title: MEKK4 stimulation of p38 and JNK activity is negatively regulated by GSK3beta.
abstract: The MAPK kinase kinase MEKK4 is required for neurulation and skeletal patterning during mouse development. MEKK4 phosphorylates and activates MKK4/MKK7 and MKK3/MKK6 leading to the activation of JNK and p38, respectively. MEKK4 is believed to be auto-inhibited, and its interaction with other proteins controls its dimerization and activation. TRAF4, GADD45, and Axin each bind and activate MEKK4, with TRAF4 and Axin binding to the kinase domain and GADD45 binding within the N-terminal regulatory domain. Here we show that similar to the interaction with TRAF4 and Axin, the kinase domain of MEKK4 interacts with the multifunctional serine/threonine kinase GSK3beta. GSK3beta binding to MEKK4 blocks MEKK4 dimerization that is required for MEKK4 activation, effectively inhibiting MEKK4 stimulation of the JNK and p38 MAPK pathways. Inhibition of GSK3beta kinase activity with SB216763 results in enhanced MEKK4 kinase activity and increased JNK and p38 activation, indicating that an active state of GSK3beta is required for binding and inhibition of MEKK4 dimerization. Furthermore, GSK3beta phosphorylates specific serines and threonines in the N terminus of MEKK4. Together, these findings demonstrate that GSK3beta binds to the kinase domain of MEKK4 and regulates MEKK4 dimerization. However, unlike TRAF4, Axin, and GADD45, GSK3beta inhibits MEKK4 activity and prevents its activation of JNK and p38. Thus, control of MEKK4 dimerization is regulated both positively and negatively by its interaction with specific proteins.
authors.affiliation: Department of Pharmacology and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7365, USA. amy_abell@med.unc.edu
authors.forename: Amy N
authors.initials: AN
authors.lastname: Abell
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Granger
authors.forename: Gary L
authors.initials: GL
authors.lastname: Johnson
mesh_terms: D000818:Animals; D060466:Axin Protein; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000378:metabolism; D002522:Chlorocebus aethiops; D019281:Dimerization; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D007211:Indoles / Q000494:pharmacology; D048371:MAP Kinase Kinase 3 / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048669:MAP Kinase Kinase 6 / Q000378:metabolism; D048688:MAP Kinase Kinase 7 / Q000378:metabolism; D048768:MAP Kinase Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D012097:Repressor Proteins / Q000378:metabolism; D053449:TNF Receptor-Associated Factor 4 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000097642:GADD45 Proteins
chemical_list: D060466:Axin Protein; D018797:Cell Cycle Proteins; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D007211:Indoles; D048371:MAP Kinase Kinase 3; D048670:MAP Kinase Kinase 4; D048669:MAP Kinase Kinase 6; D048688:MAP Kinase Kinase 7; D048768:MAP Kinase Kinase Kinase 4; D008301:Maleimides; D009687:Nuclear Proteins; D012097:Repressor Proteins; D053449:TNF Receptor-Associated Factor 4; D048051:p38 Mitogen-Activated Protein Kinases; C499072:Gadd45a protein, mouse; D000097642:GADD45 Proteins; C417521:SB 216763; C506368:Traf4 protein, mouse; C000605507:Gsk3b protein, mouse; C482780:Map3k4 protein, mouse; C482531:Map2k3 protein, mouse; C482567:Map2k6 protein, mouse; C482570:Map2k7 protein, mouse