C-terminal elements control location, activation threshold, and p38 docking of ribosomal S6 kinase B (RSKB).
RSKB, a p90 ribosomal S6 protein kinase with two catalytic domains, is activated by p38- and extracellular signal-regulated kinase mitogen-activated protein kinase pathways. The sequences between the two catalytic domains and of the C-terminal extension contain elements that control RSKB activity. The C-terminal extension of RSKB presents a putative bipartite (713)KRX(14)KRRKQKLRS(737) nuclear location signal. The distinct cytoplasmic and nuclear locations of various C-terminal truncation mutants supported the hypothesis that the nuclear location signal was essential to direct RSKB to the nuclear compartment. The (725)APLAKRRKQKLRS(737) sequence also was essential for the intermolecular association of RSKB with p38. The activation of RSKB through p38 could be dissociated from p38 docking, because RSKB truncated at Ser(681) strongly responded to p38 pathway activity. Interestingly, Delta(725-772)-RSKB was nearly nonresponsive to p38. Sequence alignment with the autoinhibitory C-terminal extension of Ca+2/calmodulin-dependent protein kinase I predicted a conserved regulatory (708)AFN(710) motif. Alanine mutation of the key Phe709 residue resulted in strongly elevated basal level RSKB activity. A regulatory role also was assigned to Thr687, which is located in a mitogen-activated protein kinase phosphorylation consensus site. These findings support that the RSKB C-terminal extension contains elements that control activation threshold, subcellular location, and p38 docking.
Tomás-Zuber
M
M
Department of Central Nervous System Diseases, F. Hoffmann-LaRoche, Ltd., CH-4070 Basel, Switzerland.
Mary
J L
JL
Lamour
F
F
Bur
D
D
Lesslauer
W
W
D000595:Amino Acid Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D004789:Enzyme Activation; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010649:Phenylalanine / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism*; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D016415:Sequence Alignment; D015398:Signal Transduction; D013912:Threonine / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010446:Peptide Fragments; D013912:Threonine; D010649:Phenylalanine; D019893:Ribosomal Protein S6 Kinases; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases