Phospholipid remodeling in human neutrophils. Parallel activation of a deacylation/reacylation cycle and platelet-activating factor synthesis.
A23187 stimulated two enzymatic activities of human neutrophils (polymorphonuclear leukocytes), phospholipase A2 and fatty acyl-CoA acyltransferase, which resulted in a stimulated deacylation/reacylation cycle. The incorporation of fatty acids, other than arachidonic or eicosapentaenoic acid, into diacyl and alkylacyl species of choline phosphoglycerides was stimulated by 10-fold by A23187. These fatty acids were exclusively incorporated into the sn-2 position, and [3H]glycerol labeling showed there was no stimulation of de novo synthesis. A23187 also stimulated fatty acid incorporation into other phospholipids, but de novo synthesis accounted for a portion of this uptake. Inhibitors of protein kinase C prevented the stimulated recycling of phosphatidylcholine, and the simultaneous induction of platelet-activating factor synthesis, by inhibiting phospholipase A2 activation. They inhibited [3H]arachidonate release from prelabeled polymorphonuclear leukocytes, but had no effect on in vitro fatty acyl-CoA acyltransferase or acetyl-CoA acetyltransferase activity. Extracts from A23187-treated cells contained a fatty acyl-CoA acyltransferase, which did not utilize arachidonoyl-CoA, that was 2.3-fold more active than that of control extracts. Phosphatase treatment decreased this stimulated activity by 66%. Thus, A23187 stimulated a phospholipase A2 activity that generated both 1-alkyl and 1-acyl lysophosphatidylcholines. A stimulated acetyltransferase used a portion of the alkyl species for platelet-activating factor synthesis, while the acyl species and residual alkyl species were rapidly reacylated to phosphatidylcholine by a stimulated acyl-transferase. Arachidonate, an eicosanoid precursor, was spared by this process.
Reinhold
S L
SL
Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City 84112.
Zimmerman
G A
GA
Prescott
S M
SM
McIntyre
T M
TM
D000215:Acylation; D000001:Calcimycin / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005990:Glycerol / Q000097:blood; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D019301:Oleic Acid; D009829:Oleic Acids / Q000097:blood; D010713:Phosphatidylcholines / Q000096:biosynthesis / Q000097:blood*; D010743:Phospholipids / Q000096:biosynthesis / Q000097:blood*; D010972:Platelet Activating Factor / Q000096:biosynthesis*
D005230:Fatty Acids, Nonesterified; D009829:Oleic Acids; D010713:Phosphatidylcholines; D010743:Phospholipids; D010972:Platelet Activating Factor; D019301:Oleic Acid; D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D005990:Glycerol