|
||
J. Cell Biol.,
Volume 144, Number 4, February 22, 1999 735-744


* Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08855; It has been demonstrated previously that
during mitosis the sites of myosin phosphorylation are
switched between the inhibitory sites, Ser 1/2, and the
activation sites, Ser 19/Thr 18 (Yamakita, Y., S. Yamashiro, and F. Matsumura. 1994. J. Cell Biol. 124:129- 137; Satterwhite, L.L., M.J. Lohka, K.L. Wilson, T.Y.
Scherson, L.J. Cisek, J.L. Corden, and T.D. Pollard.
1992. J. Cell Biol. 118:595-605), suggesting a regulatory
role of myosin phosphorylation in cell division. To explore the function of myosin phosphatase in cell division, the possibility that myosin phosphatase activity may be altered during cell division was examined. We
have found that the myosin phosphatase targeting subunit (MYPT) undergoes mitosis-specific phosphorylation and that the phosphorylation is reversed during cytokinesis. MYPT phosphorylated either in vivo or in
vitro in the mitosis-specific way showed higher binding to myosin II (two- to threefold) compared to MYPT
from cells in interphase. Furthermore, the activity of
myosin phosphatase was increased more than twice and
it is suggested this reflected the increased affinity of
myosin binding. These results indicate the presence of a
unique positive regulatory mechanism for myosin phosphatase in cell division. The activation of myosin phosphatase during mitosis would enhance dephosphorylation of the myosin regulatory light chain, thereby leading
to the disassembly of stress fibers during prophase. The
mitosis-specific effect of phosphorylation is lost on exit
from mitosis, and the resultant increase in myosin phosphorylation may act as a signal to activate cytokinesis.
Department of
Biological Science, Faculty of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan; and § Muscle
Biology Group, University of Arizona, Tucson, Arizona 85721
This article has been cited by other articles:
|
|