Mora M, Mir F, de Madariaga M A, Sagristá M L
Department of Biochemistry and Molecular Biology, Faculty of Chemistry, University of Barcelona, Spain.
Lipids. 2000 May;35(5):513-24. doi: 10.1007/s11745-000-551-9.
N-Acylphosphatidylethanolamines and N-acylphosphatidylserines have been isolated from mammalian cells and have been associated with some tissue degenerative changes, although the relationship between their synthesis and the uncontrolled sequence of events that ends in irreversible tissue damage is not completely established. Our results show that monovalent and divalent cations induce aggregation and fusion of liposomes constituted by N-palmitoylphosphatidylethanolamine (NPPE) and N-palmitoylphosphatidylserine (NPPS). The effectiveness of cations to induce the aggregation of NPPE and NPPS liposomes is Ca2+ > Mg2+ >> Na+. NPPS liposomes aggregate at lower concentrations of divalent cations than NPPE liposomes, but with sodium NPPE liposomes aggregate to a higher extent than NPPS liposomes. The reaction order for the aggregation processes depends on the lipid and the cation nature and range from 1.04 to 1.64. Dynamic light scattering shows an irreversible increase of the size of the aggregates in the presence of all cations tested. The irreversibility of the aggregation process and the intermixing of bilayer lipids, as studied by resonance energy transfer assay, suggest that fusion, rather than aggregation, occurs. The existence of a real fusion was demonstrated by the coalescence of the aqueous contents of both NPPS and NPPE liposomes in the presence of either monovalent or divalent cations. The different binding sensitivity of Ca2+ to NPPS and NPPE liposomes, determined by zeta potential measurements, agrees with the results obtained in the aggregation and fusion assays. Our results suggest that the synthesis in vivo of N-acylated phospholipids can introduce important changes in membrane-mediated processes.
N-酰基磷脂酰乙醇胺和N-酰基磷脂酰丝氨酸已从哺乳动物细胞中分离出来，并与一些组织退行性变化有关，尽管它们的合成与最终导致不可逆组织损伤的失控事件序列之间的关系尚未完全确立。我们的结果表明，单价和二价阳离子可诱导由N-棕榈酰磷脂酰乙醇胺（NPPE）和N-棕榈酰磷脂酰丝氨酸（NPPS）构成的脂质体发生聚集和融合。阳离子诱导NPPE和NPPS脂质体聚集的有效性为Ca2+>Mg2+>>Na+。NPPS脂质体在比NPPE脂质体更低浓度的二价阳离子下聚集，但对于钠离子，NPPE脂质体比NPPS脂质体聚集程度更高。聚集过程的反应级数取决于脂质和阳离子的性质，范围为1.04至1.64。动态光散射表明，在所有测试阳离子存在下，聚集体的尺寸不可逆增加。通过共振能量转移测定研究的聚集过程的不可逆性和双层脂质的混合表明发生的是融合而非聚集。在单价或二价阳离子存在下，NPPS和NPPE脂质体水相内容物的合并证明了真正融合的存在。通过ζ电位测量确定的Ca2+对NPPS和NPPE脂质体的不同结合敏感性与聚集和融合测定中获得的结果一致。我们的结果表明，体内N-酰化磷脂的合成可在膜介导的过程中引入重要变化。
