Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
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Target Concepts:
Gene/Protein
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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)
Recent studies suggest that an abnormal increase in intestinal tight junction (TJ) permeability may be an important etiologic factor in number of diseases including Crohn's disease, NSAID-associated enteritis, and various infectious diarrheal syndromes. The intracellular processes involved in regulation of intestinal epithelial TJ permeability, however, remain poorly understood. In this study, we used cultured Caco-2 intestinal epithelial cells to examine the intracellular processes involved in extracellular Ca(++) modulation of intestinal epithelial monolayer TJ barrier. Incubation of the filter-grown Caco-2 intestinal monolayers in Ca(++)-free solution (CFS), consisting of modified Krebs-buffer solution containing 0 mM Ca(++) and 1 mM EGTA, resulted in a rapid drop in Caco-2 epithelial resistance and increase in epithelial permeability to paracellular markers mannitol and inulin, indicating an increase in TJ permeability. The increase in Caco-2 TJ permeability was rapidly reversed by the re-introduction of Ca(++) (1.8 mM) into the incubation medium. The CFS-induced increase in Caco-2 TJ permeability was associated with separation of the cytoplasmic and transmembrane TJ proteins, ZO-1 and
occludin
, and formation of large intercellular openings between the adjoining cells. The CFS-induced modulation of TJ barrier was associated with activation of myosin light chain kinase (MLCK) activity and centripetal retraction of peri-junctional actin and myosin filaments. The inhibition of CFS-induced activation of Caco-2 MLCK with MLCK inhibitor (ML-7) prevented the CFS-induced retraction of actin and myosin filaments and the subsequent alteration of TJ barrier function and structure. Our results suggested that the CFS-induced alteration of TJ proteins and functional increase in TJ permeability was mediated by Caco-2 MLCK activation and the resultant contraction of the peri-junctionally located actin-myosin filaments. Consistent with the role of MLCK in this process, selected inhibitors of Mg(++)-
myosin ATPase
and metabolic energy, but not protein synthesis inhibitors, also prevented the CFS-induced retraction of actin and myosin filaments and the subsequent increase in TJ permeability. In conclusion, our results indicate that extracellular Ca(++) is crucial for the maintenance of intestinal epithelial TJ barrier function. The removal of extracellular Ca(++) from the incubation medium causes activation of Caco-2 MLCK, which in turn leads to an increase in intestinal monolayer TJ permeability.
...
PMID:Mechanism of extracellular calcium regulation of intestinal epithelial tight junction permeability: role of cytoskeletal involvement. 1105 66
Membrane-cytoskeleton interactions have been shown to be crucial to modulate polarity, cell shape and the paracellular pathway in epithelial MDCK cell monolayers. In particular, actin organization and myosin-dependent contractility play an important role in the regulation of these functions. Participation of myosin in vectorial transport, expressed as formation of domes, was investigated in confluent monolayers of high transepithelial electrical resistance (TER) plated on non-permeable supports. Cells exposed to 2,3-butanedione monoxime, a selective inhibitor of
myosin ATPase
, showed a remarkable increase in the number of domes. Replacement of extracellular Na+ and Cl- and inhibition of Na+-K+-ATPase blocked the induction of domes. The monoxime also caused a reduction of the TER leading to an increase in the paracellular flux of small molecular weight dextran. However, immunofluorescence microscopy of drug-treated cells showed that the localization and staining pattern of tight junction proteins ZO-1,
occludin
, and claudin 1, or the actin-myosin ring at the zonula adherens, were not modified. Treatment with the drug produced striking re-arrangements of actin filaments at the microvilli and at the basal level of the cells. Our data show that disruption of actin-myosin interaction at several cellular sites contributed importantly to the increased transport activity and the formation of the domes. These results point to the relevant role or actin-myosin dynamics and actin organization in the regulation of ion and water channel activity in these cells.
...
PMID:2,3-butanedione monoxime (BDM), a potent inhibitor of actin-myosin interaction, induces ion and fluid transport in MDCK monolayers. 1250 Sep 2
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
