title: RalGDS couples growth factor signaling to Akt activation.
abstract: The Akt kinase is a key regulator of cell proliferation and survival. It is activated in part by PDK1-induced phosphorylation. Here we show that RalGDS, a Ras effector protein that activates Ral GTPases, has a second function that promotes Akt phosphorylation by PDK1 by bringing these two kinases together. In support of this conclusion is our finding that suppression of RalGDS expression in cells inhibits both epidermal growth factor and insulin-induced phosphorylation of Akt. Moreover, while PDK1 complexes with N-GDS, Akt complexes with the central region of RalGDS through an intermediary, JIP1. The biological significance of this newly discovered RalGDS function is highlighted by the observation that an N-terminally deleted mutant of RalGDS that retains the ability to activate Ral proteins but loses the ability to activate Akt also fails to promote cell proliferation. Thus, RalGDS forms a nexus that transduces growth factor signaling to both Ral GTPase and Akt-mediated signaling cascades.
authors.affiliation: Sackler School of Graduate Biomedical Sciences and Department of Biochemistry, Tufts University School of Medicine, Boston, MA 02111, USA.
authors.forename: Yansheng
authors.initials: Y
authors.lastname: Hao
authors.forename: Richard
authors.initials: R
authors.lastname: Wong
authors.forename: Larry A
authors.initials: LA
authors.lastname: Feig
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D015398:Signal Transduction; D020726:ral Guanine Nucleotide Exchange Factor / Q000235:genetics / Q000502:physiology*
chemical_list: D007328:Insulin; C000631429:PDK1 protein, human; C000631433:Pdk1 protein, mouse; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D020726:ral Guanine Nucleotide Exchange Factor; D004815:Epidermal Growth Factor; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt