Kelley Robert F, Totpal Klara, Lindstrom Stephanie H, Mathieu Mary, Billeci Karen, Deforge Laura, Pai Roger, Hymowitz Sarah G, Ashkenazi Avi
Department of Protein Engineering, Genentech, Inc., South San Francisco, California 94080, USA.
J Biol Chem. 2005 Jan 21;280(3):2205-12. doi: 10.1074/jbc.M410660200. Epub 2004 Nov 1.
Apoptosis-inducing ligand 2 (Apo2L), also called tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), triggers programmed cell death in various types of cancer cells but not in most normal cells. Apo2L/TRAIL is a homotrimeric protein that interacts with five receptors: death receptor 4 (DR4) and DR5 mediate apoptosis activation, whereas decoy receptor 1 (DcR1), DcR2, and osteoprotegerin counteract this function. Many cancer cell lines express both DR4 and DR5, and each of these receptors can initiate apoptosis independently of the other. However, the relative contribution of DR4 and DR5 to ligand-induced apoptosis is unknown. To investigate this question, we generated death receptor-selective Apo2L/TRAIL variants using a novel approach that enables phage display of mutated trimeric proteins. Selective binding to DR4 or DR5 was achieved with three to six-ligand amino acid substitutions. The DR4-selective Apo2L/TRAIL variants examined in this study showed a markedly reduced ability to trigger apoptosis, whereas the DR5-selective variants had minimally decreased or slightly increased apoptosis-inducing activity. These results suggest that DR5 may contribute more than DR4 to Apo2L/TRAIL-induced apoptosis in cancer cells that express both death receptors.
凋亡诱导配体2（Apo2L），也称为肿瘤坏死因子相关凋亡诱导配体（TRAIL），可触发多种类型癌细胞的程序性细胞死亡，但大多数正常细胞不会发生。Apo2L/TRAIL是一种同源三聚体蛋白，可与五种受体相互作用：死亡受体4（DR4）和DR5介导凋亡激活，而诱饵受体1（DcR1）、DcR2和骨保护素则可抵消这种功能。许多癌细胞系同时表达DR4和DR5，且这些受体中的每一种都可独立于另一种启动凋亡。然而，DR4和DR5对配体诱导凋亡的相对贡献尚不清楚。为了研究这个问题，我们使用一种能够对突变三聚体蛋白进行噬菌体展示的新方法，生成了死亡受体选择性的Apo2L/TRAIL变体。通过三到六个配体氨基酸取代实现了对DR4或DR5的选择性结合。本研究中检测的DR4选择性Apo2L/TRAIL变体触发凋亡的能力明显降低，而DR5选择性变体的凋亡诱导活性则略有降低或略有增加。这些结果表明，在同时表达两种死亡受体的癌细胞中，DR5对Apo2L/TRAIL诱导凋亡的贡献可能比DR4更大。
