Activation of actin-activated MgATPase activity of myosin II by phosphorylation with MAPK-activated protein kinase-1b (RSK-2).
Regulatory light chain of myosin II (MRLC) was identified as a novel substrate of p90 ribosomal S6 kinase (RSK)-2, a Ser/Thr protein kinase which is phosphorylated and activated by mitogen-activated protein kinase (MAPK) in vitro and in vivo. Phosphopeptide map of MRLC phosphorylated by RSK-2 was identical to that by myosin light chain kinase (MLCK). Phosphoserine was recovered by the phosphoamino acid analysis of MRLC phosphorylated by RSK-2. Further, phosphorylation using recombinant glutathione S-transferase (GST) fusion proteins of HeLa MRLC2 revealed that RSK-2 phosphorylated wild-type MRLC2 (GST-wtMRLC2) but not its mutants GST-MRLC2(S19A) or GST-MRLC2(T18AS19A) (alanine substituted for Ser19 or both Ser19 and Thr18). These results revealed that RSK-2 phosphorylates MRLC at Ser19 as did MLCK. Phosphorylation of myosin II by RSK-2 resulted in activation of actin-activated MgATPase activity of myosin II. Interestingly, RSK-2 activity to phosphorylate MRLC was suppressed by phosphorylation with MAPK. RSK-2 might be a mediator that regulates myosin II activity through the MAPK cascade.
Suizu
F
F
Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
Ueda
K
K
Iwasaki
T
T
Murata-Hori
M
M
Hosoya
H
H
D000199:Actins / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002478:Cells, Cultured; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005895:Gizzard, Avian; D005982:Glutathione Transferase / Q000096:biosynthesis; D006801:Humans; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D008958:Models, Molecular; D009130:Muscle, Smooth / Q000201:enzymology; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000302:isolation & purification; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000302:isolation & purification; D010766:Phosphorylation; D010957:Plasmids; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*
D000199:Actins; D010446:Peptide Fragments; D010748:Phosphopeptides; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins