Isthmin targets cell-surface GRP78 and triggers apoptosis via induction of mitochondrial dysfunction
Isthmin targets cell-surface GRP78 and triggers apoptosis via induction of mitochondrial dysfunction
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DOI：
10.1038/cdd.2014.3
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发表时间：
2014-05-01
影响因子：
12.4
通讯作者：
Ge, R.
中科院分区：
文献类型：
--
作者：
Chen, M.;Zhang, Y.;Ge, R.
Isthmin（ISM）是一种分泌的60-kDa蛋白，其有效地诱导内皮细胞（EC）凋亡。当在癌细胞中稳定过表达时，它抑制小鼠肿瘤生长和血管生成。虽然α v β 5整合素作为ISM的低亲和力受体，但ISM介导内皮细胞抗血管生成和凋亡的机制仍有待完全解决。在这项工作中，我们报告了细胞表面葡萄糖调节蛋白78 kDa（GRP 78）作为ISM的高亲和力受体（Kd = 8.6 nM）的鉴定。我们证明了ISM-GRP 78相互作用不仅在活化的EC中触发凋亡，而且在表达高水平细胞表面GRP 78的癌细胞中也触发凋亡。正常细胞和良性肿瘤细胞倾向于表达低水平的细胞表面GRP 78，并且对ISM诱导的凋亡具有抗性。在与GRP 78结合后，ISM通过网格蛋白依赖性内吞作用内化到EC中，这对其促凋亡活性是必不可少的。一旦进入细胞内部，ISM与GRP 78共同靶向线粒体，在线粒体中它与内膜上的ADP/ATP载体相互作用，并阻断ATP从线粒体转运到胞质溶胶，从而引起细胞凋亡。因此，ISM是一种新的促凋亡配体，其靶向细胞表面GRP 78以通过诱导线粒体功能障碍来触发凋亡。癌细胞和癌内皮细胞上细胞表面GRP 78的限制性和高水平表达使它们对ISM靶向的细胞凋亡特别敏感。事实上，重组ISM的全身递送通过在癌细胞和癌EC中选择性地引发细胞凋亡而有效地抑制小鼠皮下4 T1乳腺癌和B16黑色素瘤生长。总之，这项工作揭示了一种新的ISM-GRP 78凋亡途径，并证明了ISM作为癌症特异性和双靶向抗癌剂的潜力。
Isthmin (ISM) is a secreted 60-kDa protein that potently induces endothelial cell (EC) apoptosis. It suppresses tumor growth and angiogenesis in mice when stably overexpressed in cancer cells. Although alpha v beta 5 integrin serves as a low-affinity receptor for ISM, the mechanism by which ISM mediates antiangiogenesis and apoptosis in ECs remain to be fully resolved. In this work, we report the identification of cell-surface glucose-regulated protein 78 kDa (GRP78) as a high-affinity receptor for ISM (K-d = 8.6 nM). We demonstrated that ISM-GRP78 interaction triggers apoptosis not only in activated ECs but also in cancer cells expressing high level of cell-surface GRP78. Normal cells and benign tumor cells tend to express low level of cell-surface GRP78 and are resistant to ISM-induced apoptosis. Upon binding to GRP78, ISM is internalized into ECs through clathrin-dependent endocytosis that is essential for its proapoptotic activity. Once inside the cell, ISM co-targets with GRP78 to mitochondria where it interacts with ADP/ATP carriers on the inner membrane and blocks ATP transport from mitochondria to cytosol, thereby causing apoptosis. Hence, ISM is a novel proapoptotic ligand that targets cell-surface GRP78 to trigger apoptosis by inducing mitochondrial dysfunction. The restricted and high-level expression of cell-surface GRP78 on cancer cells and cancer ECs make them uniquely susceptible to ISM-targeted apoptosis. Indeed, systemic delivery of recombinant ISM potently suppressed subcutaneous 4T1 breast carcinoma and B16 melanoma growth in mice by eliciting apoptosis selectively in the cancer cells and cancer ECs. Together, this work reveals a novel ISM-GRP78 apoptosis pathway and demonstrates the potential of ISM as a cancer-specific and dual-targeting anticancer agent.