Mobilization of Lysosomal Calcium Regulates the Externalization of Phosphatidylserine during Apoptosis
Mobilization of Lysosomal Calcium Regulates the Externalization of Phosphatidylserine during Apoptosis
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DOI：
10.1074/jbc.m805288200
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发表时间：
2009-03-13
影响因子：
4.8
通讯作者：
Schroit, Alan J.
中科院分区：
文献类型：
--
作者：
Mirnikjoo, Banafsheh;Balasubramanian, Krishnakumar;Schroit, Alan J.
凋亡细胞的标志是磷脂酰丝氨酸（PS）在细胞表面的Ca 2+依赖性外观，这是其从内质膜小叶到外质膜小叶的再分布的结果。虽然内质网和线粒体Ca 2+参与细胞凋亡，其作用PS外化尚未建立。在这项研究中，几个细胞器特异性荧光标记和Ca 2+敏感的探针被用来确定来源的Ca 2 + PS外化的关键。通过采用Rhod-2AM，荧光素标记的高分子量葡聚糖，和钙绿色1，我们提供的证据表明，溶酶体响应细胞凋亡刺激释放其管腔Ca 2+的胞质溶胶。用胞质磷脂酶A（2）抑制剂cPLA 2 α处理的细胞对caspase活化没有影响，但在对凋亡刺激的反应中，溶酶体Ca 2+释放和PS外化显着减少。同样，细胞耗尽溶酶体Ca 2+经历程序性细胞死亡，但未能外化PS。这些数据表明，虽然从其他细胞内的细胞器到胞质溶胶的Ca 2+释放是足够的凋亡，从溶酶体的Ca 2+的释放是至关重要的PS外化。
A hallmark of apoptotic cells is the Ca2+ dependent appearance of phosphatidylserine (PS) at the cell surface as a result of its redistribution from the inner-to-outer plasma membrane leaflet. Although endoplasmic reticulum and mitochondrial Ca2+ are known to participate in apoptosis, their role in PS externalization has not been established. In this study, several organelle-specific fluorescent markers and Ca2+-sensitive probes were used to identify the source of Ca2+ critical to PS externalization. By employing Rhod-2AM, fluorescein-labeled high molecular weight dextran, and Calcium Green 1, we provide evidence that lysosomes respond to apoptotic stimuli by releasing their luminal Ca2+ to the cytosol. Cells treated with the cytosolic phospholipase A(2) inhibitor, cPLA2 alpha, had no effect on caspase activation but exhibited a significant decrease in lysosomal Ca2+ release and externalization of PS in response to apoptotic stimuli. Similarly, cells depleted of lysosomal Ca2+ underwent programmed cell death yet failed to externalize PS. These data indicate that although Ca2+ release from other intracellular organelles to the cytosol is adequate for apoptosis, the release of Ca2+ from lysosomes is critical for PS externalization.