994:Recombinant Proteins; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*; D012270:Ribosomes / Q000502:physiology; D013379:Substrate Specificity; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D011994:Recombinant Proteins; D016179:Granulocyte Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019893:Ribosomal Protein S6 Kinases; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one