Differential activation of two JNK activators, MKK7 and SEK1, by MKN28-derived nonreceptor serine/threonine kinase/mixed lineage kinase 2.
MKN28-derived nonreceptor type of serine/threonine kinase/mixed lineage kinase 2 (MST/MLK2) directly phosphorylates and activates SEK1/MKK4/JNKK1/SKK1 in vitro, thereby acting as a mitogen-activated protein (MAP) kinase kinase kinase in the JNK/SAPK pathway (Hirai, S. -i., Katoh, M., Terada, M., Kyriakis, J. M., Zon, L. I., Rana, A., Avruch, J., and Ohno, S. (1997) J. Biol. Chem. 272, 15167-15173). The in vitro reconstitution system for the kinase cascade allowed us now to identify JNK/SAPK activators involved in the MST/MLK2-dependent activation of JNK/SAPK in vivo. We show that at least two distinct MST/MLK2-dependent JNK/SAPK activators are present in the fractionated COS-1 cell lysate, and that they appear to be SEK1/MKK4/JNKK1/SKK1 and MKK7/JNKK2/SKK4 by Western blot analysis. Notably, a majority of the MST/MLK2-dependent JNK/SAPK-activating activity is found in MKK7-containing fractions, whereas the MEKK1-dependent activity is comparably distributed in SEK1- and MKK7-containing fractions. Moreover, MST/MLK2 activates recombinant MKK7 more effectively than recombinant SEK1, whereas MEKK1 activates both to a similar extent. In addition, the deletion analysis on MST/MLK2 showed that the kinase domain is responsible for the determination of substrate specificity. These results provide a molecular aspect to the differential regulation of the two JNK activators by a variety of cellular stimuli.
Hirai
S
S
Department of Molecular Biology, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236, Japan. sh3312@med.yokohama-cu.ac.jp
Noda
K
K
Moriguchi
T
T
Nishida
E
E
Yamashita
A
A
Deyama
T
T
Fukuyama
K
K
Ohno
S
S
D000818:Animals; D019556:COS Cells; D004789:Enzyme Activation; D016350:Leucine Zippers; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013379:Substrate Specificity; D018909:src Homology Domains; D000099317:Hippo Kinases
D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011994:Recombinant Proteins; C109163:STK24 protein, human; D000099317:Hippo Kinases; C482576:MAP3K1 protein, human; C482559:MAP2K4 protein, human; C482569:MAP2K7 protein, human