Phosphatidic acid mediates the targeting of tBid to induce lysosomal membrane permeabilization and apoptosis
Phosphatidic acid mediates the targeting of tBid to induce lysosomal membrane permeabilization and apoptosis
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磷脂酸介导 tBid 靶向诱导溶酶体膜透化和细胞凋亡
DOI：
10.1194/jlr.m027557
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发表时间：
2012-10-01
影响因子：
6.5
通讯作者：
Yang, Fuyu
中科院分区：
文献类型：
--
作者：
Zhao, Kai;Zhou, Hejiang;Yang, Fuyu
在细胞凋亡刺激后，溶酶体蛋白酶（包括组织蛋白酶和胰凝乳蛋白酶）由于溶酶体膜透化（LMP）而释放到胞质溶胶中，其中它们通过细胞凋亡的溶酶体-线粒体途径触发细胞凋亡。在此，LMP的机制进行了研究。我们发现半胱天冬酶8裂解的Bid（tBid）可直接导致LMP。尽管Bax或巴克可能适度地增强tBid触发的LMP，但是它们对于LMP不是必需的。为了进一步研究这一点，大的单层囊泡（LUVs），模型膜模仿溶酶体的脂质组成，被用来重建膜透化过程中在体外。我们发现，磷脂酸（PA），在溶酶体膜中发现的主要酸性磷脂之一，是必不可少的tBid诱导的LMP。PA促进tBid深深插入到脂质双层中，在那里它经历同源寡聚化并触发高度弯曲的非双层脂质相的形成。这些事件通过孔形成机制诱导LMP，因为包封的荧光素缀合的葡聚糖（FD）-20由于其较小的分子尺寸而比FD-70或FD-250更显著地从LUV释放。基于这些数据，我们提出tBid-PA相互作用在溶酶体膜形成的微泡孔，并导致LMP。我们进一步注意到，胰凝乳蛋白酶裂解的Bid在结合PA、插入脂质双层和促进LMP方面比tBid更有效。这种放大机制可能有助于细胞凋亡信号传导的高潮。赵，K.，H. Zhou，X. Zhao，中国粘蝇D. W. Wolff，Y. Tu，H. Liu，T. Wei和F.杨磷脂酸介导tBid靶向诱导溶酶体膜透化和凋亡。J. Lipid Res. 2012. 53：2102-2114。
Upon apoptotic stimuli, lysosomal proteases, including cathepsins and chymotrypsin, are released into cytosol due to lysosomal membrane permeabilization (LMP), where they trigger apoptosis via the lysosomal-mitochondrial pathway of apoptosis. Herein, the mechanism of LMP was investigated. We found that caspase 8-cleaved Bid (tBid) could result in LMP directly. Although Bax or Bak might modestly enhance tBid-triggered LMP, they are not necessary for LMP. To study this further, large unilamellar vesicles (LUVs), model membranes mimicking the lipid constitution of lysosomes, were used to reconstitute the membrane permeabilization process in vitro. We found that phosphatidic acid (PA), one of the major acidic phospholipids found in lysosome membrane, is essential for tBid-induced LMP. PA facilitates the insertion of tBid deeply into lipid bilayers, where it undergoes homo-oligomerization and triggers the formation of highly curved nonbilayer lipid phases. These events induce LMP via pore formation mechanisms because encapsulated fluorescein-conjugated dextran (FD)-20 was released more significantly than FD-70 or FD-250 from LUVs due to its smaller molecular size. On the basis of these data, we proposed tBid-PA interactions in the lysosomal membranes form lipidic pores and result in LMP. We further noted that chymotrypsin-cleaved Bid is more potent than tBid at binding to PA, inserting into the lipid bilayer, and promoting LMP. This amplification mechanism likely contributes to the culmination of apoptotic signaling. Zhao, K., H. Zhou, X. Zhao, D. W. Wolff, Y. Tu, H. Liu, T. Wei, and F. Yang. Phosphatidic acid mediates the targeting of tBid to induce lysosomal membrane permeabilization and apoptosis. J. Lipid Res. 2012. 53: 2102-2114.