BIOSYNTHESIS OF PLATELET-ACTIVATING-FACTOR IN CULTURED MAST-CELLS - INVOLVEMENT OF THE COA-INDEPENDENT TRANSACYLASE DEMONSTRATED BY ANALYSIS OF THE MOLECULAR-SPECIES OF PLATELET-ACTIVATING-FACTOR

被引:14
作者
COLARD, O [1 ]
BIDAULT, J [1 ]
BRETON, M [1 ]
NINIO, E [1 ]
机构
[1] INSERM, U200, F-92140 CLAMART, FRANCE
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1993年 / 216卷 / 03期
关键词
D O I
10.1111/j.1432-1033.1993.tb18205.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
We have recently demonstrated that arachidonate [20:4(5,8,11,14)] was primarily linked to the hexadecyl (16:0) and octadecenyl (18:1) species of alkylacyl derivatives of glycerolphosphocholine (GroPCho). Consistent with the involvement of arachidonate-specific CoA-independent transacylase in the synthesis of platelet-activating factor (PAF; 1-0-alkyl-2-acetyl-GroPcho), 16:0 and 18:1 PAF species were formed upon antigen stimulation [Joly, F., Breton, M., Wolf, C., Ninio, E. & Colard, 0. (1992) Biochim. Biophys. Acta 1125, 305-312]. In the present work, addition of lyso-PAF to mast cells resulted in PAF production. We analyzed the PAF species formed in the presence of a defined lyso-PAF molecular species in order to differentiate between either direct acetylation or involvement of the membrane precursor. The 18:1 lyso-PAF was more effective than the 16:0 in producing PAF which was composed of 95% 18:1 PAF, the balance being 16:0, indicating that part of the acetylated lyso-PAF originated from the cellular pool of alkyl-arachidonyl-GroPCho in resting cells. Consistent with alkyl-arachidonyl-GroPCho species content and acetyltransferase specificity, similar amounts of 16:0 and 18:1 PAF species were formed when mast cells were stimulated with antigen. Supplemented with 16:0 or 18:1 lyso-PAF, antigen-stimulated mast cells responded by 230% and 125% increase in PAF synthesis, respectively. As expected, the amount of the PAF species corresponding to the added lyso-PAF was increased. More interestingly, addition of 16:0 lyso-PAF almost doubled the amount of 18:1 PAF content as compared to antigen alone, thus indicating that the lyso-PAF formed via the CoA-independent transacylase was significantly used for PAF synthesis, despite a large excess of exogenous lyso-PAF. The CoA-independent transacylase, measured using [H-3]lyso-PAF as a substrate in sonicates from antigen-stimulated cells, was decreased concurrently with PAF formation. In conclusion, we show that when lyso-PAF is added to mast cells, a direct acetylation may occur. However, PAF is preferentially synthesized through a mechanism involving the CoA-independent transacylase reaction.
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页码:835 / 840
页数:6
相关论文
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