Inhibitors of CoA-Independent Transacylase Block the Movement of Arachidonate into 1-Ether-Linked Phospholipids of Human Neutrophils

Floyd H. Chilton, Alfred N. Fonteh, Javid D. Heravi, Chiu Mei Sung, Theodore J. Torphy, Lisa A. Marshall, James D. Winkler, Deirdre M.B. Hickey, Ruth J. Mayer

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42 Scopus citations

Abstract

The enzyme CoA-independent transacylase (CoA-IT) has been proposed to mediate the movement of arachidonate between phospholipid subclasses and influence the formation of arachidonic acid metabolites and platelet-activating factor. To substantiate the critical role of CoA-IT, we have developed two structurally diverse inhibitors of CoA-IT activity, SK&F 98625 [diethyl 7-(3,4,5-triphenyl- 2-oxo-2,3-dihydro-imidazole-1-yl)heptane phosphonate] and SK&F 45905 [2-[2-(3-4-chloro-3-(trifluoromethyl)phenyl)ureido]-4-(trifluoromethyl)phenoxy]-4,5-dichlorobenzenesulfonic acid]. These compounds were tested for their capacity to block microsomal CoA-IT activity using two assay systems, the transacylation of l-alkyl-2-lyso-5n-glycero-3-phosphocholine (GPC) and the transfer of [14C]arachidonate from 1 -acyl-2-[14C]arachidonoy 1-GPC to lyso-PE. Both SK&F 98625 and SK&F 45905 inhibited CoA-IT activity (IC50s 6-19 pM) in these two assays. In contrast, SK&F 98625 or SK&F 45905 had little or no effect on other lipid-modifying activities, including CoA-dependent acyltransferase or acetyltransferase. Kinetic analysis revealed that both SK&F 98625 and SK&F 45905 interact directly with the enzyme and prevented the acylation of lysophospholipids in a competitive manner. In intact human neutrophils, both SK&F 98625 and SK&F 45905 completely blocked the movement of [3H]arachidonate from 1-acyl-linked phospholipids into l-alkyl-2-arachidonoyl-GPC and l-alk-r-enyl-2-arachidonoyl-GPE. In contrast, these compounds did not inhibit the incorporation of free arachidonic acid into cellular lipids indicating that they did not alter CoA-dependent acyl transferase activities in the intact cell. This is the first report to utilize an inhibitor to address the importance of CoA-IT in arachidonate-phospholipid remodeling. These results provide further evidence that CoA-IT mediates the movement of arachidonate into the large pools of 1 -ether-linked phospholipids in human neutrophils and suggest that it may be possible to regulate AA levels in cellular phospholipids with CoA-IT inhibitors.

Original languageEnglish (US)
Pages (from-to)5403-5410
Number of pages8
JournalBiochemistry
Volume34
Issue number16
DOIs
StatePublished - Apr 1 1995
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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