Xu Ying-Ying, Lu Yi, Fan Kai-Yi, Shen Zong-Hou
Department of Biochemistry and Molecular Biology, Shanghai Medical College, Fudan University, Shanghai, PR China.
J Cell Biochem. 2007 Feb 15;100(3):773-82. doi: 10.1002/jcb.21088.
We previously demonstrated that endoplasmic reticulum (ER) stress was triggered in human hepatocarcinoma 7721 cells transfected with antisense cDNA of N-acetylglucosaminyltransferase V (GnT-V-AS/7721) which were more susceptible to apoptosis induced by all-trans retinoic acid (ATRA). In the present study, we report that ATRA-induced apoptosis in GnT-V-AS/7721 cells is mediated through ER stress. We show here that ER stress is enhanced in GnT-V-AS/7721 cells with 80 microM ATRA treatment for 24 h, which is evidenced by the increase of GRP78/Bip, C/EBP-homologous protein-10 (CHOP, also known as GADD153) and spliced XBP1. Additionally, activation of caspase-12, caspase-9, and -3 was detected, and apoptosis morphology was observed in GnT-V-AS/7721 cells with ATRA treatment. These results suggest that ATRA enhances the ER stress triggered in GnT-V-AS/7721 cells, which represents a novel mechanism of ATRA to induce apoptosis. We further observed that GnT-V was significantly repressed and the structure of N-glycans was changed in GnT-V-AS/7721 cells with 80 microM ATRA treatment for 24 h, suggesting that repression of GnT-V by ATRA causes the enhanced ER stress and ER stress-mediated apoptosis in GnT-V-AS/7721 cells.
我们先前证明，在用N-乙酰葡糖胺转移酶V反义cDNA转染的人肝癌7721细胞（GnT-V-AS/7721）中会引发内质网（ER）应激，这些细胞对全反式维甲酸（ATRA）诱导的凋亡更敏感。在本研究中，我们报告ATRA诱导GnT-V-AS/7721细胞凋亡是通过ER应激介导的。我们在此表明，用80微摩尔ATRA处理24小时后，GnT-V-AS/7721细胞中的ER应激增强，这通过葡萄糖调节蛋白78/免疫球蛋白重链结合蛋白（GRP78/Bip）、C/EBP同源蛋白10（CHOP，也称为生长停滞和DNA损伤诱导蛋白153，GADD153）和剪接的X盒结合蛋白1（XBP1）的增加得到证实。此外，检测到半胱天冬酶-12、半胱天冬酶-9和半胱天冬酶-3的激活，并且在接受ATRA处理的GnT-V-AS/7721细胞中观察到凋亡形态。这些结果表明，ATRA增强了GnT-V-AS/7721细胞中引发的ER应激，这代表了ATRA诱导凋亡的一种新机制。我们进一步观察到，用80微摩尔ATRA处理24小时后，GnT-V-AS/7721细胞中GnT-V被显著抑制，N-聚糖结构发生改变，这表明ATRA对GnT-V的抑制导致GnT-V-AS/7721细胞中ER应激增强和ER应激介导的凋亡。
