Role of poly(ADP-ribose) polymerase-1 as a controlling switch between DNA damage-induced apoptosis and necrosis

POLY（adp -核糖）聚合酶-1 （PARP）是高等真核生物中存在的一种核酶，在DNA损伤的快速反应中，它被催化激活消耗NAD并形成adp -核糖聚合物，从而短暂地改变某些染色质结构和DNA代谢相关蛋白的功能。最近的研究，包括我们nserc支持的研究，已经在不同的细胞死亡模型中表明，高水平DNA损伤的早期PARP激活可以影响导致细胞凋亡或坏死的关键起始事件，如NAD和ATP的消耗，细胞凋亡诱导因子的核易位，细胞内酸化等。因此，我们假设，在暴露于不同程度DNA损伤的特定细胞中，由细胞凋亡或坏死死亡的决定受到PARP这些直接作用的平衡的影响。我们将使用具有或不具有功能性PARP的细胞，表达野生型或caspase 3抗性突变PARP的细胞；以及具有或不具有功能性PARP的质子去除泵Na/H+交换器-1的细胞。在这些模型中，我们将研究对不同水平DNA损伤反应的死亡模式，并将其与控制细胞死亡模式的parp相关事件联系起来。该项目的具体目标是确定：1)PARP的存在和作用是否影响细胞对不同程度DNA损伤的凋亡或坏死反应；2) caspase 3切割PARP促进细胞凋亡的机制；3) parp介导的细胞酸化阻断细胞凋亡、允许细胞坏死的机制；4)凋亡或坏死起始过程中受PARP调控的死亡相关基因。

ROLE OF POLY(ADP-RIBOSE) POLYMERASE-1 AS A CONTROLLING SWITCH BETWEEN DNA DAMAGE-INDUCED APOPTOSIS AND NECROSIS         In a rapid response to DNA damage, poly(ADP-ribose) polymerase-1 (PARP), a nuclear enzyme present in higher eukaryotes, is catalytically activated to consume NAD and form polymers of ADP-ribose, which transiently modify functions of selected chromatin structure- and DNA metabolism-related proteins. Recent studies, including those from our NSERC-supported research, have shown in different models of cell death that early PARP activation in response to high levels of DNA damage can influence key initiating events which can lead to either apoptosis or necrosis, such as depletion of NAD and ATP, nuclear translocation of apoptosis inducing factor, intracellular acidification, etc. Hence, we hypothesize that in a given cell exposed to varying levels of DNA damage, the decision to die by apoptosis or necrosis is influenced by a balance of these immediate actions of PARP. We will use cells with or without functional PARP, cells expressing wild type or caspase 3-resistant mutant PARP; and cells which are proficient or deficient in proton-removal pump Na/H+ exchanger-1 with or without functional PARP. In these models, we will examine mode of death in responses to different levels of DNA damage and correlate it with PARP-related events that control the mode of cell death.         The specific objectives of the project are to determine: 1) Whether the presence and actions of PARP influence apoptotic or necrotic response of cells to varying levels of DNA damage; 2) The mechanism by which cleavage of PARP by caspases 3 promotes apoptosis; 3) The mechanism by which PARP-mediated cellular acidification blocks apoptosis and allows necrosis; and 4) The death-related genes whose expression is controlled by PARP during initiation of apoptosis or necrosis.