Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:3.4.21.5 (
thrombin
)
33,306
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Cytosolic phospholipase A2
(
cPLA2
) binds to natural membrane vesicles in a Ca(2+)-dependent fashion, resulting in the selective release of arachidonic acid, thus implicating
cPLA2
in the hormonally regulated production of eicosanoids. Here we report that the treatment of Chinese hamster ovary (CHO) cells overexpressing
cPLA2
with ATP or
thrombin
resulted in an increased release of arachidonic acid as compared with parental CHO cells, demonstrating the hormonal coupling of
cPLA2
. In contrast, CHO cells overexpressing a secreted form of mammalian PLA2 (sPLA2-II) failed to show any increased hormonal responsiveness. Interestingly, we have noted that the activation of
cPLA2
with a wide variety of agents stimulates the phosphorylation of
cPLA2
on serine residues. Pretreatment of cells with staurosporin blocked the ATP-mediated phosphorylation of
cPLA2
and strongly inhibited the activation of the enzyme. Increased
cPLA2
activity was also observed in lysates prepared from ATP-treated cells and was sensitive to phosphatase treatment. These results suggest that in addition to Ca2+, the phosphorylation of
cPLA2
plays an important role in the agonist-induced activation of
cPLA2
.
...
PMID:Cytosolic phospholipase A2 is coupled to hormonally regulated release of arachidonic acid. 163 Nov 1
Cytosolic phospholipase A2
-alpha (cPLA2-alpha) is a calcium-activated enzyme involved in agonist-induced arachidonic acid release. In endothelial cells, free arachidonic acid is predominantly converted into prostacyclin, a potent vasodilator and inhibitor of platelet activation. As the rate-limiting step in prostacyclin production is the generation of free arachidonic acid by cPLA2-alpha, this enzyme has become an attractive pharmacological target and the focus of many studies. Following stimulation with calcium-mobilizing agonists, cPLA2-alpha translocates to intracellular phospholipid membranes via its C2 domain. In this study, the calcium-induced association of cPLA2-alpha with EA.hy.926 endothelial cell membranes was investigated. Subcellular fractionation and immunofluorescence studies showed that following stimulation with histamine,
thrombin
or the calcium ionophore A23187, cPLA2-alpha relocated to intracellular membranes. Treatment of A23187-stimulated cells with EGTA or BAPTA-AM demonstrated that a substantial pool of cPLA2-alpha remained associated with membrane fractions in a calcium-independent manner. Furthermore, immunofluorescence microscopy studies revealed that cells stimulated for periods of greater than 10 min showed a high proportion of calcium-independent membrane-associated cPLA2-alpha. Calcium-independent membrane association of cPLA2-alpha was not due to hydrophobic or cytoskeletal interactions. Finally, the recombinant C2 domain of cPLA2-alpha exhibited calcium-independent membrane binding to membranes isolated from A23187-stimulated cells but not those isolated from nonstimulated cells. These findings suggest that novel mechanisms involving accessory proteins at the target membrane play a role in the regulation of cPLA2-alpha. Such regulatory associations could enable the cell to discriminate between the varying levels of cytosolic calcium induced by different stimuli.
...
PMID:Stimulation-dependent recruitment of cytosolic phospholipase A2-alpha to EA.hy.926 endothelial cell membranes leads to calcium-independent association. 1468 20
