Molecular mechanism by which acyclic retinoid induces nuclear localization of transglutaminase 2 in human hepatocellular carcinoma cells.
Molecular mechanism by which acyclic retinoid induces nuclear localization of transglutaminase 2 in human hepatocellular carcinoma cells.
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DOI：
10.1038/cddis.2015.339
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发表时间：
2015-12-03
影响因子：
9
通讯作者：
Kojima S
中科院分区：
文献类型：
--
作者：
Shrestha R;Tatsukawa H;Shrestha R;Ishibashi N;Matsuura T;Kagechika H;Kose S;Hitomi K;Imamoto N;Kojima S
谷氨酰胺转氨酶2(TG2)的核积聚是TG2依赖性细胞死亡的重要步骤。然而，TG2核转位的潜在分子机制仍然知之甚少。在本研究中，我们证明了去环维A酸类化合物(ACR)可诱导肝细胞癌JHH-7细胞中TG2的核积聚，从而导致其凋亡。我们进一步阐明了TG2核质转运的分子机制以及ACR对其的影响。我们在‘C’区发现了一个新的14个氨基酸的核定位信号(NLS)466AEKEETGMAMRIRV479，在‘D’区发现了一个富含亮氨酸的核输出信号(NES)657LHMGLHKL664，它允许TG2在核和胞质环境之间穿梭。观察到GAPDHmyc-His与已鉴定的NLS融合的核进口增加，证实了其核进口能力。出口蛋白-1的抑制剂Leptomycin B以及TG2的NES中所有亮氨酸残基到谷氨酰胺残基的点突变破坏了其核出口。Tg2与Importin-α和Importin-β形成一个独立于转氨酶活性的三聚体复合体，这强烈地表明Tg2参与了基于NLS的核转位。ACR促进了三聚体复合体的形成，这可能是ACR处理的肝癌细胞中TG2核定位增强的至少部分原因。
Nuclear accumulation of transglutaminase 2 (TG2) is an important step in TG2-dependent cell death. However, the underlying molecular mechanisms for nuclear translocation of TG2 are still poorly understood. In this study, we demonstrated that acyclic retinoid (ACR) induced nuclear accumulation of TG2 in JHH-7 cells, a hepatocellular carcinoma (HCC) leading to their apoptosis. We further demonstrated molecular mechanism in nuclear-cytoplasmic trafficking of TG2 and an effect of ACR on it. We identified a novel 14-amino acid nuclear localization signal (NLS) 466AEKEETGMAMRIRV479 in the ‘C' domain and a leucine-rich nuclear export signal (NES) 657LHMGLHKL664 in the ‘D' domain that allowed TG2 to shuttle between the nuclear and cytosolic milieu. Increased nuclear import of GAPDH myc-HIS fused with the identified NLS was observed, confirming its nuclear import ability. Leptomycin B, an inhibitor of exportin-1 as well as point mutation of all leucine residues to glutamine residues in the NES of TG2 demolished its nuclear export. TG2 formed a trimeric complex with importin-α and importin-β independently from transamidase activity which strongly suggested the involvement of a NLS-based translocation of TG2 to the nucleus. ACR accelerated the formation of the trimeric complex and that may be at least in part responsible for enhanced nuclear localization of TG2 in HCC cells treated with ACR.