Human mitogen-activated protein kinase kinase kinase mediates the stress-induced activation of mitogen-activated protein kinase cascades.
The mitogen-activated protein kinase (MAPK) cascades represent one of the important signalling mechanisms in response to environmental stimuli. We report the identification of a human MAPK kinase kinase, MAPKKK4, via sequence similarity with other MAPKKKs. When truncated MAPKKK4 (DeltaMAPKKK4) was overexpressed in HEK293 cells, it was constitutively active and induced the activation of endogenous p38alpha, c-Jun N-terminal kinase (JNK)1/2 and extracellular signal-regulated kinase (ERK)2 in vivo. Kinase-inactive DeltaMAPKKK4 partly inhibited the activation of p38alpha, JNK1/2 and ERK2 induced by stress, tumour necrosis factor alpha or epidermal growth factor, suggesting that MAPKKK4 might be physiologically involved in all three MAPK cascades. Co-expressed MAP kinase kinase (MKK)-1, MKK-4, MKK-3 and MKK-6 were activated in vivo by DeltaMAPKKK4. All of the above MKKs purified from Escherichia coli were phosphorylated and activated by DeltaMAPKKK4 immunoprecipitates in vitro. When expressed by lower plasmid doses, DeltaMAPKKK4 preferentially activated MKK-3 and p38alpha in vivo. Overexpression of DeltaMAPKKK4 did not activate the NF-kappaB pathway. Immunoprecipitation of endogenous MAPKKK4 by specific antibodies showed that MAPKKK4 was activated after the treatment of K562 cells with various stress conditions. As a broadly distributed kinase, MAPKKK4 might serve as a stress responder. MAPKKK4 is 91% identical with the recently described murine MEKK-4beta and might be its human homologue. It is also identical with the recently cloned human MAP three kinase 1 except for the lack of an internal sequence homologous to the murine MEKK-4alpha isoform. Differences in the reported functional activities of the three kinases are discussed.
Chan-Hui
P Y
PY
Amgen, Department of Inflammation Research, 3200 Walnut Street, Boulder, CO 80301, USA. povying@stratabio.com
Weaver
R
R
D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D020672:I-kappa B Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D007668:Kidney / Q000201:enzymology; D048369:MAP Kinase Kinase 1; D048371:MAP Kinase Kinase 3; D048670:MAP Kinase Kinase 4; D048669:MAP Kinase Kinase 6; D048768:MAP Kinase Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048056:Mitogen-Activated Protein Kinase 9; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D016415:Sequence Alignment; D013312:Stress, Physiological / Q000201:enzymology; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D004268:DNA-Binding Proteins; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; D047428:Protein Kinase Inhibitors; D014409:Tumor Necrosis Factor-alpha; D004815:Epidermal Growth Factor; D048056:Mitogen-Activated Protein Kinase 9; 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; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048768:MAP Kinase Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases; C482779:MAP3K4 protein, human; D048369:MAP Kinase Kinase 1; D048371:MAP Kinase Kinase 3; D048670:MAP Kinase Kinase 4; D048669:MAP Kinase Kinase 6; C482125:MAP2K1 protein, human; C482530:MAP2K3 protein, human; C482559:MAP2K4 protein, human; C482566:MAP2K6 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases