title: B56-containing PP2A dephosphorylate ERK and their activity is controlled by the early gene IEX-1 and ERK.
abstract: The protein phosphatase 2A (PP2A) acts on several kinases in the extracellular signal-regulated kinase (ERK) signaling pathway but whether a specific holoenzyme dephosphorylates ERK and whether this activity is controlled during mitogenic stimulation is unknown. By using both RNA interference and overexpression of PP2A B regulatory subunits, we show that B56, but not B, family members of PP2A increase ERK dephosphorylation, without affecting its activation by MEK. Induction of the early gene product and ERK substrate IEX-1 (ier3) by growth factors leads to opposite effects and reverses B56-PP2A-mediated ERK dephosphorylation. IEX-1 binds to B56 subunits and pERK independently, enhances B56 phosphorylation by ERK at a conserved Ser/Pro site in this complex and triggers dissociation from the catalytic subunit. This is the first demonstration of the involvement of B56-containing PP2A in ERK dephosphorylation and of a B56-specific cellular protein inhibitor regulating its activity in an ERK-dependent fashion. In addition, our results raise a new paradigm in ERK signaling in which ERK associated to a substrate can transphosphorylate nearby proteins.
authors.affiliation: Department of Hematology, Institut Cochin, INSERM U567, Paris, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Letourneux
authors.forename: Géraldine
authors.initials: G
authors.lastname: Rocher
authors.forename: Françoise
authors.initials: F
authors.lastname: Porteu
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D019556:COS Cells; D002522:Chlorocebus aethiops; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006133:Growth Substances / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D054648:Protein Phosphatase 2; D011499:Protein Processing, Post-Translational / Q000502:physiology; D021122:Protein Subunits / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D006133:Growth Substances; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D021122:Protein Subunits; D048049:Extracellular Signal-Regulated MAP Kinases; D020930:MAP Kinase Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2