Tucholski Janusz, Johnson Gail V W
Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 1720 7th Avenue South, SC 1061, Birmingham, AL 35294-0017, USA.
J Neurochem. 2002 May;81(4):780-91. doi: 10.1046/j.1471-4159.2002.00859.x.
Tissue transglutaminase is a unique member of the transglutaminase family as it not only catalyzes a transamidating reaction, but also binds and hydrolyzes GTP and ATP. Tissue transglutaminase has been reported to be pro-apoptotic, however, conclusive evidence is still lacking. To elucidate the role of tissue transglutaminase in the apoptotic process human neuroblastoma SH-SY5Y cells were stably transfected with vector only (SH/pcDNA), wild-type tissue transglutaminase (SH/tTG) and tissue transglutaminase that has no transamidating activity but retains its other functions (SH/C277S). In these studies three different apoptotic stimuli were used osmotic stress, staurosporine treatment and heat shock to delineate the role of tissue transglutaminase as a transamidating enzyme in the apoptotic process. In SH/tTG cells, osmotic stress and staurosporine treatments resulted in significantly greater caspase-3 activation and apoptotic nuclear changes then in SH/pcDNA or SH/C277S cells. This potentiation of apoptosis in SH/tTG cells was concomitant with a significant increase in the in situ transamidating activity of tissue transglutaminase. However, in the heat shock paradigm, which did not result in any increase in the transamidating activity in SH/tTG cells, there was a significant attenuation of caspase-3 activity, LDH release and apoptotic chromatin condensation in SH/tTG and SH/C277S cells compared with SH/pcDNA cells. These findings indicate for the first time that the effect of tissue transglutaminase on the apoptotic process is highly dependent on the type of the stimuli and how the transamidating activity of the enzyme is affected. Tissue transglutaminase facilitates apoptosis in response to stressors that result in an increase in the transamidating activity of the enzyme. However, when the stressors do not result in an increase in the transamidating activity of tissue transglutaminase, than tissue transglutaminase can ameliorate the apoptotic response through a mechanism that is independent of its transamidating function. Further, neither the phosphatidylinositol-3-kinase pathway nor the extracellular-regulated kinase pathway is downstream of the modulatory effects of wild-type tissue transglutaminase or C277S-tissue transglutaminase in the apoptotic cascade.
组织转谷氨酰胺酶是转谷氨酰胺酶家族中的独特成员，因为它不仅催化转酰胺反应，还能结合并水解GTP和ATP。据报道，组织转谷氨酰胺酶具有促凋亡作用，然而，确凿的证据仍然缺乏。为了阐明组织转谷氨酰胺酶在凋亡过程中的作用，用仅含载体（SH/pcDNA）、野生型组织转谷氨酰胺酶（SH/tTG）和无转酰胺活性但保留其他功能的组织转谷氨酰胺酶（SH/C277S）稳定转染人神经母细胞瘤SH-SY5Y细胞。在这些研究中，使用了三种不同的凋亡刺激因素：渗透压应激、星形孢菌素处理和热休克，以阐明组织转谷氨酰胺酶作为转酰胺酶在凋亡过程中的作用。在SH/tTG细胞中，渗透压应激和星形孢菌素处理导致的半胱天冬酶-3激活和凋亡性核变化比SH/pcDNA或SH/C277S细胞显著更明显。SH/tTG细胞中这种凋亡增强与组织转谷氨酰胺酶原位转酰胺活性的显著增加同时出现。然而，在热休克模式下（该模式未导致SH/tTG细胞中转酰胺活性增加），与SH/pcDNA细胞相比，SH/tTG和SH/C277S细胞中的半胱天冬酶-3活性、乳酸脱氢酶释放和凋亡染色质浓缩均显著减弱。这些发现首次表明，组织转谷氨酰胺酶对凋亡过程的影响高度依赖于刺激类型以及该酶的转酰胺活性如何受到影响。组织转谷氨酰胺酶在对导致该酶转酰胺活性增加的应激源作出反应时促进凋亡。然而，当应激源未导致组织转谷氨酰胺酶转酰胺活性增加时，组织转谷氨酰胺酶可通过一种独立于其转酰胺功能的机制改善凋亡反应。此外，磷脂酰肌醇-3-激酶途径和细胞外调节激酶途径均不在野生型组织转谷氨酰胺酶或C277S-组织转谷氨酰胺酶在凋亡级联反应中的调节作用下游。
