title: MEK kinases are regulated by EGF and selectively interact with Rac/Cdc42.
abstract: MEK kinases (MEKKs) 1, 2, 3 and 4 are members of sequential kinase pathways that regulate MAP kinases including c-Jun NH2-terminal kinases (JNKs) and extracellular regulated kinases (ERKs). Confocal immunofluorescence microscopy of COS cells demonstrated differential MEKK subcellular localization: MEKK1 was nuclear and in post-Golgi vesicular-like structures; MEKK2 and 4 were localized to distinct Golgi-associated vesicles that were dispersed by brefeldin A. MEKK1 and 2 were activated by EGF, and kinase-inactive mutants of each MEKK partially inhibited EGF-stimulated JNK activity. Kinase-inactive MEKK1, but not MEKK2, 3 or 4, strongly inhibited EGF-stimulated ERK activity. In contrast to MEKK2 and 3, MEKK1 and 4 specifically associated with Rac and Cdc42 and kinase-inactive mutants blocked Rac/Cdc42 stimulation of JNK activity. Inhibitory mutants of MEKK1-4 did not affect p21-activated kinase (PAK) activation of JNK, indicating that the PAK-regulated JNK pathway is independent of MEKKs. Thus, in different cellular locations, specific MEKKs are required for the regulation of MAPK family members, and MEKK1 and 4 are involved in the regulation of JNK activation by Rac/Cdc42 independent of PAK. Differential MEKK subcellular distribution and interaction with small GTP-binding proteins provides a mechanism to regulate MAP kinase responses in localized regions of the cell and to different upstream stimuli.
authors.affiliation: Division of Basic Sciences, National Jewish Medical and Research Center, Denver, CO 80206, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Fanger
authors.forename: N L
authors.initials: NL
authors.lastname: Johnson
authors.forename: G L
authors.initials: GL
authors.lastname: Johnson
mesh_terms: D000818:Animals; D015153:Blotting, Western; D020126:Brefeldin A; D016466:CHO Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D006224:Cricetinae; D003517:Cyclopentanes / Q000494:pharmacology; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D008954:Models, Biological; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D020764:cdc42 GTP-Binding Protein
chemical_list: D018797:Cell Cycle Proteins; D003517:Cyclopentanes; D020126:Brefeldin A; D004815:Epidermal Growth Factor; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D048371:MAP Kinase Kinase 3; D048670:MAP Kinase Kinase 4; C482530:MAP2K3 protein, human; C482559:MAP2K4 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein