Fonteh A N, Samet J M, Surette M, Reed W, Chilton F H
Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
Biochim Biophys Acta. 1998 Aug 28;1393(2-3):253-66. doi: 10.1016/s0005-2760(98)00079-4.
The current study examined mechanisms that account for the selective release of arachidonic acid (AA) from cells by secretory phospholipase A2 (sPLA2). Initial studies demonstrated that low concentrations of group I and group III PLA2 isotypes and an sPLA2-enriched extract from bone marrow-derived mast cells (BMMC) selectively released AA from mast cells. Much higher concentrations of group II PLA2 were required to release comparable quantities of AA. Group I PLA2 also selectively released AA from another mast cell line (CFTL-15) and a monocytic cell line (THP-1). In contrast, high concentrations of group I PLA2 were required to release fatty acids from a promyelocytic cell line (HL-60) and this release was not selective for AA. Binding studies revealed that cell types (BMMC, CFTL-15 and THP-1) which selectively released AA also had the capacity to specifically bind group I PLA2. However, group II PLA2, which did not selectively release AA from cells, also did not specifically bind to these same cell types. Additional studies revealed that sPLA2 binding to the mast cell receptor was attenuated after stimulation with antigen or ionophore A23187. Reverse transcriptase-polymerase chain reaction analyses indicated the presence of mRNA for the sPLA2 receptor in BMMC, CFTL-15 and THP-1 and the absence of this mRNA in HL-60. Final studies demonstrated that p-aminophenyl-alpha-D-mannopyranoside BSA, a known ligand of the sPLA2 receptor, also selectively released AA from mast cells but not from HL-60 cells. These experiments indicated that receptor occupancy alone (without PLA2 activity) is sufficient to induce the release of AA from mast cells. Together, these data reveal that specific isotypes of sPLA2 have the capacity to selectively release AA from certain cells by their capacity to bind to sPLA2 receptors on the cell surface.
本研究探讨了分泌型磷脂酶A2（sPLA2）介导细胞选择性释放花生四烯酸（AA）的机制。初步研究表明，低浓度的I型和III型PLA2亚型以及来自骨髓源性肥大细胞（BMMC）的富含sPLA2的提取物可选择性地从肥大细胞中释放AA。而释放等量的AA则需要高得多浓度的II型PLA2。I型PLA2还能从另一种肥大细胞系（CFTL-15）和单核细胞系（THP-1）中选择性地释放AA。相比之下，需要高浓度的I型PLA2才能从早幼粒细胞系（HL-60）中释放脂肪酸，且这种释放对AA没有选择性。结合研究表明，能够选择性释放AA的细胞类型（BMMC、CFTL-15和THP-1）也具有特异性结合I型PLA2的能力。然而，不能从细胞中选择性释放AA的II型PLA2也不会特异性结合这些相同的细胞类型。进一步的研究表明，在用抗原或离子载体A23187刺激后，sPLA2与肥大细胞受体的结合减弱。逆转录酶-聚合酶链反应分析表明，BMMC、CFTL-15和THP-1中存在sPLA2受体的mRNA，而HL-60中不存在该mRNA。最终研究表明，sPLA2受体的已知配体对氨基苯基-α-D-甘露吡喃糖苷牛血清白蛋白（p-aminophenyl-alpha-D-mannopyranoside BSA）也能从肥大细胞中选择性地释放AA，但不能从HL-60细胞中释放。这些实验表明，仅受体占据（无PLA2活性）就足以诱导肥大细胞释放AA。总之，这些数据表明，特定亚型的sPLA2能够通过其与细胞表面sPLA2受体结合的能力，选择性地从某些细胞中释放AA。
