title: Cloning of a novel mitogen-activated protein kinase kinase kinase, MEKK4, that selectively regulates the c-Jun amino terminal kinase pathway.
abstract: Mitogen-activated protein kinases (MAPKs) are components of sequential kinase cascades that are activated in response to a variety of extracellular signals. Members of the MAPK family include the extracellular response kinases (ERKs or p42/44(MAPK)), the c-Jun amino-terminal kinases (JNKs), and the p38/Hog 1 protein kinases. MAPKs are phosphorylated and activated by MAPK kinases (MKKs or MEKs), which in turn are phosphorylated and activated by MKK/MEK kinases (Raf and MKKK/MEKKs). We have isolated two cDNAs encoding splice variants of a novel MEK kinase, MEKK4. The MEKK4 mRNA is widely expressed in mouse tissues and encodes for a protein of approximately 180 kDa. The MEKK4 carboxyl-terminal catalytic domain is approximately 55% homologous to the catalytic domains of MEKKs 1, 2, and 3. The amino-terminal region of MEKK4 has little sequence homology to the previously cloned MEKK proteins. MEKK4 specifically activates the JNK pathway but not ERKs or p38, distinguishing it from MEKKs 1, 2 and 3, which are capable of activating the ERK pathway. MEKK4 is localized in a perinuclear, vesicular compartment similar to the Golgi. MEKK4 binds to Cdc42 and Rac; kinase-inactive mutants of MEKK4 block Cdc42/Rac stimulation of the JNK pathway. MEKK4 has a putative pleckstrin homology domain and a proline-rich motif, suggesting specific regulatory functions different from those of the previously characterized MEKKs.
authors.affiliation: Division of Basic Sciences and Program in Molecular Signal Transduction, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206, USA.
authors.forename: P
authors.initials: P
authors.lastname: Gerwins
authors.forename: J L
authors.initials: JL
authors.lastname: Blank
authors.forename: G L
authors.initials: GL
authors.lastname: Johnson
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D003001:Cloning, Molecular; D004789:Enzyme Activation; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011817:Rabbits; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; C482562:Map2k4 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases