TY - JOUR
T1 - Protein kinase C mediates phosphorylation of the regulatory light chain of myosin-II during mitosis
AU - Varlamova, O.
AU - Spektor, A.
AU - Bresnick, A. R.
N1 - Funding Information:
We are grateful to Dr Lee Sweeney and Amber Wells for providing us with chicken smooth muscle HMM. We thank Dr Steven Almo for critical reading of the manuscript. This work was supported by the American Heart Association.
PY - 2001
Y1 - 2001
N2 - Phosphorylation of the regulatory light chain (RLC) of myosin-II is cell cycle dependent. Early in mitosis the RLC is phosphorylated predominantly on Ser-1/2, while during cytokinesis the primary site of phosphorylation is Ser-19 (Yamakita et al., 1994). To identify candidate kinases likely to mediate the mitotic phosphorylation on Ser-1/2, we assayed RLC kinase activity in mitotic cell extracts and measured apparent steady-state kinetic constants using purified enzymes. The mitotic RLC kinase is distinct from cdc2 kinase, protein kinase A and protein kinase G, as activators or inhibitors specific for these kinases do not affect the mitotic kinase activity. The activity of the mitotic RLC kinase is enhanced by the addition of Ca2+ and DAG and/or phorbol esters, characteristics of a conventional protein kinase C (PKC). Moreover, the PKC inhibitors, Gö6983 and Gö6976, significantly attenuate the phosphorylation of the RLC in mitotic extracts. Apparent steady-state kinetic studies indicate that several PKC isoforms display high specificity for myosin-II. These results suggest that current models describing Ser-1/2 phosphorylation during mitosis need to be re-evaluated.
AB - Phosphorylation of the regulatory light chain (RLC) of myosin-II is cell cycle dependent. Early in mitosis the RLC is phosphorylated predominantly on Ser-1/2, while during cytokinesis the primary site of phosphorylation is Ser-19 (Yamakita et al., 1994). To identify candidate kinases likely to mediate the mitotic phosphorylation on Ser-1/2, we assayed RLC kinase activity in mitotic cell extracts and measured apparent steady-state kinetic constants using purified enzymes. The mitotic RLC kinase is distinct from cdc2 kinase, protein kinase A and protein kinase G, as activators or inhibitors specific for these kinases do not affect the mitotic kinase activity. The activity of the mitotic RLC kinase is enhanced by the addition of Ca2+ and DAG and/or phorbol esters, characteristics of a conventional protein kinase C (PKC). Moreover, the PKC inhibitors, Gö6983 and Gö6976, significantly attenuate the phosphorylation of the RLC in mitotic extracts. Apparent steady-state kinetic studies indicate that several PKC isoforms display high specificity for myosin-II. These results suggest that current models describing Ser-1/2 phosphorylation during mitosis need to be re-evaluated.
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U2 - 10.1023/A:1012289905754
DO - 10.1023/A:1012289905754
M3 - Article
C2 - 11763196
AN - SCOPUS:0035184911
SN - 0142-4319
VL - 22
SP - 243
EP - 250
JO - Journal of Muscle Research and Cell Motility
JF - Journal of Muscle Research and Cell Motility
IS - 3
M1 - 353654
ER -