Macrophage recognition of externalized phosphatidylserine and phagocytosis of apoptotic Jurkat cells - existence of a threshold
Macrophage recognition of externalized phosphatidylserine and phagocytosis of apoptotic Jurkat cells - existence of a threshold
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DOI：
10.1016/s0003-9861(03)00083-3
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发表时间：
2003-05-01
影响因子：
3.9
通讯作者：
Kagan, VE
中科院分区：
文献类型：
--
作者：
Borisenko, GG;Matsura, T;Kagan, VE
磷脂酰丝氨酸（PS）在细胞内主要分布于细胞膜的内层，而在细胞凋亡过程中则外化于细胞表面。这种外化的PS是巨噬细胞有效吞噬凋亡细胞所必需的。由于PS跨双层不对称性在不同类型的非凋亡细胞中并不是绝对的，我们假设外化PS的量可能是巨噬细胞区分凋亡细胞和非凋亡细胞的关键。我们开发了一种灵敏的电子顺磁共振方法来定量的基础上，特异性结合的顺磁性膜联蛋白V-微珠共轭物与PS细胞表面的外部PS的量。使用这种技术，我们发现非凋亡Jurkat细胞外化0.9 pmol内源性PS/10（6）Jurkat细胞。对于在其表面上具有不同量的整合的外源PS的细胞，在PS水平< 5 pmol/10（6）Jurkat细胞时未观察到吞噬反应;在较高PS浓度下，吞噬作用以浓度依赖性方式增加。Jurkat细胞的凋亡引起了类似于240 pmol PS/10（6）Jurkat细胞的外化;这些外化的PS的量比吞噬作用所需的PS的阈值量高许多倍。因此，巨噬细胞对细胞表面上的PS外化具有敏感性阈值，其提供了具有低含量的外化PS的正常细胞和具有显著升高的PS水平的凋亡细胞之间的可靠识别和区分。(C)2003 Elsevier Science（美国）。All rights reserved.
Phosphatidylserine (PS) is predominantly confined to the inner leaflet of plasma membrane in cells, but it is externalized on the cell surface during apoptosis. This externalized PS is required for effective phagocytosis of apoptotic cells by macrophages. Because PS trans-bilayer asymmetry is not absolute in different types of nonapoptotic cells, we hypothesized that the amounts of externalized PS may be critical for macrophage discrimination between apoptotic and nonapoptotic cells. We developed a sensitive electron paramagnetic resonance method to quantify the amounts of externalized PS based on specific binding of paramagnetic annexin V-microbead conjugates with PS on cell surfaces. Using this technique, we found that nonapoptotic Jurkat cells externalize 0.9 pmol of endogenous PS/10(6) Jurkat cells. For cells with different amounts of integrated exogenous PS on their surface, no phagocytic response was observed at PS levels < 5 pmol/10(6) Jurkat cells; at higher PS concentrations, phagocytosis increased in a concentration-dependent manner. Apoptosis in Jurkat cells caused externalization of similar to240 pmol PS/10(6) Jurkat cells; these amounts of externalized PS are manyfold higher than the threshold amounts of PS required for phagocytosis. Thus, macrophages have a sensitivity threshold for PS externalized on the cell surface that provides for reliable recognition and distinction between normal cells with low contents of externalized PS and apoptotic cells with remarkably elevated PS levels. (C) 2003 Elsevier Science (USA). All rights reserved.