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Query: EC:3.6.4.1 (
myosin ATPase
)
1,140
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Smooth muscle contraction is initiated by myosin light chain (MLC) phosphorylation catalyzed by the Ca(2+) dependent MLC kinase. However, many aspects of smooth muscle contraction cannot be accounted for by MLC phosphorylation. One hypothesis that has received experimental support involves the thin filament protein caldesmon. Caldesmon inhibits
myosin ATPase
activity; phosphorylation of caldesmon relieves this inhibitory effect. The primary candidates for catalysis of caldesmon phosphorylation are the p42/p44
ERK
MAP kinases. However, we and others have shown that inhibition of the
ERK
MAP kinases has no effect on many smooth muscles. The goal of this study was to determine if evidence for a second endogenous caldesmon kinase may be obtained. We used Triton X-100 skinned and intact tissues of the swine carotid artery to address this goal. Caldesmon phosphorylation was evident in resting and Ca(2+) stimulated Triton X-100 skinned fibers. Ca(2+)-dependent caldesmon phosphorylation was partially sensitive to the
ERK
MAP kinase inhibitor PD98059, whereas all caldesmon phosphorylation was sensitive to the general kinase inhibitor, staurosporine. Histamine increased caldesmon phosphorylation levels in intact swine carotid artery, which was sensitive to both PD98059 and staurosporine. Histamine increased
ERK
MAP kinase activity, which was reversed by PD98059, staurosporine, and EGTA. Histamine-induced contractions were inhibited by staurosporine but not by PD98059. We interpret these results to suggest that although
ERK
MAP kinases catalyze caldesmon phosphorylation, a second staurosporine sensitive kinase is also important in caldesmon phosphorylation and it is this pathway that may be more important in contractile regulation.
...
PMID:Caldesmon phosphorylation is catalyzed by two kinases in permeabilized and intact vascular smooth muscle. 1475 51
We previously demonstrated that
ERK
/PKC signaling pathways play a key role in regulation of Ca(2+) sensitivity and contractility of the uterine artery. The present study tested the hypothesis that
ERK
and PKC differentially regulated myosin light chain phosphatase activity by phosphorylation of myosin phosphatase target protein-1 (MYPT-1) and CPI-17. Agonist-induced contractions and phosphorylation of MYPT-1/Thr(696), MYPT-1/Thr(850), and CPI-17/Thr(38) were measured simultaneously in the same tissues of isolated near-term pregnant ovine uterine arteries. Phenylephrine produced time-dependent concurrent increases in the phosphorylation of
ERK
(44/42) and MYPT-1/Thr(850) that preceded contractions. In addition, phenylephrine induced phosphorylation of CPI-17/Thr(38) that was concurrent with the contractions. In contrast, phenylephrine did not induce phosphorylation of MYPT-1/Thr(696) in the uterine artery. PD-098059 inhibited phosphorylation of
ERK
(44/42) and the initial peak phosphorylation of MYPT-1/Thr(850) but did not affect CPI-17/Thr(38) phosphorylation. Activation of PKC by phorbol 12,13-dibutyrate induced a time-dependent phosphorylation of CPI-17/Thr(38) that preceded contractions of the uterine artery. In addition, phorbol 12,13-dibutyrate activated PKC-alpha and induced a coimmunoprecipitation of PKC-alpha with caldesmon. The results suggest that phosphorylation of MYPT-1/Thr(850) and CPI-17/Thr(38) play important roles in regulation of agonist-mediated Ca(2+) sensitivity in the uterine artery, in part by
ERK
and PKC, respectively. In addition, phosphorylated CPI-17 may regulate Ca(2+) sensitivity by interacting with caldesmon and reversing its inhibitory effect on
myosin ATPase
.
...
PMID:Alpha1-adrenoceptor-mediated phosphorylation of MYPT-1 and CPI-17 in the uterine artery: role of ERK/PKC. 1566 49
Investigations of actin function during the cell cycle have focused primarily on cytokinesis. Here, we describe the role of actin at the entry into mitosis in primary mammalian cells. Depolymerization of actin with cytochalasin D or inhibition of
myosin ATPase
with butanedione-2-monoxime (BDM) at G(2) blocked the mitotic spindle formation and central positioning of the nucleus in synchronized MEF and IMR90 cells. Time-lapse microscopy confirmed that these treatments inhibit both spindle formation and separation of duplicated centrosomes to the opposite poles. Concurrent with actin dysfunction, activation of Cdc2 and nuclear localization of cyclin B1 were delayed. Furthermore, cyclin A degradation that is necessary for nuclear envelope breakdown (NEBD) in early mitosis was deferred, supporting the conclusion that mitotic onset was delayed. The activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) was sustained in these cells, and the use of a specific
ERK
inhibitor or a dominant negative form of ERK2 abrogated this delay of entry into mitosis. This delay of mitotic entry and the sustained ERK1/2 activity by actin dysfunction was observed only in primary cells and not in transformed cancer cell lines. These observations demonstrate that an intact actin cytoskeleton is necessary for entry into mitosis and that ERK1/2 is involved in monitoring actin dysfunction to control the onset of mitosis, suggesting the presence of an actin checkpoint at the G(2)/M transition in primary mammalian cells.
...
PMID:Actin dysfunction activates ERK1/2 and delays entry into mitosis in mammalian cells. 1758 24
Hydrogen peroxide (H
2
O
2
) increases paracellular permeability of Madin-Darby canine kidney (MDCK) cells, but the mechanism mediating this effect remains unclear. Treatment of MDCK cells with H
2
O
2
activated
ERK
1/2. Inhibition of
ERK
1/2 activation blocked the ability of H
2
O
2
to increase paracellular permeability. Knockdown of zonula occludens-1 (ZO-1) protein but not occludin eliminated the ability of H
2
O
2
to increase paracellular permeability. H
2
O
2
treatment did not, however, affect the total cell content or contents of the Triton X-100-soluble and -insoluble fractions for occludin, ZO-1, or ZO-2. H
2
O
2
treatment decreased the number of F-actin stress fibers in the basal portion of the cells. Similar to wild-type MDCK cells, H
2
O
2
increased
ERK
1/2 activation in ZO-1 knockdown and occludin knockdown cells. Inhibition of
ERK
1/2 activation blocked the increase in paracellular permeability in occludin knockdown cells. ZO-1 knockdown cell paracellular permeability was regulated by PP1, an src inhibitor, indicating that the loss of response to H
2
O
2
was not a general loss of the ability to regulate the paracellular barrier. Inhibition of
myosin ATPase
activity with blebbistatin increased paracellular permeability in ZO-1 knockdown cells but not in wild-type MDCK cells. H
2
O
2
treatment sensitized wild-type MDCK cells to inhibition of
myosin ATPase
. Knockdown of TOCA-1 protein, which promotes formation of local branched actin networks, reproduced the effects of ZO-1 protein knockdown. These results demonstrate that H
2
O
2
increases MDCK cell paracellular permeability through activation of
ERK
1/2. This H
2
O
2
action requires ZO-1 protein and TOCA-1 protein, suggesting involvement of the actin cytoskeleton.
...
PMID:ZO-1 protein is required for hydrogen peroxide to increase MDCK cell paracellular permeability in an ERK 1/2-dependent manner. 2987 7
