Synergistic activation of SAPK1/JNK1 by two MAP kinase kinases in vitro.
Mitogen-activated protein kinases (MAPKs) mediate many of the cellular effects of growth factors, cytokines and stress stimuli. Their activation requires the phosphorylation of a threonine and a tyrosine residue located in a Thr-X-Tyr motif (where X is any amino acid) [1]. This phosphorylation is catalysed by MAPK kinases (MKKs), which are all thought to be 'dual specificity' enzymes that phosphorylate both the threonine and the tyrosine residue of the Thr-X-Tyr motif [2]. Here, we report that the MAPK family member known as stress-activated protein kinase-1c (SAPK1c, also known as JNK1) [3] is activated synergistically in vitro by MKK4 ([4] [5] [6]; also called SKK1 and JNKK1) and MKK7 ([7] [8] [9]; also called SKK4 and JNKK2). We found that MKK4 had a preference for the tyrosine residue, and MKK7 for the threonine residue, within the Thr-X-Tyr motif. These observations suggest that the full activation of SAPK1c in vivo may sometimes require phosphorylation by two different MKKs, providing the potential for integrating the effects of different extracellular signals. They also raise the possibility that other MAPK family members may be activated by two or more MKKs and that some MKKs may have gone undetected because they phosphorylate the tyrosine residue only, and therefore do not induce any activation unless the threonine has first been phosphorylated by another MKK.
Lawler
S
S
MRC Protein Phosphorylation Unit, Department of Biochemistry, University of Dundee, MSI/WTB Complex, Dundee DD1 5EH, UK.
Fleming
Y
Y
Goedert
M
M
Cohen
P
P
D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D007624:KB Cells / Q000187:drug effects / Q000528:radiation effects; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017421:Sequence Analysis; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D014466:Ultraviolet Rays
D007375:Interleukin-1; D011993:Recombinant Fusion Proteins; D013912:Threonine; D014443:Tyrosine; D011494:Protein Kinases; 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; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; C482559:MAP2K4 protein, human; C482569:MAP2K7 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases