PIG7 promotes leukemia cell chemosensitivity via lysosomal membrane permeabilization.
PIG7 promotes leukemia cell chemosensitivity via lysosomal membrane permeabilization.
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PIG7通过溶酶体膜透化促进白血病细胞化疗敏感性
DOI：
10.18632/oncotarget.6739
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发表时间：
2016-01-26
期刊：
影响因子：
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通讯作者：
Liu T
中科院分区：
文献类型：
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作者：
Liu J;Peng L;Niu T;Wu Y;Li J;Wang F;Zheng Y;Liu T
PIG 7定位于白血病细胞中的溶酶体膜。我们以前的工作已经表明，pig 7转导到一系列白血病细胞系中不会导致大多数测试细胞系的凋亡或分化。有趣的是，它确实显著地使这些细胞系对化疗药物敏感。在这里，我们进一步研究了pig 7诱导急性白血病细胞对化疗敏感性提高的机制。我们的研究结果表明，由外源性pig 7驱动的致敏作用在内源性pig 7表达较低的耐药白血病细胞系中更有效。pig 7的过表达并不直接激活caspase凋亡途径，但降低了溶酶体的稳定性。pig 7的表达导致溶酶体膜透化（LMP）和溶酶体蛋白酶（例如组织蛋白酶B、D、L）释放。此外，我们还观察到pig 7诱导的活性氧（ROS）增加和线粒体膜电位（Δ Vm）降低。一些自噬标记物如LC 3 I/II、ATG 5和Beclin-1以及坏死性凋亡标记物MLKL也被刺激。然而，内在的拮抗作用，如丝氨酸/半胱氨酸蛋白酶抑制剂Spi 2A和胱抑素C阻止下游效应触发白血病细胞，这只是在“凋亡的边缘”。当与化疗结合时，LMP增加，释放更多的蛋白酶。一旦这一过程超出了内在拮抗作用的限度，它就会通过半胱天冬酶非依赖性途径和半胱天冬酶依赖性途径协同诱导细胞程序性死亡。
PIG7 localizes to lysosomal membrane in leukemia cells. Our previous work has shown that transduction of pig7 into a series of leukemia cell lines did not result in either apoptosis or differentiation of most tested cell lines. Interestingly, it did significantly sensitize these cell lines to chemotherapeutic drugs. Here, we further investigated the mechanism underlying pig7-induced improved sensitivity of acute leukemia cells to chemotherapy. Our results demonstrated that the sensitization effect driven by exogenous pig7 was more effective in drug-resistant leukemia cell lines which had lower endogenous pig7 expression. Overexpression of pig7 did not directly activate the caspase apoptotic pathway, but decreased the lysosomal stability. The expression of pig7 resulted in lysosomal membrane permeabilization (LMP) and lysosomal protease (e.g. cathepsin B, D, L) release. Moreover, we also observed increased reactive oxygen species (ROS) and decreased mitochondrial membrane potential (ΔΨm) induced by pig7. Some autophagy markers such as LC3I/II, ATG5 and Beclin-1, and necroptosis maker MLKL were also stimulated. However, intrinsic antagonism such as serine/cysteine protease inhibitors Spi2A and Cystatin C prevented downstream effectors from triggering leukemia cells, which were only on the “verge of apoptosis”. When combined with chemotherapy, LMP increased and more proteases were released. Once this process was beyond the limit of intrinsic antagonism, it induced programmed cell death cooperatively via caspase-independent and caspase-dependent pathways.