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Department of Physiology, University of Connecticut Health Center, Farmington, CT 06030
Kinases mediating phosphorylation and activation of cytosolic
phospholipase A2 (cPLA2) in intact cells remain
to be fully characterized. Platelet-activating factor stimulation of
human neutrophils increases cPLA2 phosphorylation. This
increase is inhibited by PD 98059, a mitogen-activated protein
(MAP)/extracellular signal-regulating kinase (erk) 1 inhibitor,
but not by SB 203580, a p38 MAP kinase inhibitor, indicating that this
action is mediated through activation of the p42 MAP kinase (erk2).
However, platelet-activating factor-induced arachidonic acid release is
inhibited by both PD 98059 and SB 203580. Stimulation by TNF-
increases cPLA2 phosphorylation, which is inhibited by SB
203580, but not PD 98059, suggesting a role for p38 MAP kinase. LPS
increases cPLA2 phosphorylation and arachidonic acid
release. However, neither of these actions is inhibited by either PD
98059 or SB 203580. PMA increases cPLA2 phosphorylation.
This action is inhibited by PD 98059 but not SB 203580. Finally, FMLP
increases cPLA2 phosphorylation and arachidonic acid
release. Interestingly, while the FMLP-induced phosphorylation of
cPLA2 is not affected by the inhibitors of the p38 MAP
kinase or erk cascades, both inhibitors significantly decrease
arachidonic acid release stimulated by FMLP. SB 203580 or PD 98059 has
no inhibitory effects on the activity of coenzyme A-independent
transacylase.
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