N-glycosylation of MDA-7/IL-24 is dispensable for tumor cell-specific apoptosis and "bystander" antitumor activity
N-glycosylation of MDA-7/IL-24 is dispensable for tumor cell-specific apoptosis and "bystander" antitumor activity
复制标题
DOI：
10.1158/0008-5472.can-06-1887
复制
发表时间：
2006-12-15
期刊：
影响因子：
11.2
通讯作者：
Fisher, Paul B.
中科院分区：
文献类型：
--
作者：
Sauane, Moira;Gupta, Pankaj;Fisher, Paul B.
基于生化和基因突变的分析证实，MDA-7/IL-24 蛋白可以通过涉及内质网 (ER) 应激相关途径的机制诱导转化细胞特异性凋亡。内质网中 N 连接聚糖的共价修饰有助于许多蛋白质的构象成熟和生物学功能。由于 MDA-7/IL-24 是一种糖基化蛋白，因此我们研究了糖基化在介导该细胞因子的特定生物学和“旁观者”抗肿瘤活性中的作用。通过删除其信号肽和三个 N-糖基化位点的点突变，产生表达非分泌型和非糖基化版本的 MDA-7/IL-24 蛋白的腺病毒载体。在这项研究中，我们证明这种细胞内非糖基化蛋白在诱导多种肿瘤细胞系凋亡方面与野生型 MDA-7/11,-24 蛋白一样有效。两种构建体 (a) 均表现出转化细胞特异性并定位于 ER 区室，(b) 通过 JAK/STAT 独立性和 p38(MAPK) 依赖性途径介导细胞凋亡，(c) 诱导持续的 ER 应激，如 ER 应激标记物（BiP/GRP78、GRI`94、XBP-I 和 eIF2 α）的表达所证明的那样，以及 (d) 产生与 BiP/GRP78 物理相互作用的蛋白质。此外。含有与突变的非糖基化 mda-71IL-24 基因连接的 MDA-71 IL-24 信号肽的表达构建体保留了诱导旁观者抗肿瘤活性的能力。这些研究表明，MDA-7/IL-24 糖基化对于诱导不同癌细胞中的细胞死亡或旁观者活动不是必需的，这为 MDA-7/IL-24 诱导细胞凋亡和 ER 应激的机制提供了新的见解。
Biochemical and genetic mutation-based analyses confirm that the MDA-7/IL-24 protein can induce transformed cell-specific apoptosis through a mechanism involving endoplasmic reticulum (ER) stress -associated pathways. Covalent modifications by N-linked glycans in the ER contribute to the conformational maturation and biological functions of many proteins. Because MDA-7/IL-24 is a glycosylated protein, we investigated the role of glycosylation in mediating the specific biological and "bystander" antitumor activities of this cytokine. An adenovirus vector expressing a nonsecreted and nonglycosylated -version of MDA-7/IL-24 protein was generated via deletion of its signal peptide and point mutations of its three N-glycosylated sites. In this study, we showed that this intracellular nonglycosylated protein was as effective as wild-type MDA-7/11,-24 protein in inducing apoptosis in multiple tumor cell lines. Both constructs (a) displayed transformed cell specificity and localization to the ER compartment, (b) mediated apoptosis through JAK/STAT-independent and p38(MAPK)-dependent pathways, (c) induced sustained ER stress as evidenced by expression of ER stress markers (BiP/GRP78, GRI`94, XBP-I, and eIF2 alpha), and (d) generated proteins that physically interacted with BiP/GRP78. Additionally. an expression construct containing the MDA-71 IL-24 signal peptide linked to the mutated nonglycosylated mda-71IL-24 gene retained the ability to induce bystander antitumor activity. These studies reveal that MDA-7/IL-24 glycosylation is not mandatory for inducing cell death or bystander activities in different cancer cells, providing new insights into the mechanism by which MDA-7/IL-24 induces apoptosis and ER stress.