title: Thioredoxin Activates MKK4-NFκB Pathway in a Redox-dependent Manner to Control Manganese Superoxide Dismutase Gene Expression in Endothelial Cells.
abstract: The mitogen-activated protein kinase kinase 4 (MKK4) is activated via phosphorylation of Ser-257 and Thr-261 by upstream MAP3Ks and activates JNK and p38 MAPKs in response to cellular stress. We show that thioredoxin (Trx), a cellular redox protein, activates MKK4 via Cys-246 and Cys-266 residues as mutation of these residues renders MKK4 insensitive to phosphorylation by MAP3Ks, TNFα, or Trx. MKK4 is activated in vitro by reduced Trx but not oxidized Trx in the absence of an upstream kinase, suggesting that autophosphorylation of this protein occurs due to reduction of Cys-246 and Cys-266 by Trx. Additionally, mutation of Cys-246 and Cys-266 resulted in loss of kinase activity suggesting that the redox state of Cys-246 and Cys-266 is a critical determinant of MKK4 activation. Trx induces manganese superoxide dismutase (MnSOD) gene transcription by activating MKK4 via redox control of Cys-246 and Cys-266, as mutation of these residues abrogates MKK4 activation and MnSOD expression. We further show that MKK4 activates NFκB for its binding to the MnSOD promoter, which leads to AP-1 dissociation followed by MnSOD transcription. Taken together, our studies show that the redox status of Cys-246 and Cys-266 in MKK4 controls its activities independent of MAP3K, demonstrating integration of the endothelial redox environment to MAPK signaling.
authors.affiliation: From the Department of Anesthesiology and Center for Excellence in Cardiovascular Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Kundumani-Sridharan
authors.affiliation: From the Department of Anesthesiology and Center for Excellence in Cardiovascular Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430.
authors.forename: Jaganathan
authors.initials: J
authors.lastname: Subramani
authors.affiliation: From the Department of Anesthesiology and Center for Excellence in Cardiovascular Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430 kumuda.das@ttuhsc.edu.
authors.forename: Kumuda C
authors.initials: KC
authors.lastname: Das
mesh_terms: D019943:Amino Acid Substitution; D002478:Cells, Cultured; D003545:Cysteine / Q000737:chemistry; D042783:Endothelial Cells / Q000378:metabolism*; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D057809:HEK293 Cells; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D048728:MAP Kinase Kinase Kinase 1 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism*; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics*; D013879:Thioredoxins / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000099156:Superoxide Dismutase 2
chemical_list: D003545:Cysteine; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D016328:NF-kappa B; D034741:RNA, Small Interfering; D013482:Superoxide Dismutase; D013879:Thioredoxins; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D000099156:Superoxide Dismutase 2; C491203:TXN protein, human; C482576:MAP3K1 protein, human; C482559:MAP2K4 protein, human
keywords: AP-1 transcription factor (AP-1); NF-κB transcription factor; Sod2; endothelial cell; manganese superoxide dismutase; mitogen-activated protein kinase (MAPK); redox regulation; redox signaling; thioredoxin