title: Ubiquitylation of MEKK1 inhibits its phosphorylation of MKK1 and MKK4 and activation of the ERK1/2 and JNK pathways.
abstract: MEKK1 is a MAPK kinase kinase that is activated in response to stimuli that alter the cytoskeleton and cell shape. MEKK1 phosphorylates and activates MKK1 and MKK4, leading to ERK1/2 and JNK activation. MEKK1 has a plant homeobox domain (PHD) that has been shown to have E3 ligase activity. (Lu, Z., Xu, S., Joazeiro, C., Cobb, M. H., and Hunter, T. (2002) Mol. Cell 9, 945-956). MEKK1 kinase activity is required for ubiquitylation of MEKK1. MEKK1 ubiquitylation is inhibited by mutation of cysteine 441 to alanine (C441A) within the PHD. The functional consequence of MEKK1 ubiquitylation is the inhibition of MEKK1 catalyzed phosphorylation of MKK1 and MKK4 resulting in inhibition of ERK1/2 and JNK activation. The C441A mutation within the PHD of MEKK1 prevents ubiquitylation and preserves the ability of MEKK1 to catalyze MKK1 and MKK4 phosphorylation. MEKK1 ubiquitylation represents a mechanism for inhibiting the ability of a protein kinase to phosphorylate substrates and regulate downstream signaling pathways.
authors.affiliation: Department of Pharmacology, University of Colorado Health Sciences Center and University of Colorado Cancer Center, Denver, Colorado 80262, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Witowsky
authors.forename: Gary L
authors.initials: GL
authors.lastname: Johnson
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D004789:Enzyme Activation; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016296:Mutagenesis; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D025801:Ubiquitin; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D048369:MAP Kinase Kinase 1; D048670:MAP Kinase Kinase 4; C482125:MAP2K1 protein, human; C482559:MAP2K4 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases