title: Ras-dependent activation of the small GTPase Ral.
abstract: The small GTPase Ral is a Ras-like GTPase [1] that has been implicated in growth-factor-induced and Ras-induced DNA synthesis [2-4], and Ras-induced oncogenic transformation [3,5]. Recently, we and others found that three different Ral guanine nucleotide exchange factors (Ral GEFs) - Ral GDS, Rgl and Rlf - bind specifically to the GTP-bound form of several Ras-like GTPases [6-9]. Although oncogenic Ras is able to activate these Ral GEFs [2,5,10], it is unknown whether growth factors can induce the activation of Ral and, if so, which small GTPase is involved in this process. Here, we show that stimulation of various growth factor receptors, including receptor tyrosine kinases and serpentine receptors, results in rapid activation of Ral. This activation correlates with the activation of Ras, and dominant-negative Ras completely inhibits Ral activation induced by insulin and epidermal growth factor (EGF). From these results, we conclude that Ral activation is a direct downstream effect of growth-factor-induced Ras activation.
authors.affiliation: Laboratory for Physiological Chemistry, Utrecht University, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands.
authors.forename: R M
authors.initials: RM
authors.lastname: Wolthuis
authors.forename: F
authors.initials: F
authors.lastname: Zwartkruis
authors.forename: T C
authors.initials: TC
authors.lastname: Moen
authors.forename: J L
authors.initials: JL
authors.lastname: Bos
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D011905:Genes, ras / Q000502:physiology*; D007328:Insulin / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D009154:Mutation; D051381:Rats; D017466:Receptors, Endothelin / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D020725:ral GTP-Binding Proteins
chemical_list: D007328:Insulin; D008246:Lysophospholipids; D017466:Receptors, Endothelin; D011993:Recombinant Fusion Proteins; D004815:Epidermal Growth Factor; D017479:Receptors, Platelet-Derived Growth Factor; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020725:ral GTP-Binding Proteins