Garcia M C, Garcia C, Gijon M A, Fernandez-Gallardo S, Mollinedo F, Sanchez Crespo M
Instituto de Investigaciones Médicas de la Fundación Jiménez Díaz, Centro Asociado al CSIC, Madrid, Spain.
Biochem J. 1991 Feb 1;273 ( Pt 3)(Pt 3):573-8. doi: 10.1042/bj2730573.
The binding and metabolism of platelet-activating factor (PAF) was studied in human cell lines resembling myeloid cells (HL60 and U937) and B and T lymphocytes (Daudi and Jurkat). All of the cell lines were found to bind and catabolize exogenous [3H]PAF in a time- and temperature-dependent manner. PAF binding could also be demonstrated in isolated membrane fractions, which provides further evidence of the existence of true membrane receptors. Myeloid cell lines contained numbers of receptors at least 10-fold higher than in lymphoid cell lines. Biosynthesis of PAF upon challenge by ionophore A23187 could be demonstrated in HL60 and U937 cells. In contrast, lymphoid cell lines were unable to produce PAF. Incubation with [14C]acetate showed incorporation of the label into three main fractions: neutral lipids, phosphatidylcholine and PAF, but the distribution of the label varied depending on the cell line. Significant incorporation into phosphatidylcholine was observed in uninduced myeloid cell lines. A phospholipase A2 acting on 1-O-hexadecyl-2-arachidonoyl-sn-glycero-3-phosphocholine and an acetyl-CoA:lyso-PAF acetyltransferase were expressed in the HL60 cell line and showed variations in specific activity with granulocytic differentiation. In contrast, these enzyme activities were not expressed in Daudi and Jurkat cell lines. These data indicate (1) the occurrence of PAF binding and catabolism in both myeloid and lymphoid cell lines; (2) the restriction of PAF biosynthesis to myeloid cell lines, especially HL60 cells; (3) the occurrence of differentiation-elicited changes in the specific activities of the enzymes involved in PAF biosynthesis by the remodelling pathway; and (4) the central role played by the disposal of lyso-PAF, a product of the phospholipase A2 reaction, in PAF biosynthesis.
在类似于髓样细胞（HL60和U937）以及B和T淋巴细胞（Daudi和Jurkat）的人类细胞系中研究了血小板活化因子（PAF）的结合与代谢。发现所有细胞系均以时间和温度依赖性方式结合并分解外源性[3H]PAF。在分离的膜组分中也可证明PAF结合，这为真正的膜受体的存在提供了进一步证据。髓样细胞系中的受体数量比淋巴细胞系至少高10倍。在HL60和U937细胞中可证明在离子载体A23187刺激下PAF的生物合成。相反，淋巴细胞系无法产生PAF。用[14C]乙酸孵育显示标记物掺入三个主要组分：中性脂质、磷脂酰胆碱和PAF，但标记物的分布因细胞系而异。在未诱导的髓样细胞系中观察到标记物大量掺入磷脂酰胆碱。作用于1-O-十六烷基-2-花生四烯酰基-sn-甘油-3-磷酸胆碱的磷脂酶A2和乙酰辅酶A：溶血PAF乙酰转移酶在HL60细胞系中表达，并随粒细胞分化显示出比活性的变化。相反，这些酶活性在Daudi和Jurkat细胞系中未表达。这些数据表明：（1）髓样和淋巴细胞系中均存在PAF结合与分解代谢；（2）PAF生物合成限于髓样细胞系，尤其是HL60细胞；（3）通过重塑途径参与PAF生物合成的酶的比活性发生分化诱导变化；（4）磷脂酶A2反应产物溶血PAF的处理在PAF生物合成中起核心作用。
