Cytosolic phospholipase A(2) activity associated with nuclei is not inhibited by arachidonyl trifluoromethyl ketone in macrophages stimulated with receptor-recognized forms of alpha(2)-macroglobulin.
We have studied the translocation of cytosolic phospholipase A(2) (cPLA(2)) to nuclei in macrophages stimulated with receptor-recognized forms of alpha(2)-macroglobulin (alpha(2)M*). Translocation of phosphorylated cPLA(2) to nuclei was determined by immunoprecipitation of cPLA(2) in (32)P(i)-labeled cells. The identity of cPLA(2) was established by comparing its mobility on gels with an authentic cPLA(2) standard. cPLA(2) activity was quantified by measuring the release of [(14)C]arachidonic acid from the substrate 1-palmitoyl-2-[1-(14)C]arachidonyl-sn-glycerophosphatidylcholine. alpha(2)M* caused a two- to threefold increase in cPLA(2) phosphorylation and its translocation to nuclei. The p38 MAPK inhibitor SB203580, PKC inhibitor chelerythrin, or depletion of intracellular Ca(2+) profoundly decreased cPLA(2) activity in nuclei isolated from agonist-stimulated cells. The requirement for Ca(2+), PKC, and p38 MAPK activation appears to be of major importance for nuclear cPLA(2) activity. In contrast to cellular cPLA(2) activity, nuclear cPLA(2) activity was not inhibited by arachidonyl trifluoromethyl ketone (AACOCF(3)) in agonist-stimulated cells. It is concluded that the association of cPLA(2) with nuclear membranes in agonist-stimulated cells modifies the activity and the sensitivity of the enzyme to inhibition by AACOCF(3) in this phospholipid environment.
Misra
U K
UK
Department of Pathology, Duke University Medical Center, Durham, North Carolina, 27710, USA.
Pizzo
S V
SV
D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000494:pharmacology; D002467:Cell Nucleus / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors; D007093:Imidazoles / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects; D017737:Macrophages, Peritoneal / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D010713:Phosphatidylcholines / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D000511:alpha-Macroglobulins / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D001095:Arachidonic Acids; D004791:Enzyme Inhibitors; D007093:Imidazoles; D010713:Phosphatidylcholines; D011725:Pyridines; D000511:alpha-Macroglobulins; C081565:arachidonyltrifluoromethane; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010741:Phospholipases A; C093642:SB 203580; D002118:Calcium