Intracellular localization and activity state of tissue transglutaminase differentially impacts cell death
Intracellular localization and activity state of tissue transglutaminase differentially impacts cell death
复制标题
DOI：
10.1074/jbc.m308479200
复制
发表时间：
2004-03-05
影响因子：
4.8
通讯作者：
Johnson, GVW
中科院分区：
文献类型：
--
作者：
Milakovic, T;Tucholski, J;Johnson, GVW
组织转氨酶（tTG）是转氨酶家族的独特成员，因为它既是一种转酰胺酶，又是一种GTG。在细胞中，tTG主要存在于胞质中，但也存在于细胞核中并与质膜相关。tTG可以是促凋亡的，然而也已经报道了该酶的抗凋亡活性。为了确定tTG的细胞内定位和转酰胺活性如何调节其对细胞凋亡的影响，用靶向不同细胞内区室的tTG或[C277S] tTG（其缺乏转酰胺活性）构建体瞬时转染HEK293细胞。毒胡萝卜素处理诱导细胞凋亡，导致细胞内钙浓度增加。胞质tTG是促凋亡的，而[C277S] tTG的核定位减弱了凋亡。膜靶向tTG既没有促凋亡功能，也没有抗凋亡功能。这一发现首次表明细胞内定位是tTG对细胞凋亡作用的重要决定因素。以前的研究表明，tTG可以调节视网膜母细胞瘤（Rb）蛋白，一个重要的细胞凋亡抑制因子。tTG与Rb相互作用，诱导凋亡后，核靶向的[ C277S] tTG与Rb的相互作用显著增加，同时凋亡减弱。与此相反，核靶向tTG与Rb的相互作用显着减少，细胞凋亡没有减弱。这些数据表明，tTG保护细胞凋亡的刺激，不导致增加transamidating活性的易位到细胞核，和复合Rb可能是一个重要方面的保护作用的tTG。
Tissue transglutaminase (tTG) is a unique member of the transglutaminase family as it is both a transamidating enzyme and a GTPase. In the cell tTG is mostly cytosolic, however it is also found in the nucleus and associated with the plasma membrane. tTG can be proapoptotic, however anti-apoptotic activities of the enzyme have also been reported. To determine how the intracellular localization and transamidating activity of tTG modulates its effects on apoptosis, HEK293 cells were transiently transfected with tTG or [C277S] tTG ( which lacks transamidating activity) constructs that were targeted to different intracellular compartments. Apoptosis was induced by thapsigargin treatment, which results in increased intracellular calcium concentrations. Cytosolic tTG was pro-apoptotic, while nuclear localization of [C277S] tTG attenuated apoptosis. Membrane-targeted tTG had neither pro- nor anti-apoptotic functions. This finding indicates for the first time that intracellular localization is an important determinant of the effect of tTG on apoptosis. Previous studies have suggested that tTG may modulate retinoblastoma (Rb) protein, an important suppressor of apoptosis. tTG interacted with Rb and after induction of apoptosis, the interaction of nuclear-targeted [ C277S] tTG with Rb was increased significantly concomitant with an attenuation of apoptosis. In contrast, the interaction of nuclear-targeted tTG with Rb was significantly decreased and apoptosis was not attenuated. These data suggest that tTG protects cells against apoptosis in response to stimuli that do not result in increased transamidating activity by translocating to the nucleus, and that complexing with Rb may be an important aspect of the protective effects of tTG.