Wagner Klaus W, Punnoose Elizabeth A, Januario Thomas, Lawrence David A, Pitti Robert M, Lancaster Kate, Lee Dori, von Goetz Melissa, Yee Sharon Fong, Totpal Klara, Huw Ling, Katta Viswanatham, Cavet Guy, Hymowitz Sarah G, Amler Lukas, Ashkenazi Avi
Department of Molecular Diagnostics, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, USA.
Nat Med. 2007 Sep;13(9):1070-7. doi: 10.1038/nm1627. Epub 2007 Sep 2.
Apo2L/TRAIL stimulates cancer cell death through the proapoptotic receptors DR4 and DR5, but the determinants of tumor susceptibility to this ligand are not fully defined. mRNA expression of the peptidyl O-glycosyltransferase GALNT14 correlated with Apo2L/TRAIL sensitivity in pancreatic carcinoma, non-small-cell lung carcinoma and melanoma cell lines, and up to 30% of samples from various human malignancies showed GALNT14 overexpression. RNA interference of GALNT14 reduced cellular Apo2L/TRAIL sensitivity, whereas overexpression increased responsiveness. Biochemical analysis of DR5 identified several ectodomain O-(N-acetyl galactosamine-galactose-sialic acid) structures. Sequence comparison predicted conserved extracellular DR4 and DR5 O-glycosylation sites; progressive mutation of the DR5 sites attenuated apoptotic signaling. O-glycosylation promoted ligand-stimulated clustering of DR4 and DR5, which mediated recruitment and activation of the apoptosis-initiating protease caspase-8. These results uncover a new link between death-receptor O-glycosylation and apoptotic signaling, providing potential predictive biomarkers for Apo2L/TRAIL-based cancer therapy.
Apo2L/TRAIL通过促凋亡受体DR4和DR5刺激癌细胞死亡，但肿瘤对该配体敏感性的决定因素尚未完全明确。肽基O-糖基转移酶GALNT14的mRNA表达与胰腺癌、非小细胞肺癌和黑色素瘤细胞系中的Apo2L/TRAIL敏感性相关，高达30%的来自各种人类恶性肿瘤的样本显示GALNT14过表达。GALNT14的RNA干扰降低了细胞对Apo2L/TRAIL的敏感性，而过表达则增加了反应性。对DR5的生化分析确定了几个胞外域O-(N-乙酰半乳糖胺-半乳糖-唾液酸)结构。序列比较预测了保守的细胞外DR4和DR5 O-糖基化位点；DR5位点的逐步突变减弱了凋亡信号。O-糖基化促进了DR4和DR5的配体刺激聚集，这介导了凋亡起始蛋白酶caspase-8的募集和激活。这些结果揭示了死亡受体O-糖基化与凋亡信号之间的新联系，为基于Apo2L/TRAIL的癌症治疗提供了潜在的预测生物标志物。
