title: Protein Kinase A-independent Ras Protein Activation Cooperates with Rap1 Protein to Mediate Activation of the Extracellular Signal-regulated Kinases (ERK) by cAMP.
abstract: Cyclic adenosine monophosphate (cAMP) is an important mediator of hormonal stimulation of cell growth and differentiation through its activation of the extracellular signal-regulated kinase (ERK) cascade. Two small G proteins, Ras and Rap1, have been proposed to mediate this activation, with either Ras or Rap1 acting in distinct cell types. Using Hek293 cells, we show that both Ras and Rap1 are required for cAMP signaling to ERKs. The roles of Ras and Rap1 were distinguished by their mechanism of activation, dependence on the cAMP-dependent protein kinase (PKA), and the magnitude and kinetics of their effects on ERKs. Ras was required for the early portion of ERK activation by cAMP and was activated independently of PKA. Ras activation required the Ras/Rap guanine nucleotide exchange factor (GEF) PDZ-GEF1. Importantly, this action of PDZ-GEF1 was disrupted by mutation within its putative cyclic nucleotide-binding domain within PDZ-GEF1. Compared with Ras, Rap1 activation of ERKs was of longer duration. Rap1 activation was dependent on PKA and required Src family kinases and the Rap1 exchanger C3G. This is the first report of a mechanism for the cooperative actions of Ras and Rap1 in cAMP activation of ERKs. One physiological role for the sustained activation of ERKs is the transcription and stabilization of a range of transcription factors, including c-FOS. We show that the induction of c-FOS by cAMP required both the early and sustained phases of ERK activation, requiring Ras and Rap1, as well as for each of the Raf isoforms, B-Raf and C-Raf.
authors.affiliation: From the Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239-3098.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Li
authors.affiliation: From the Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239-3098.
authors.forename: Tara J
authors.initials: TJ
authors.lastname: Dillon
authors.affiliation: From the Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239-3098.
authors.forename: Maho
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: From the Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239-3098.
authors.forename: Keith T
authors.initials: KT
authors.lastname: Earley
authors.affiliation: From the Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239-3098 stork@ohsu.edu.
authors.forename: Philip J S
authors.identifier: http://orcid.org/0000-0003-2518-4646
authors.initials: PJ
authors.lastname: Stork
mesh_terms: D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C508086:CNrasGEF protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D009419:Nerve Tissue Proteins; D016760:Proto-Oncogene Proteins c-fos; C403525:RAPGEF2 protein, human; D000089804:Shelterin Complex; C440809:TERF2IP protein, human; D034501:Telomere-Binding Proteins; D000242:Cyclic AMP; C482119:BRAF protein, human; C482120:Braf protein, mouse; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: Ras protein; Ras-related protein 1 (Rap1); cyclic AMP (cAMP); extracellular-signal-regulated kinase (ERK); guanine nucleotide exchange factor (GEF)