Modeling a snap-action, variable-delay switch controlling extrinsic cell death.
Modeling a snap-action, variable-delay switch controlling extrinsic cell death.
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DOI：
10.1371/journal.pbio.0060299
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发表时间：
2008-12-02
期刊：
影响因子：
9.8
通讯作者：
Sorger PK
中科院分区：
文献类型：
--
作者：
Albeck JG;Burke JM;Spencer SL;Lauffenburger DA;Sorger PK
当暴露于肿瘤坏死因子（TNF）或TNF相关凋亡诱导配体（TRAIL）（一种密切相关的死亡配体和研究性治疗剂）时，细胞进入一个持续时间可变的延长期，其中只有上游起始半胱天冬酶是活性的。随后的突然转变标志着下游效应物半胱天冬酶的激活，该酶迅速分解细胞。因此，外源性细胞凋亡是由一个不寻常的可变延迟，速动开关，强制执行生与死之间的明确选择。为了了解外源性凋亡开关如何在定量方面发挥作用，我们构建了一个数学模型的基础上的质量作用表示已知的反应途径。该模型针对通过活细胞成像、流式细胞术和蛋白质耗尽和过表达干扰的细胞的免疫印迹获得的实验数据进行训练。经过训练的模型准确地再现了暴露于TRAIL的正常细胞和受干扰细胞的行为，使得详细研究开关机制成为可能。模型分析表明，实验证实，在效应caspase激活之前的延迟的持续时间是由引发剂caspase-8活性和其他反应的速率直接位于下游的TRAIL受体。效应半胱天冬酶的突然激活是通过参与线粒体膜的透化和蛋白质如Smac的重新定位的反应在下游实现的。我们发现Bcl-2家族成员之间的相互作用模式，Smac从其结合伙伴XIAP的分区，以及孔组装的力学都是至关重要的快动控制。在高等真核生物中，组织发育和体内平衡涉及细胞出生和死亡率之间的微妙平衡。细胞死亡（凋亡）是由半胱天冬酶激活触发的，半胱天冬酶是消化必需细胞成分并触发基因组DNA降解的专门酶。在正常情况下，受体依赖性细胞死亡被非常紧密地抑制，但是在接收到适当的信号时，它被不可逆地诱导。干扰这种全或无控制的突变会导致发育异常、自身免疫性疾病和癌症。大多数凋亡蛋白的生物化学特性已经被很好地理解，但还不清楚这些蛋白如何一起工作。通过结合活细胞显微镜，遗传扰动和数学建模，我们寻求对细胞死亡的定量洞察，重点是网络动力学和控制。我们发现，细胞在收到凋亡信号和死亡承诺之间的时间变化很大。这种变异性来自于受体近端生化反应活性的细胞间差异。从承诺到实际死亡的快速全或无进展是通过线粒体膜中发现的促凋亡蛋白下游实现的。我们的工作提供了一个定量的细胞凋亡的图片，推进致癌机制的理解，并最终应有助于促凋亡癌症治疗的发展。结合单细胞实验和数学建模揭示了受体诱导的细胞凋亡过程中caspase激活的机制。
When exposed to tumor necrosis factor (TNF) or TNF-related apoptosis-inducing ligand (TRAIL), a closely related death ligand and investigational therapeutic, cells enter a protracted period of variable duration in which only upstream initiator caspases are active. A subsequent and sudden transition marks activation of the downstream effector caspases that rapidly dismantle the cell. Thus, extrinsic apoptosis is controlled by an unusual variable-delay, snap-action switch that enforces an unambiguous choice between life and death. To understand how the extrinsic apoptosis switch functions in quantitative terms, we constructed a mathematical model based on a mass-action representation of known reaction pathways. The model was trained against experimental data obtained by live-cell imaging, flow cytometry, and immunoblotting of cells perturbed by protein depletion and overexpression. The trained model accurately reproduces the behavior of normal and perturbed cells exposed to TRAIL, making it possible to study switching mechanisms in detail. Model analysis shows, and experiments confirm, that the duration of the delay prior to effector caspase activation is determined by initiator caspase-8 activity and the rates of other reactions lying immediately downstream of the TRAIL receptor. Sudden activation of effector caspases is achieved downstream by reactions involved in permeabilization of the mitochondrial membrane and relocalization of proteins such as Smac. We find that the pattern of interactions among Bcl-2 family members, the partitioning of Smac from its binding partner XIAP, and the mechanics of pore assembly are all critical for snap-action control. In higher eukaryotes, tissue development and homeostasis involves a subtle balance between rates of cell birth and death. Cell death (apoptosis) is triggered by activation of caspases, specialized enzymes that digest essential cellular constituents and trigger degradation of genomic DNA. Under normal circumstances receptor-dependent cell death is very tightly repressed, but it is irreversibly induced upon receipt of an appropriate signal. Mutations that interfere with this all-or-none control contribute to developmental abnormalities, autoimmune disease, and cancer. The biochemical properties of most apoptotic proteins are quite well understood, but it is unclear how these proteins work together. By combining live-cell microscopy, genetic perturbation, and mathematical modeling, we seek quantitative insight into cell death with a focus on network dynamics and control. We find that cells vary dramatically in the time between receipt of an apoptotic signal and the commitment to death. This variability arises from cell-to-cell differences in the activities of receptor-proximal biochemical reactions. Rapid all-or-none progress from commitment to actual death is achieved downstream by pro-apoptotic proteins found in the mitochondrial membrane. Our work provides a quantitative picture of apoptosis that advances understanding of oncogenic mechanisms and should eventually assist in the development of pro-apoptotic cancer therapies. A combination of single-cell experiments and mathematical modeling reveals the mechanisms underlying all-or-none caspase activation during receptor-induced apoptosis.
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影响因子：
64.5
作者：
Du, CY;Fang, M;Wang, XD
通讯作者：
Wang, XD
影响因子：
3.5
作者：
Chen, Chun;Cui, Jun;Shen, Pingping
通讯作者：
Shen, Pingping
影响因子：
46.9
作者：
Fussenegger, M;Bailey, JE;Varner, J
通讯作者：
Varner, J
Bcl-2凋亡开关中的两个独立的正反馈和双重性。
影响因子：
3.7
作者：
Cui, Jun;Chen, Chun;Lu, Haizhu;Sun, Tingzhe;Shen, Pingping
通讯作者：
Shen, Pingping
DOI：
10.1049/ip-syb:20050065
发表时间：
2006-11-01
期刊：
IEE PROCEEDINGS SYSTEMS BIOLOGY
影响因子：
--
作者：
Aldridge, B. B.;Haller, G.;Lauffenburger, D. A.
通讯作者：
Lauffenburger, D. A.