EVIDENCE THAT BCL-2 REPRESSES APOPTOSIS BY REGULATING ENDOPLASMIC RETICULUM-ASSOCIATED CA2+ FLUXES
EVIDENCE THAT BCL-2 REPRESSES APOPTOSIS BY REGULATING ENDOPLASMIC RETICULUM-ASSOCIATED CA2+ FLUXES
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DOI：
10.1073/pnas.91.14.6569
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发表时间：
1994-07-05
影响因子：
11.1
通讯作者：
DISTELHORST, CW
中科院分区：
文献类型：
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作者：
LAM, M;DUBYAK, G;DISTELHORST, CW
BCL-2是一种26 kDa的整合膜蛋白，其抑制细胞凋亡的机制未知。最近的研究表明，内质网(ER)中的钙离子释放介导了小鼠淋巴瘤细胞的凋亡。鉴于越来越多的证据表明bcl2定位于内质网、线粒体和核周膜，我们探讨了bcl2通过调节内质网钙离子流量来抑制细胞凋亡的可能性。将编码bcl2的基因导入WEHI7.2细胞，筛选出高表达bcl2基因的亚克隆W.Hb12和低水平表达bcl2蛋白的亚克隆W.Hb13。WEHI7.2细胞在糖皮质激素地塞米松的作用下发生了凋亡，而W.Hb12抗W.Hb13细胞则受到保护，这表明bcl2的表达水平与保护程度直接相关。值得注意的是，bcl2还阻断了thapsigargin(TG)诱导的细胞凋亡，thapsigargin是一种高度特异的内质网相关钙泵抑制剂。甘油三酯完全抑制WEHI7.2和W.Hb12细胞的内质网钙泵，但W.Hb12细胞抑制内质网钙泵后胞浆内钙的释放明显少于WEHI7.2细胞，表明bcl2减少了胞浆内钙的外流。通过减少内质网钙离子的外流，bcl2干扰了细胞外钙离子“容量性”进入的信号，阻止了TG处理的细胞内钙离子的持续增加。这些发现表明，bcl2直接或间接地调节内质网细胞膜上的钙离子流量，从而取消细胞凋亡的钙信号。
BCL-2 is a 26-kDa integral membrane protein that represses apoptosis by an unknown mechanism. Recent findings indicate that Ca2+ release from the endoplasmic reticulum (ER) mediates apoptosis in mouse lymphoma cells. In view of growing evidence that BCL-2 localizes to the ER, as well as mitochondria and the perinuclear membrane, we investigated the possibility that BCL-2 represses apoptosis by regulating Ca2+ fluxes through the ER membrane. A cDNA encoding BCL-2 was introduced into WEHI7.2 cells and two subclones, W.Hb12 and W.Hb13, which express high and low levels of BCL-2 mRNA and protein, respectively, were isolated. WEHI7.2 cells underwent apoptosis in response to treatment with the glucocorticoid hormone dexamethasone, whereas W.Hb12 anti W.Hb13 cells were protected from apoptosis, revealing a direct relationship between the level of BCL-2 expression and the degree of protection. Significantly, BCL-2 also blocked induction of apoptosis by thapsigargin (TG), a highly specific inhibitor of the ER-associated Ca2+ pump. TG completely inhibited ER Ca2+ pumping in both WEHI7.2 and W.Hb12 cells, but the release of Ca2+ into the cytosol after inhibition of ER Ca2+ pumping was significantly less in W.Hb12 cells than in WEHI7.2 cells, indicating that BCL-2 reduces Ca2+ efflux through the ER membrane. By reducing ER Ca2+ efflux, BCL-2 interfered with a signal for ''capacitative'' entry of extracellular Ca2+, preventing a sustained increase of cytosolic Ca2+ in TG-treated cells. These findings suggest that BCL-2 either directly or indirectly regulates the flux of Ca2+ across the ER membrane, thereby abrogating Ca2+ signaling of apoptosis.